JavaTM EE Patterns SL-314 JavaTM EE Patterns EE Patterns Java™ EE Patterns Java SL-314 TM EE...

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Java™ EE Patterns

Java™ EE Patterns

SL-314JavaTM EE Patterns

L-314-EE5

JavaTM EE Patterns

L-500-EE5

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Java™ EE Pattern 12008 Sun Microsystem

...................................Preface-i...................................... Preface-ii.....................................Preface- iii......................................Preface-iv.......................................Preface-v.....................................Preface-vii................................... Preface-viii..................................... Preface-ix....................................... Preface-x

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ss, Inc. All Rights Reserved. Sun Services, Revision C.1

Table of Contents

About This Course .........................................................................Course Goals...........................................................................................Course Map.............................................................................................Topics Not Covered ..............................................................................How Prepared Are You?.......................................................................Introductions ..........................................................................................Icons ........................................................................................................Typographical Conventions .................................................................Additional Conventions........................................................................

Developing a View Component ..........................................Objectives ...............................................................................................Reviewing Design Goals .......................................................................Course Flow............................................................................................Exploring Object-Oriented Design Concepts.....................................Cohesion..................................................................................................Low and High Cohesion Examples.....................................................Encapsulation .........................................................................................Encapsulation Example.........................................................................Coupling .................................................................................................Four Levels of Coupling .......................................................................Implementation Inheritance .................................................................Implementation Inheritance Example.................................................Composition............................................................................................Interface Inheritance .............................................................................

Java™ 2Copyrig

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EE Patternsht 2008 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision C.1

Interface Inheritance Example .............................................................Polymorphism .......................................................................................Polymorphism Example .......................................................................Favoring Composition ..........................................................................Programming to an Interface ...............................................................Designing for Change............................................................................Introducing Design Patterns ...............................................................Origin of the Pattern Concept ..............................................................Design Pattern Catalogs .......................................................................Gang of Four (GoF) Patterns ................................................................Gang of Four (GoF) Patterns: Description..........................................Gang of Four (GoF) Patterns: Groups .................................................Design Pattern Selection ......................................................................Design Pattern Elements .......................................................................Design Pattern Notation .......................................................................When and How to Apply Patterns ......................................................

Using Gang of Four Behavioral Patterns...........................Objectives ................................................................................................Introducing Behavioral Patterns .........................................................Strategy Pattern Example Problem .....................................................Applying the Strategy Pattern: Problem Forces ...............................Applying the Strategy Pattern: Solution.............................................Strategy Pattern Structure.....................................................................Strategy Pattern Example Solution......................................................Applying the Strategy Pattern ............................................................Command Pattern Example Problem .................................................Applying the Command Pattern:

Problem Forces ...................................................................................

Java™ 3Copyrig

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............................................... 2-19 Language............................ 2-20............................................... 2-21............................................... 2-22............................................... 2-24............................................... 2-25............................................... 2-26............................................... 2-27............................................... 2-28uage ..................................... 2-29............................................... 2-31............................................... 2-33............................................... 2-34............................................... 2-35............................................... 2-36............................................... 2-37nguage .................................. 2-42............................................... 2-43............................................... 2-45

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Applying the Command Pattern: Solution .......................................Command Pattern Structure ................................................................Command Pattern Example Solution ................................................Applying the Command Pattern: Use in the Java™ ProgrammingEJB Command Pattern Dynamic Structure .......................................Applying the Command Pattern: Consequences .............................Applying the Iterator Pattern: Example Problem ............................Applying the Iterator Pattern: Problem Forces .................................Applying the Iterator Pattern: Solution ..............................................Iterator Pattern Structure .....................................................................Iterator Pattern Example Solution ......................................................Applying the Iterator Pattern: Use in the Java Programming LangApplying the Iterator Pattern: Consequences ...................................Applying the Observer Pattern: Example Problem .........................Applying the Observer Pattern: Problem Forces ..............................Applying the Observer Pattern: Solution...........................................Observer Pattern Structure ..................................................................Observer Pattern Example Solution ...................................................Applying the Observer Pattern: Use in the Java Programming LaApplying the Observer Pattern: Consequences ................................Summary ................................................................................................

Using Gang of Four Creational Patterns............................Objectives 2Factory Method Pattern Example Problem........................................Applying the Factory Method Pattern: Problem Forces ..................Applying the Factory Method Pattern: Solution ...............................Factory Method Pattern Structure ......................................................Factory Method Pattern Example Solution ........................................

Java™ 4Copyrig

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JDBC API Factory Method Scheme Class Diagram ..........................Applying the Factory Method Pattern: Consequences ....................Abstract Factory Pattern Example Problem.......................................Applying the Abstract Factory Pattern: Problem Forces .................Applying the Abstract Factory Pattern: Solution .............................Abstract Factory Pattern Structure ......................................................Abstract Factory Pattern Example Solution .......................................Applying the Abstract Factory Pattern: Consequences....................Applying the Singleton Pattern: Example Problem .........................Applying the Singleton Pattern: Problem Forces .............................Singleton Pattern Structure ..................................................................Singleton Pattern Example Solution....................................................Applying the Singleton Pattern: Consequences ................................Summary .................................................................................................

Using Gang of Four Structural Patterns ............................Objectives ................................................................................................Façade Pattern Example Problem .......................................................Applying the Façade Pattern: Problem Forces .................................Applying the Façade Pattern: Solution...............................................Façade Pattern Structure ......................................................................Façade Pattern Example Solution........................................................Façade Pattern Example Sequence ......................................................Applying the Façade Pattern: Consequences ....................................Proxy Pattern Example Problem..........................................................Applying the Proxy Pattern: Problem Forces ...................................Applying the Proxy Pattern: Solution.................................................Proxy Pattern Structure ........................................................................Applying the Proxy Pattern: Solution ................................................

Java™ 5Copyrig

................................................ 4-16age ........................................ 4-17............................................... 4-18............................................... 4-19............................................... 4-20................................................ 4-21................................................ 4-22............................................... 4-23............................................... 4-24................................................ 4-26................................................ 4-28................................................ 4-29............................................... 4-30............................................... 4-31............................................... 4-32anguage ............................... 4-35................................................ 4-36................................................ 4-37................................................ 4-38............................................... 4-39................................................ 4-40............................................... 4-41............................................... 4-43nguage................................. 4-44............................................... 4-45

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Proxy Pattern Example Solution .........................................................Applying the Proxy Pattern: Use in the Java Programming LanguApplying the Proxy Pattern: Consequences ......................................Adapter Pattern Example Problem .....................................................Applying the Adapter Pattern: Problem Forces ................................Applying the Adapter Pattern: Solution ...........................................Object Adapter Strategy Structure ......................................................Class Adapter Strategy Structure ........................................................Object Adapter Strategy Example Solution .......................................Applying the Adapter Pattern: Consequences .................................Composite Pattern Example Problem ................................................Applying the Composite Pattern: Problem Forces ..........................Applying the Composite Pattern: Solution ........................................Composite Pattern Structure ................................................................Composite Pattern Example Solution .................................................Applying the Composite Pattern: Use in the Java Programming LApplying the Composite Pattern: Consequences .............................Decorator Pattern Example Problem ..................................................Applying the Decorator Pattern: Problem Forces ............................Applying the Decorator Pattern: Solution..........................................Decorator Pattern Structure .................................................................Decorator Pattern Example Solution...................................................Decorator Pattern Example Sequence.................................................Applying the Decorator Pattern: Use in the Java Programming LaApplying the Decorator Pattern: Consequences ...............................Summary 46

Using Architectural Building Blocks .................................Objectives ...............................................................................................

Java™ 6Copyrig

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Comparing Architectural Patterns to Design Patterns ....................Applying the Model View Controller (MVC) Pattern......................Applying the MVC Pattern: Example Problem .................................Applying the MVC Pattern: Problem Forces .....................................Applying the MVC Pattern: Solution..................................................Model View Controller Pattern Structure .........................................Model View Controller Pattern Example Solution ..........................Applying the MVC Pattern: Consequences .......................................Applying the Layers Pattern ...............................................................Applying the Layers Pattern: Example Problem...............................Applying the Layers Pattern: Problem Forces ..................................Applying the Layers Pattern: Solution ..............................................Layers Pattern: Example Solution ......................................................Applying the Layers Pattern: Consequences ....................................Applying Layers and Tiers in Java™ EE Platform Enterprise AppSunToneTM Architecture Methodology Layers ................................SunTone Architecture Methodology Tiers ........................................Java EE Technologies in Each Tier ......................................................Java EE Platform Example – Layers and Tiers ..................................Summary ................................................................................................

Introducing Java EE™ Patterns..........................................Objectives ................................................................................................Purpose of the Java EE Patterns ..........................................................Benefits ....................................................................................................Relation to the Java EE BluePrints Design Guidelines ....................Gang of Four and Java EE Patterns .....................................................Describing the Patterns and Tiers of the Java EE Pattern Catalog..Integration Tier Patterns .......................................................................

Java™ 7Copyrig

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Business Tier Patterns ...........................................................................Presentation Tier Patterns ....................................................................Java EE Pattern Relationships ..............................................................Summary 14

Using Integration Tier Patterns ..........................................Objectives ...............................................................................................Introducing Integration Tier Patterns .................................................Integration Tier Java EE Patterns Overview .....................................Applying the Service Activator Pattern: Problem Forces ................Applying the Service Activator: Solution ..........................................Service Activator Pattern Structure ....................................................Service Activator Pattern Sequence.....................................................Applying the Service Activator Pattern: Strategies ..........................Service Activator Pattern Example......................................................Service Activator Pattern Example......................................................Service Activator Pattern Example......................................................Applying the Service Activator: Consequences ...............................Applying the DAO Pattern: Problem Forces .....................................Applying the DAO Pattern: Solution..................................................DAO Pattern Structure..........................................................................DAO Pattern Sequence..........................................................................Applying the DAO Pattern: Strategies ...............................................DAO Abstract Factory Strategy Structure .........................................DAO Pattern Example...........................................................................DAO Pattern Example ..........................................................................Applying the DAO Pattern: Consequences .......................................Applying the Domain Store Pattern: Problem Forces .....................Applying the Domain Store Pattern: Solution ..................................

Java™ 8Copyrig

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Domain Store Pattern Structure...........................................................Domain Store Persistence Sequence....................................................Domain Store Query Sequence ............................................................Applying the Domain Store: Example ................................................Applying the Domain Store Pattern: Example ..................................Applying the Domain Store Pattern: Strategies ...............................Applying the Domain Store Pattern: Consequences .......................Applying the Web Service Broker Pattern: Problem Forces ............Applying the Web Service Broker Pattern: Solution .......................Web Service Broker Pattern Structure.................................................Web Service Broker Pattern Sequence ...............................................Applying the Web Service Broker Pattern: Strategies ......................Web Service Broker Pattern Example ................................................Applying the Web Service Broker Pattern: Consequences 50Summary .................................................................................................

Using Presentation-to-Business Tier Patterns .................Objectives ...............................................................................................Introducing Business Tier Patterns ....................................................Java EE Platform Business Tier Patterns ............................................Applying the Service Locator Pattern: Problem Forces ...................Applying the Service Locator Pattern: Solution ...............................Service Locator Pattern Structure .......................................................Service Locator Pattern Sequence........................................................Applying the Service Locator Pattern: Strategies .............................Service Locator Pattern Example ........................................................Applying the Service Locator Pattern: Consequences .....................Applying the Session Façade Pattern: Problem Forces ...................Applying the Session Façade Pattern: Solution.................................

Java™ 9Copyrig

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Session Façade Pattern Structure.........................................................Session Façade Pattern Sequence.........................................................Applying the Session Façade Pattern: Strategies .............................Session Façade Pattern Example..........................................................Applying the Session Façade Pattern: Consequences ......................Applying the Business Delegate Pattern: Problem Forces...............Applying the Business Delegate Pattern: Solution ..........................Business Delegate Pattern Structure ...................................................Business Delegate Pattern Sequence ...................................................Applying the Business Delegate Pattern: Strategies .........................Business Delegate Pattern Example ...................................................Applying the Business Delegate Pattern: Consequences .................Applying the Transfer Object Pattern: Problem Forces ...................Applying the Transfer Object Pattern: Solution ...............................Transfer Object Pattern Structure ........................................................Transfer Object Pattern Sequence........................................................Applying the Transfer Object Pattern: Strategies .............................Updatable Transfer Objects Sequence ...............................................Transfer Object Pattern Example ........................................................Applying the Transfer Object Pattern: Consequences .....................Summary .................................................................................................

Using Intra-Business Tier Patterns ....................................Objectives ................................................................................................Applying the Application Service Pattern: Problem Forces ............Applying the Application Service Pattern: Solution.........................Application Service Pattern Structure.................................................Application Service Pattern Sequence ................................................Applying the Application Service Pattern: Strategies .....................

Java™ 10Copyrig

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Application Service Pattern Example ................................................Applying the Application Service Pattern: Consequences .............Applying the Business Object Pattern: Problem Forces ..................Applying the Business Object Pattern: Solution................................Business Object Pattern Structure .......................................................Business Object Pattern Sequence .......................................................Applying the Business Object Pattern: Strategies ............................Business Object Pattern Example .......................................................Applying the Business Object Pattern: Consequences ....................Applying the Transfer Object Assembler Pattern: Problem ForcesApplying the Transfer Object Assembler Pattern: Solution ............Transfer Object Assembler Pattern Structure ...................................Transfer Object Assembler Pattern Sequence ....................................Applying the Transfer Object Assembler Pattern: Strategies..........Transfer Object Assembler Pattern Example ....................................Applying the Transfer Object Assembler Pattern: Consequences..Applying the Composite Entity Pattern: Problem Forces................Comparing BMP and CMP ..................................................................Applying the Composite Entity Pattern: Solution ............................Composite Entity Pattern Structure ...................................................Composite Entity Pattern Sequence ...................................................Applying the Composite Entity Pattern: Strategies..........................Composite Entity Pattern Example ....................................................Applying the Composite Entity Pattern: Consequences..................Applying the Value List Handler Pattern: Problem Forces ............Applying the Value List Handler Pattern: Solution .........................Value List Handler Pattern Structure .................................................Value List Handler Pattern Sequence .................................................Applying the Value List Handler Pattern: Strategies ......................Value List Handler Pattern Example ..................................................Applying the Value List Handler Pattern: Consequences ...............

Java™ 11Copyrig

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Summary .................................................................................................

Using Presentation Tier Patterns ......................................Objectives ................................................................................................Introducing the Presentation Tier Patterns ........................................Presentation Tier Patterns ....................................................................Traditional Model View Controller Architecture .............................Model 2 Architecture ............................................................................Apache Struts Framework ....................................................................Applying the Intercepting Filter Pattern: Problem Forces ..............Applying the Intercepting Filter Pattern: Solution ..........................Intercepting Filter Pattern Structure ..................................................Intercepting Filter Pattern Sequence ..................................................Applying the Intercepting Filter Pattern: Strategies ........................Applying the Intercepting Filter Pattern: Example...........................Applying the Intercepting Filter Pattern: Example...........................Applying the Intercepting Filter Pattern: Consequences ................Applying the Front Controller Pattern: Problem Forces .................Applying the Front Controller Pattern: Solution .............................Front Controller Pattern Structure .....................................................Front Controller Pattern Sequence .....................................................Applying the Front Controller Pattern: Strategies ...........................Front Controller Pattern Example ......................................................Applying the Front Controller Pattern: Consequences ...................Applying the Application Controller Pattern: Problem Forces ......Applying the Application Controller Pattern: Solution ..................Application Controller Pattern Structure ...........................................Application Controller Pattern Sequence ..........................................Applying the Application Controller Pattern: Strategies.................

Java™ 12Copyrig

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Application Controller Pattern Example ...........................................Applying the Application Controller Pattern: Consequences.........Applying the Context Object Pattern: Problem Forces ....................Applying the Context Object Pattern: Solution ................................Context Object Pattern Structure ........................................................Context Object Pattern Sequence ........................................................Applying the Context Object Pattern: Strategies ..............................Context Object Pattern Example .........................................................Applying the Context Object Pattern: Consequences ......................

More Presentation Tier Patterns.........................................Objectives ................................................................................................More Presentation Tier Patterns ..........................................................Applying the View Helper Pattern:

Problem Forces ...................................................................................Applying the View Helper Pattern: Solution.....................................View Helper Pattern Structure.............................................................View Helper Pattern Sequence ............................................................Applying the View Helper Pattern: Strategies .................................View Helper Pattern Example..............................................................Applying the View Helper Pattern: Consequences .........................Applying the Composite View Pattern: Problem Forces .................Applying the Composite View Pattern: Solution .............................Composite View Pattern Structure .....................................................Composite View Pattern Sequence .....................................................Applying the Composite View Pattern: Strategies ..........................Composite View Pattern Example ......................................................Applying the Composite View Pattern: Consequences ...................Applying the Dispatcher View Pattern ..............................................

Java™ 13Copyrig

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.............................................. 12-24


Applying the Dispatcher View Pattern: Problem Forces ................Applying the Dispatcher View Pattern: Solution..............................Dispatcher View Pattern Structure .....................................................Dispatcher View Pattern Sequence ....................................................Dispatcher View Pattern Example ......................................................Applying the Dispatcher View Pattern: Consequences ..................Applying the Service to Worker Pattern ...........................................Applying the Service to Worker Pattern: Problem Forces ...............Applying the Service to Worker Pattern: Solution ...........................Service to Worker Pattern Structure ...................................................Service to Worker Pattern Sequence ...................................................Service to Worker Pattern Example ....................................................Applying the Service to Worker Pattern: Consequences .................Service to Worker Pattern In Struts ....................................................

Exploring AntiPatterns ........................................................Objectives ...............................................................................................Introducing AntiPatterns .....................................................................Describing Integration Tier AntiPatterns ..........................................Not Pooling Connections AntiPattern ................................................Monolithic Consumer AntiPattern .....................................................Fat Message AntiPattern ......................................................................Hot Potato AntiPattern..........................................................................Describing Business Tier AntiPatterns ...............................................Sledgehammer for a Fly AntiPattern .................................................Local and Remote Interfaces Simultaneously AntiPattern ..............Accesses Entities Directly AntiPattern ...............................................Mirage AntiPattern ...............................................................................Cacheless Cow AntiPattern ..................................................................

Java™ 14Copyrig

............................................. 12-27

............................................. 12-29

.............................................. 12-31

.............................................. 12-32

............................................. 12-34

.............................................. 12-36

.............................................. 12-38

.................................. 13-1

............................................... 13-2

................................................ 13-3

................................................ 13-4

............................................... 13-5

............................................... 13-6

............................................... 13-7

............................................... 13-9

.............................................. 13-10

............................................. 13-11

.............................................. 13-12

............................................. 13-13

............................................. 13-14

.............................................. 13-15

.............................................. 13-16

............................................. 13-18

.............................................. 13-20

.............................................. 13-21

............................................. 13-22

............................................. 13-23


Conversational Baggage AntiPattern..................................................Golden Hammers of Session State AntiPattern.................................Describing Presentation Tier AntiPatterns ........................................Including Common Functionality in Every Servlet AntiPattern ...Embedded Navigational Information AntiPattern ...........................Ad Lib TagLibs AntiPattern ................................................................Summary ................................................................................................

Applying Java EE BluePrints Design Guidelines..............Objectives ................................................................................................Describing the Java EE BluePrints Design Guidelines ....................Object-Oriented Guidelines..................................................................Client Tier Guidelines ...........................................................................Web Tier Guidelines ..............................................................................Business Tier Guidelines.......................................................................Integration Tier Guidelines ..................................................................Describing the Java Pet Store Demo Software ..................................Analyzing Java EE Patterns in the Java Pet Store Demo SoftwareWeb Application Framework...............................................................Java Pet Store Demo Software Web Application Framework .........Java EE Patterns in the Web Application Framework......................The SignOnFilter Class Mapping in the web.xml File..................The SignOnFilter Class .....................................................................The SignOnFilter Class .....................................................................The SignOnFilter Class ......................................................................Front Controller Servlet Mapping in the web.xml File ...................The mapping.xml Class Mapping ......................................................The MainServlet Class ........................................................................The MainServlet Class ........................................................................

Java™ 15Copyrig

............................................. 13-25

.............................................. 13-26

.............................................. 13-27

.............................................. 13-28

.............................................. 13-29

............................................. 13-30

.............................................. 13-31

.............................................. 13-32

.............................................. 13-33

.............................................. 13-34

............................................. 13-35

............................................. 13-36

.............................................. 13-37

............................................. 13-38

.............................................. 13-39

............................................. 13-40are Administrative............................................. 13-42ctionality ............................. 13-43.............................................. 13-44.............................................. 13-45.............................................. 13-46............................................. 13-47.............................................. 13-49............................................. 13-50.............................................. 13-51.............................................. 13-52............................................. 13-54.............................................. 13-55


The RequestProcessor Class processRequest Method ..............The RequestProcessor Class processRequest Method .............The DefaultWebController Class ..................................................The EJBControllerLocalEJB Class .................................................The EJBControllerLocalEJB Class .................................................The StateMachine Class ......................................................................The StateMachine Class .....................................................................The ScreenFlowManager Class ..........................................................The ScreenFlowManager Class ...........................................................The screendefinitions_en_US.xml File .......................................The screendefinitions_en_US.xml File ........................................The TemplateServlet Class ...............................................................The TemplateServlet Class ..............................................................The Template.jsp Page.......................................................................The Template.jsp Page ......................................................................The InsertTag Custom Tag ................................................................Analyzing the Java EE Patterns in the Java Pet Store Demo SoftwClasses .....................................................................................................Design Pattern Implementation in the Administrative Client FunThe AdminRequestBD Class..................................................................The AdminRequestBD Class .................................................................The ServiceLocator Class .................................................................The ServiceLocator Class..................................................................The ServiceLocator Class .................................................................The MutableOrderTO Class..................................................................The OPCAdminFacadeEJB Class ...........................................................The OPCAdminFacadeEJB Class ..........................................................The OPCAdminFacadeEJB Class ...........................................................Summary ................................................................................................

Java™ EE Pattern 162008 Sun Microsystem

.....................................A-1

.....................................B-1

..................................................B-2

..................................................B-3

................................................. B-6

................................................. B-7

................................................B-15

................................................B-17) API .....................................B-24............................................... B-25............................................... B-27................................................B-28................................................B-32................................................B-33................................................B-34................................................B-35................................................B-38................................................B-39................................................B-40................................................B-41............................................... B-48................................................B-49onent .....................................B-50................................................B-54

ss, Inc. All Rights Reserved. Sun Services, Revision C.1

Table of Contents

Quick Reference for UML ...................................................

J2EE Technology Review ...................................................Objectives ................................................................................................Reviewing the J2EE Platform ..............................................................Multi-Tier J2EE Architecture Basics ....................................................Understanding Java Remote Method Invocation..............................Understanding the Java IDL API ........................................................Understanding the JAX-RPC API .......................................................Understanding the Java Naming and Directory Interface™ (JNDIJNDI API Class .......................................................................................Understanding Servlets.........................................................................Servlet Class ...........................................................................................Understanding JavaServer Pages™ Technology ..............................JSP Page Flow ........................................................................................HTML Form Processed by a JSP Page ................................................JSP Page ..................................................................................................Understanding the Java Message Service (JMS) API .......................Understanding the JMS API ................................................................Understanding the JMS API ................................................................Understanding the JMS API ................................................................Understanding Enterprise JavaBeans™ Technology ComponentsOverall Enterprise JavaBeans Architecture........................................Overall Enterprise JavaBeans Architecture: Parts of an EJB CompThree Types of EJB Components ........................................................

Java™ 17Copyrig

................................................B-55

................................................B-56

................................................B-57

................................................B-58

............................................... B-62

................................................B-63

................................................B-64

............................................... B-65

................................................B-74

................................................B-75

................................................B-76

................................................B-79

................................................B-80

................................................B-83

................................................B-84

............................................... B-85

................................................B-87

............................................... B-88

............................................... B-91


Session Beans ..........................................................................................Session Bean Home Interface ..............................................................Session Bean Component Interface ....................................................Session Bean Class ................................................................................Entity Beans ............................................................................................BMP Entity Bean Home Interface .......................................................BMP Entity Bean Component Interface .............................................BMP Entity Bean Class ..........................................................................CMP Entity Bean Home Interface .......................................................CMP Entity Bean Component Interface .............................................CMP Entity Bean Class .........................................................................Message-Driven Beans .........................................................................Message-Driven Bean Class .................................................................Understanding JDBC™ Technology ..................................................JDBC Technology Class Interactions on the J2EE Platform ............JDBC Technology Using the DataSource Class .................................JDBC Technology Using the DataSource Class ................................Understanding J2EE Connector Architecture....................................Summary .................................................................................................

P

A

Java EE™ Patterns

Preface

About This Coursereface

bout The Course

Preface

About The Course

Preface, slide 2 of 10

e able to:

tterns,

(Integration, 2 Platform,) applicationa Java EE

Java EE™ PatternsCopyright 2008 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision C.1

Course Goals

Upon completion of this course, you should b

• Describe the fundamentals of design paincluding key Gang of Four patterns

• Apply appropriate patterns in the tiersBusiness, and Presentation) of a Java™Enterprise Edition (Java EE™ platform

• Use patterns to apply best practices in platform environment

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. Many of these Sun Services:

overed insign Using UMLent – CoveredApplicationsin SL-425:cations

nformation


Topics Not Covered

This course does not cover the following topicstopics are covered in other courses offered by

• Object-oriented analysis and design – COO-226: Object-Oriented Analysis and De

• Java EE platform application developmin FJ-310: Developing Java EE Compliant

• Java EE system architecture – Covered Architecting and Designing Java EE Appli

Refer to the Sun Services catalog for specific iand registration.


e, can you

g the Java


How Prepared Are You?

To be sure you are prepared to take this coursanswer yes to the following questions?

• Have you designed systems usingobject-oriented techniques?

• Have you developed applications usinprogramming language?


nologies, such JavaBeans™let technologyeology?uage (UML)gram?


How Prepared Are You?

• Can you describe Java EE platform techas components based on the Enterprisespecification (EJB™ components), servcomponents, and pages created with thJavaServer Pages™ (JSP™ pages) techn

• Can you read a Unified Modeling Langclass diagram and a UML sequence dia


in this course


Introductions

• Name• Company affiliation• Title, function, and job responsibility• Experience related to topics presented • Reasons for enrolling in this course• Expectations for this course

Icons

Additional resources

Demonstration

Discussion

Note

123

?!


ns

ands, files,mmingtput.and numbersramming coden.es andplaced with a

epresentby the student


Typographical Conventio

• Courier is used for the names of commdirectories, programming code, prograconstructs, and on-screen computer ou

• Courier bold is used for characters that you type, and for each line of progthat is referenced in a textual descriptio

• Courier italics is used for variablcommand-line placeholders that are rereal name or value.

• Courier italics bold is used to rvariables whose values are to be enteredas part of an activity.


e following

ethods,

es unless an.rations,e.


Additional Conventions

Java programming language examples use thadditional conventions:

• Courier is used for the class names, mand keywords.

• Methods are not followed by parenthesformal or actual parameter list is show

• Line breaks occur where there are sepaconjunctions, or white space in the cod

onentM

EODD

Java EE™ Patterns

Module 1

Developing a View Compodule 1

xploringbject-Orientedesign Principles andesign Patterns

Module 1

ExploringObject OrientedDesign Principles AndDesign Patterns

Module 1, slide 2 of 38

ed

ed

atterns


Objectives

• Describe the fundamental object-orientdesign concepts

• Describe the fundamental object-orientdesign principles

• Describe the characteristics of design p


tterns forals:


Reviewing Design Goals

This course presents design principles and pareaching the following Java EE™ platform go

• Adaptability• Extensibility• Maintainability• Reusability• Performance• Scalability• Reliability• Development efficiency


ach these goals:


Course Flow

The course presents the following topics to reObject-Oriented Design Principles

Architectural Patterns

Anti-Patterns Java EE BluePrints Design Guidelines

Gang of Four Design Patterns

Java EE Design Patterns

Behavioral

Creational

Structural

Presentation Tier

Business Tier

Integration Tier


sign

re the buildingerns:

ition inheritancephism


Exploring Object-Oriented DeConcepts

These fundamental object-oriented concepts ablocks of the object-oriented and Java EE patt

• Cohesion• Encapsulation• Coupling• Implementation

inheritance

• Compos• Interface• Polymor


thods andurpose

nrelated code

e class’ roleble components


Cohesion

• Cohesion is the degree to which the meattributes of a class focus on only one pin the system

• Advantages of high cohesion:• Avoids the side affects of changing u

within the same class• Improves readability by clarifying th• Facilitates the creation of small reusa


ples

vice

ee()()yName()

rvice

ment()nt()ByID()

ice

sion


Low and High Cohesion Exam

SystemServices

+deleteDepartment()+deleteEmployee()+login()+logout()+makeDepartment()+makeEmployee()+retrieveDeptByID()+retrieveEmpByName()

EmployeeSer

+deleteEmploy+makeEmployee+retrieveEmpB

DepartmentSe

+deleteDepart+makeDepartme+retrieveDept

LoginServ

+login()+logout()

High CoheLow Cohesion


n object should

apsulation:

ld provide an

ithout

t knowing all of

s are prevented


Encapsulation

• The internal structure and behavior of anot be exposed

• Information hiding is key to proper enc• Data should be kept private• Accessor and mutator methods shou

abstract interface to the data• Advantages:

• Implementation of a class can vary wchanging its interface

• Developers can use the class withouits implementation details

• Inappropriate attribute modification


Name();

amantha");


Encapsulation Example

ObjectsClasses

Stack

main employee

department

:Engineer

fname="Fred"lname="Cartz"salary=US$47,000

Engineer

-fname:String-lname:String-salary:Money

+getFirstName():String+getLastName():String+setFirstName(:String)+increaseSalary(amt)+analyzeReq()+designSoftware()+implementCode()

name = employee.fname; name = employee.getFirst

employee.fname = "Samantha"; employee.setFirstName("S

Encapsulation Example

1 class Engineer {2 private String fname;3 private String lname;4 private Money salary;56 public String getFirstName() {7 return fname;8 }910 public String getLastName() {11 return lname;12 }1314 public void setFirstName(String fn) {15 fname = fn;16 }17 ...18 }


t classes are on

sesclasse interface

tem rather than


Coupling

• Coupling is a measure of how dependanother classes

• To reduce coupling:• Hide the implementation of the clas• Couple to the abstract interface of a • Reduce the number of methods in th

of the class• Consider the coupling of the entire sys

just between individual classes


Service

Coupling

upling

Service


Four Levels of Coupling

<<interface>>

Service

ServiceClient

Looser Abstract Coupling

Looser Tight Coupling

Client

Client

No Co

Client

ServiceImpl


e

ed attributes

on to subtypesnce

om

the subclass


Implementation Inheritanc

Implementation inheritance is inheriting sharand methods from a superclass

Advantages:

• Avoids duplication of code that is comm• Organizes classes according to inherita

Disadvantages:

• Forces subclass to inherit everything frits superclass

• Changes to the superclass might affect


mple

oyee

ggy

StringString Moneyy( : int )me : String )me : String )lary : Money )

Engineer

-education : String-hardware : String

+analyzeReq()+designSoftware()+getEducation()+getHardware()+implementCode()


Implementation Inheritance Exa

1 class Employee2 {3 . . .4 }56 class Manager extends Employee7 {8 . . .9 }1011 class Engineer extends Employee12 {13 . . .14 }

Empl

-fname : Strin-lname : Strin-salary : Mone

+getFname() : +getLname() : +getSalary() :+increaseSalar+setFname( fna+setLname( lna+setSalary( sa

Manager

-quarterlyBonus : Money

+increaseBonus()+playGolfWithClient()


jects


Composition

• Builds complex objects from simpler ob• Forms a looser coupling than

implementation inheritance

1 class Department {2 private Employee worker;3 .. .4 }

Department Employee


terface

ment a

ing modifiedinterfaces)tract classes

ossible andhether anpriate for them


Interface Inheritance

Interface inheritance is the separation of an indefinition from its implementation:

• Similar to hardware devices that implecommon interface

• Can make a class extensible without be• Java technology-based interfaces (Java

provide pure interface inheritance; absallow a mixture of implementation andinterface inheritance

• This course uses interfaces whenever pleaves it to the attendee to determine wabstract class or interface is more appro


le

ation}ementation}

renceRoom


Interface Inheritance Examp

1 interface Schedulable {2 public void cancelActivity();3 public void notifyAboutActivity();4 }5 class Equipment implements Scheduable {6 public void cancelActivity() {//implement7 public void notifyAboutActivity() {//impl8 }

<<interface>>Schedulable

+cancelActivity()+notifyAboutActivity()

ConfeEquipment

Schedule

Employee


erations ofces

ypes at runtimeed by the object

oes not depend

use a supertype


Polymorphism

• Polymorphism allows invocation of opspecific objects through generic referen

• Aspects of polymorphism:• A variable can be assigned different t• Method implementation is determin

type, not the reference type

Advantages:

• Enables you to write generic code that dupon a specific subclass

• Allows you to code fewer methods becacan be specified as the parameter type


:List

er


Polymorphism Example

List list = getProjectTeam();for ( int i=0; i<list.size(); i++ ) { Employee employee = (Employee) list.get(i); employee.increaseSalary(0.10); //10%}

ObjectsClasses

Stack

main employee

list

Employee Kathy:Manag

Fred:Engineer

Samantha:EngineerManager Engineer


sign

riented


Exploring Object-Oriented DePrinciples

The Gang of Four book outlines three object-odesign principles:

• Favoring composition• Programming to an interface• Designing for change


ementation], and Vlissides,bject-Oriented

ead of

x reuse


Favoring Composition

“Favor object composition over [implinheritance.” (Gamma, Helm, JohnsonDesign Patterns: Elements of Reusable OSoftware)

Reuse functionality through composition instimplementation inheritance:

• Implementation inheritance is white-bo• Composition is black-box reuse


ArrayList

lementData : Objectize : int.

dd( o : Object ) : booleanrrayList( initialCapacity : int )lear()et( index : int ) : Objectemove( index : int )ize() : int.


Favoring Composition

ArrayList

-elementData : Object-size : int...

+add( o : Object ) : boolean+ArrayList( initialCapacity : int )+clear()+get( index : int ) : Object+remove( index : int )+size() : int...

DepartmentEmployeeList

-departmentName : String

+getDepartmentName() : String+setDeptName( deptName ) : String

Implementation Inheritance



+addEmployee( e : Employee ) : boolean+fireEmployee( e : Employee )+getDepartmentName() : String+getEmployee( ssn : String ) : Employee+getNumEmployees() : int+setDeptName( deptName : String )...

-e-s..

+a+A+c+g+r+s..

Composition

-employees


e

ion.” (Gamma,: Elements of

ooleanacity : int )

Object

>>n

: boolean

ooleanlean


Programming to an Interfac

“Program to an interface, not an implementatHelm, Johnson, and Vlissides, Design PatternsReusable Object-Oriented Software)



+addEmployee( e : Employee ) : boolean+fireEmployee( e : Employee )+getDepartmentName() : String+getEmployee( ssn : String ) : Employee+getNumEmployees() : int+setDepartmentName( departmentName ) : String...

ArrayList

-elementData-size : int...

+add( o : Object ) : b+ArrayList( initialCap

+clear()+get( index : int ) : +remove( index : int )+size() : int...

<<interfaceCollectio

+add( o : Object )+clear()+contains( o ) : b+remove( o ) : boo+size() : int

-employees


e

ion:

st();

ist();


Programming to an Interfac

Programming to the ArrayList Implementat

1 public class DepartmentEmployeeList {2 private ArrayList employees = new ArrayLi3 . . .4 }

Programming to the Collection Interface:

1 public class DepartmentEmployeeList {2 private Collection employees = new ArrayL3 . . .4 }


ing for change:

designing for

n-Closedsses, should befication


Designing for Change

The previous two principles are about design

• Requirements do change, which makeschange very important

• This is more formally stated in the Opeprinciple: Software entities, such as claopen for extension but closed for modi


s

experiencerade-offs to

gn

turessign decisions


Introducing Design Pattern

Design patterns:

• Identify and document proven design • Capture recurring solutions and their t

similar problems in a given context• Provide a common vocabulary for desi

and architecture• Clarify and document existing architec• Move design forward and influence de


pt

concept. They

t occurs overnd thenat problem, in

tion a millionsame

guage: Towns,


Origin of the Pattern Conce

Building architects first developed the patternstated that:

“Each pattern describes a problem thaand over again in our environment, adescribes the core of the solution to thsuch a way that you can use this solutimes over, without ever doing it theway twice.”(Christopher Alexander, A Pattern LanBuildings, Construction)


are catalogs ofure, building


Design Pattern Catalogs

Pattern catalogs are groups of patterns. Theredesign patterns for analysis, design, architectarchitecture, and other topics.

This course focuses on two pattern catalogs:

• Gang of Four Design Pattern catalog• Java EE Pattern catalog


s

Object-Orientedh Johnson, and

eral design

booktions toms

ere built upon


Gang of Four (GoF) Pattern

The book Design Patterns: Elements of ReusableSoftware by Erich Gamma, Richard Helm, RalpJohn Vlissides:

• Represented the first publication of sevpatterns organized together

• Is often called the Gang of Four or GoF• Provided common object-oriented solu

common object-oriented design proble• Includes 23 design patterns• Influenced many Java EE patterns that w

the GoF patterns


cription

ifies the keyke it useful fordesign patternes, their rolesponsibilities.ject-oriented

pplies, whethertraints, and the

n Patterns)


Gang of Four (GoF) Patterns: Des

“A design pattern names, abstracts, and identaspects of a common design structure that macreating a reusable object-oriented design. Theidentifies the participating classes and instancand collaborations, and the distribution of resEach design pattern focuses on a particular obdesign problem or issue. It describes when it ait can be applied in view of other design consconsequences and trade-offs of its use.”(Gamma, Helm, Johnson, and Vlissides, Desig


roups

ups:

jects interact

ust ways to

cts are


Gang of Four (GoF) Patterns: G

The GoF patterns are organized into three gro

• Behavioral patterns – Describe how oband distribute responsibility

• Creational patterns – Provide more robcreate objects

• Structural patterns – Discuss how objewired together


pecific patterns

milaritieshe forces of the

e a


Design Pattern Selection

There is no one best pattern, rather there are sthat apply to particular problems:

• Pattern selection should be based on sibetween the context, the problem, and tpattern and a design problem

• Multiple patterns might be used to solvparticular problem


ts:

m being

addresses must satisfye problemvantages of

ilar or are used


Design Pattern Elements

Design patterns include the following elemen

• Context – Situation in which the probleaddressed occurs

• Problem – Design issue that the pattern• Forces – Requirements that the solution• Solution and Structure – Solution to th• Consequences – Advantages and disad

using the pattern• Related Patterns – Patterns that are sim

to build this pattern


grams.

nt s;

t void y(int i);

tFname)


Design Pattern Notation

This course uses UML class and sequence dia

Employee{abstract}

-fname : String-lname : String-numEmployees : int-salary : Money

+getFname() : String+increaseSalary( : int )+setFname( fname : String )...

Manager

-quarterlyBonus : Money

+increaseBonus()+increaseSalary( : int )+playGolfWithClient()

Engineer

-education : String-hardware : String

+analyzeReq()+designSoftware()+increaseSalary( : int )...

<<interface>>Schedulable

+cancelActivity()+notifyAboutActivity()

ConferenceRoomEquipment

Interface

creates

0..* -scheduleItems

+addActivity( : Schedulable )

Scheduler

Dependency

Multiplicity

Association

Role names

Realization (implements)

Abstract class

private Stringfname;

private static inumEmployee

public String getFname()

public abstracincreaseSalar

public void se(String fname

Generalization (extends)

Schedule


loor: ConferenceRoom

5.1.1:notifyObservers

notifyAboutActivity method calls

otifyObservers method in the same class


Design Pattern Notation

fifthF

projector : Equipment

: Scheduler

: Schedule

Creation of object Objects

5.1:notifyAboutActivity

4:create()

3.1: notifyAboutActivity3.1.1: notifyObservers

5: addActivity( fifthFloor )

1: create()

2: create()

3: addActivity( projector )

n

Method call orsome form of

communication

Activation barshows when theobject is actively

working or waitingfor a response


rns

e proactively

tterns and only

n balance of

u might be with a

er to solve


When and How to Apply Patte

• Some literature suggests that patterns bapplied to designs

• Some literature suggests using fewer parefactoring them into a design

• Either way, you should look for a desigflexibility and simplicity

• After taking a design pattern course, yoinclined to try and solve every problemdesign pattern

• Design patterns are not a golden hammevery problem


Object-Oriented Design Principles


-Patterns Java EE BluePrints Design Guidelines



Behavioral

Creational

Structural

Presentation Tier

Business Tier

Integration Tier


Summary

The following object-oriented conceptscan help you focus on improvingJava EE designs:

• Cohesion• Encapsulation• Implementation inheritance• Interface inheritance• Polymorphism• Coupling• Composition

Anti


hieve the Java

ience of otheroftware


Summary

The following GoF principles can help you acEE platform design goals:

• Favoring composition• Programming to an interface• Designing for change

Design patterns will help you reuse the experdesigners to improve your Java EE platform s

l PatternsM

UB

Java EE™ Patterns

Module 2

Using Gang of Four Behavioraodule 2

sing Gang of Fourehavioral Patterns

Module 2

Using Gang Of FourBehavioral Patterns

Objectives

• Describe the basic characteristics of theBehavioral patterns

• Apply the Strategy pattern• Apply the Command pattern• Apply the Iterator pattern• Apply the Observer pattern


erns

he distribution

rithms for

cts for execution

loosely coupled

ts without


Introducing Behavioral Patt

Behavioral patterns focus on algorithms and tof responsibility between classes

Pattern Primary FunctionStrategy Encapsulates a family of algo

interchangeable useCommand Encapsulates requests in obje

by another objectIterator Traverses any collection in a

wayObserver Provides notification of even

polling


oblem

uld use

sorting strategy

rt


Strategy Pattern Example Pr

• The library system’s search method comultiple algorithms to sort the results

• You need a way to easily exchange the

CatalogSearchEngine

+search() : ArrayList

//perform search//perform merge soreturn list;


rn:

iple algorithms from

s of conditional


Applying the Strategy PatteProblem Forces

• Classes often need to choose from mult• Details of algorithms should be hidden

client classes• Algorithms implemented in large serie

statements are difficult to maintain


Solution

arate class that

trategy objectked, it forwards

btype of the


Applying the Strategy Pattern:

• Each algorithm is implemented in a sepimplements the Strategy interface

• The Clientobject has a reference to a S• When aClientobject operation is invo

the request to that strategy• The Client object can specify which su

Strategy interface should be used


re

rategy3


Strategy Pattern Structu

ConcreteSt

doTask()doTask()

<<interface>>Strategy

doTask()

strategy.doTask();

Client

+task()

-strategy

ConcreteStrategy2

doTask()

ConcreteStrategy1


lution

rgeSort

: ArrayList )

)


Strategy Pattern Example So

QuickSort

+sort( : ArrayList )

Me

+sort(

CatalogSearchEngine

+search() : ArrayList

<<interface>>SortStrategy

+sort( : ArrayList

//perform searchsorter.sort(list);return list;

-sorter


lution

s) {



Strategy pattern client:

1 public class CatalogSearchEngine {23 private SortStrategy sorter;45 public CatalogSearchEngine(SortStrategy s6 sorter = ss;7 }8 public ArrayList search() {9 ArrayList list = //perform search10 sorter.sort(list);11 return list;12 }13 }


lution

egy {



Strategy pattern interface:

1 public interface SortStrategy {2 public void sort(ArrayList al);3 }

First strategy implementation:

1 public class QuickSort implements SortStrat2 public void sort(ArrayList al) {3 //implement Quick sort code4 }5 }


ern

gorithms

gorithmstementss or changes to


Applying the Strategy Patt

Advantages:

• Allows multiple implementations of alwithout subclassing the client class

• Allows multiple implementations of alwithout placing them in conditional sta

• Allows easy additions of new algorithmexisting algorithms


ern

are

ad


Applying the Strategy Patt

Disadvantages:

• To select a strategy, clients must be awof the strategies

• There can be a slight increase in overhe


roblem

can be executedabilities

ions and

rce )urce )ource )


Command Pattern Example P

• A library system has many actions that• The system requires undo and redo cap• You need a simple way to structure act

their invocationsLibraryActions

+checkIn( p : Patron, r : Resou+checkOut( p : Patron, r : Reso+putOnHold( p : Patron, r : Res

Client


tern:

ated from how

ically add new

mechanics of

ld be simple


Applying the Command PatProblem Forces

Useful when the client class needs to be separthat request is executed:

• There needs to be an easy way to dynamactions and modify existing actions

• The client should be simple• The client should not need to know the

handling a specific requests• The interface to carry out requests shou


tern:

tionsmotely, or in a


Applying the Command PatProblem Forces

• Undo and redo previously executed ac• Execute commands asynchronously, re

different thread


: Solution

ute method ofand interfaceicCommandctof whatkes the


Applying the Command Pattern

• Each action is implemented in the execits own class that implements the Comm

• The client creates the necessary Specifobject and passes it to an Invoker obje

• The Invoker object has no knowledge SpecificCommand does, it simply invoexecute method


re

f action

ificCommand2

cute()

>


Command Pattern Structu

Invoker

+doCommand( c : Command )

implementation o

SpecificCommand1

+execute()

Spec

+exe

<<interface>Command

+execute()

c.execute();

create

create

Client


: Solution

state data

ment the actionk an

d, process, or

execute


Applying the Command Pattern

Implementation strategies include:

• The SpecificCommand can also containrelating to the command

• TheSpecificCommandcan either impleitself or call other objects to do the wor

• The Command interface can also includeundo method

• The Invoker can be in a separate threaserver from the Client

• The Invoker can queue the actions andthem asynchronously


olution

Command

esource, p : Patron )

)

and

rce, p : Patron )

te())

erface>>mmand


Command Pattern Example S

PutOnHold

-item : Resource-thePatron : Patron

+execute()+PutOnHoldCommand( r : R+undo()

CheckOutCommand


+CheckOutCommand( p : Patron, r : Resource+execute()+undo()

CheckInComm


+CheckInCommand( r : Resou+execute()+undo()

LibraryCommandInvoker

-lastCommand : int

+executeCommand( lc : Command )+redoNextCommand()+undoLastCommand()

lastCommand++;if (lastCommand < history.size() history.get(lastCommand).execute();

history.get(lastCommand).undo();lastCommand--;

lc.execute();history.add(lc);lastCommand = history.size()-1;

check out the resource

+execu+undo(

undo the check out of the resource

item = r;thePatron = p;

Client

create

create

create

0..*

history

<<intCo


Use in theage

us enterprise

documents the

lient from thee business logicCommand and is a stateless

ern


Applying the Command Pattern:Java™ Programming Langu

• GoF Command pattern is used in varioframeworks, such as Struts

• EJB Design Patterns, by Floyd MarinescuEJB Command pattern

• EJB Command pattern decouples the cbusiness tier and simplifies changing th

• The major distinction between the GoFEJB Command patterns is that Invokersession bean in the EJB Command patt


StructureBusiness Objectsmand

1.1.1: doWork

return


EJB Command Pattern Dynamic<<SessionBean>>

Invokerremote:Com

local : Command

RoutingLogicClient

2.

2.1: doCommand( remote:Command )

return

2.1.1: execute

3: getResults

1: Command( InitialState )

2: doCommand( local:Command )

return

return

return


tern:

seueads or remotely


Applying the Command PatConsequences

Advantages:

• Reduces complexity of decision logic• Provides easy extensibility• Can readily provide for undo operation• Can place multiple commands on a qu• Can execute commands in separate thre


tern:

on, destruction,

ore complex


Applying the Command PatConsequences

Disadvantages:

• Might increase overhead in object creatiand use

• Makes the structure of an application m


rn:

g data fromnal database, aof test datas various

source classesions of the data


Applying the Iterator PatteExample Problem

• The library system needs to read cataloseveral data sources including a relatioproprietary legacy database, and a file

• Each of the data source classes providemethods for traversing the data

• The traversal logic complicates the dataand exposes clients to the implementatsource classes

Java E Module 2, slide 25 of 45Copyrig

:

Pla data source isno

ightly custom

ithout a time-

d support the

E™ Patternsht 2008 Sun Microsystems, Inc. All Rights Reserved. Sun Services, Revision C.1

Applying the Iterator PatternProblem Forces

cing traversal logic directly in a collection ort always desirable:

• Callers become needlessly complex and tcoupled to the collection if they must usetraversal logic to access that collection

• Accessing the elements should be easy wconsuming lookup

• Multiple traversals should be supported• For uniformity, different collections shoul

same model for traversal


olution

e in an

r subtype fromvance through

l collections ofan be an


Applying the Iterator Pattern: S

• Place the Aggregate object’s access codIterator object

• The Client object requests an Iteratothe Aggregate and uses Iterator to adthe elements of Aggregate

• Iterators do not need to iterate over reaobjects (for example, an input stream citerator source)


e

ce>>or

booleanect

erator


Iterator Pattern Structur

<<interface>>Aggregate

+createIterator() : Iterator

<<interfaIterat

+hasNext() : +next() : Obj

Client

-data

createConcreteAggregate ConcreteIt


lution

)

)

or

leIterator

erator


Iterator Pattern Example So

ResultSetWrapper

+getIterator() : CatalogIterator

TestIFileSource


LegacyDataSource


<<interface>>CatalogDataSource


return new ResultSetIterator();

return new TestFileIterator();

return new LegacyIterator();

<<interface>>CatalogIterator

+currentElement()+hasMoreElements(+nextElement()+previousElement(

ResultSetIterat

TestFi

LegacyIt

Client

creates

creates

creates


in the Java

e>>tor

lean boolean

nt

: int

e>>r

oolean

id


Applying the Iterator Pattern: UseProgramming Language

<<interface>>List

+listIterator() : ListIterator...

<<interfacListItera

+add( o ) : void+hasNext() : boo+hasPrevious() :+next()+nextIndex() : i+previous()+previousIndex()+remove() : void+set( o ) : void

<<interface>>Collection

+iterator() : Iterator...

<<interfacIterato

+hasNext() : b+next()+remove() : vo

LinkedList ArrayListHashSet Vector

Set


in the Java


Applying the Iterator Pattern: UseProgramming Language

Collection subtype:

1 public void printData(Collection data) {2 Iterator dataI = data.iterator();3 while (dataI.hasNext()) {4 System.out.println(dataI.next());5 }6 }


sequences

g out traversal-

t collections on the

sals


Applying the Iterator Pattern: Con

Advantages:

• Simplifies the collection interface, liftinrelated methods

• Supports uniform traversal on differen• Supports different traversal algorithms

same collection• Supports simultaneous multiple traver


sequences

e


Applying the Iterator Pattern: Con

Disadvantages:

• Introduces additional objects at runtim• Not inherently thread-safe


ern:

application, thend sendEMail

ult handlers

ultMsg : String )

Msg : String )


Applying the Observer PattExample Problem

• When a serious fault occurs in the hotelfaultOccurred method calls the log amethods in the FaultLogger andFaultEMailer classes

• You need a way to flexibly add more fa

FaultMessageGenerator

+faultOccurred( faultType : int, faultMsg : String )

FaultEMailer

+sendEMail( faultTyoe : int, fa

FaultLogger

+log( faultType : int, fault

logger.log(faultType, faultMsg);eMailer.sendEMail(faultType, faultMsg);

-eMailer

-logger


ern:

f changes in

essive memoryesource usaget can lead to

the observablebject must be

upled to the


Applying the Observer PattProblem Forces

Sometimes several classes need to be aware oanother class:

• Polling an object for its state leads to excand the central processing unit (CPU) r

• Multiple object queries of a single objecsynchronization problems

• The observer objects must be aware of object; for notification, the observable oaware of its observers

• The observable object should not be cotypes of observer objects


Solution

observers canclass typesserverobjects

ferencellow aner with

lls a method in collection

hein a superclassd to be coupled


Applying the Observer Pattern:

• An interface is provided through whichbe called, irrespective of their concrete

• TheSubjectobject has a collection ofObreferenced by an Observer interface re

• The Subject object has methods that aObserver object to register or de-registthe Subject

• When the Subject object changes, it caeach Observer object in the observers

• The Observer pattern functionality of tConcreteSubject class can be placed so that Observer objects might not neeto the ConcreteSubject


re

Observer

)

face>>rver

)


Observer Pattern Structu

Subject{abstract}

+attach( o : Observer )+detach( o : Observer )+notify()

for (each observer o) o.update();

Concrete

+update(

ConcreteSubject

<<interObse

+update(

add o to observers

-subject

1

-observes

0..*


olution

ger

nt, faultMsg : String )

ault(faultType, faultMsg);


Observer Pattern Example S

FaultListener

FaultEMailer

FaultMessageGenerator

+addFaultListener( listener : FaultListener )+faultOccurred( faultType : int, faultMsg : String )+removeFaultListener( listener : FaultListener )

FaultLogger

+handleFault( faultType : int, faultMsg : String )

FaultPa

+handleFault( faultType : i



while (listener.hasNext()) listeners.next().handleF

-listeners 0..*


olution

st();

r listener) {

String faultMsg) {r();

stenersI.next();

ener listener) {



Observable class:

1 import java.util.*;2 public class FaultMessageGenerator {3 private ArrayList listeners = new ArrayLi45 public void addFaultListener(FaultListene6 listeners.add(listener);7 }8 public void faultOccurred(int faultType, 9 Iterator listenersI = listeners.iterato10 while(listenersI.hasNext()) {11 FaultListener fl = (FaultListener) li12 fl.handleFault(faultType,faultMsg);13 } }14 public void removeFaultListener(FaultList15 listeners.remove(listener);16 }17 }


olution

ring faultMsg);



Observer interface:

1 public interface FaultListener {2 public void handleFault(int faultType, St3 }


olution

stener{Logger("");

fmg) {

ring faultMsg) {

faultMsg);



Logging observer:

1 import java.util.logging.*;23 public class FaultLogger implements FaultLi4 private static Logger logger = Logger.get56 public FaultLogger(FaultMessageGenerator 7 fmg.addFaultListener(this);8 }9 public void handleFault(int faultType, St10 logger.log(Level.WARNING,11 "A " + faultType + " occurred: " + 12 }13 }


olution

ssageGenerator();

a: Peters, V.");



Simple test class:

1 public class FaultTester {2 public static void main(String args[]) {3 FaultMessageGenerator fmg = new FaultMe4 new FaultLogger(fmg);5 new FaultPager(fmg);6 new FaultEMailer(fmg);7 fmg.faultOccurred(72,"Lost customer dat8 }9 }


se in thege

etHandler

cord : LogRecord )

g the record to a socket


Applying the Observer Pattern: UJava Programming Langua

Logger

+addHandler( handler : Handler )+log( record : LogRecord )+removeHandler( handler : Handler )

ConsoleHandler

+publish( record : LogRecord )...

Sock

+publish( re...

Handler{abstract}


FileHandler


if (handlers != null) { for (int i = 0; i < handlers.length; i++) handlers[i].publish(record);

Log the record to the console

handlers.remove(handler);

Lo

handlers.add(handler);

Log the record to a file

-handlers


ern:

dependentlyinterfaces) and

hanging


Applying the Observer PattConsequences

Advantages:

• Subjects and observers can be reused in• Coupling is between abstract classes (or

not between concrete classes• Observers are easily changed without c

the subject


ern:

d with updatesject when itate a bottleneck


Applying the Observer PattConsequences

Disadvantages:

• An observer system can become floode• The observer often calls back to the sub

receives a notification, which might cre


nts



atterns Java EE BluePrints Design Guidelines



Behavioral

Creational

Structural

Presentation Tier

Business Tier

Integration Tier


Summary

Behavioral patterns focus on algorithmsand the distribution of responsibilitiesbetween classes:

• Strategy – Encapsulates a family ofalgorithms for interchangeable use

• Command – Encapsulates requestsin objects for execution byother objects

• Iterator – Traverses any collectionin a loosely coupled way

• Observer – Provides notification of evewithout polling

Anti-P

l Patterns

Java EE™ Patterns

Module 3

Using Gang of Four CreationaModule 3

Using Gang of FourCreational Patterns

Module 3

Using Gang Of FourCreational Patterns


the


Objectives

• Describe the basic characteristics of Creational patterns

• Apply the Factory Method pattern• Apply the Abstract Factory pattern• Apply the Singleton pattern


erns

reation.

class or itsa method call

objectsterfaceone globally


Introducing Creational Patt

Creational patterns hide the details of object c

Pattern Primary FunctionFactory Method Creates objects of a

subclasses throughAbstract Factory Creates a family of

through a single inSingleton Restricts a class to

accessible instance


Problem

which

RoomList

ist

ist

ist


Factory Method Pattern Example

• Three hotel systems have been merged• The Client class must directly decide

HotelRoomList object to create• The Client is tightly coupled to Hotel

classes due to the creation process

HotelBRoomL

HotelARoomL

HotelCRoomL

Client

uses

uses

create

create

create

uses


rn: Problem

tightly coupledf the client codeo add new


Applying the Factory Method PatteForces

• Clients that call target constructors areto the constructors, limiting flexibility o

• Reusable frameworks must allow you tconcrete subclasses


rn: Solution

tory reference

actory method

reference to a

ifferenterent


Applying the Factory Method Patte

• The Client class obtains a generic Facto a ConcreteFactory object

• The Client calls the createProduct fon the ConcreteFactory

• The factory method returns a Product new ConcreteProduct

• If the Client obtains a reference to a dConcreteFactory, it will receive a diffConcreteProduct


cture

rn new ConcreteProduct1();

rn new ConcreteProduct2();


Factory Method Pattern Stru

The client code might look like:

Factory f = new ConcreteFactory1();Product p = f.createProduct();

<<interface>>Factory

+createProduct() : Product

ConcreteFactory1


ConcreteFactory2


retu

retu

<<interface>>Product

ConcreteProduct2

ConcreteProduct1

Clientrequests

create

create

uses


Solution

turn new HotelCRoomList();

turn new HotelARoomList();

turn new HotelBRoomList();


Factory Method Pattern Example

<<interface>>RoomFinder

+createList() : RoomList

HotelCRoomFinder


HotelARoomFinder


HotelBRoomFinder


re

re

re

<<interface>>RoomList

moreRooms()nextRoom()

HotelBRoomList

HotelCRoomList

HotelARoomList

Client-finder

create

create

create

-rooms


me Class

reation of

OracleResultSet

SybaseResultSet

interface>>ResultSet

create

create


JDBC API Factory Method ScheDiagram

The JDBC API uses two factory methods for cStatement and ResultSet objects

<<interface>>Connection

+createStatement() : Statement...

SybaseConnection


OracleConnection


<<interface>>Statement

+executeQuery() : ResultSet...

SybaseStatement


OracleStatement


<<

create

create


attern:

ation to thes

withoutn details

ace to create


Applying the Factory Method PConsequences

Advantages:

• Factories restore control of object cresystem; clients merely request object

• Client code works with any subclassknowing the name or implementatio

Disadvantage:

You have to subtype the factory interfnew product types


e Problem

l objects

RoomB

Description()Rate()

RoomA

Description()Rate()


Abstract Factory Pattern Exampl

The Client class must create a family of hoteCustomerA

+getPreferences()

+get+get

+get+get

CustomerB

+getPreferences()

ReservationB

+calculateBill()+confirm()

ReservationA


HotelChainB

HotelChainA

Client

create

create

create

create

createcreate

create create


attern:

to

objectscts from

n you expose


Applying the Abstract Factory PProblem Forces

• The client does not need to know how instantiate products

• A client needs to use a family of related• You might not want a client to mix obje

different families• Client maintainability is sacrificed whe

details of the related objects to a client


attern:

y reference to a

iple factorywithin a family

ory, theClientucts


Applying the Abstract Factory PSolution

• The client obtains an AbstractFactorConcreteFactory object

• The ConcreteFactory object has multmethods that produce different objectsof products

• By obtaining a differentConcreteFactis switched to a different family of prod


cture

e>>

oductA2

e>>

oductB2


Abstract Factory Pattern Stru

ConcreteFactory1

+createProductA()+createProductB()

ConcreteFactory2


<<interface>>Factory


<<interfacProductA

PrProductA1

<<interfacProductB

PrProductB1

Client uses

create

uses

create

create

create

requests


e Solution

ionB

ill()

rB

nces()


Abstract Factory Pattern Exampl

<<interface>>HotelChain

+createCustomer() : Customer+createReservation() : Reservation+createRoom() : Room

HotelChainA


HotelChainB


RoomA

+getDescription()+getRate()

RoomB


<<interface>>Room


ReservationA


Reservat

+calculateB+confirm()

<<interface>>Reservation


CustomerA

+getPreferences()

Custome

+getPrefere

<<interface>>Customer

+getPreferences()

Client uses

create

uses

create

create

create

create

create

uses


attern:

for anothernt viewr

ime consumingeme


Applying the Abstract Factory PConsequences

Advantages:

• Simplifies exchanging one product family • Hides concrete family classes from the clie• Imposes a consistent naming convention fo

family members

Disadvantages:

• Developing new families correctly can be t• Adding family members to an existing sch

can be difficult


ern:

to

e thread pool soowing threads

le throughout


Applying the Singleton PattExample Problem

• The hotel system uses a pool of threadsinvoke processing

• There should only be one instance of ththat all parts of the application are borrfrom the same pool

• The thread pool must be easily accessibthe application


ern:

to only have a

to be easilyication to hide it


Applying the Singleton PattProblem Forces

• There are some classes that are intendedsingle instance

• The single instance of a class may needaccessible to different parts of the appl

• The only way to secure a constructor is


re

class:

rivate or

tic reference to

ic method that

== null) { new Singleton();

nce;


Singleton Pattern Structu

Three steps are needed to create a Singleton

1. The Singleton class’ constructor is pprotected, hiding it from client view

2. The Singleton class has a private stathe only instance of itself

3. The Singleton class has a public statreturns the single instance

if (uniqueInstance uniqueInstance =}return uniqueInsta

Singleton

-uniqueInstance : Singleton

+getInstance() : Singleton-Singleton()


re

nctionality


Singleton Pattern Structu

Singleton structure code:

1 public class Singleton {2 private static Singleton uniqueInstance;34 public static Singleton getInstance( ) {5 if (uniqueInstance == null) {6 uniqueInstance = new Singleton();7 }8 return uniqueInstance;9 }10 private Singleton( ) {11 }12 //Add attributes and methods for class fu13 }


olution

dPool

Pool

d )


Singleton Pattern Example S

ThreadPool

-singleInstance : Threa

+getInstance() : Thread+getThread() : Thread+returnThread( : Threa-ThreadPool()

ClientB

ClientA

uses

uses


ern:

single objecte class loading

ce, not just one

this hint is

s thread-safe


Applying the Singleton PattConsequences

Advantages:

• A client can easily obtain a reference to the• A singleton can construct the instance at th

time or on-demand• Singleton can guard several instances at on

Disadvantages:

• Singleton can replace global variables, butoften misapplied

• Singleton must make on-demand instance




Patterns Java EE BluePrints Design Guidelines



Behavioral

Creational

Structural

Presentation Tier

Business Tier

Integration Tier


Summary

Gang of Four creational patterns hide thedetails of object creation:

• Factory Method – Creates objectsof a class or its subclasses througha method call

• Abstract Factory – Creates a familyof objects through a single interface

• Singleton – Restricts objectcreation to a single globallyaccessible instance

Anti-

l PatternsM

US

Java EE™ Patterns

Module 4

Using Gang of Four Structuraodule 4

sing Gang of Fourtructural Patterns

Module 4

Using Gang Of FourStructural Patterns


the


Objectives

• Describe the basic characteristics of Structural patterns

• Apply the Façade pattern• Apply the Proxy pattern• Apply the Adapter pattern• Apply the Composite pattern• Apply the Decorator pattern


rns

face to a

object whichobject.bject that has an

t-whole tree

to an object


Introducing Structural Patte

Pattern Primary FunctionFaçade Provides a simplified inter

subsystem.Proxy Provides an intermediate

controls access to another Adapter Enables a caller to use an o

incompatible interface.Composite Composes objects into par

structures.Decorator Attaches new functionality

dynamically.


blem

n subsystem.

om

eUpCall()atus()

chService

s()

t

ofile()

on

0..*

0..*


Façade Pattern Example Pro

Client is coupled to many classes in reservatio

HotelSearchService hss = new HotelSearchService();Room[] rooms = hss.findRooms();Room theRoom = //chosen roomGuest theGuest = new Guest();//set guest informationReservation r = new Reservation(theRoom, theGuest);theRoom.updateStatus();

Ro

+issueWak+updateSt

HotelSear

+findRoomClient

+makeReservation() Gues

+updatePr

Reservati

+cancel()+create()+update()


rn:

s in any of

the interfaces of

rations in then between

ls to subsystem


Applying the Façade PatteProblem Forces

When clients directly link to many classes:

• Client classes are vulnerable to changethose classes

• The programmer must be familiar withmany classes

• The client must call the subsystem opecorrect order and pass state informatiothe operations

• In a distributed environment, client calobjects can increase network overhead


olution

-level interface

ommunicatingyfor sequencing,ith each

municater


Applying the Façade Pattern: S

Provide a Facade class that has a simple, highto a subsystem:

• Clients use a Facade object instead of cwith each subsystem object individuall

• The Facade contains the logic requiredmanaging state, and communicating wsubsystem object

• The Client may also be allowed to comdirectly with other subsystem classes foadditional functionality


e


Façade Pattern Structur

Facade

+request()

Class1

Class2Client

Class3


lution

ll())

rvice

()

..*

0..*


Façade Pattern Example So

The client uses the facade class object. It does not know there are HotelSearchService, Room, Guest, or Reservation objects.

ReservationServiceFacade

+cancelReservation()+confirmReservation()+findRoom()+makeReservation()+modifyReservation()

Room

+issueWakeUpCa+updateStatus(

HotelSearchSe

+findRooms()

Guest

+updateProfile

Reservation

+cancel()+create()+update()

Client

0


uence

: Reservationt


Façade Pattern Example Seq

: ReservationServiceFacade : HotelSearchService: Client : Gues: Room

1: makeReservation

1.1: findRooms

1.4: create

1.3: updateProfile

1.2: updateStatus


sequences

onents, making

subsystems

ght


Applying the Façade Pattern: Con

Advantages:

• Clients are shielded from subsystem compthe clients less brittle

• Network overhead may be decreased in adistributed environment

• Clients are loosely-coupled to subsystems• Clients can still communicate directly with

Disadvantage:

Introduces an extra level of indirection, which miimpact performance.


blem

bjects thatually neededient class


Proxy Pattern Example Pro

• RoomTypeImage objects are expensive oshould not be created until they are act

• You might want to avoid having the Cldecide when to create expensiveRoomTypeImage objects

RoomTypeImage

-imageData : byte[][]

+getImage() : byte[][]+getSize() : Dimension+RoomTypeImage()

Client0..*


em Forces

cess these types

ode in the client

ntensive objects

de in a


Applying the Proxy Pattern: Probl

It may be undesirable for a client to directly acof classes:

• Remote objects – Placing networking cand remote class decreases cohesion

• Expensive objects – Creating resource ibefore they are actually needed candecrease performance

• Restricted objects – Placing security corestricted class decreases cohesion


olution

nds in for the

plement the

t interface type

ealSubject

o RealSubject


Applying the Proxy Pattern: S

• The Client uses a Proxy object that staRealSubject object

• The Proxy and RealSubject classes imSubject interface

• The client has a reference of the Subjecwhich only refers to Proxy objects

• The Proxy object keeps a reference to R• The Proxy object propagates requests t

as appropriate


entation


Proxy Pattern Structure

Client has a reference variable of type Subject that refers to a Proxy object

actual implem

<<interface>>Subject

+request()

RealSubject

+request()

impl.request()

Proxy

+request()

Client

-impl


olution

municates to a

tes the resourceakes a request

determinesgated


Applying the Proxy Pattern: S

• Remote proxy – A Proxyobject that comremote RealSubject

• Virtual proxy – AProxyobject that creaintensive RealSubject after a client mon Proxy

• Restricted proxy – A Proxy object thatwhether an invocation should be propato RealSubject


tion

age();

do the actual work


Proxy Pattern Example Solu

Client has a reference with type RoomTypeImage that refers to a ProxyRoomTypeImage

if (realImage == null) realImage = new ActualRoomTypeImage();return realImage.getImage();

if (realImage == null) realImage = new ActualRoomTypeImreturn realImage.getSize();

<<interface>>RoomTypeImage

+getImage() : byte[][]+getSize() : Dimension

ProxyRoomTypeImage

+getImage() : byte[][]+getSize() : Dimension

ActualRoomTypeImage

-imageData : byte[][]

+ActualRoomTypeImage()+getImage() : byte[][]+getSize() : Dimension

Client 0..*

-realImage


n the Java

Impl

entation


Applying the Proxy Pattern: Use iProgramming Language

The Client acquires a RemoteBusiness type reference to a Stub object. It calls the business methods on the Stub.

Networking logic to propogate the request to the RemoteBusinessImpl on the remote machine.

Stub

+doTask()

Client RemoteBusiness

+doTask()

Actual Implem

<<interface>>RemoteBusiness

+doTask()


equences

ng capabilities the real object

ed that might

s transparent


Applying the Proxy Pattern: Cons

Advantages:

• The proxy is transparent to the client• The proxy simplifies client access• The proxy provides a point for extendi• The proxy can control or limit access to

Disadvantages:

• An extra level of indirection is introducimpact performance

• Interaction with the proxy is not alway


blem

s to be adapted

modified

rchEngine

: String ) : ArrayList) : ArrayList

tible Interface


Adapter Pattern Example Pro

• The Library3SearchEngine class needto the Searchable interface

• Library3SearchEngine should not be

Library1SearchEngine

+searchByAuthor( author : String ) : ArrayList+searchByCallNumber( callNum : String ) : ArrayList+searchByTitle( title : String ) : ArrayList

Library3Sea

+recall()+searchByCallNumber( callNum +titleSearch( title : char[]

<<interface>>Searchable




Incompa

SearchInvoker


rn:

patible

e functionalityundant code


Applying the Adapter PatteProblem Forces

• Forcing clients to use classes with incominterfaces can complicate code

• Creating different interfaces for the samby copy-and-paste reuse can lead to red


olution

apterred interface: on Adapter

to theAdaptee

re complex or

has a reference

is a subclass


Applying the Adapter Pattern: S

• The solution is similar to a hardware ad• Create an Adapter class with the requi

• The Client object invokes methods• TheAdapterobject forwards calls on

class for some methods• The Adapter object can provide mo

additional methods when required• In the Object Adapter strategy,Adapter

to Adaptee• In the Class Adapter strategy, Adapter

of Adaptee


cture

Task2()

stTask()

n


Object Adapter Strategy Stru

return adaptee.do

return adaptee.fir

<<interface>>DesiredInterface

+doTask1()+doTask2()+doTask3()

full implementatio

Adaptee

+doTask2()+firstTask()

Adapter


Client

-adaptee


cture

ation

k()

)


Class Adapter Strategy Stru

<<interface>>DesiredInterface


full implement

return firstTas

Adaptee

+doTask2()+firstTask(

Adapter

+doTask1()+doTask3()

Client


e Solution

chEngine

: String ) : ArrayList) : ArrayList

rchByCallNumber(callNum);

e.toCharArray();tee.titleSearch(t);

ntation


Object Adapter Strategy Exampl



Library3Sear

+recall()+searchByCallNumber( callNum +titleSearch( title : char[]

Library3SearchEngineAdapter


<<interface>>Searchable




return adaptee.sea

char t[] = titlreturn adap

full impleme

-adaptee


e Solution

thor) {author

g callNum) {um);

le) {


Object Adapter Strategy Exampl

The library adapter class code:

1 import java.util.ArrayList;2 public class Library3SearchEngineAdapter3 implements Searchable {4 private Library3SearchEngine adaptee =5 new Library3SearchEngine();6 public ArrayList searchByAuthor(String au7 //... full implementation of search by 8 return results;9 }10 public ArrayList searchByCallNumber(Strin11 return adaptee.searchByCallNumber(callN12 }13 public ArrayList searchByTitle(String tit14 char t[] = title.toCharArray();15 return adaptee.titleSearch(t);16 }17 }


sequences

aving to use a

r without


Applying the Adapter Pattern: Con

Advantages:

• The client class is not complicated by hdifferent interface

• The adaptee class is not modified• Clients can use the adaptee class with o

the adapter


sequences

t

upports thent is coupled to

e adaptee class


Applying the Adapter Pattern: Con

Object Adapter strategy disadvantages:

• You must create an additional object• Requests are forwarded, causing a sligh

overhead increase

Class Adapter strategy disadvantages:

• The interface of the adapter class also sinterface of the adaptee class, so the cliethe adaptee class

• The single inheritance slot is used by th


roblem

red

manOperations: Manager

anager

: Concierge

BerlinHotel: Manager

: SalesPerson

: Clerk


Composite Pattern Example P

A composite-part employee structure is requi

CanadianOperations: Manager FrenchOperations: Manager Ger

MarkhamHotel: Manager

VPOperations: M

OttawaHotel: Manager ParisHotel: Manager

President : Manager

VPSales : Manager

: SalesPerson

: SalesPerson : SalesPerson: SalesPerson

: Concierge

: Concierge

: Concierge : Concierge

: Clerk

: Clerk: Clerk

: Clerk

: Clerk

: Clerk


: Problem

that can

ted down the

of the parts in

e of the and parts


Applying the Composite PatternForces

Objects exist in a composite-part hierarchy:

• Variable number of levels of objects change dynamically

• Some operations should be propagacomposite hierarchy

• Need to treat the composite and eacha uniform way

• It can be inappropriate to handle somoperations uniformly on composites


: Solution

individual part

onent, some of which

and Part

n the


Applying the Composite Pattern

Provide a common interface for the classes ofobjects and grouped composite objects:

• The Composite object has a set of Compreferences that refers to its componentsmay be other Composite objects

• The client manipulates both Compositeobjects through a common interface

• Some method calls are propagated dowcomposition hierarchy


ure

t

i++


Composite Pattern Struct

Composite

+add( comp : Component )+getChild( index : int ) : Componen+operation()+remove( comp : Component )

for (int i=0; i<children.length; children[i].operation();

<<interface>>Component

+operation()

full implementation

Part

+operation()

-children

0..*


olution

nager

double

: Employee )) : doubledouble : int ) : Employee( e : Employee )

ulatePay();s.length; i++)ates[i].calculateDeptPay();


Composite Pattern Example S

Ma

-individualBonus :

+addSubordinate( e+calculateDeptPay(+calculatePay() : +getSubordinate( i+removeSubordinate

double totalPay = calcfor (i=0; i<subordinate totalPay += subordinreturn totalPay;

<<interface>>Employee

+calculateDeptPay() : double+calculatePay() : double

Clerk

-basePayRate : double-individualBonus : double-overtimeHours : int


SalesPerson

-basePayRate : double-comissionRate : double-totalSales : double


Concierge

-basePayRate : double-individualBonus : double-tips : double


return calculatePay();

0..*

-subordinates


olution

l pay



The Clerk class code:

1 public class Clerk implements Employee2 {3 private double basePayRate;4 private double individualBonus;5 private int overtimeHours;67 public double calculateDeptPay() {8 return calculatePay();9 }10 public double calculatePay() {11 double pay = // ... calculate individua12 return pay;13 }14 }


olution

+) {DeptPay();

l pay return pay;



The Manager class code:

1 public class Manager implements Employee {2 private Employee subordinates[];3 public void addSubordinate(Employee e) {4 // ... add e to the subordinates array5 }6 public double calculateDeptPay() {7 double totalPay = calculatePay();8 for (int i=0; i<subordinates.length; i+9 totalPay += subordinates[i].calculate10 }11 return totalPay;12 }13 public double calculatePay() {14 double pay = // ... calculate individua15 }16 . . .17 }


Use in thege

iner

nent ) int ) : Componentcs )mponent )


Applying the Composite Pattern:Java Programming Langua

Conta

+add( comp : Compo+getComponent( n :+paint( g : Graphi+remove( comp : Co

Component{abstract}

+paint( g : Graphics )

List


Button


0..*


tern:

rmlypth

le

provides but not


Applying the Composite PatConsequences

Advantages:

• Composites and parts are treated unifo• Composite hierarchy is an arbitrary de

• Composite hierarchy is highly extensib

Disadvantages:

• The design can become too general

• The component interface might have tomethods that make sense for compositefor parts


roblem

calculations,ent

lculator

rementFund()entFund()

sePay();lateRetirement(pay);lateTax(pay);


Decorator Pattern Example P

Calculating an employee’s pay involves base various tax calculations, and possibly retiremfund calculations

FrenchPayWithTaxCalculator

+calculatePayWithoutRetirementFund()+calculatePayWithRetirementFund()

CanadianPayWthTaxCa

+calculatePayWithoutReti+calculatePayWithRetirem

GermanPayWithTaxCalculator


<<interface>>PayCalculator


double pay =calculateBapay -= calcupay -= calcu


tern:

t subclassing

simple mannerdded or removede duplication


Applying the Decorator PatProblem Forces

Adding extended functionality through direcmay lead to:

• An explosion of subclasses• Code duplication in subclasses

A solution is needed that:

• Allows functionalities to be expanded in a• Allows functionalities to be dynamically a• Maintains high cohesion and minimizes th

of code


Solution

om theorator classes

ality to

t reference toecorates

ir functionalitymponent class

nt to the caller


Applying the Decorator Pattern:

• Additional functionalities are moved frConcreteComponent class into the Dec

• The Decorator class adds one functionanother class

• The Decorator class keeps a Componenthe ConcreteComponent class that it d

• The Decoratormethods implement theand propagate the invocation to the Cothey decorate

• The chain of Decorators are transparewhen dealing with a decorated class


re

of

on();

eration();

;

ctionality


Decorator Pattern Structu

ConcreteDecorator

-additionalAttribute

+ConcreteDecorator( d : Component )+operation()

Decorator

+Decorator( d : Component )+operation()

ConcreteComponent

<<interface>>Component

+operation()

1

//implentation

super.operati

implement base functionality

decoratee.op+operation()

decoratee = d

super(d);

-decoratee

decorator fun


olution

ator

PayCalculator )

e.calculatePay();


Decorator Pattern Example S

PayCalculatorDecorator

+calculatePay()

Implement tax calculationsuper.calculatePay();

BasePayCalculator

+calculatePay()

<<interface>>PayCalculator

+calculatePay()

-decoratee

1

Implement RetirementFund Calculationsuper.calculatePay();

RetirementFundCalcul

+calculatePay()+RetirementFundCalculator( :

CanadianTaxCalculator

+calculatePay()+CanadianTaxCalculator( : PayCalculator )

FrenchTaxCalculator

+calculatePay()+FrenchTaxCalculator( : PayCalculator )

GermanTaxCalculator

+calculatePay()+GermanTaxCalculator( : PayCalculator )

+PayCalculatorDecorator( : PayCalculator ) decorate


olution

();culator(calc1);ator(calc2);


Decorator Pattern Example S

Pay calculation code:

1 PayCalculator calc1 = new BasePayCalculator2 PayCalculator calc2 = new RetirementFundCal3 PayCalculator calc3 = new CanadianTaxCalcul4 calc3.calculatePay();


quence

ntFundCalculator


Decorator Pattern Example Se

calc3: Retireme

calc2: CanadianTaxCalculator

calc1: BasePayCalculator

: Client

4: calculatePay

return

3: create( calc2 )

4.1: calculatePay

return

2: create( calc1 )

4.2: calculatePay

1: create()

return


Use in thege

FilterInputStream

utStream( is : InputStream )

DataInputStream

tStream( is : InputStream )

() : charle() : double) : int


Applying the Decorator Pattern:Java Programming Langua

BufferedInputStream

+BufferedInputStream( is : InputStream )+close()+read( byte[] )...

+close()+FilterInp+read()...

FileInputStream

+close()+FileInputStream( filename : String )+read()...

ByteArrayInputStream

+ByteArrayInputStream( buf : byte[] )+close()+read()...

+close()+DataInpu+read()+readChar+readDoub+readInt(...

InputStream{abstract}

+close()+read()...

-is

1


tern:

nd behavior

rchies because of

ehavior

same, so object

lightly decrease


Applying the Decorator PatConsequences

Advantages:

• Can dynamically modify an object’s state a

• Does not modify or break inheritance hieraan addition to a base class

• Can nest decorators to add new state and b

Disadvantages:

• Decorator and decorated object are not theidentity becomes an issue

• Many little objects get created, which can sperformance


to an






Behavioral

Creational

Structural

Presentation Tier

Business Tier

Integration Tier


Summary

The GoF structural patterns:

• Façade – Provides a simplifiedinterface to a subsystem

• Proxy – Provides an intermediateobject that controls access toanother object

• Adapter – Enables a caller to use anincompatible interface

• Composite – Composes objectsinto part-whole tree structures

• Decorator – Attaches new functionalityobject dynamically

Anti-

BlocksM

UB

Java EE™ Patterns

Module 5

Using Architectural BuildingModule 5

Using ArchitecturalBuilding Blocks

odule 5

sing Architecturaluilding Blocks


n patternsrn


Objectives

• Compare architectural patterns to desig• Apply the Model View Controller patte• Apply the Layers pattern• Explain tiers and layers in Java EE

platform applications


to Design

e tacticaloblem

mposite

design patterns the


Comparing Architectural PatternsPatterns

• Design patterns concentrate more on thaspects required to solve a low-level pr

• Architectural patterns:• Focus on the strategic, high-level co

structure of a solution• Usually implemented with multiple• Define the role of each subsystem in

overall solution


ler (MVC)

is an

va Foundation

ent from core

nterface might

ns


Applying the Model View ControlPattern

• Model View Controller (MVC) pattern architectural pattern

• Found in many places, including the JaClasses/Swing (JFC/Swing) API

• MVC separates presentation managemapplication logic

• Useful in applications where the user ifrequently change

• MVC can be adapted to Web applicatio


n:

r interface tonformation and

to parts so that: interface

thout changing

s non-Web userss logic


Applying the MVC PatterExample Problem

• The hotel system needs a non-Web useallow hotel clerks to access reservation icheck guests in and out

• You need a way to divide the system in• Programmers can specialize on user

development or business logic• The user interface can be changed wi

the business logic• The Web reservation system and thi

interface can access the same busine


m Forces

changele user interface

in

eflect changes

tely to changes

from the data


Applying the MVC Pattern: Proble

User interfaces and business processing oftenindependently and some systems have multipviews:

• You can display the same information different views

• The views might need to immediately rto the model data

• The model data must respond immediainitiated in the views

• The user interface should be decoupledand processing


lution

e system into

user, invokesnd determineslayedace (GUI)to the user ander componentsocessing, andetails about the


Applying the MVC Pattern: So

The Model View Controller pattern divides ththree sets of components:

• Controller – Accepts requests from theprocessing on the Model components, awhich View component should be disp

• View – Displays a graphical user interfcontaining the Model components datausually passes GUI events to Controll

• Model – Contains the business data, prrules. The Model should not have any duser interface


tructure

hanges androcessing

statestionality

nd behaviorel updatese


Model View Controller Pattern S

Controller

Model

View

Select View

Send User Gestures

Notify of Changes

Get Data

Set Data CRequest P

● Renders the models● Requests updates from model● Sends user gestures to controller

● Encapsulates application● Responds to state querie● Exposes application func

● Defines application flow a● Maps user actions to mod● Selects views for respons


lution

ented usingg:

nts can be

ents can be a


Applying the MVC Pattern: So

The MVC architectural pattern may be implemseveral Gang of Four design patterns includin

• Observer Pattern – The View componeobservers of the Model components

• Composite Pattern – The View componcomposite of other GUI components


xample

RoomObserver

vailabilityListScreen


Model View Controller Pattern ESolution

Model

GuestList

ReservationService

RoomList

ReservationList

RoomObservable

ReservationObservable

View

CheckInAndOutScreen

ReservationListScreen

ReservationObserver

RoomA

Controller

CheckOutEventHandler

CheckInEventHandler

set dataset data

set data

notify

notify

get data

get data

get data

get data

invoke

invoke displays


equences

businessspectivesiew, and the

on the userdel

model


Applying the MVC Pattern: Cons

Advantages:

• Multiple views can allow access to the processing and data from different per

• It is simpler to modify the model, the vcontroller separately

• It is easier for some developers to focusinterface and others to focus on the mo

Disadvantage:

Dividing the subsystems can increasecommunication overhead between theand the view


rn

ctureups of subtaskslar level of

, Sommerlad,):

in numerouscethe basis for the EE BluePrintsrns


Applying the Layers Patte

“The Layers architectural pattern helps to struapplications that can be decomposed into groin which each group of subtasks is at a particuabstraction.” (Buschmann, Meunier, Rohmertand Stal. Pattern Oriented Software Architecture

• The Layers architectural pattern is seenand diverse systems in computer scien

• The principles behind this pattern formarchitecture recommended by the Javadesign guidelines and the Java EE Patte


rn:

send Web

low and high

sending the

g flexiblelopment


Applying the Layers PatteExample Problem

• A communication protocol is needed torequests between services written inheterogeneous environments

• This protocol must address a variety oflevel issues

• The low level issues include physicallyrequest across the network

• The high level issues include structurinmessages between heterogeneous deveenvironments


rn:

of issues. A

ot ripple

be stable exchanged

subsystems can


Applying the Layers PatteProblem Forces

Complicated systems often have many layerslayering solution must deal with these forces:

• System functionality changes should nthrough the system

• Interfaces between components should• Parts of the system should be able to be

without affecting the rest of the system• Parts of the system should be reusable• Data that is passed frequently between

lead to poor performance


olution

er below it.


Applying the Layers Pattern: S

Each layer can only communicate with the lay

LayerN-1

LayerN

Layer1

Layer2


lution


Layers Pattern: Example So

TCP

HTTP

IP

SOAP

Ethernet


equences

be developed

ting other layers

ery layertion overhead


Applying the Layers Pattern: Cons

Advantages:

• Layers may be reusable• Layers are loosely coupled so that they can

and maintained separately• Layers can be exchangeable without rewri

Disadvantages:

• Adding a new functionality might affect ev• Separating layers can increase communica


va EE™tions

practicepplications

EE Patternselines arere


Applying Layers and Tiers in JaPlatform Enterprise Applica

• Layering is a Java EE architecture best • The size and complexity of enterprise a

makes layering a natural choice• The layering approach used by the Java

and the Java EE BluePrints design guiddescribed in the SunToneSM ArchitectuMethodology


logy Layers

a more specific

re stack thaters represent(SunTone


SunToneTM Architecture Methodo

The SunTone Architecture Methodology usesdefinition of layers than the Layers pattern:

Layers are “The hardware and softwahosts services within a given tier. (laycomponent/container relationships)”Architecture Methodology page 11)


gy Layers

lementation ofquirementshat application

ucture for the

ng systems that

dware required


SunTone Architecture Methodolo

• Application – Provides a concrete impcomponents to satisfy the functional re

• Virtual Platform – Provides the APIs tcomponents implement

• Upper Platform – Provides the infrastrapplication layer components

• Lower Platform – Provides the operatisupport the previous layers

• Hardware Platform – Provides the harto support the previous layers


ogy Tiers

e Layers

ization ofservicerchitecture


SunTone Architecture Methodol

SunTone Architecture Methodology applies thpattern to define tiers

Tiers are “A logical or physical organcomponents into an ordered chain ofproviders and consumers.”(SunTone AMethodology page 10)


ogy Tiers

the system markupt are sent to therequestsces and entitiesintegrate the

rces, such as a) or Enterprise


SunTone Architecture Methodol

• Client – Provides user interaction with• Presentation – Provides the hyper-text

language (HTML) pages and forms thaWeb browser and processes the user’s

• Business – Provides the business servi• Integration – Provides components to

Business tier with the Resource tier• Resource – Contains all backend resou

DataBase Management System (DBMSInformation System (EIS)


h Tier

ces tiers sinceE platform.

irectory Service

egacy SystemsERP Systems

esource Tier

Database


Java EE Technologies in Eac

There are no patterns for the client and resourthose tiers are implemented outside the Java E

<%

%>

ServletJSP

EJB Container

EJB

Java Beans/Plain Old Java

Objects (POJO)

JDBC

Java EE Connector

JavaMail

JAX-RPC

JavaIDL

JTA/JTS

JMS

D

L

Client Tier

Web Browser

Java SE AWT or SwingApplication or Applet

Non-Java Client

Java SE Client

Presentation Tier

Dependency

Business Tier Integration Tier R

Web Container


s and Tiers

sent

ation

ueuin

g

uste

ring

nd R

obin

ntal

Scalin

g

ScalingStrategy

cyerm


Java EE Platform Example – Layer

Client

Prese

ntat

ion

PreQ

ClRou

Busine

ss

Inte

grat

ion

Resou

rces

Horizo

Virtual HTML JSP EJB JMS APPO

UpperAny

BrowseriES iAS

MQSeries

CICS

Orderform

Formhandler

Orderservice

Ordersystem

interface

Legaord

syste

LowerAnyOS

Solaris Solaris Solaris MVS

HardwareAnyHW

E450 E5500 ES9000E250


umers



i-Patterns Java EE BluePrints Design Guidelines



Behavioral

Creational

Structural

Presentation Tier

Business Tier

Integration Tier


Summary

• Architectural patterns focus on thestrategic, high-level compositestructure of a solution

• The MVC pattern separatespresentation management frombusiness logic

• Layers are the hardware andsoftware stack within a given tier

• Tiers are the logical or physicalorganization of components intoan ordered chain of providers and cons

Ant

tterns

Java EE™ Patterns

Module 6

Introducing Java EE™ PaModule 6

IntroducingJava EE Patterns

Module 6

IntroducingJava EE Patterns


y in the Java EE


Objectives

• Describe the Java EE pattern philosoph• Describe the Java EE patterns and tiers

pattern catalog


terns

n Professionalfor a wide

r experienceing the Java EE

e familiardocument and

evelop entirely


Purpose of the Java EE Pat

• The Java CenterSM program, part of SuServices, has built enterprise solutions variety of customers

• The Java EE patterns evolved from thei• The Java EE patterns solve problems us

platform technologies• Some Java EE patterns might already b• The purpose of the Java EE patterns is to

recommend best practices rather than dnew techniques


de:

ticesy’s primary role


Benefits

The key benefits of the Java EE patterns inclu

• Using sound design principles• Leveraging documented, accepted prac• Understanding each Java EE technolog• Reducing coupling and dependencies

between components• Minimizing network traffic• Reducing costs of network latency


ts Design

ing complexscale and

erns thats to


Relation to the Java EE BluePrinGuidelines

The Java EE BluePrints design guidelines:

• Describe standard techniques for buildJava EE platform applications that can change quickly

• Are complemented by the Java EE pattprovide formally documented solutionspecific problems


tterns

nted in very

tterns

or other


Gang of Four and Java EE Pa

Gang of Four Patterns:

• Abstract solutions that can be implemediverse ways

• Can be used with any object-orientedprogramming language

• Often build on or expand other GoF pa

Java EE Patterns:

• Designed for the Java EE platform• Often build on or expand GoF patterns

Java EE patterns


of the Java

hree tiers:


Describing the Patterns and TiersEE Pattern Catalog

The Java EE patterns catalog is grouped into t

• Integration tier• Business tier• Presentation tier


platform codestems:

synchronouslyva Message

-specific codented interfacetencesiness objects

services


Integration Tier Patterns

Concerned with the integration of the Java EEwith other types of applications and legacy sy

• Service Activator – Allows a client to ainvoke an EJB component, using the JaService (JMS) API

• Data Access Object – Isolates databaseinto classes that expose a business-orie

• Domain Store – Creates a robust persismechanism that is transparent to the buwithout using entity beans

• Web Service Broker – Makes business available as web services


r a Java EENaming and acquiring

tion tier with atierupled access to

of remotees in one object


Business Tier Patterns

Concerned with managing persistence andbusiness processing:

• Service Locator – Removes the need foplatform client to be aware of the Java Directory Interface™ (JNDI) API whenbusiness components

• Session Façade – Provides the presentasimple interface to access the business

• Business Delegate – Provides loosely cobusiness tier components

• Transfer Object – Reduces the numbermethod calls by returning multiple valu


ness logicsiness objectsata from

es transferctsf related, fine- entity,, containing

ent mechanisma large numbersults


Business Tier Patterns

• Application Service – Centralizes busibetween the service facades and the bu

• Business Object – Separates business dbusiness logic and workflow logic

• Transfer Object Assembler – Assemblobject data from multiple business obje

• Composite Entity – Wraps a number ograined, persistent objects into a singlerepresenting a structured organizationthose objects

• Value List Handler – Provides an efficifor executing queries that might returnof objects and browsing through the re


s

essing and post-

sm forts actionatchingcomponenttext specificut of


Presentation Tier Pattern

Concerned with organizing the application’spresentation components:

• Intercepting Filter – Manages pre-procprocessing of a client request

• Front Controller – Provides a mechanicentralized management of user reques

• Application Controller – Separates theinvocation management and view dispmanagement from the front controller

• Context Object – Passes data from conobjects without passing those objects otheir context


s

ieval for a view

rom many

Controller and

atcher View takes moresiness



• View Helper – Factors out content retrfrom the logic needed to build the view

• Composite View – Constructs a view fdifferent sub-views

• Dispatcher View – Combines the FrontView Helper patterns

• Service to Worker – Similar to the Disppattern, except that the front controllerresponsibility for view selection and buprocess invocation


ips

tes

Might Invoke

sparentlysts

vice Broker

ss Object

vice

licationntroller


Java EE Pattern Relationsh

Business Tier Java EE Patterns

Presentation Tier Java EE Patterns

Integration Tier Java EE Patterns

Behavioral Gang of Four Patterns

Creational Gang of Four Patterns

Structural Gang of Four Patterns

Might Get Data From

Might Create

Might Get Data From

Has Similar Result To

Uses

Based On

Might invoke

Might Invoke

Might Invoke

Might Be A

Might Be A

Might Execute

Might Be Created By

Might Be Created By

Based On

Might InvokeMight Invoke

Uses

Might Be Created By

MightCreate

Uses CreatesCrea

Might Invoke

Uses Functionality Of

Might Create

Contains

Might Be A

Might Invoke

MightInvoke

Might Use

Uses

Might Be A

MightInvoke

Controller Invokes

Creates

Uses

Delegates To

Forward To

Uses

Uses

Invokes

Creates

TranPersi

MightCreate

Might Include

Singleton

Factory Method

Iterator

Composite Entity

Value List Handler

Transfer Object

Dispatcher View Context Object

Decorator

Strategy

Composite

Command

Observer

GoF

GoF

GoF

Proxy

Adapter

Facade

Abstract Factory

View Helper

Composite View

Session Facade

Business Delegate

Data Access Object

Transfer ObjectAssembler

Front Controller

Intercepting Filter

Service To Worker

Service Locator

Web Ser

Busine

Application Ser

Service Activator

Domain Store

AppCo

Could BeImplemented As







Behavioral

Creational

Structural

Presentation Tier

Business Tier

Integration Tier


Summary

Java EE patterns help to improve theinternal structure of applications by:

• Consolidating common services• Minimizing traffic between tiers• Emphasizing loose coupling

of objects

Anti-


tterns


Module 7

Using Integration Tier PaModule 7

Using IntegrationTier Patterns

Module 7

Using IntegrationTier Patterns


egration

attern


Objectives

• List the features and purpose of the IntTier patterns

• Apply the Service Activator pattern• Apply the Data Access Object (DAO) p• Apply the Domain Store pattern• Apply the Web Service Broker pattern


tterns

AO)

h

ey technologies


Introducing Integration Tier Pa

• Encapsulate access to the data stores (D• Provide messaging to the business tier• Provide integration of web services wit

business components• Rely on the JDBC API and JMS API as k


Overview

tie together asstudent guide.

ging for businessmponents.

. Simplifies access to

echanism that isjects without using

e business services


Integration Tier Java EE Patterns

All examples in the next five modulesshown in the reference diagram in the

Pattern Primary FunctionService Activator Provides asynchronous messa

components, including EJB co

Data Access Object(DAO)

Encapsulates data access logicdisparate data sources.

Domain Store Creates a robust persistence mtransparent to the business obentity beans.

Web Service Broker Provides a flexible way to makavailable as web services.


Pattern:

seful for:gts with

d componentsponents to be

rchitecture (EJBw to mostsing messages


Applying the Service ActivatorProblem Forces

• Invocation through messaging is very u• Establishing asynchronous processin• Communicating between componen

different lifetimes• Communicating with loosely couple

• A mechanism is needed for EJB 1.x cominvoked indirectly using messages

• Even with containers based on EJB 2.x a2.x containers), you should consider hoflexibly invoke business components u


Solution

API

tor is a plain

tor can also be

Messages andthe requestofability


Applying the Service Activator:

• The ServiceActivator class is a JMS MessageListener implementation

• For EJB 1.x containers, ServiceActivaold Java object (POJO)

• For EJB 2.x containers, ServiceActivaa message-driven bean

• The ServiceActivator class receivesinvokes business components to fulfill

• Keeping substantial business logic out ServiceActivator improves maintainand reusability


uctureListener>>ctivator

Component

0..*

activates


Service Activator Pattern Str<<MessageServiceA

Business

<<Message>>Request

Client

receives

creates/sends


uence<<POJO>>

BusinessComponent2

: Acknowledgement


Service Activator Pattern Seq

<<Message>>: Request

2. send( : Request )

1. create()

Message ServerMessage Server <<MessageListener>>: ServiceActivator :

<<SessionEJB>>: BusinessComponent

3.1. parseMessage

3.3 process

3.4 create()˚

3.2 process

3: send( :Request )

3.5: sendAcknowledgement

: Client


Pattern:

r is mostly used

or – This.x container

contain a GOFe activatorponse – Annse to the clientther


Applying the Service ActivatorStrategies

• POJO Service Activator – This activatowith EJB 1.x containers or when no EJBcontainers are used

• Message-Driven Bean Service Activatactivator is only available with an EJB 2

• Command Request – The message cancommand that is invoked by the servic

• Database, Email, or JMS Message Resasynchronous process can place a respoin a database, an email message, or anoJMS message


mple

ceActivator

FactoryName, queueName )

n bean>>onfirmerBean

n( reservationID )

activates


Service Activator Pattern Exa

<<JMS Listener>>ReservationConfirmationServi

+close()+onMessage( msg )+ReservationConfirmationServiceActivator( conn-startListener()

<<JMS Sender>>ReservationConfirmationClient

+sendReservationConfirmation( reservationID )

<<sessioReservationC

+confirmReservatio

<<JMS Message>>ObjectMessage

+getObject()+setObject( )

recieves

creates/sends


mple



1 import javax.jms.*;2 public class ResConfirmServiceActivator3 implements MessageListener{4 private QueueSession qSession;5 private QueueReceiver qReceiver;6 private String connFactoryName;7 private String queueName;8 private JMSServiceLocator serviceLocator;9 public ResConfirmServiceActivator10 (String cfn, String qn) {11 connFactoryName = cfn;12 this.queueName = qn;13 startListener();14 }15 private void startListener() {16 try {17 serviceLocator =18 new JMSServiceLocator(connFactoryName);19 QueueConnectionFactory qConnFactory =20 serviceLocator.getQueueConnectionFactory();


mple



21 QueueConnection qConn =22 qConnFactory.createQueueConnection();23 qSession = qConn.createQueueSession24 (true,Session.AUTO_ACKNOWLEDGE);25 Queue shipBookQueue =26 serviceLocator.getQueue(queueName);27 qReceiver =28 qSession.createReceiver(shipBookQueue);29 qReceiver.setMessageListener(this);}30 catch (JMSException e) {31 e.printStackTrace();32 }33 }34 public void onMessage(Message msg) {35 try {36 ObjectMessage objMsg = (ObjectMessage) msg;37 String reservationID =38 (String) objMsg.getObject();39 //. . .Lookup and create bean40 ReservationConfirmerLocal resConfirmer =...


mple



41 resConfirmer.confirmReservation42 (reservationID);43 }44 catch (JMSException e) {45 e.printStackTrace();46 }47 }48 public void close() {49 try {50 qReceiver.setMessageListener(null);51 qSession.close();52 }53 catch(Exception e) {54 e.printStackTrace();55 }56 }57 }


tor:

nents from a

ions of any type

ssage


Applying the Service ActivaConsequences

Advantages:

• Allows the invocation of EJB 1.x compomessaging server

• Provides flexible asynchronous invocatof business component

• Separates business processing from meconsuming and parsing


m Forces

y requires

ewrites of the

ind and createnot integrated


Applying the DAO Pattern: Proble

• Accessing different data sources usualldifferent code

• Data source changes should not force rbusiness logic

• Data access objects need to be easy to f• Persistence code is more reusable if it is

with business logic


lution

usiness objects

ject interfaceg transparency

ess classese classes from


Applying the DAO Pattern: So

• Data access code is factored out of the binto POJOs called DataAccessObjects

• When product changes take place, newimplementations of the DataAccessObcan be added to the system, maintaininto the BusinessComponent

• DataAccessObjects are usually statel• DataAccessObjects should not expos

packages like java.sql


DataSourcecapsulates


DAO Pattern StructureDataAccessObject

+DataAcessObject()+delete( : TransferObject )+find( . . . ) : TransferObject[]+insert( : TransferObject )+update( : TransferObject )

TransferObject

-propertyA-propertyB

+getPropertyA()+getPropertyB()+setPropertyA()+setPropertyB()

BusinessComponent

obtains, modifies

creates, uses

enuses


ansferObject


DAO Pattern Sequence

: DataAccessObject

: BusinessComponent

: Tr

: DataSource

2. find( . . . )

4. update

1. Create()

return TransferObject

3. Set Property

4.1 GetProperty

2.2 Create()

2.1 SELECT

4.2 UPDATE


ategies

er methodssfer objects, for

y and placed in

rning transfert is a wrapperhnology rowsethe GoF Factorycan be a useful


Applying the DAO Pattern: Str

• Transfer Object Collection – DAO findcreate simple data structures, called traneach row that is returned from the quera collection

• Rowset Wrapper List – Instead of retuobjects, the DAO can return a class thaaround a caching or read-only JDBC tec

• Factory for the Data Access Object – TMethod and Abstract Factory patterns way to create DAO objects


tructure

Object )


DAO Abstract Factory Strategy S

<<interface>>DAO1

+update( : TransferObject )...

<<interface>>DAO2

+update( : Transfer...

<<interface>>DAOFactory

+createDAO1()+createDAO2()

RdbDAOFactory


XmlDAOFactory


XmlDAO1RdbDAO1 XmlDAO2RdbDAO2

createscreates


tonTO[]ReservationTO[]ationTO[] int

int


DAO Pattern ExampleReservationDAO

+deleteReservation( reservationID ) : in+findAvailableReservations() : Reservati+findReservationsByCustomer( custID ) : +findReservationsByDate( date ) : Reserv+insertReservation( : ReservationTO ) :+ReservationDAO()+updateReservation( : ReservationTO ) :...

ReservationTO

-endDate-startDate...

+getCustomer()+getEndDate()+getRoom()+getStartDate()+ReservationTO( . . . )...

BusinessObject

obtains/provides creates/uses

DAO Pattern Example

1 import java.sql.*;2 import java.util.*;3 import javax.sql.*;4 import javax.naming.*;56 public class ReservationDAO {7 private DataSource ds;89 public ReservationDAO() throws DAOException {10 try {11 InitialContext ic = new InitialContext();12 ds=(DataSource)13 ic.lookup("java:comp/env/jdbc/hotelDS");14 } catch (NamingException e) {15 throw new DAOException16 ("Error obtaining DataSource", e);17 }18 }19 public ArrayList findReservationByDate

DAO Pattern Example

20 (java.util.Date theDate)21 throws DAOException {22 ArrayList data = new ArrayList();23 Connection conn=null;24 PreparedStatement stmt = null;25 ResultSet results = null;26 try {27 conn = ds.getConnection();28 String query = "SELECT * FROM RESERVATION“ +29 “ WHERE DATE = ?";30 stmt = conn.prepareStatement(query);31 stmt.setDate(1,32 new java.sql.Date(theDate.getTime()));33 results = stmt.executeQuery();3435 java.util.Date startDate, endDate;36 while (results.next()) {37 startDate = results.getDate("startDate");38 endDate = results.getDate("endDate");

DAO Pattern Example

39 data.add(40 new ReservationTO(startDate, endDate));41 }42 }43 catch (SQLException e) {44 throw new DAOException45 ("Error finding reservation", e);46 }47 finally {48 try {49 if (results != null)50 results.close();51 if (stmt != null)52 stmt.close();53 if (conn != null)54 conn.close();55 } catch (SQLException e) {56 throw new DAOException57 ("Error closing connection", e);

DAO Pattern Example

58 }59 }60 return data;61 }62 public int deleteReservation63 (String reservationID) throws DAOException{64 Connection conn=null;65 PreparedStatement stmt = null;66 int count=0;67 try {68 conn=ds.getConnection();69 String query= "DELETE FROM Reservation “70 + “WHERE ReservationID = ?";71 stmt=conn.prepareStatement(query);72 stmt.setString(1, reservationID);73 count = stmt.executeUpdate();

DAO Pattern Example

74 }75 //. . .implement exception handling76 }77 //. . .implement other access methods78 }


equences

ctsre

ctsier


Applying the DAO Pattern: Cons

Advantages:

• Factors data access out of business obje• Creates a more flexible system for futu

migration efforts• Increases cohesiveness in business obje• Isolates data access logic in a separate t

Disadvantages:

• An extra layer of infrastructure to bedeveloped is added

• It is not useful with CMP entity beans


n: Problem

nce code fromes not make thesophisticated

ution for

re not requiredntainerheritance

table


Applying the Domain Store PatterForces

• The DAO pattern separates the persistethe business objects, but the pattern docode transparent to the business object

• Many enterprise applications require spersistence mechanisms

• Entity beans are not an appropriate solsome systems:• If many of the services of entity beans a• If the application does not use an EJB co• If entity beans constraints, such as no in

between business objects, are not accep


n: Solution

lasses that

toref worktence product) or aroductmplement thisn will help you


Applying the Domain Store Patter

• A domain store is a set of persistence ctransparently persist business objects

• You can implement a custom domain simplementation, but this is quite a bit o

• More frequently you might use a persisthat is based on Java Data Objects (JDOproprietary object relational mapping p

• Although few developers are likely to ipattern themselves, learning the patterlearn how these products work


ture

<<interface>>PeristenceCapable

BusinessObject

DataSource

0..*

1..*

UD

1

ata

0..*

ML file>>rsistMap

s

lts


Domain Store Pattern StrucPersistenceManagerFactory

+getPersistenceManager() : PersistenceManager

PersistenceManager

+close()+currentTransaction() : Transaction+deletePersistent( : PersistenceCapable )+makePersistent( : PersistenceCapable )+newQuery( Class, String ) : Query

Query

+declareOperations( )+execute( ) : Collection

ApplicationService

<<DAO>>StoreManager

StateManager

Transaction

+begin()+commit()+rollback()

0..*

executes1..*

<<creates>>

1..*CR

<<creates>>

1

get/set d

1 1<<XPe

CRUDupdates

consult

consu


quence<<DAO>>toreManager

: DataSource

.1: insert( data )

7.1.1.1.1.1: INSERT


Domain Store Persistence Se: PersistenceManagerFactory : PersistenceManager: ApplicationService

: BusinessObject

: StateManager

: S

: Transaction

3: getPersistenceManager

6: makePersistent( busObj )

4: currentTransaction

7.1: flushData

2: setData

6.1.1: setStateManager

7.1.1.1: getData

1: create()

6.1: create()

7.1.1: flushData

7.1.1.1

5: begin

7: commit

4.1: create()

7.2: commit


ncenessObject : DataSource


Domain Store Query Seque: PersistenceManager: ApplicationService : Busi<<DAO>>

: StoreManager

: StateManager

: Query

1: newQuery( class, queryString )

2.2.1: repeat for each row

2.2: returnRows

2.2.1.2: create

2.2.1.3: setData

3: getData

2.1: getData

2.1.1: SELECT

2.2.1.1: create()

2: execute( queryParameters )

1.1: create()


xample

{


Applying the Domain Store: E

The Payment Business Object:

1 package sl500;2 import java.util.Date;3 public class Payment {4 private double amount;5 private Date datePaid;6 private PaymentMethod payMethod;78 private Payment() {}9 public Payment(double a, Date d, PaymentMethod p)10 amount = a;11 datePaid = d;12 payMethod = p;13 }14 //. . .standard plain get/set methods15 }


xample

{


Applying the Domain Store: E

The PaymentMethod Business Object:

1 package sl500;23 import java.util.Date;45 public class PaymentMethod {6 private String type;7 private String number;8 private Date expiration;910 private PaymentMethod() {}11 public PaymentMethod(String t, String n, Date e) 12 type = t;13 number = n;14 expiration = e;15 }16 //. . .standard plain get/set methods17 }


n: Example

D Java Data Objectsdtd">



JDO Descriptor:

1 <?xml version="1.0" encoding="UTF-8"?>2 <!DOCTYPE jdo PUBLIC "-//Sun Microsystems, Inc.//DT

Metadata 1.0//EN" "http://java.sun.com/dtd/jdo_1_0.3 <jdo>4 <package name="sl500">5 <class name="Payment">6 <field name="payMethod">7 <collection element-type="PaymentMethod"/>8 </field>9 </class>10 <class name="PaymentMethod"/>11 </package>12 </jdo>


n: Example

ops);



The PaymentService Application Service:

1 package sl500;2 import javax.jdo.*;3 import java.io.*;4 import java.util.*;56 public class PaymentService {7 private PersistenceManager pm;89 public PaymentService() throws IOException {10 InputStream propertyStream =11 new FileInputStream("jdo.properties");12 Properties jdoProps = new Properties();13 jdoProps.load(propertyStream);14 PersistenceManagerFactory pmf =15 JDOHelper.getPersistenceManagerFactory(jdoPr


n: Example

e(), method);



16 pm = pmf.getPersistenceManager();17 }18 public void makePayment(double amount,19 String type, String number, Date expiration){20 Transaction tx = pm.currentTransaction();21 tx.begin();22 PaymentMethod method = new PaymentMethod23 (type, number, expiration);24 Payment thePayment = new Payment(amount, new Dat25 pm.makePersistent(thePayment);26 tx.commit();27 }28 public void queryPayments() {29 Extent e = pm.getExtent(Payment.class, true);30 Iterator i = e.iterator();31 while (i.hasNext())32 {33 Payment p = (Payment) i.next();


n: Example



34 System.out.println(p.getAmount() + " - " +35 p.getPayMethod().getType());36 }37 e.close(i);38 }39 }


: Strategies

the entire

ess objects, thehe core

he


Applying the Domain Store Pattern

• Custom Persistence – You implement domain store pattern from scratch.

• Java Data Objects – You write the businqueries, and the application services. Tpersistence code is provided by the JDOimplementation and is transparent to tdeveloper’s code.


attern:

ithout the

ersistence

ness objects


Applying the Domain Store PConsequences

Advantages:

• Allows many benefits of entity beans woverhead of other entity beans services

• Creates more robust and transparent pcapabilities than the DAO pattern

• Separates the persistence from the busi


attern:

m scratch onlyle overkill for


Applying the Domain Store PConsequences

Disadvantages:

• You should implement this pattern frowhen all other options seem undesirab

• A full persistence framework might besome applications


r Pattern:

d as web

sufficientlyices should not be

e adapted to

ing, auditing,


Applying the Web Service BrokeProblem Forces

If business service facades are directly exposeservices the following problems can occur:

• They might contain methods that are incoarse grained to be effective web serv

• They might contain some methods thatexposed as web services

• Some of their methods might need to bmake effective web services

• They might require additional monitorlogging, or security code


r Pattern:

t thatng the web

the invokes the

ght be a EJB 2.1a object


Applying the Web Service BrokeSolution

• Create a WebServiceBroker componenimplements any code specific to handliservice request and then invokes theBusinessService component

• The web services request is received byEndPointProcessor component whichWebServiceBroker

• The WebServiceBroker component mistateless session bean or a plain old Jav


tructure

BusinessService


Web Service Broker Pattern S

<<servlet>>EndpointProcessor

WebServiceBrokerClientsend request

1..*

invoke

1..*

accesses


quence BusinessService


Web Service Broker Pattern Se<<servlet>>

: EndpointProcessor: WebServiceBroker :: Client

1: send request1.1: extract Request

1.1.1: invoke

1.1.1.1: invoke


r Pattern:

(XML)m

RPC) – Thed by JAX-RPCecture for XMLthe XML andML


Applying the Web Service BrokeStrategies

• Custom Extensible Markup LanguageMessaging – You write your own custoEndPointProcessor component

• Java™ API for XML-based RPC (JAX-EndPointProcessor servlet is provide

• Java Binder Strategy – The Java ArchitBinding (JAXB) can be used to process generate transfer objects based on the X


xample

session bean>>servationSessionFacade

r( ... )rvation( ... )omer( ... )er( ... )ation( ... )tionData()ation( ... )ationConfirmation( ... )

<session bean>>nMgmtApplicationService

rvation( ... )ation( ... )tionData()ation( ... )ationConfirmation( ... )


Web Service Broker Pattern E

<<CustomerRe

+addCustome+cancelRese+deleteCust+editCustom+findReserv+getReserva+makeReserv+sendReserv...

<<session bean>>ReservationWebServiceBean

+cancelReservation( ... )+findReservation( ... )+makeReservation( ... )

<<servlet>><<JAX-RPC>>

EndpointProcessor

DotNetClient

send request

accesses

invokes1..*

<Reservatio

+cancelRese+findReserv+getReserva+makeReserv+sendReserv

<<session bean>>CustomerMgmtApplicationService

+addCustomer( ... )+deleteCustomer( ... )+editCustomer( ... )


xample

te {teException;moteException;



The ReservationWebService Interface:

1 package sl500;23 import java.rmi.*;45 public interface ReservationWebService extends Remo6 public boolean makeReservation(. . .) throws Remo7 public boolean cancelReservation(. . .) throws Re8 }


xample

essionBean {

ean

bean

{}



The ReservationWebServiceBeanClass:

1 package sl500;2 import javax.ejb.*;3 public class ReservationWebServiceBean implements S4 public void ejbCreate() {5 //. . . Obtain session facade bean6 }7 public boolean makeReservation(. . .) {8 //. . .Call makeReservation on session facade b9 }10 public boolean cancelReservation(. . .) {11 //. . .Call cancelReservation on session facade12 }13 public void ejbRemove() {}14 public void ejbActivate() {}15 public void ejbPassivate() {}16 public void setSessionContext(SessionContext sc) 17 }


r Pattern:

ice specific

head due to the

ly to have antation tier. Athe web service


Applying the Web Service BrokeConsequences

Advantages:

A layer is introduced where web servcode can be added.

Disadvantages:

• Web services can increase network overprotocols used.

• The business service component is likeremote interface for access by the preselocal interface must be added for use bybroker component.


s a flexible wayeb services






Behavioral

Creational

Structural

Presentation Tier

Business Tier

Integration Tier


Summary

• Service Activator pattern –Provides asynchronous messagingfor business components,including EJB components

• Data Access Object pattern –Encapsulates data store details

• Domain Store pattern – Creates arobust persistence mechanism thatis transparent to the businessobjects without using entity beans

• Web Service Broker pattern – Provideto make business services available as w

Anti-

ess Tier

Java EE™ Patterns

Module 8

Using Presentation-to-BusinPatterns

Module 8

Presentation-to-Business TierPatterns

Module 8

Presentation-To -Business TierPatterns


iness tier Javaon with the


Objectives

• Describe basic characteristics of the busEE patterns that facilitate communicatipresentation tier

• Apply the Service Locator pattern• Apply the Session Façade pattern• Apply the Business Delegate pattern• Apply the Transfer Object pattern


tterns

ing theiness tiers


Introducing Business Tier Pa

Business Tier patterns:

• Built primarily with EJB components• Organize business logic• Reduce coupling• Reduce network overhead

The patterns in this module focus on structurinteraction between the presentation and bus


Patterns

r service

ent detail with a

clients and

encapsulatinge object.


Java EE Platform Business Tier

Pattern Primary FunctionService Locator Provides one interface fo

lookups.Session Façade Hides business compon

simpler interface.BusinessDelegate

Decouples presentation business services.

Transfer Object Reduces remote calls byreturn value data into on


rn: Problem

the same JNDI create a beanach client:

to write bean

dg up JMS


Applying the Service Locator PatteForces

• All session or entity beans clients needAPI code to locate a home object and to

• Disadvantages of putting this code in e• Code is duplicated• Client programmer has to know how

client code• Reusable home objects are not cache

• The same issues apply to clients lookinConnectionFactory objects


rn: Solution

nted

NDI Context

nt class that uses

eviously found


Applying the Service Locator Patte

• The ServiceLocator class is implemeas a singleton

• The ServiceLocator object creates a Jobject and does a lookup of theComponentFactory object

• The ServiceLocator can either:• Return ComponentFactory to the Clie

it to create Component instances• Use ComponentFactory to create the

Component instances• The ServiceLocator has a cache of pr

ComponentFactory instances


cture

ComponentFactory

MS tory y.

Context

uses


Service Locator Pattern Stru<<Singleton>>ServiceLocator

+getComponentFactory( jndiName, homeClass ) : +getInstance() : ServiceLocator-ServiceLocator()

An EJB Home object, or JAPI QueueConnectionFacor TopicConnectionFactor

ComponentFactoryComponent

Client

1..*

1..*

uses1..*

1..*

uses (caches)

creates

1..* 1

uses

creates

For EJB components, an entity or session bean. For the JMS API, a QueueConnection or TopicConnection.


uence

tory

: Component

: Create and Find


Service Locator Pattern Seq

: ComponentFac

<<Singleton>>: ServiceLocator

: Context

: Client

2.2: Create and Find Component

2.1.1: Create()

1: Get Instance

2: Get Component

return ComponentFactory

2.2.1

2.1: Lookup

1.1: Create()

return Component


attern:

r

ation of the

ponent’s JNDId in thes in a parameter

he last strategy,e are specified in


Applying the Service Locator PStrategies

• EJB Component Service Locator• JMS API Topic and Queue Service Locato• Web Service Locator• Combined Service Locator – Some combin

above three strategies• Type Checked Service Locator – The com

name and the resource class are hard codeServiceLocator class and the client passeto specify which set of values to use

• Service Locator Properties – The same as tbut the JNDI name and resource class nama configuration file


mple

EJBHome


Service Locator Pattern Exa

<<Singleton>>ServiceLocator

+getHomeObject( jndiName, homeClass ) : +getInstance() : ServiceLocator-ServiceLocator()

<<session bean>>CustomerReservationSessionFacadeBean

+cancelReservation( ... ) : boolean+findReservation( ... )+getReservationData()+makeReservation( ... ) : boolean...

CustomerReservationSFHome<<Servlet>>

Client

create

lookup/cache


mple



1 public class ServiceLocator {2 private HashMap nameHomePairs = null;3 private Context ctx = null;4 private static ServiceLocator singleton = null;56 private ServiceLocator() throws NamingException{7 nameHomePairs = new HashMap();8 ctx = new InitialContext();9 }10 public static ServiceLocator getInstance()11 throws NamingException {12 if (singleton == null) {13 singleton = new ServiceLocator();14 }15 return singleton;16 }


mple

;

.



17 public EJBHome getHomeObject18 (String jndiName, Class homeClass)19 throws NamingException {20 if (nameHomePairs.containsKey(jndiName)) {21 return (EJBHome) nameHomePairs.get(jndiName)22 }23 Object ejbRef = ctx.lookup(jndiName);24 EJBHome ejbHome = (EJBHome)PortableRemoteObject25 narrow(ejbRef, homeClass);26 nameHomePairs.put(jndiName, ejbHome);27 return ejbHome;28 }29 }


attern:

is hidden uniform

ded to the

ng previously


Applying the Service Locator PConsequences

Advantages:

• The complexity of lookup and creation• Access to the service is centralized and

without duplication of the lookup code• New business components are easily ad

lookup service• Performance can be improved by cachi

looked up objects


attern:

ice Locator


Applying the Service Locator PConsequences

Disadvantage:

Even as a Singleton, there is one Servinstance per Java virtual machine


attern:

e services ofe

tiple businessupledmponents

interactionwork trafficsinessnt and misuse


Applying the Session Façade PProblem Forces

To fulfill a user request, a client might need thmultiple business components. This causes thfollowing problems:

• When clients interact directly with mulcomponents, the tiers become tightly co

• Clients that deal with many business cobecome responsible for managing their

• Fine-grained client access increases net• Lack of a uniform access strategy to bu

components leads to ad hoc developme


rn: Solution

a session beantsess servicenent

creates, andent instances usually not

de will create


Applying the Session Façade Patte

• You apply the GoF Façade pattern within front of the other business componen

• The client invokes coarse-grained businmethods on the SessionFacade compo

• The SessionFacade component finds,invokes the necessary BusinessCompon

• The SessionFacade component shouldcontain significant business logic

• Mapping each use case to a session facatoo many session facades


cture

)


Session Façade Pattern Stru

<<session bean>>SessionFacade

+doService1( ... )+doService2( ... )...

BusinessComponent

+doService3( ... +getData( ... )+setData( ... )...

Client 1..*

accesses


uencee2 : BusinessComponent


Session Façade Pattern SeqappService1 : BusinessComponent appServic<<session bean>>

: SessionFacade: Client

1.1: doPart1( ... )

2.1: doSomething( ... )

1.3: doPart3( ... )

1.2: doPart2( ... )

1: doService1( ... )

2: doService2( ... )


attern:

thod callsethod calls with


Applying the Session Façade PStrategies

• Stateless Session Bean – For single me• Stateful Session Bean – For multiple m

intermediate state information


mple

: EJBHome

>onService

ion( ... )

ervice


Session Façade Pattern Exa

<<Servlet>>Client


+getHomeObject( jndiName, homeClass )+getInstance() : ServiceLocator-ServiceLocator()

<<session bean>>CustomerReservationSessionFacade

+addCustomer( ... )+cancelReservation( ... )+deleteCustomer( ... )+editCustomer( ... )+findReservation( ... )+getReservationData()+makeReservation( ... )+sendReservationConfirmation( ... )...

<<session bean>ReservationMgmtApplicati

+cancelReservation( ... )+findReservation( ... )+getReservationData()+makeReservation( ... )+sendReservationConfirmat

<<session bean>>CustomerMgmtApplicationS



mple

e = null;ice = null;

nstance();ect

ject



1 public class CustomerReservationSessionFacade2 implements SessionBean {3 private CustMgmtASHome custHome = null;4 private ResMgmtASHome resHome = null;5 private CustomerMgmtApplicationService custServic6 private ReservationMgmtApplicationService resServ78 public void ejbCreate() throws CreateException {9 try {10 ServiceLocator locator = ServiceLocator.getI11 resHome = (ResMgmtASHome) locator.getHomeObj12 ("ejb/ResAS", ResMgmtASHome.class);13 custHome = (CustMgmtASHome) locator.getHomeOb14 ("ejb/custAS", CustMgmtASHome.class);15 resService = resHome.create();16 custService = custHome.create();17 }18 catch (Exception e) {19 System.err.println(e);


mple



20 throw new CreateException21 ("Unable to initialize facade");22 }23 }24 public boolean makeReservation(. . .)25 throws Exception {26 if (newCustomer==true)27 custService.addCustomer(. . .);28 return resService.makeReservation(. . .);29 }30 . . .31 }


attern:

ier components on multiple

rvice tiersy managementssion façadeiness tier


Applying the Session Façade PConsequences

Advantages:

• Simplifies client access to the business t• Eliminates a client’s direct dependency

business objects• Reduces network traffic between the se• Provides a place for centralized securit• Centralizes transaction control in the se• Provides a uniform interface to the bus


attern:


Applying the Session Façade PConsequences

Disadvantage:

Adds an extra layer


Pattern:

h business

mplementation

ntt make too

of caching or

know how tos


Applying the Business DelegateProblem Forces

If presentation tier clients interact directly witservices:

• Clients are exposed to the underlying idetails of the service API

• Business service changes affect the clie• The presentation tier components migh

many remote invocations due to a lackrequest aggregation

• Presentation tier programmers needs toinvoke the business service component


Pattern:

nessDelegaten an invokes

chnologyxceptionstically retry

sults


Applying the Business DelegateSolution

• On behalf of the Client class, the Busiuses a ServiceLocator object to obtaiBusinessService component and thebusiness methods on it

• The BusinessDelegate might catch tespecific exceptions and throw generic e

• The BusinessDelegate might automafailed requests

• The BusinessDelegate might cache re


ructure

omponent orPI component

essService


Business Delegate Pattern St

EJB cJMS A

BusinessDelegate Busin

ServiceLocator

Client

lookup and create

creates and uses

uses

uses


quenceusinessService


Business Delegate Pattern Se

: BusinessDelegate

: B: ServiceLocator: Client

return Service

2: invoke

1: Create()

1.1.1: Lookup

2.1: Invoke

1.1: Get Service


Pattern:

acts as a proxyinterface as the

can sendate thatquests to Java


Applying the Business DelegateStrategies

• Delegate Proxy – The business delegatethat supports approximately the same business component

• Delegate Adapter – Disparate systemsrequests using XML to a business delegtranslates the requests and sends the reEE components


ample

>>or

eClass ) : EJBHometor

acade

( ... )


Business Delegate Pattern Ex

<<SingletonServiceLocat

+getHomeObject( jndiName, hom+getInstance() : ServiceLoca-ServiceLocator()

<<session bean>>CustomerReservationSessionF

+addCustomer( ... )+cancelReservation( ... )+deleteCustomer( ... )+editCustomer( ... )+findReservation( ... )+getReservationData()+makeReservation( ... )+sendReservationConfirmation...

ReservationBusinessDelegate

+cancelReservation( ... )+findReservation( ... )+makeReservation( ... )...

<<Servlet>>Client

invokes


ample

null;

or.getInstance();e =

ionSF",;



1 public class ReservationBusinessDelegate {2 private ReservationSessionFacade resSF = 3 public ReservationBusinessDelegate()4 throws ReservationException {5 try {6 ServiceLocator locator = ServiceLocat7 ReservationSessionFacadeHome resSFHom8 (ReservationSessionFacadeHome)9 locator.getHomeObject("ejb/Reservat10 ReservationSessionFacadeHome.class)11 resSF = resSFHome.create();12 }13 catch (NamingException e) {14 throw new ReservationException();15 }16 catch (CreateException e) {17 throw new ReservationException();18 }


ample

Data)

;



19 catch (RemoteException e) {20 throw new ReservationException();21 }22 }23 public boolean makeReservation(String res24 throws ReservationException {25 try {26 return resSF.makeReservation(resData)27 }28 catch (Exception e) {29 throw new ReservationException();30 }31 }32 }


Pattern:

tation tier and

the clients to

by caching


Applying the Business DelegateConsequences

Advantages:

• Reducing coupling between the presenthe business tier

• Adding a simple, uniform interface foruse to access business components

• Improving performance made possiblerequests


Pattern:

elopers totion


Applying the Business DelegateConsequences

Disadvantages:

• Adding an additional layer to manage• Hiding remoteness which can lead dev

ignore the costs of these method invoca


rn: Problem

een remote tiers getter

one remote

whenever

y data than


Applying the Transfer Object PatteForces

• Data often needs to be exchanged betw• If components only expose fine grained

methods, the remote client must make method invocation per attribute

• Remote calls should be coarse-grained possible

• Clients typically require more read-onlupdatable data


rn: Solution

eansvalues and

mponents it, and returns

et the data from

ecause only the


Applying the Transfer Object Patte

• A Transfer Object is a serializable JavaBcomponent that encapsulates attribute provides accessor methods

• The getTransferObject method of Cocreates the TransferObject, populateit to the Client class

• TheClientclass callsgetmethods to gthe TransferObject

• The network overhead should be low bgetTransferObject method is remote


cture

sfer objectransfer objectsfer object


Transfer Object Pattern Stru

Component

+getTransferObject() : TransferObject

create tranpopulate treturn tran

<<Serializable>>TransferObject

-attribute1-attribute2-attribute3

+getAttribute1()+getAttribute2()+getAttribute3()

Client

creates


ence

<<Serializable>>tCopy: TransferObject


Transfer Object Pattern Sequ

<<Serializable>>ServerCopy: TransferObject

Clien

: Component: Client

1.1: Create()

2: getAttribute1

3: getAttribute2

1: getTransferObject



attern:

onent objectmethods that

ansferObject

ts:odsect method

sed to protectther clients


Applying the Transfer Object PStrategies

• Multiple Transfer Objects – The Compprovides several getTransferObject return different TransferObject types

• Entity Inherits Transfer Object - TheBusinessObject is a subclass of the Tr

• Updateable (Mutable) Transfer Objec• A TransferObject provides set meth• A Component object’s setTransferObj

updates the Component data• Time stamp or version number can be u

against overwriting changes made by o


quence

alizable>>: TransferObject


Updatable Transfer Objects Se

<<Serializable>>ServerCopy: TransferObject

<<SeriClientCopy

: BusinessObject: Client

3: getAttribute2

2: getAttribute1

4. setAttribute1

5. setAttribute2

1: getTransferObject

6. setTransferObject


1.1: Create()


mple

ate, end : Dtae )

servationTO

<<entity bean>>CustomerBean

create


Transfer Object Pattern Exa

ReservationTO

-endDate : Date-startDate : Date...

+getCustomer()+getEndDate() : Date+getRoom()+getStartDate() : Date+ReservationTO( . . ., start : D...

ReservationDAO

+findReservationByCustomer():Re+findAvailableReservations()+findReservationByDate()...

<<session bean>>ReservationMgmtApplicationService

+cancelReservation( ... )+findReservation( ... ) : ReservationTO+getReservationData()+makeReservation( ... )+sendReservationConfirmation( ... )

<<session bean>>CustomerReservationSessionFacade

...


...

<<session bean>>PaymentService

...

<<entity bean>>ReservationBean

...


...

<<Servlet>>Client

create


mple

lizable

) {


Transfer Object Pattern Exa

1 public class ReservationTO implements Seria2 {3 private Date startDate;4 private Date endDate;56 public ReservationTO() { }7 public ReservationTO(Date start, Date end8 startDate = start;9 endDate = end;10 }11 public Date getStartDate() {12 return startDate;13 }14 public Date getEndDate() {15 return endDate;16 }17 }


attern:

terfaces

lee the systemn usingocesses


Applying the Transfer Object PConsequences

Advantages:

• Simplifies entity bean and remote in• Reduces network traffic

Disadvantages:

• Transfer object data may become sta• Synchronization logic can complicat• The system can be complicated whe

concurrent access and transaction pr


n the tiers






Behavioral

Creational

Structural

Presentation Tier

Business Tier

Integration Tier


Summary

Presentation to business tier patterns:

• Service Locator – Focuses allservice lookups through oneinterface

• Session Façade – Provides simplerinterfaces to business components

• Business Delegate – Decouplespresentation tier components frombusiness components

• Transfer Object – Improvesefficiency of the transfer of data betwee

Anti

atternsM

UT

Java EE™ Patterns

Module 9

Using Intra-Business Tier PModule 9

Tier PatternsUsing Intra-Business

odule 9

sing Intra-Businessier Patterns


Intra-Business

attern


Objectives

• Describe the basic characteristics of theTier patterns

• Apply the Application Service pattern• Apply the Business Object pattern• Apply the Transfer Object Assembler p• Apply the Composite Entity pattern• Apply the Value List Handler pattern


ier Patterns

usiness logic betweenness objects

eparate business dataw

jects into a composite

client requirements


Java EE Platform Intra-Business T

Pattern Primary Function

Application Service Provides a central place to put bthe service façades and the busi

Business Object Describes how to organize and sfrom business logic and workflo

Transfer ObjectAssembler

Builds complex transfer objects

Composite Entity Organizes related persistence obstructure

Value List Handler Manages result sets according toand limits


Pattern:

façades or

tities.t in the business

couplings

ced in the servicewhen the same

c somewhere incts.


Applying the Application ServiceProblem Forces

• Service façade is a generic term for sessionPOJO façades.

• Business objects represent business data en• Business processing logic should not be pu

objects. This can lead to a lot of expensive between the business objects.

• Business processing logic should not be plafaçades. This can lead to code duplication logic is needed for multiple use cases.

• You need to place business processing logibetween service façades and business obje


Pattern:

e code and

ve the businessjects and

s can also usets, ordinaryts


Applying the Application ServiceSolution

• The ServiceFacade class has very littlprimarily just invokes the appropriateApplicationService methods

• The ApplicationServicemethods halogic that encapsulates the business obcoordinates their invocations

• The ApplicationService componentother ApplicationService componenService objects, and DataAcessObjec


ructure

ataAccessObject

usinessObject

ervice


Application Service Pattern St

ApplicationService D

B

ServiceFacade

S

uses

uses

uses


quencenessObject : DataAccessObject


Application Service Pattern Sesecond : Busifirst : BusinessObject: SecondAppService: FirstAppService: ServiceFacade

3.2: invoke

1.2: invoke

3.1: invoke

2: invoke

2.2: process

2.1: invoke

1: invoke

1.1: process

3: invoke

3.3: process


Pattern:

pplicationas specified byly, themand.

– If there areve the samemight be

ou can havehat invoke eachent generict client specific.


Applying the Application ServiceStrategies

• Application Service Command – An aservice might be invoked by a commandthe GoF Command pattern. Alternativeapplication service might itself be a com

• GoF Strategy for Application Servicemultiple application services that achieresult using different algorithms, they implemented using a Strategy pattern.

• Application Service Layer Strategy – Ymultiple layers of application services tother. The lower layers are the most clilayers, and the upper layers are the mos


ample

<<JMS Sender>>ervationConfirmationClient

<entity bean>>RoomBean

tRoomTO() : RoomTO

ession bean>>mentServiceBean

ntity bean>>ervationBean

ntity bean>>stomerBean

ervationDAO

tomerDAO


Application Service Pattern Ex




+cancelReservation( ... )+findReservation( ... )+getReservationData()+makeReservation( ... )+sendReservationConfirmation( ... )



Res

...

<

+ge...

<<sPay

...

<<eRes

...

<<eCu

...

Res

...

Cus

...


ample



1 public class ReservationMgmtAS2 implements SessionBean {3 private ReservationHome resHome = null;4 private PaymentHome payHome = null;5 private PaymentService payService = null;6 public void ejbCreate() throws CreateException {7 try {8 ServiceLocator locator =9 ServiceLocator.getInstance();10 resHome = (ReservationHome) locator.11 getHomeObject("ejb/Reservation",12 ReservationHome.class);13 payHome = (PaymentHome) locator.14 getHomeObject("ejb/Payment",15 PaymentHome.class);16 payService = payHome.create();17 }18 catch (Exception e) {19 throw new CreateException20 ("Unable to initialize AS");


ample



21 }22 }23 public boolean makeReservation(. . .)24 throws Exception {25 Reservation res = resHome.create(. . .);26 double cost = res.getCost();27 return payService.verifyPayment(cost);28 }29 . . .


Pattern:

kflow logicdes

e unnecessary


Applying the Application ServiceConsequences

Advantages:

• Encourages reusability of business wor• Avoids duplicating code in service faca

Disadvantage:

Introduces an extra layer that might bfor smaller applications


attern:

the data store:

are likely to

to be moree with the

tentiallydling, data

ode might needice classes


Applying the Business Object PProblem Forces

If business service components directly access

• Changes to the data store or its schemaaffect the business services

• The business service components haveaware of how to properly communicatdata store

• Many applications have to deal with pocomplex issues such as transaction hancaching, and data synchronization

• Much of the data access and handling cto be repeated in multiple business serv


attern:

to a separate

s logic in them,inimal and not

hould be logicalidation

ed into anothercess Object


Applying the Business Object PSolution

• Business entities should be separated inlayer of reusable business objects

• Business objects can have some businesbut the business logic should be fairly muse case specific

• The business logic in business objects sthat is very data oriented such as data vand manipulation

• Data persistence code should be separatlayer such as described by the Data Acpattern or the Domain Store pattern


cture

ependantBO

0..*

contains


Business Object Pattern Stru

ApplicationService D

DataStore

ParentBO

0..*

contains

persisted inpersisted in

accesses


uencetaStore


Business Object Pattern Seq: ApplicationService : DependantBO : Da: ParentBO

2.1: invoke

1.1: persist

2.1.1: persist

1: invoke

2: invoke


attern:

JO businessit might be thees such as

usiness objects


Applying the Business Object PStrategies

• POJO Business Object – Although POobjects might seem faster and simpler, opposite if you need entity bean servictransactional and concurrency control

• Composite Entity Business Object – Bcan be implemented as entity beans


mple<<entity bean>>

RoomBean

+getRoomTO() : RoomTO...


...


...


Business Object Pattern Exa




+cancelReservation( ... )+findReservation( ... )+getReservationData()+makeReservation( ... )+sendReservationConfirmation( ... )




attern:

riented data is centralizedm the


Applying the Business Object PConsequences

Advantages:

• Business data can be viewed as object-o• Data validation and manipulation code• The business data logic is separated fro

persistence logic• The business service layer is simplified


attern:

too much

extra layer


Applying the Business Object PConsequences

Disadvantages:

• Business objects can become bloated if business logic is placed in them

• Small applications might not need this


semblers

ired fromise beans, datat gets themponents:

he

uired obtain and


Applying the Transfer Object AsPattern: Problem Force

Client classes often need data that can be acqunumerous business objects, including enterpraccess objects, and transfer objects. If the clienneeded data directly from several business co

• The client becomes tightly coupled to tbusiness components

• Many remote invocations might be req• Client cohesion decreases by having to

construct the data model


sembler

that exposesethodsers data from

a compositeclient

ovide the datas, or other


Applying the Transfer Object AsPattern: Solution

• In the business tier, use a session bean coarse-grained getTransferObject m

• This getTransferObject method gathother business tier components, buildsTransferObject, and returns it to the

• The BusinessObject instances that prcan be session beans, entity beans, DAOobject types


sembler

single object or

mutable


Applying the Transfer Object AsPattern: Solution

• The TransferObject instance can be acan be a composite that contains otherTransferObject instances

• These TransferObject instances are im


n Structure

ssObject

Object

acade


Transfer Object Assembler Patter

<<session bean>>TransferObjectAssembler

+getCompositeTransferObject()

TransferObject

Client

0..*

contains

builds

DataAcce

Business

ServiceF

Service


SequencesObject

: TransferObject


Transfer Object Assembler Pattern<<session bean>>

: TransferObjectAssembler: DataAcces<<session bean>>

: BusinessSession<<entity bean>>: BusinessEntity

: Client

1.4: Get Data

1.3: Get Data

1.2: Get Data

1.6: Add Data From BusinessSession

1.5: Add Data From BusinessEntity

1.7: Add Data From DAO

1.1: Create()

return

CompositeTransferObject

1: GetComposoteTransferObject


sembler

mplemented asusually frontedade componentler – Ifsfer object

bean


Applying the Transfer Object AsPattern: Strategies

• POJO Transfer Object Assembler – If ia POJO, the transfer object assembler isby a session bean such as the session fac

• Session Bean Transfer Object Assembimplemented as a session bean, the tranassembler is usually a stateless session


n Example

bean>>ean

) : RoomTO

mTO

creates



ReservationTO

-endDate : Date-startDate : Date...

+getCustomer()+getEndDate() : Date+getRoom()+getStartDate() : Date+ReservationTO( , , start : Date, end : Date )...

<<session bean>>ReservationReportTOAssemblerBean

+findReservation( ... )+getReservationAndHotelData( reservationID )+getReservationData()+junk()+makeReservation( ... )

ReservationHotelTO

+getHotel() : HotelTO+getReservation()+ReservationHotelTO( : HotelTO, )

HotelDAO

+getHotelData( . . . ) : HotelTO...


+getCustomerTO() : CustomerTO...

<<entityRoomB

+getRoomTO(...


+create( ... )+getReservationTO()+remove()...

HotelTO

-amenities-location...

+getAmenities()+getLocation()...

CustomerTO

Roo

creates

creates

-room-customer

uses1

-reservation

-hotel

creates

creates


n Example

otelData

ta();ReservationTO();, resData);



Transfer object assembler code:

1 public ReservationHotelTO getReservationH2 (String reservationID) {3 HotelTO hotelData = hotelDAO.getHotelDa4 ReservationTO resData = reservation.get5 return new ReservationHotelTO(hotelData


sembler


Applying the Transfer Object AsPattern: Consequences

Advantages:

• Removes business logic from client• Reduces coupling• Reduces network traffic• Improves client performance• Improves transaction performance


sembler

side increases

ly


Applying the Transfer Object AsPattern: Consequences

Disadvantages:

• Object creation overhead on the server• Data in transfer objects might get stale• Update logic must be handled separate


Pattern:

veral decisions:


Applying the Composite EntityProblem Forces

When using entity beans you need to make se

• Local or remote interfaces• BMP or CMP• Whether to use CMR


Pattern:

ntity beansacy persistencen desirable for

from the client


Applying the Composite EntityProblem Forces

Consider the following forces:

• Avoid dependencies between remote e• You might need BMP for custom or leg• Entity beans container services are ofte

business objects• The database schema should be hidden


P


Comparing BMP and CM

TM

JDBC

Data Access Object

Container

Data

Data

BMP

TM

Container

Deployment Descriptor

EJB QL

CMP


Pattern:

tly deployable, cycles.cessed only by

t should behe dependantJO.t should be dependant

OJOs or localR can be used.


Applying the Composite EntitySolution

• Parent objects are reusable, independencomponents that manage their own life

• Dependant objects are managed and actheir parent objects.

• For EJB 1.1 containers, the parent objecimplemented as a remote entity bean. Tobjects should be implemented as a PO

• For EJB 2.0 containers, the parent objecimplemented as a local entity bean. Theobjects can be implemented as either Pentity beans. If you are using CMP, CM


ucture

ct 0..*

contains


Composite Entity Pattern Str

Local entity bean or plain Java technology object

<<local entity bean>>CompositeEntity

DependentObjeClient 1 0..*

contains


uencey object>>entObject

: DataStore

.2.1: processRequest


Composite Entity Pattern Seq<<Java technologsecond : Depend

<<local entity bean>>first : DependentObject

<<local entity bean>>: CompositeEntity

: Client

2.2: getData

2

2.1: getData

2: busMethod

1.2: processRequest

1: busMethod

1.1: loadData

3: storeData


Pattern:

applicationsade can be as an entitypplications.ethod onlyed by business

ith BMP, is marked


Applying the Composite EntityStrategies

• Composite Entity Remote Façade – In with trivial business logic, a session façreplaced by a composite entity that actsfaçade. This is dangerous for complex a

• Lazy Loading – With BMP, ejbLoad mloads some data. The other data is loadmethods if and when it is required.

• Store Optimization (Dirty Marker) – WejbStore method only stores data thatas dirty.


mple

ity bean>>erBean

ity bean>>Bean

Address


Composite Entity Pattern Exa

<<session bean>>ReservationSessionFacade

...

<<local entity bean>>ReservationBean

...

<<local entCustom

...

<<local entRoom

...

uses

accesses

1..*


mple



Composite entity code:

1 public abstract class ReservationBean2 implements EntityBean {3 //virtual persistence fields4 public abstract String getReservationID();5 public abstract void6 setReservationID(String resID);7 public abstract Date getStartDate();8 public abstract void setStartDate(Date d);9 public abstract Date getEndDate();10 public abstract void setEndDate(Date d);11 //virtual relationship fields12 public abstract CustomerLocal getCustomer();13 public abstract void14 setCustomer(CustomerLocal c);15 public abstract RoomLocal getRoom();16 public abstract void setRoom(RoomLocal r);17 private EntityContext context;


mple



18 public String ejbCreate(String resID,19 Date start, Date end, CustomerLocal cust,20 RoomLocal room) throws CreateException {21 setReservationID(resID);22 setStartDate(start);23 setEndDate(end);24 setCustomer(cust);25 setRoom(room);26 return null;


mple



27 }28 public void ejbPostCreate(String resID,29 Date start, Date end, CustomerLocal cust,30 RoomLocal room) throws CreateException {31 setCustomer(cust);32 setRoom(room);33 }34 public void setEntityContext35 (EntityContext ctx){36 context = ctx;37 }38 public void unsetEntityContext() {39 context = null;40 }41 public void ejbRemove() { }42 public void ejbActivate() { }43 public void ejbPassivate() { }44 public void ejbStore() { }45 public void ejbLoad() { }


mple



46 public ReservationTO getReservationTO() {47 return new ReservationTO();48 }49 }


mple



CMR relationship in deployment descriptor:

1 . . .2 <ejb-relation>3 <ejb-relationship-role>4 <ejb-relationship-role-name>5 ReservationBean6 </ejb-relationshiprole-name>7 <multiplicity>One</multiplicity>8 <relationship-role-source>9 <ejb-name>ReservationBean</ejb-name>10 </relationship-role-source>11 <cmr-field>12 <cmr-field-name>customer</cmr-field-name>13 </cmr-field>14 </ejb-relationship-role>15 <ejb-relationship-role>16 <ejb-relationship-role-name>17 CustomerBean


mple



18 </ejb-relationship-rolename>19 <multiplicity>One</multiplicity>20 <relationship-role-source>21 <ejb-name>CustomerBean</ejb-name>22 </relationship-role-source>23 </ejb-relationship-role>24 </ejb-relation>25 . . .


Pattern:

g entity

less remote

ing a façade

base


Applying the Composite EntityConsequences

Advantages:

• Improves maintainability by simplifyinbean interactions

• Decreases network overhead by using entity beans

• Decreases network overhead by providand composite transfer objects

• Shields clients from changes in the data


Pattern:

CMR, entityell as POJOs


Applying the Composite EntityConsequences

Disadvantage:

Even with local interfaces, CMP, andbeans might not always perform as w


Pattern:

ery facility

port result sets

ily read-onlyource-intensive sets

, as well as


Applying the Value List HandlerProblem Forces

• Client applications need an efficient qu

• Clients need server-side caching to supthat are too large for the client

• Large search results are usually primar• EJB componentfindermethods are res

and ill-suited for browsing large result

• Clients might want to scroll backwardsforwards, through the search results


Pattern:

a search query,to retrieve the

arch methodequest to the

ery and createsct instances


Applying the Value List HandlerSolution

• The ValueListHandler class executesholds the results, and allows the client results they need

• When the client invokes the executeSeon ValueListHandler, it passes that rDataAccessObject

• TheDataAccessObjectexecutes the quthe ValueList object of TransferObje


Pattern:

ents and results


Applying the Value List HandlerSolution

• The ValueListHandler keeps theValueList reference

• The client can invoke the getNextElemgetPreviousElements methods to get


ucture

ransferObject


Value List Handler Pattern Str

<<interface>>ValueListIterator

+getNextElements( count : int )+getPreviousElements( count : int )+getSize() : int+resetIndex()

ValueListHandler

+executeSearch( . . . )

DataAccessObject

+executeSearch( . . . )

<<interface>>List

TValueListClient collects

provides data

iterates

accesses


uence

: TransferObject

st


Value List Handler Pattern Seq: ValueListHandler : DataAccessObject

: ValueLi

: Client

1: executeSearch( . . . )

2: getNextElements( 10 )

2.1: Create Sub-List from ValueList

3: getPreviousElemenets( 10 )

3.1: Create Sub-List from ValueList

return valueList

1.1: executeSearch( . . . )

1.1.2: create()

1.1.3: add( transferObjects )

1.1.1: create()

return subList

return sublist


Pattern:

e list handler isd by a stateful

not use EJBe implementedessed by a

urn results in asultSet, a JDBC


Applying the Value List HandlerStrategies

• Stateful Session Bean Handler – A valuusually a stateful session bean or frontesession bean

• POJO Handler – If an application doescomponents, the value list handler can bas a plain Java object that is directly accbusiness delegate

• Value List from DAO – A DAO can retvariety of formats including a JDBC ReRowset, or a collection


ample

ReservationTO

dDate : DateartDate : Date

tEndDate() : DatetStartDate() : Date


Value List Handler Pattern Ex

ValueListHandler

-endIndex : int-startIndex : int

+findReservationByDate( theDate : Date ) : void+getNextElements( count : int )+getPreviousElements( count : int )+getSize() : int+resetIndex() : void

ReservationDAO

+findAvailableReservations()+findReservationsByCustomer()+findReservationsByDate()+ReservationDAO()...

-en-st...

+ge+ge...

Client

create

iterates

0..*


ample



Value list handler code:

1 public class ValueListHandler {2 private List allResults;3 private int startIndex, endIndex;45 public void findReservationByDate(Date theDate)6 throws Exception {7 ReservationDAO dao = new ReservationDAO();8 allResults =9 dao.findReservationByDate(theDate);10 }11 public ReservationTO[] getNextElements12 (int howMany) {13 if (howMany > allResults.size()-endIndex) {14 howMany = allResults.size() - endIndex;15 }16 ReservationTO[] subset =17 new ReservationTO[howMany];


ample



18 int index;19 for (index=0; index<howMany; index++) {20 subset[index] = (ReservationTO)21 allResults.get(startIndex+index);22 }23 startIndex = endIndex;24 endIndex = startIndex+index;25 return subset;26 }


ample

any) {

any];



27 public ReservationTO[] getPreviousElements(int howM28 if (howMany > startIndex) {29 howMany = startIndex;30 }31 ReservationTO[] subset = new ReservationTO[howM3233 startIndex -= howMany;34 int index;35 for (index=0; index<howMany; index++) {36 subset[index] = (ReservationTO)37 allResults.get(startIndex+index);38 }39 endIndex = startIndex+index;40 return subset;41 }42 public int getSize() {43 return allResults.size();44 }45 public void resetIndex() {


ample



46 startIndex = endIndex = 0;47 }48 }


Pattern:

od overheadsng results


Applying the Value List HandlerConsequences

Advantages:

• Avoids EJB component finder meth• Supports server caching of result set• Enables client control over dispatchi• Reduces network overhead


Pattern:

caching some

sults are


Applying the Value List HandlerConsequences

Disadvantages:

• Performance can be impeded when query patterns

• This pattern is less effective when reupdated frequently


.mplex business






Behavioral

Creational

Structural

Presentation Tier

Business Tier

Integration Tier


Summary

Intra-Business Tier patterns help expediteclient access to business objects. Insummary, these patterns contribute asfollows:

• Application Service – Provides acentral place to put business logicbetween the service facades andthe business objects.

• Business Object – Describes howto organize and separate businessdata from business logic and workflow

• Transfer Object Assembler – Builds coobjects from multiple transfer objects.

Anti


persistence

sult sets on


Summary

• Composite Entity – Organizes related objects into a composite structure.

• Value List Handler – Manages large rebehalf of a client.

atterns

Java EE™ Patterns

Module 10

Using Presentation Tier PModule 10

Tier PatternsUsing Presentation

Module 10

Using PresentationTier Patterns


sentation Tier

the Apache

rn


Objectives

• Describe basic characteristics of the PreJava EE Patterns

• Describe the Model 2 Architecture andStruts Framework

• Apply the Intercepting Filter pattern• Apply the Front Controller pattern• Apply the Application Controller patte• Apply the Context Object pattern


r Patterns

ual

d-paste reusend


Introducing the Presentation Tie

Presentation Tier patterns:

• Provide guidance for designing individpresentation tier components by role

• Provide mechanisms to reduce copy-an• Enforce role separation between logic a

presentation components


s

-processing and post-ponses.

resentation tier. It cancontrol.

gement and viewont controller

objects withouttext.



Pattern Primary FunctionInterceptingFilter

Provides a simple mechanism for preprocessing of HTTP requests and res

Front Controller Provides a single entry point to the phandle security, validation, and flow

ApplicationController

Separates the action invocation manadispatching management from the frcomponent.

Context Object Passes data that is in context-specificpassing those objects out of their con


rchitecture

dification to be

d behaviorl updates

ate

nality

ng


Traditional Model View Controller A

The traditional MVC architecture requires mouseful for Web applications

- Defines application flow an- Maps user actions to mode- Selects view for response

- Renders the models- Requests updates from models- Sends user gestures to controller

- Encapsulates application st- Responds to state queries- Exposes application functio

Controller

Send User Gestures

Select View

Notify of Changes

Set Data ChangesRequest Processi

View

Get Data

Model


apply the MVCpplicationhis architecture

estpdates

ng


Model 2 Architecture

• Model 2 architecture describes how to architecture to a Java technology web a

• The Presentation Tier patterns fit into t

- Renders the model with an HTML response- Requests updates from models- Creates HTML forms and hyperlinks that can trigger the next request to the Controller

- Verifies data from HTTP requ- Maps user actions to model u- Selects view for response

Select View

Model

<<JSP page>>ViewComponent

Get Data

View

<<servlet>>FrontController

Controller

- Encapsulates application state- Responds to state queries- Exposes application functionality

Set Data ChangesRequest Processi


rk

l 2 architectureework

popular Model

avaBeanstate theure applicationTier patternstruts


Apache Struts Framewo

• Many development teams create Modeapplications without a pre-written fram

• You might want to use a Model 2architecture framework

• Apache Jakarta Struts is one of the most2 Architecture frameworks

• Struts provides a servlet, custom tags, Jcomponents, and other helpers to faciliimplementation of a Model 2 Architect

• The second edition of the Presentation discuss how they are implemented in S


Pattern:

nd some

ng Tasks

mization for aclient

ption

ression

lation


Applying the Intercepting FilterProblem Forces

Some requests might require pre-processing aresponses may require post-processing.

Pre-Processing Tasks Post-Processi

User authentication Response custocertain type of

Session validate Response encry

Denial of service attack detection Response comp

Request decryption Language trans

Request decompression Debugging

Request auditing


Pattern:

cessing tasks in

vedesirable copy-


Applying the Intercepting FilterProblem Forces

Placing all of the pre-processing and post-proone component can result in:

• Components with poor cohesion• Tasks that are difficult to add and remo• Tasks that are reusable only through un

and-paste techniques


Pattern:

lared filterach

different the GoF

ativelyide built-in

plement a


Applying the Intercepting FilterSolution

• Incoming requests go through each dec• Outgoing responses go back through e

declared filter• The pattern can be implemented using

designs, but the result is comparable toDecorator pattern

• Filters can be added or removed declar• Java Servlet 2.3 or later containers prov

support for filters• Pre-2.3 Java Servlet containers must im

custom filter strategy


ucture

ain : FilterChain )

: ServletResponse )

t, response);

<<Servlet>>Target

-servlet


Intercepting Filter Pattern Str

<<interface>>Filter

+destroy()+doFilter( request : ServletRequest, response : ServletResponse, ch+init( : FilterConfig )

<<interface>>FilterChain

+doFilter( : ServletRequest,

Filter nextFilter = filtersIterator.next();if (nextFilter != null) nextFilter.doFilter(request, response, this);else servlet.service(request, response);

//pre-processingchain.doFilter(reques//post-processing

FilterB

+destroy()+doFilter( . . . )+init( . . . )

FilterChainImpl

+doFilter( . . . )

FilterA

+destroy()+doFilter( . . . )+init( . . . )

FilterManagerWebClient

-filters0..*


uence<<Servlet>>: Target

: FilterB

Filter


Intercepting Filter Pattern Seq: FilterChainImpl: FilterManager: WebClient : FilterA

1.1: doFilter

1.1.1.1: doFilter

1.1.1.1.1.1 do

1: Request

1.1.1.1.1.1.1 service

1.1.1.1.1: doFilter

1.1.1: doFilter


Pattern:

let containers,ammaticallytainers, filters

superclass for

used with the

e client or


Applying the Intercepting FilterStrategies

• Custom Filter – With pre-2.3 Java Servyou must define the filter pattern progr

• Standard Filter – In Java Servlet 2.3 conare added declaratively through thedeployment descriptor

• Base Filter – Base filter class serves as aall other filter classes

• Template Filter – The base filter can beGoF Template Method pattern

• JAX-RPC Filter – The filter is used in thintegration tier in front of a web service


Pattern:


Applying the Intercepting FilterExample

The timing filter:

1 package sl500;2 import java.io.*;3 import javax.servlet.*;4 public class TimerFilter implements Filter {5 private FilterConfig filterConfig = null;67 public void init(FilterConfig filterConfig)8 throws ServletException {9 this.filterConfig = filterConfig;10 }1112 public void destroy() { }1314 public void doFilter(ServletRequest request,15 ServletResponse response,16 FilterChain chain)


Pattern:



17 throws IOException, ServletException {18 long start = System.currentTimeMillis();1920 chain.doFilter(request, response);2122 long end = System.currentTimeMillis();23 filterConfig.getServletContext().log24 ("Request processed in " + (end - start) +25 " milliseconds");26 }27 }


Pattern:

lass>



Part of the web.xml file

1 <filter>2 <filter-name>TimerFilter</filter-name>3 <filter-class>sl500.TimerFilter</filter-c4 </filter>5 <filter-mapping>6 <filter-name>TimerFilter</filter-name>7 <url-pattern>/*</url-pattern>8 </filter-mapping>


Pattern:

quests without

ationsaratively


Applying the Intercepting FilterConsequences

Advantages:

• Filters can be applied to all incoming rehaving to duplicate code

• Filters can easily be combined indifferent combinations

• Filters are easily reusable across applic• Filters can be added and removed decl


Pattern:

a is shared


Applying the Intercepting FilterConsequences

Disadvantage:

Filters can be inefficient if a lot of datbetween them


rn: Problem

ng mechanism request. Thisany

and auditing,ponente neededimilar

is easier with a


Applying the Front Controller PatteForces

The system lacks a centralized request-handlifor activities needing to be completed for eachleads to these activities being littered across mcomponents

• Common system services, such as securityshould not be duplicated in each view com

• Workflow management and a controller ar• Multiple views can be used to respond to s

business requests• Tracking a user’s progress through the site

centralized point of contact


rn: Solution

ontact forquest

view

ion strategies


Applying the Front Controller Patte

Use a Front Controller as the initial point of chandling a request. The controller manages reprocessing, including:

• Invoking security services• Delegating business processing• Managing the choice of an appropriate• Handling errors• Managing the selection of content creat


cture

JSP Page>>View

Action


Front Controller Pattern Stru

ApplicationController<<Servlet>>

FrontController

<<

Client

forwards

invokesdelegates


ence>> : Action

.1.1: Process Request


Front Controller Pattern Sequ: ApplicationController<<Servlet>>

: FrontController<<JSP Page

: View: Client

1.1: Delegate

2.1: Delegate

3.2: Delegate

1: Send Request

3: Send Request

2: Send Request

1.1.1: Forward Request



1.1

3.2.1: Process Request


attern:

ront Controllerletr functionalitynt controllerr functionalities


Applying the Front Controller PStrategies

• Servlet Front Controller vs. JSP Page F– A FrontController is usually a serv

• Dispatcher in Controller – If dispatcheis minimal, it can be included in the fro

• Filter Controller – Some front controllecan be placed in a filter


attern:

g – Rather thansuch as http:/.Controller,or the servletical resources *.dowhich isontroller


Applying the Front Controller PStrategies

• Physical vs. Logical Resource Mappinclients requesting actual physical URLs/www.server.com/servlet/packageuse a logical URL mapping as an alias f

• Multiplexed Resource Mapping – Logmapping can include wildcards, such amapped to the Struts ActionServlet c


mple

ns CancelReservation

+execute()


Front Controller Pattern Exa

<<JSP Page>>ReservationSearchResults

<<JSP Page>>ReservationConfirmation

RequestContextObjectFactory

AuthenticationBean

SearchReservatio

+execute()

MakeReservation

+execute()

<<Filter>>DebuggingFilter

+doFilter()

<<Servlet>>FrontController

+doPost()

<<interface>>Command

+execute()

<<Filter>>TimingFilter

+doFilter()

<<JSP Page>>ErrorPage


Client request

forwardforward

forward

forward

forward


attern:

ication flowand logging of

centrally

hesion


Applying the Front Controller PConsequences

Advantages:

• Avoids duplication of common requestprocessing code

• Allows central control of the Web appl• Allows the tracking of a particular user

related activity• Manages validation and error handling

Disadvantage:

The front controller can have poor co


er Pattern:

responsibilities:

ecides whaty invokes the

cides which


Applying the Application ControllProblem Forces

The controller has two particularly important

• Action Management – The controller daction to invoke, which in turn typicallbusiness processing

• View Management – The controller deview to forward the request to


er Pattern:

agement in thes:

hesionology, making


Applying the Application ControllProblem Forces

Placing the action management and view manfront controller component can cause problem

• The front controller might have poor co• This code is coupled to the servlet techn

the code harder to reuse and test


er Pattern:

agement are class initial requestonController

uses a Mapperoke and what


Applying the Application ControllSolution

• The action management and view manplaced in the ApplicationController

• The FrontController servlet does theprocessing and invokes the Applicati

• The ApplicationController usually class that determines what action to invview to forward to


tructure

<<JSP Page>>View

Action

okes

vokes


Application Controller Pattern S

ApplicationControllerFrontController

Mapper

Map

creates

creates

inv

delegates in

uses

searches


equence<<JSP Page>>

: View

Action


Application Controller Pattern S: ApplicationController<<Servlet>>

: FrontController: Mapper

:

: Map

1: delegate

1.4: forward

1.1: getAction

1.3: getView

1.2: invoke

1.1.2:create()

1.1.1: resolve


er Pattern:

troller that controllersand pattern and

configuration fileld be invoked

r that performsplication a view handler. used to which view the


Applying the Application ControllStrategies

• Command Handler – An application conperforms action management. Applicationusually invoke actions using the GoF Commthe mapper component might use an XMLto determine which action command shoubased on the request URL.

• View Handler – An application controlleview management. Most commonly an apcontroller is both a command handler andThe result of the action command might bedetermine from the XML configuration filerequest should be forwarded to.


er Pattern:

Languaged of JSP pages

ontrollernd invokes

e way, theication flow.



• Transform Handler – XML Stylesheet Transformations (XSLT) are used insteato generate the view. The application cdetermines an XSLT stylesheet to use athat stylesheet.

• Navigation and Flow Control – In somapplication controller controls the appl


er Pattern:

l (SOAP)a request from

rvices message.ategy is similarstrategy, but it

work.



• Custom Simple Object Access ProtocoMessage Handling – Rather than beinga web user, the request can be a web se

• JAX-RPC Message Handling – This strto the Custom SOAP Message Handlinguses JAX-RPC to automate much of the


xample

sDelegate

ions CancelReservation

+execute()

>>


Application Controller Pattern E

ReservationBusines

...




SearchReservat

+execute()

MakeReservation

+execute()


+doPost()

<<interfaceCommand

+execute()

<<JSP Page>>ErrorPage

Mapper

Map

uses

searches

forwardforward forward


xample

troller with the

hen a request is(Action) object

susiness logic

guration file, class



• Struts implements the Application ConRequestProcessor class

• Each action that should be performed wreceived is implemented as a command

• For each type of request that requiresbusiness processing:• Create a subclass of the Action clas• Implement the process and invoke b

from the execute method• Create a mapping in the Struts confi

from the request URI to that Action


xample

ervation">Confirmation.jsp"/>sp"/>

e methodfying “success”

the request tor



Example Struts Mapping Code:

<action path="/reserveRoom" type="hotel.MakeRes<forward name=”success” path="/Reservation<forward name=”failure” path="/ErrorPage.j

</action>

• The MakeReservation object’s executreturns an ActionForward object specior “failure”

• The RequestProcessor then forwardsthe ReservationConfirmation.jsp oErrorPage.jsp page


er Pattern:

managementontrollerplicationsable by

ight be


Applying the Application ControllConsequences

Advantages:

• Improves cohesion by separating actionand view management from the front c

• Improves reusability by keeping the apcontroller protocol generic and thus reudifferent client types

Disadvantage:

Introduces an extra component that munnecessary for smaller applications


n: Problem

rvletRequesthroughout theontexts such as

o classes inbility of those


Applying the Context Object PatterForces

• Context specific objects, such as HttpSeobjects often contain data that is used trequest processing, including in other cthe business tier

• If context specific objects are passed intother contexts, the flexibility and reusaclasses is reduced


rn: Solution

m the context

e get methods,er method to the protocole data from the

ata validation

transfer object,


Applying the Context Object Patte

• An object that encapsulates the data frospecific object is created

• The context object can be a set of simplor it can have one HashMap generic gett

• The context object can keep a referencespecific class, or it can keep a copy of thprotocol specific object

• The context object might also contain dand conversion logic

• A context object might seem similar to abut they have different intents


cture

ContextObject


Context Object Pattern Stru

ProtocolSpecificObject

ContextFactoryClient

uses

uses

uses creates


ence

rotocolSpecificObject

t


Context Object Pattern Sequ

: P

: ContextFactory

: ContextObjec

Container : Client

2.2: getData

1: create()

2: getContextObject( :ProtocolSpecificObject )

2.3: setData

3: getData1

4: getData2

2.1: create( :ProtocolSpecificObject )


attern:

s:

ext object holds therMap method

OJO contextf data. The populatesletRequest

For either ofe method


Applying the Context Object PStrategies

Strategies for ServletRequest context object

• Request Context Map Strategy – Contthe immutable Map object returned byServletRequest object’s getParamete

• Request Context POJO Strategy – A Pobject has a get method for each piece oconstructor takes ServletRequest andinstance variables with the data in Serv

• Request Context Validation Strategy –the above strategies, provide a validat


attern:

ext object stores

ject stores

Context



• Configuration Context Strategy – Contconfiguration state, for examplejavax.servlet.jsp.PageContext

• Security Context Strategy – Context obsecurity state, for examplejavax.security.auth.login.Login


attern:

a factory to

egy – Ratherta from thebject onet automatically



• Context Object Factory Strategy – Usecreate context objects

• Context Object Auto-Population Stratthan calling the methods to pass the daprotocol-specific object to the context oattribute at a time, you can use code thacopies all data over


mple

ssDelegate

ations CancelReservation

+execute()

e>>


Context Object Pattern Exa

SearchReservationRequestData

ReservationBusine

...

MakeReservationRequestData


AuthenticationBean

SearchReserv

+execute()

HttpServletRequest

MakeReservation

+execute()


+doPost()

<<interfacCommand

+execute()

ContextFactory

creates

uses

uses

creates


mple

uest{



1 import javax.servlet.*;23 public class MakeReservationRequestData extends Req4 private String roomType;5 private int numNights;6 //...other fields78 public void initialize(ServletRequest request) {9 setRoomType(request.getParameter("roomType"));10 int numNights = Integer.parseInt11 (request.getParameter("numNights"));12 setNumNights(numNights);13 }14 public boolean validate() {15 //...Validation rules checked here16 return true;17 }


mple



18 public void setRoomType(String rt) {19 roomType = rt;20 }21 public void setNumNights(int nn) {22 numNights = nn;23 }24 public String getRoomType() {25 return roomType;26 }27 public int getNumNights() {28 return numNights;29 }30 //...more get/set methods31 }


attern:

sts can be filled

ific classes thatersions


Applying the Context Object PConsequences

Advantages:

• Improves the reusability of component• Improves testability since context objec

with test data• Reduces dependencies on protocol spec

might change in different technology v


attern:

be developed

ing copies of


Applying the Context Object PConsequences

Disadvantage:

• Increases the amount of code that mustand maintained

• Slightly decreases performance by makdata and adding a layer of indirection


ntrollertext-specific






Behavioral

Creational

Structural

Presentation Tier

Business Tier

Integration Tier


Summary

• Intercepting Filter – Provides asimple mechanism for pre-processing and post-processingHTTP requests and responses

• Front Controller – Provides asingle entry point to thepresentation tier; may handlesecurity and validation

• Application Controller –Separates the action invocationand view dispatching from the front co

• Context Object – Passes data from conobjects to other scopes

Anti-P

tterns

Java EE™ Patterns

Module 11

More Presentation Tier PaModule 11

Tier PatternsMore Presentation

Module 11

More PresentationTier Patterns

Objectives

• Apply the View Helper pattern• Apply the Composite View pattern• Apply the Dispatcher View pattern• Apply the Service to Worker pattern


erns

tation tier logic inents, like JSP pages.

s from smaller view

iew Helper patterns.ss processes and thusr responsibility.

iew Helper patterns.esses.


More Presentation Tier Patt

Pattern Primary Function

View Helper Provides an object to carry out presenorder to remove it from view compon

CompositeView

Provides a simple way to create viewcomponents.

DispatcherView

Combines the Front Controller and VThe view components request businemight have to assume some controlle

Service ToWorker

Combines the Front Controller and VThe controller requests business proc


ttern:

ogic with view

tent developers


Applying the View Helper PaProblem Forces

Combining data preparation and formatting lgeneration logic leads to:

• Poor role separation between Web conand programmers

• Brittle view components• Copy-and-paste reuse


: Solution

c moved to

components,


Applying the View Helper Pattern

• The view focuses on presentation logic• Business logic and data formatting logi

helper classes• Helper classes can be either JavaBeans

custom tags or simple tag files


ure

iewHelper


View Helper Pattern Struct

The View is responsible for dynamically formatting the presentation response. The View requests data from its Helpers.

<<JSP Page>>View

VClient requests

0..*

uses


nce

: TransferObjectBean


View Helper Pattern Seque

: BusinessService: ViewHelper<<JSP Page>>: View

: Client

1.2: Get Property

1.1.1.1: Create()

1.1.1: Get Data

1.1: Get Data

1: Send Request


Strategies

View

iewHelper

custom tag 2.0 tag filelper is a

mplemented assformer (XSLT)


Applying the View Helper Pattern:

• JSP Page View vs. Servlet View – Thecomponent is usually a JSP page

• JavaBeans Component Helper – The Vcomponent is a JavaBeans component

• Custom Tag Helper – ViewHelper is a• Tag File Helper – ViewHelper is a JSP• Business Delegate as Helper – ViewHe

business delegate• Transformer Helper – ViewHelper is i

an eXtensible Stylesheet Language Tran


ple

Tag

ag


View Helper Pattern Exam


ReservationTO

...

...

CustomerTO

...

...

Loop

IfT

uses uses

uses

uses

-customer


: Example

ollection" %>/core" %>

s">

</td>></td>/td>


Applying the View Helper Pattern

1 <%@ attribute name="reservations" type="java.util.C2 <%@ taglib prefix="c" uri="http://java.sun.com/jstl3 <table>4 <c:forEach var="reservation"5 items="${reservations}" varStatus="statu6 <tr>7 <td><c:out value="${status.count}"/></td>8 <td><c:out value="${reservation.roomType}"/>9 <td><c:out value="${reservation.startDate}"/10 <td><c:out value="${reservation.endDate}"/><11 </tr>12 </c:forEach>13 </table>

1 <%@ taglib prefix="tag" tagdir="/WEB-INF/tags" %>2 <tag:buildResTable reservations="${reservations}"/>


ttern:

in a cleanerata

om the viewmight have on

s more reusable


Applying the View Helper PaConsequences

Advantages:

• Using ViewHelper components resultsseparation between the view and the dprocessing logic

• Separating the data preparation logic frreduces dependencies that developers the same resources

• Data preparation and formatting logic i


attern:

es causes

many JSP pages maintaininations


Applying the Composite View PProblem Forces

Copying and pasting content on multiple pagseveral problems:

• A content change can require changing• A consistent look and feel is difficult to• Many views are needed to create comb

of content


attern:

desiteView pagesre the layout


Applying the Composite View PSolution

• Make a CompositeView page that incluViewFragment pages and other Compos

• Use the CompositeView page to structuof a page


cture


Composite View Pattern Stru

<<JSP Page>>CompositeView

<<JSP Page>>View

<<JSP Page>>ViewFragment

0..*

includes


uence

<<JSP Page>>oter : ViewFragment


Composite View Pattern Seq

<<JSP Page>>header : ViewFragment fo

<<JSP Page>>: CompositeView

: ViewManager

2: include

4: include

1: include

3: include


attern:

es of theude>)s of the

ent – Viewsntss are included

used tosed with Struts.

s are managed


Applying the Composite View PStrategies

• Early-Binding Resource – Include piectemplate at translation time (<%@ incl

• Late-Binding Resource – Include piecetemplate at runtime (<jsp:include>)

• JavaBeans Component View Managemare included using JavaBeans compone

• Custom Tag View Management – Viewusing custom tags. Apache Tiles can beimplement this pattern. Tiles is often u

• Transformer View Management – Viewusing an XSL Transformer


mple

P Page>>nSearchResults

>Header

1<<JSP Page>>Advertisement2


Composite View Pattern Exa

<<JSReservatio


<<JSP Page>ReservationList

<<JSP Page>>ReservationData

<<JSP Page>>Advertisement

<<JSP Page>>NavigationBar

<<JSP Page>>Header


mple

%>

Bar.jsp"/>

nData.jsp"/>


Composite View Pattern Exa

1 <TABLE BORDER='0'>2 <TR>3 <TD>4 <%@ include file="../incl/Header.jsp"5 </TD>6 </TR>7 <TR>8 <TD>9 <jsp:include page="../incl/Navigation10 </TD>11 <TD>12 <jsp:include page="../incl/Reservatio13 </TD>14 </TR>15 </TABLE>


attern:

viewsgments or

ferent


Applying the Composite View PConsequences

Advantages:

• Fragments can be reused in numerous • Manageability is improved because fra

templates can be changed in one place• Templates can dynamically include dif

fragments based on the request or user


attern:

tes and


Applying the Composite View PConsequences

Disadvantages:

• Invalid content can be created if templafragments are not properly configured

• Runtime inclusion of fragments candecrease performance


Pattern

to combine theplication

rnative to thisate for more


Applying the Dispatcher View

• The Dispatcher View pattern is one wayView Helper, Front Controller, and ApController patterns

• This pattern reduces the role of thecontroller components

• The Service to Worker pattern is an altepattern, and it might be more appropricomplex Web applications


attern:

ller activities

have large

troller, and theed to decideents should


Applying the Dispatcher View PProblem Forces

• Without controller components, controcan be dispersed throughout the system

• Without view helpers, JSP pages mightquantities of scriptlet code

• If the Front Controller, Application ConView Helper patterns are used, you newhether the controller or view componrequest the business services


attern:

apt the

in the request

gateents or custom display model


Applying the Dispatcher View PSolution

The controller component:

• Invokes common Service components• Does not invoke business services or ad

display model• Dispatches using information included

state, as opposed to return values fromBusinessService objects

The View component uses the BusinessDelecomponents, which can be JavaBeans compontags to invoke business services and adapt the


cture

BusinessServicekes

adapts

creates

<<transfer object>>PresentationModel

lper


Dispatcher View Pattern Stru


<<JSP page>>View

Service

Client

invokes

invo

forward

1..*

1..*

BusinessDelegate

View He



uencegate :TransferObject: View Helper

rocess

1.2.1.5 Adapt

t

nt


Dispatcher View Pattern Seq: ApplicationController : BusinessDelesecurity : Service<<servlet>>

: FrontController<<JSP page>>

: View: Client

1.2: Dispatch

1.2.1.1: Request Business P

1.1: Authenticate

1: Request

1.2.1.4: Get Data

return transferObject

1.2.1.2: Select View Conten

1.2.1.3: Display View Conte

1.2.1: Forward


mple

ce>>d

HttpServletResponse ) : String

rvation SearchReservations


+findReservation( ... )+makeReservation( ... )...

O

()

recieves/stores


Dispatcher View Pattern Exa

View Model



+doPost()

AuthenticationBean <<interfaComman

+execute( : HttpServletRequest, :

MakeRese

<<JSP page>>ErrorPage

<<JSP page>>ReservationConfirmation

<<JSP page>>ReservationSearchResults

ReservationT


+getEndDate()+getStartDate...

Client

forwardforward

forward

queries

recieves/stores

Controller

queries

request

Mapper

Map searches


mple



The front controller code:

1 public class ApplicationController {2 //. . .3 public void process(HttpServletRequest request,4 HttpServletResponse response)5 throws IOException, ServletException {6 String action = request.getParameter("action");7 String viewName=mapper.getView(action);8 RequestDispatcher view;9 view = request.getRequestDispatcher(viewName);10 view.forward(request, response);11 }


mple

{ate");

. . .);



The command code:

1 public class MakeReservation implements Command {2 public String execute(HttpServletRequest request,3 HttpServletResponse response) 4 String startDate = request.getParameter("startd5 //. . .get other request parameters6 //. . .validate request parameters7 try {8 ReservationBusinessDelegate rbd =9 new ReservationBusinessDelegate();10 ReservationTO resData = rbd.makeReservation(11 if (resData == null) {12 return "failure";13 } else {14 request.setAttribute("resData", resData);15 return "success";16 } . . .


mple

a.lang.String'/>

'/>,



The pattern view page:

1 <myTag:executeLogic>2 <jsp:useBean id='result' scope='request' class='jav3 <%if (result.equals("failure") {%>4 <jsp:forward page="errorPage.jsp">5 <%}%>67 <jsp:useBean id='resData'8 scope='request' class='ReservationTO'/>9 Your reservation for10 <jsp:getProperty name='resData' property='startDate11 has been confirmed.


attern:

ont Controller,er patterns


Applying the Dispatcher View PConsequences

Advantage:

Offers most of the advantages of the FrApplication Controller, and View Help


attern:

amount ofssingtical code to

producew components results


Applying the Dispatcher View PConsequences

Disadvantages:

• The View components can have a largescriptlet code to request business proce

• Many View components can have idenrequest the same business processing

• The View components will likely eitherdifferent views or dispatch to other Vieto react to different business processing


Pattern

er way tooller, and


Applying the Service to Worker

• The Service to Worker pattern is anothcombine the View Helper, Front ContrApplication Controller patterns

• This pattern increases the role of thecontroller components


Pattern:

ller activitiesmave large

troller, and theed to decideents should


Applying the Service to WorkerProblem Forces

• Without controller components, contromay be dispersed throughout the syste

• Without view helpers, JSP pages may hquantities of scriptlet code

• If the Front Controller, Application ConView Helper patterns are used, you newhether the controller or view componrequest the business services


Pattern:

ppropriate for

nt, based on theness processing

uerying theoller’s businessntent.


Applying the Service to WorkerSolution

The controller components:

• Invoke common Service components• Invoke the business processing that is a

this request• Dispatch to a particular View compone

request state and the results of the busi

The View component is only responsible for qHelperobjects for data produced by the contrprocessing request and creating the display co


ucture

BusinessServiceokes

adapts

creates

<<transfer object>>PresentationModel

lper


Service to Worker Pattern Str


Service

Client <<JSP page>>View

invokes

inv

forward

1..*

1..*

BusinessDelegate

View He



uenceate :TransferObject: View Helper

1.2.1.5 Adapt

t


Service to Worker Pattern Seq: ApplicationController : BusinessDeleg

1.2: Dispatch

1.2.1: Request Business Process

1.1: Authenticate

1: Request

1.2.1.3: Display View Conten

1.2.2: Forward

1.2.1.2: Select View Content

: Client <<servlet>>: FrontController

security : Service <<JSP page>>: View

1.2.1.4: Get Data


ample

ce>>d

HttpServletResponse ) : String

rvation SearchReservations



O

()

receives/stores


Service to Worker Pattern Ex

View Model


+doPost()

AuthenticationBean <<interfaComman

+execute( : HttpServletRequest, :

MakeRese




ReservationT


+getEndDate()+getStartDate...

Client

forwardforwardforward

queries

receives/stores

Controller

queries1

request


Mapper

Map searches


ample

);



The controller code:

1 public class ApplicationController {2 //. . .3 public void process(HttpServletRequest request,4 HttpServletResponse response)5 throws IOException, ServletException {6 String action = request.getParameter("action");7 Command cmd = mapper.getCommand(action);8 String result = cmd.execute(request, response);9 String viewName = mapper.getView(action, result10 RequestDispatcher view;11 view = request.getRequestDispatcher(viewName);12 view.forward(request, response);13 }


ample

'/>,



The view page:

1 <jsp:useBean id='resData'2 scope='request' class='ReservationTO'/>3 Your reservation for4 <jsp:getProperty name='resData' property='startDate5 has been confirmed.


Pattern:

ontroller,er patternsern, Viewe, have lessd maintain

, thee


Applying the Service to WorkerConsequences

Advantages:

• Offers all the advantages of the Front CApplication Controller, and View Help

• Compared to the Dispatcher View pattcomponents are likely be more cohesivscriptlet code, and be easier to adapt an

Disadvantage:

Depending on how it is implementedFrontController component can havpoor cohesion


Struts

Actionpache.struts.action}

te( . . . )

tion SearchReservations



recieves

. . ) +execute( . . . )


Service to Worker Pattern In

{org.a

+execu

<<servlet>>ActionServlet

{org.apache.struts.action}

View Model

MakeReserva




ReservationTO


+getEndDate()+getStartDate()...

Client

forwardforwardforward

queries

recieves

Controller

queries

creates

+execute( .


rry out view

ay to create

he Fronthe viewand thus mightsibility. the Fronthe controller


Summary

• View Helper – Provides an object to capresentation tier logic to remove it fromcomponents, like JSP pages.

• Composite View – Provides a simple wviews from smaller view components.

• Dispatcher View Pattern – Combines tController and View Helper patterns. Tcomponents request business processeshave to assume some controller respon

• Service to Worker Pattern – CombinesController and View Helper patterns. Trequests business processes.

sM

AE

Java EE™ Patterns

Module 11

Exploring AntiPatternodule 12

ntiPatternsxploring

Module 12

ExploringAntiPatterns


s


Objectives

• Define AntiPatterns• Describe Integration Tier AntiPatterns• Describe Business Tier AntiPatterns• Describe Presentation Tier AntiPattern


s

ell-known codetive impact on

them and learn

d into three sets


Introducing AntiPattern

• AntiPatterns identify and document wdevelopment practices that have a negaa software system

• Studying AntiPatterns helps you avoidrefactored solutions

• In this module, AntiPatterns are groupeof patterns:• Integration Tier AntiPatterns• Business Tier AntiPatterns• Presentation Tier AntiPatterns


Patterns

of the Java EE

n tier Java EE good designs


Describing Integration Tier Anti

• These AntiPatterns involve poor usageplatform integration tier technologies

• Work hand in hand with the integratiopatterns to avoid poor designs and findfor the integration tier


attern

nections every

t be hardcoded


Not Pooling Connections AntiP

AntiPattern problem:

Creating and destroying database contime a query is run is expensive

Symptoms and consequences:

• Performance is poor• Scalability is poor• Database driver and location data migh

in many parts of the system


attern


Not Pooling Connections AntiP

Refactored solution:

• Use a connection pool• Use the DataSource interface


ttern

ge method of a

by sending a

g business logicnfficult


Monolithic Consumer AntiPa


• Business logic is placed in the onMessamessage driven bean

• This business logic can only be invokedJMS message to a messaging server


• Clients don’t have the option of invokinusing a synchronous method invocatio

• Testing of the business logic is more di


ttern

essage or

uest a services objectn be used to


Monolithic Consumer AntiPa


• The message driven bean:• Reads and prepares the data in the m• Invokes a method on a regular class

a session bean• Clients that want to synchronously req

can call the logic directly in the busines• Service Activator pattern’s structure ca

achieve the refactored solution


n

ugh messaging

ht have to

ave to marshall


Fat Message AntiPatter


• Asynchronous messages delivered throservers can become too fat

• Fat messages cause:• Network overhead increases• Strain on messaging server that mig

persist the messages• Strain on senders and receivers that h

and unmarshall the data


n

ses

eters for anr remote

an ID or a


Fat Message AntiPatter


• Network overhead increased• Strain on the messaging server increase• Strain on senders and receivers increas


• Carefully consider the necessary paramasynchronous service, just as you do fomethod invocations

• Consider the possibility of only passingreference to the data


g server has tonowledgement: tied to the

ot tied to the

n ongoingntinuously


Hot Potato AntiPattern


• With guaranteed delivery, the messaginre-deliver messages until it receives ack• With CMT, the acknowledgement is

transaction outcome• With BMT, the acknowledgment is n

transaction outcome• If the message is not processed due to a

condition, the messaging server will coresend the message


eiversessages

are burdenedng messages




• Message driven beans or other JMS reccontinually receive the same invalid mfor processing

• The messaging server and the receiversfrom repeatedly delivering and receivithat can not be processed


nother bean, the problem email orsagesan rollback theessagessage Queues

n




• Message that cannot be processed by ashould probably be acknowledged, andshould be announced, perhaps throughthrough another queue of problem mes

• It can be necessary to use BMT so you ctransaction and still acknowledge the m

• Some messaging servers have Dead Mewhere the message is sent after a certainumber of attempts


atterns

or usage of thegies with thepoor designs tier


Describing Business Tier AntiP

• This group of AntiPatterns involves poJava EE platform business tier technolo

• These AntiPatterns work hand in handbusiness tier Java EE patterns to avoid and find good designs for the business


attern

s are verye problems:

increasedeased

aintenancen the costs are

en you areare not using


Sledgehammer for a Fly AntiP


Like a sledgehammer, EJB componentpowerful tools—too powerful for som• EJB component services can lead to

overhead, increased complexity, incrdevelopment time, and increased m

• If you need many of the services, thegreatly outweighed by the savings

• If you do not need these services, thpaying a price for services that you


attern

decreased

interfaces than




• Increased development complexity anddeveloper efficiency

• More lines of code and more classes andare required for the job

• Slower performance


attern

going to benefit

ponent

ent descriptorsde ten files and

technologyted transaction,security offer




• Consider whether EJB components areyour situation

• Bitter EJB has a simple logging EJB comexample:• The interfaces, classes, and deploym

for the session and entity bean inclu300 lines of code

• For logging functionality, all the EJBservices such as, scalability, distribustate management, persistence, and little value


ltaneously

clare that theycts

effects,ed

grainede should be


Local and Remote Interfaces SimuAntiPattern


• The local interface methods must demight throw RemoteException obje

• The code can have unintended side depending on whether it was invoklocally or remotely

• Remote interfaces should be coarse • The choice between local and remot

carefully made and enforced


ltaneously

nsideration of

s not properlyation

ent


Local and Remote Interfaces SimuAntiPattern


• Poor performance due to inadequate colocal versus remote invocation issues

• Unexpected side affects because code idesigned for local versus remote invoc


• Carefully choose remote boundaries• Use local or remote interfaces to implem

your decisions


iPattern

ly access

cations to the

ponsible fornating theroper


Accesses Entities Directly Ant


If presentation tier components directentity beans:• You can have too many remote invo

entity beans• Presentation tier components are res

finding or creating the beans, coordimethod invocations, and ensuring ptransactional control


iPattern

emote

dled correctly much more

sentation tiercomponents


Accesses Entities Directly Ant


• Performance suffers due to too many rmethod invocations

• Transactions barriers might not be han• Presentation tier developers must have

intimate knowledge of the business tierimplementation


Uses session beans to separate the precomponents from the business entity


r’s based on EJBitations

loading, and

specific SQLaind


Mirage AntiPattern


• Many developers use BMP due to serve1.x architecture (EJB server’s) CMP lim

• CMP offers many benefits over BMP:• CMP can provide data caching, lazy

other server optimizations• CMP code does not contain vendor • CMP is easier to develop and maint• CMP 2.0 provides container manage

relationships (CMR)


to:

ce

optionrs CMP

rmance tests


Mirage AntiPattern


Using BMP unnecessarily might lead• Needlessly high development and

maintenance effort• Less efficient entity bean performan


• Consider using CMP instead of BMP• There are times when BMP is the only • Check into the reputation of your serve

implementation, or do your own perfo


rn

d if you neverand reuset makes the

could becausethat have


Cacheless Cow AntiPatte


Considerable server capacity is wastecache the results of previous requeststhem when the same or different cliensame request


The system does not scale as well as itit wastes time recalculating responsesalready been acquired


rn

onentsnts

or

ns like caching caching in the




• Places where cache might be added:• In front of the Web server• In front of the presentation tier comp• In front of the business tier compone• In the integration tier

• Might use vendor provided hardware software caching

• Might use home grown caching solutiocommands in the Command pattern orValue List Handler pattern


rn

en developing

nt and that

and for

ht become

nt reads whilemodified




There are many issues to consider wha cache:• Ensure the cached results are sufficie

there is no need to rerun the process• Decide what data should be cached

how long• Consider when the cached data mig

out of date• Consider how to allow fast concurre

protecting the data when it is being


attern

te, Clark, Lee,

tions require do not to an

ase scalability are likely to

session state


Conversational Baggage AntiP


This pattern is documented in Bitter EJB by Taand Linskey:

• While many tasks in enterprise applicakeeping session state, many other tasks

• Session state adds substantial overheadapplication and can significantly decre

• If you are not focused on this issue, youcreate stateful tasks that do not require


attern

ever you


Conversational Baggage AntiP


Performance and scalability degrades


Attempt to make tasks stateless whenreasonably can


State

ate:

lasss

statete the choice


Golden Hammers of SessionAntiPattern


• Four common places to store session st• Client tier, perhaps in cookies• Presentation tier in a HttpSession c• Business tier in stateful session bean• Resource tier in a database

• There is no golden hammer for sessionmanagement; the situation should dicta


State

ement tool canlity

ice, consider:


Golden Hammers of SessionAntiPattern


Using an inappropriate session managlead to poor performance and scalabi


When making a session state tool cho• The location of the data to be used• The size and type of the data• The implications of losing the data• Types of clients


tiPatterns

r usage of thenologiesentation Tier and find goo


Describing Presentation Tier An

• This group of AntiPatterns involve pooJava EE platform presentation tier tech

• These AntiPatterns work with the PresJava EE patterns to avoid poor designsdesigns for the presentation tier


in Every

ks are methods

.3 and

and removed


Including Common FunctionalityServlet AntiPattern


• Pre-processing and post-processing tasimplemented or invoked in the serviceof each servlet

• An AntiPattern only with Java Servlet 2later containers


• Tasks must be programmatically addedfrom multiple servlets

• The servlets have poor cohesion


in Every

ks are

s as well

factored


Including Common FunctionalityServlet AntiPattern


• Pre-processing and post-processing tasplaced in filters

• These filters can be applied to JSP pageas servlets

• The Intercepting Filter pattern is the resolution for this AntiPattern


mation

erlinks orincluded in the

ile names or

ify


Embedded Navigational InforAntiPattern


• JSP pages usually include URLs for hypbuttons and for fragment files that are JSP page

• The JSP pages must be modified if the fURLs change


• Users receive page not found errors• The application flow is difficult to mod


mation

al resourceuently change.

gments insteadude> directive.ic attributeiguration file tog maps to


Embedded Navigational InforAntiPattern


• With Front Controller pattern and logicmapping, the URLs are unlikely to freq

• You can use custom tags to include fraof the jsp:include action or <%@inclAn include custom tag can take a genervalue such as bannerand look in a confsee what specific resource that the strin


rn

ht be moved

s, it will not be

ntrollerttributesated to create,a


Ad Lib TagLibs AntiPatte


Model or controller functionality migfrom JSP pages into custom tags


• If business logic is placed in custom tageasily used by rich clients

• Custom tags that are doing model or cofunctionality are likely to need many a

• Custom tags are slightly more complicdebug, and maintain than ordinary Javtechnology classes


rn

k yourselfvoked by the


Ad Lib TagLibs AntiPatte


When you are writing custom tags, aswhether this logic should really be inJSP page







Behavioral

Creational

Structural

Presentation Tier

Business Tier

Integration Tier


Summary

• AntiPatterns help us focus on thecommon mistakes made indevelopment and providerefactored solutions to avoid orremedy these problems

• Studying patterns andAntiPatterns provide a naturalbenefit of seeing developmentissues from both a positive and anegative perspective

Anti-P

s DesignM

ABG

Java EE™ Patterns

Module 13

Applying Java EE BluePrintGuidelines

odule 13

pplying Java EEluePrints Designuidelines

Module 13

Applying Java EEBluePrints DesignGuidelines


guidelinesaree Java Pet Store


Objectives

• Describe the Java EE BluePrints design• Describe the Java Pet Store demo softw• Describe the Java EE patterns used in th

demo software


ts Design

pers with theciples needed, and

les to show youcture and


Describing the Java EE BluePrinGuidelines

• Provides enterprise application develoconcepts, technologies, and design printo quickly make secure, robust, scalableextensible applications

• Includes guidance and practical examphow to make the best use of the architefeatures of the Java EE platform


es

ines areelines.

developed

ith as few other

er two modules declarations


Object-Oriented Guidelin

Many of the Java EE BluePrints design guidelspecializations of general object-oriented guidModules should:

• Be separately compilable so they can beindependently

• Have few interfaces to communicate wmodules as possible

• Use loose coupling to other modules• Have explicit interfaces so that whenev

communicate, it is obvious from public


s a:

nt


Client Tier Guidelines

The Java EE Client tier can be implemented a

• Browser client• Java technology-based Application clie• Java technology-based MIDlet client• Non-Java technology-based client


mmends using

eparation oficzed control andn, data

framework

hly tested, and


Web Tier Guidelines

The Java EE BluePrints design guidelines recoan existing Web framework, because:

• Most Web frameworks encourage the spresentation, control, and business log

• Most Web frameworks provide centralicustomization of templating, localizatiovalidation, access control, and logging

• Time can be saved by not building the structure from scratch

• A framework should be stable, thoroughave a community support structure


s

rsistent

ata

mannerinside

conversationalrg services


Business Tier Guideline

• Entity beans may be appropriate for pedata when:• Multiple clients need to access the d• The data is not tied to a user session• Data must be available in a portable• The data must be handled properly

of transactions• Use stateful session beans to keep most

state, instead of in the client or Web tie• Use stateless session beans for providin

without maintenance of client state


s

nous services or other systemshe type of client tierbeans objectsainer managedappropriate


Business Tier Guideline

• Use message driven beans for asynchroto loosely couple EJB components with

• Keep EJB technology code agnostic of t• Keep the business logic in the business• Use session beans as a façade to entity • Avoid using fine grained remote entity• Use Data Access Objects (DAO), if cont

persistence (CMP) entity beans are not


s

Information

nctions, and

mponent typesements of the


Integration Tier Guideline

• Uses access objects to access EnterpriseSystems (EIS) functions and data

• Use command beans that invoke EIS fudata access objects to access EIS data

• Access objects guidelines:• Do not make assumptions about the

deployment environment• Ensure they are usable by different co• Use transaction and security manag• Follow the programming restriction

components that might use them• Use connection pooling


o Software

ood design andng behind the


Describing the Java Pet Store Dem

The Java Pet Store demo software illustrates gconstruction while demonstrating the reasonidesign choices


e Java Petlication

mer Web siteWAF)re framework,t also quite


Analyzing Java EE Patterns in thStore Demo Software Web App

Framework

• The Java Pet Store demo software custouses the Web Application Framework (

• This framework is a Model 2 Architectuwhich is somewhat similar to Struts, budifferent in many regards


e Web

ger

n( . . . )

>t

. )

vlet>>eServlet

... )( ... )s( ... )

page>>ntPages

page>>atePage

rtTag

forward

forward

uses

include


Java Pet Store Demo SoftwarApplication Framework

<<interface>>HTMLAction

+perform( : HttpServletRequest ) : Event...

WebController

+handleEvent( : Event, : HttpSession )...

RequestProcessor

+processRequest( : HttpServletRequest )...

<<interface>>EJBAction

+perform( : Event ) : EventResponse...

<<interface>>Event

+getEJBActionClassName() : String+getEventName()+setEJBActionClassName( : String )

ScreenFlowMana

+forwardToNextScree+init()

StateMachine

+processEvent( : Event )...

<<session bean>>EJBControllerLocalEJB

+processEvent( : Event )...

<<Servlet>MainServle

+doGet( ... )+doPost( ... )+doProcess( .....

<<Filter>>SignOnFilter

+doFilter( ... )...

<<Filter>>EncodingFilter

+doFilter( ... )...

<<SerTemplat

+doGet(+doPost+proces

<<JSPFragme

<<JSP page>>SignOnPage

<<JSPTempl

<<Browser>>Client

Inse

request invoke

invoke

forward

create invoke

create invoke

create


plication

ation Patterns:

rvlet classingFilterand

se custom tagscriptlet usagecomponents

nclude


Java EE Patterns in the Web ApFramework

The Java Pet Store demo software Web Applicframework implements the following Java EE

• Front Controller pattern – The MainSe• Intercepting Filter pattern – TheEncod

SignOnFilter classes• View Helper pattern – The JSP pages u

and JavaBeans components to reduce s• Service to Worker pattern – The view

invoke the RequestProcesses class• Composite View Pattern – The views i

fragment views


ing in the

OnFilter


The SignOnFilterClass Mappweb.xmlFile

1 <filter>2 <filter-name>SignOnFilter</filter-name>3 ...4 <filter-class>5 com.sun.j2ee.blueprints.signon.web.Sign6 </filter-class>7 </filter>8 <filter-mapping>9 <filter-name>SignOnFilter</filter-name>10 <url-pattern>/*</url-pattern>11 </filter-mapping>


s


The SignOnFilterClas

1 package com.sun.j2ee.blueprints.signon.web;23 import javax.servlet.*;4 ...5 public class SignOnFilter implements Filter {67 private HashMap protectedResources;8 private FilterConfig config = null;9 ...10 public void init(FilterConfig config)11 throws ServletException {12 this.config = config;13 URL protectedResourcesURL=14 config.getServletContext().getResource15 ("/WEB-INF/signon-config.xml");16 SignOnDAO dao =17 new SignOnDAO(protectedResourcesURL);18 ...19 protectedResources =


s



20 dao.getProtectedResources();21 }2223 public void doFilter( ServletRequest request,24 ServletResponse response, FilterChain chain)25 throws IOException, ServletException {26 HttpServletRequest hreq =27 (HttpServletRequest) request;28 String targetURL = hreq.getRequestURI();


s

L



29 ...30 // check if the user is signed on31 boolean signedOn = false;32 if (hreq.getSession().getAttribute33 (SIGNED_ON_USER)!= null {34 signedOn = ((Boolean) hreq.getSession().35 getAttribute(SIGNED_ON_USER)).booleanValue();36 } else {37 hreq.getSession().setAttribute38 (SIGNED_ON_USER, new Boolean(false));39 }4041 // jump to the resource if signed on42 if (signedOn) {43 chain.doFilter(request, response);44 return;45 }4647 // find out if the patterns match the target UR


s



48 Iterator it =49 protectedResources.keySet().iterator();50 while (it.hasNext()) {51 String protectedName = (String) it.next();52 ProtectedResource resource =53 (ProtectedResource)54 protectedResources.get(protectedName);55 String urlPattern = resource.getURLPattern();56


s



57 // now check against the targetURL58 if (urlPattern.equals(targetURL)) {59 // put the orginal url in the session60 hreq.getSession().setAttribute61 (ORIGINAL_URL, targetURL);62 config.getServletContext()63 .getRequestDispatcher("/" + signOnPage)64 .forward(request, response);65 return;66 }67 }68 // No matches if we made it to here69 chain.doFilter(request, response);70 }71 ...72 }


g in the

Pet Store

web.MainServlet


Front Controller Servlet Mappinweb.xmlFile

1 <servlet>2 <servlet-name>MainServlet</servlet-name>3 <description>The Front Controller for the4 </description>5 <servlet-class>6 com.sun.j2ee.blueprints.waf.controller.7 </servlet-class>8 ...9 </servlet>10 ...11 <servlet-mapping>12 <servlet-name>MainServlet</servlet-name>13 <url-pattern>*.do</url-pattern>14 </servlet-mapping>


pping

omplete.screen">

tion

wHandler="true" >

Handler"/>


The mapping.xmlClass Ma

1 <url-mapping url="order.do" screen="order_c2 <web-action-class>3 com.sun.j2ee.blueprints.....OrderHTMLAc4 </web-action-class>5 </url-mapping>67 <url-mapping url="createcustomer.do" useFlo8 <web-action-class>9 com.sun.j2ee.....CustomerHTMLAction10 </web-action-class>11 <flow-handler12 class="com.sun.j2ee......CreateUserFlow13 </url-mapping>


s


The MainServletClas

1 package com.sun.j2ee.blueprints.waf.controller.web;2 ...3 public class MainServlet extends HttpServlet {4 ...5 private HashMap urlMappings;6 private HashMap eventMappings;78 public void init(ServletConfig config)9 throws ServletException {10 ...11 urlMappings =12 URLMappingsXmlDAO.loadRequestMappings13 (requestMappingsURL);14 context.setAttribute15 (WebKeys.URL_MAPPINGS, urlMappings);16 eventMappings = URLMappingsXmlDAO.17 loadEventMappings(requestMappingsURL);18 context.setAttribute19 (WebKeys.EVENT_MAPPINGS, eventMappings);


s


The MainServletClas

20 ...21 }22 public void doGet(...) ... {23 doProcess(request, response);24 }25 public void doPost(...) ... {26 doProcess(request, response);27 }


s


The MainServletClas

2829 private void doProcess30 (HttpServletRequest request,31 HttpServletResponse response)32 throws IOException, ServletException {33 ...34 getRequestProcessor().35 processRequest(request);36 getScreenFlowManager().37 forwardToNextScreen(request,response);38 ...39 }40 ...41 }


lassd


The RequestProcessorCprocessRequestMetho

1 String actionClassString = //appropriate2 //<web-action-class> for the request3 //URL that came in4 HTMLAction action = (HTMLAction)5 getClass().getClassLoader().

loadClass(actionClassString).newInstance();6 ...7 action.doStart(request);8 Event ev = action.perform(request);9 EventResponse eventResponse = null;10 if (ev != null) {11 // set the ejb action class name on the event12 EventMapping eventMapping= getEventMapping(ev);13 if (eventMapping != null) {14 ev.setEJBActionClassName15 (eventMapping.getEJBActionClassName());16 }17 ComponentManager sl = (ComponentManager)


lassd


The RequestProcessorCprocessRequestMetho

18 request.getSession().19 getAttribute(WebKeys.COMPONENT_MANAGER);20 WebController wcc = sl.getWebController21 (request.getSession());22 eventResponse =23 wcc.handleEvent(ev, request.getSession());24 }25 action.doEnd(request, eventResponse);


Class

.web;

ebController {

t

onentManager)MANAGER);


The DefaultWebController

1 package com.sun.j2ee.blueprints.waf.controller2 ...3 public class DefaultWebController implements W4 ...56 public synchronized EventResponse handleEven7 (Event ev, HttpSession session)8 throws EventException {9 DefaultComponentManager cm = (DefaultComp10 session.getAttribute(WebKeys.COMPONENT_11 EJBControllerLocal controllerEJB12 =cm.getEJBController(session);13 return controllerEJB.processEvent(ev);14 }15 ...16 }


BClass


The EJBControllerLocalEJ

1 package com.sun.j2ee.blueprints.waf.controller.ejb;2 ...3 public class EJBControllerLocalEJB4 implements SessionBean {56 protected StateMachine sm;7 protected SessionContext sc;89 public void ejbCreate() {10 sm = new StateMachine(this, sc);11 }1213 public EventResponse processEvent(Event ev)14 throws EventException {15 return (sm.processEvent(ev));16 }17 public void setSessionContext18 (SessionContext sc) {19 this.sc = sc;


BClass


The EJBControllerLocalEJ

20 }21 public void ejbRemove() {22 sm = null;23 }24 public void ejbActivate() {}25 public void ejbPassivate() {}26 }


s


The StateMachineClas

1 package com.sun.j2ee.blueprints.waf.controller.ejb;2 ...3 public class StateMachine4 implements java.io.Serializable {5 ...6 public EventResponse processEvent(Event ev)

throws EventException {7 String actionName =8 ev.getEJBActionClassName();9 EventResponse response = null;10 ...11 action = (EJBAction)12 Class.forName(actionName).newInstance();13 ...14 action.init(this);15 action.doStart();16 response = action.perform(ev);17 action.doEnd();18 ...


s


The StateMachineClas

19 return response;20 }21 }


lass

flow;


The ScreenFlowManagerC

1 package com.sun.j2ee.blueprints.waf.controller.web.2 ...3 public class ScreenFlowManager4 implements java.io.Serializable {5 ...6 public void forwardToNextScreen7 (HttpServletRequest request,8 HttpServletResponse response)9 throws java.io.IOException,10 FlowHandlerException,11 javax.servlet.ServletException {12 String selectedURL = request.getRequestURI();13 ...14 URLMapping urlMapping =15 getURLMapping(selectedURL);16 if (!urlMapping.useFlowHandler()) {17 currentScreen = urlMapping.getScreen();18 } else {19 FlowHandler handler = null;


lass

r();


The ScreenFlowManagerC

20 String flowHandlerString = urlMapping.getFlowHandle21 handler = (FlowHandler) getClass().22 getClassLoader().23 loadClass(flowHandlerString).24 newInstance();25 handler.doStart(request);String flowResult =26 handler.processFlow(request);27 handler.doEnd(request);28 currentScreen =29 urlMapping.getResultScreen(flowResult);30 if (currentScreen == null)31 currentScreen = flowResult;32 ...33 }34 ...35 context.getRequestDispatcher("/"36 +currentScreen).forward(request, response);37 }38 }


s_

e"/>


The screendefinitionen_US.xmlFile

1 <screen-definitions>2 <default-template>/template.jsp3 </default-template>4 <screen name="main">5 <parameter key="title"6 value="Welcome to the BluePrints Petstore"7 direct="true"/>8 <parameter key="banner" value="/banner.jsp" />9 <parameter key="sidebar"10 value="/sidebar.jsp" />11 <parameter key="body" value="/main.jsp" />12 <parameter key="mylist" value="/mylist.jsp" />13 <parameter key="advicebanner"14 value="/advice_banner.jsp" />15 <parameter key="footer" value="/footer.jsp" />16 </screen>17 <screen name="cart">18 <parameter key="title" value="Cart" direct="tru


s_


The screendefinitionen_US.xmlFile

19 <parameter key="banner" value="/banner.jsp" />20 <parameter key="sidebar"21 value="/sidebar.jsp" />22 <parameter key="body" value="/cart.jsp" />23 <parameter key="mylist" value="/mylist.jsp" />24 <parameter key="footer" value="/footer.jsp" />25 <parameter key="advicebanner"26 value="/advice_banner.jsp" />27 </screen>


ass


The TemplateServletCl

1 package com.sun.j2ee.blueprints.waf.view.template;2 ...3 public class TemplateServlet extends HttpServlet {4 ...5 public void process (HttpServletRequest request,6 HttpServletResponse response)7 throws IOException,ServletException {8 String screenName = null;9 String selectedUrl = request.getRequestURI();10 int lastPathSeparator =11 selectedUrl.lastIndexOf("/") + 1;12 int lastDot = selectedUrl.lastIndexOf(".");13 if (lastPathSeparator != -1 && lastDot != -114 && lastDot > lastPathSeparator) {15 screenName = selectedUrl.substring16 (lastPathSeparator, lastDot);17 }18 //code omitted to cache request parameters

//and request attributes


ass


The TemplateServletCl

19 ...20 String templateName = localeScreens.21 getTemplate(screenName);22 if (templateName != null) {23 ...24 context.getRequestDispatcher(templateName).25 forward(request, response);26 ...


e


The Template.jspPag

1 <%@ taglib uri="/WEB-INF/template.tld"2 prefix="template" %>3 <%@ page contentType="text/html;charset=UTF-8" %>4 <html>5 <head>6 ...7 <body bgcolor="#FFFFFF">8 <table width="100%" height="100%" border="0"9 cellpadding="5" cellspacing="0">10 <tr height="100" valign="top">11 <td colspan="3">12 <template:insert parameter="banner" />13 </td>14 </tr>15 <tr valign="top">16 <td width="20%" valign="top">17 <template:insert parameter="sidebar" />18 </td>19 <td width="60%" valign="top">


e


The Template.jspPag

20 <template:insert parameter="body" />21 </td>22 <td valign="top">23 <template:insert parameter="mylist" />24 </td>25 </tr>26 ...


ag


The InsertTagCustom T

1 public class InsertTag extends TagSupport {2 private boolean directInclude = false;3 private String parameter = null;4 private Parameter parameterRef = null;5 private Screen screen = null;6 public void setParameter(String parameter){7 this.parameter = parameter;8 }9 public int doStartTag() throws JspTagException {10 screen = (Screen)pageContext.getRequest().11 getAttribute(WebKeys.CURRENT_SCREEN);12 if ((screen != null) && (parameter != null))13 parameterRef = (Parameter)14 screen.getParameter(parameter);15 ...16 if (parameterRef != null)17 directInclude = parameterRef.isDirect();18 return SKIP_BODY;19 }


ag

alue());

r


The InsertTagCustom T

20 public int doEndTag() throws JspTagException {21 if (directInclude && parameterRef != null) {22 pageContext.getOut().print(parameterRef.getV23 } else if (parameterRef != null) {24 if (parameterRef.getValue() != null)25 pageContext.getRequest().getRequestDispatche26 (parameterRef.getValue()).include27 (pageContext.getRequest(),28 pageContext.getResponse());29 }30 return EVAL_PAGE;31 }32 }


he Java Petive Classes

ceptioneption


Analyzing the Java EE Patterns in tStore Demo Software Administrat

<<session bean>>OPCAdminFacadeEJB

getChartInfo(:String, Date, Date, String) throws OPCAdminFacadeExgetOrdersByStatus( : String ) : OrdersTO throws OPCAdminFacadeExc...

AdminRequestBD

AdminRequestDB() throws AdminDBExceptiongetChartInfo(:String, Date, Date, String) throws AdminDBExceptiongetOrdersByStatus( : String ) : OrdersTO throws AdminDBExceptionupdateOrders( OrderApproval ) throws AdminDBException

<<singleton>>ServiceLocator

+getInstance() : ServiceLocator+getLocalHome( : String ) : EJBLocalHome...

<<session bean>>AsynchSenderEJB

+sendAMessage( : String )...

<<Servlet>>ApplRequestProcessor

...

<<session bean>>ProcessManagerEJB

...

<<entity bean>>PurchaseOrderEJB

...

<<entity bean>>ManagerEJB

...


n in thenality

RequestBD

Locator class

nFacadeEJB unifiedeans class is aack to


Design Pattern ImplementatioAdministrative Client Functio

• Business Delegate pattern – The Adminclass is a business delegate

• Service Locator pattern – The Servicelocates various resources such as EJBtechnology references

• Session Façade pattern – The OPCAdmiclass is a session façade that provides ainterface to several session and entity b

• Transfer Object pattern – The OrderTOtransfer object that returns order data bthe client tier


ss


The AdminRequestBDCla

1 package com.sun.j2ee.blueprints.admin.web;2 ...3 public class AdminRequestBD {4 private String OPC_ADMIN_NAME =5 "java:comp/env/ejb/remote/OPCAdminFacade";6 private OPCAdminFacade opcAdminEJB = null;7 public AdminRequestBD()8 throws AdminBDException{9 try {10 OPCAdminFacadeHome home =11 (OPCAdminFacadeHome)12 ServiceLocator.getInstance().13 getRemoteHome(OPC_ADMIN_NAME,14 OPCAdminFacadeHome.class);15 opcAdminEJB = home.create();16 } catch (CreateException ce) {17 ce.printStackTrace();18 throw new AdminBDException(ce.getMessage());19 }


ss


The AdminRequestBDCla

20 ...21 }22 public OrdersTO getOrdersByStatus(String status)23 throws AdminBDException {24 try {25 return26 opcAdminEJB.getOrdersByStatus(status);27 } catch (RemoteException re) {28 re.printStackTrace();29 throw new AdminBDException(re.getMessage());}}}


ss


The ServiceLocatorCla

1 package2 com.sun.j2ee.blueprints.servicelocator.web;3 ...4 public class ServiceLocator {5 private InitialContext ic;6 private Map cache; //holds references to EJBHomes7 private static ServiceLocator me;89 static {10 me = new ServiceLocator();11 ...12 }13 private ServiceLocator()14 throws ServiceLocatorException {15 try {16 ic = new InitialContext();17 cache = Collections.synchronizedMap18 (new HashMap());19 } catch (NamingException ne) {


ss



20 throw new ServiceLocatorException(ne);21 } ...22 }23 static public ServiceLocator getInstance() {24 return me;25 }26 public EJBLocalHome getLocalHome27 (String jndiHomeName)28 throws ServiceLocatorException {


ss



29 EJBLocalHome home = null;30 try {31 if (cache.containsKey(jndiHomeName)) {32 home = (EJBLocalHome)33 cache.get(jndiHomeName);34 } else {35 home = (EJBLocalHome)36 ic.lookup(jndiHomeName);37 cache.put(jndiHomeName, home);38 }39 } catch (NamingException ne) {40 throw new ServiceLocatorException(ne);41 } catch (Exception e) {42 throw new ServiceLocatorException(e);43 }44 return home;45 }46 public EJBHome getRemoteHome(...) ... {...}47 public QueueConnectionFactory


ss



48 getQueueConnectionFactory(...) ...{...}49 public Queue getQueue(...) ... {...}50 public TopicConnectionFactory

getTopicConnectionFactory(...) ...{...}51 public Topic getTopic(...) ... {...}52 public DataSource getDataSource(...) ... {...}53 public URL getUrl(...) ... {...}54 public boolean getBoolean(...) ... {...}55 public String getString(...) ... {...}56 }


ss

{


The MutableOrderTOCla

1 package com.sun.j2ee.blueprints.opc.admin.ejb;2 ...3 public interface OrdersTO extends Serializable4 public Iterator iterator();5 public int size();6 public boolean contains(Object o);7 public boolean containsAll(Collection c);8 public boolean equals(Object o);9 public int hashCode();10 public boolean isEmpty();11 public Object[] toArray();12 public Object[] toArray(Object[] a);1314 static class MutableOrdersTO15 extends ArrayList implements OrdersTO {16 }17 }


lass


The OPCAdminFacadeEJBC

1 package com.sun.j2ee.blueprints.opc.admin.ejb;2 ...3 public class OPCAdminFacadeEJB4 implements SessionBean {5 private String PURCHASE_ORDER_EJB =6 "java:comp/env/ejb/local/PurchaseOrder";7 private String PROCMGR_ORDER_EJB =8 "java:comp/env/ejb/local/ProcessManager";9 private SessionContext sc;10 private PurchaseOrderLocalHome poLocalHome;11 private ProcessManagerLocal processManagerLocal;1213 public void ejbCreate() throws CreateException {14 try {15 ServiceLocator serviceLocator =16 new ServiceLocator();17 poLocalHome = (PurchaseOrderLocalHome)18 serviceLocator.getLocalHome19 (PURCHASE_ORDER_EJB);


lass



20 ProcessManagerLocalHome21 processManagerLocalHome =22 (ProcessManagerLocalHome)23 serviceLocator.getLocalHome24 (PROCMGR_ORDER_EJB);25 processManagerLocal =26 processManagerLocalHome.create();27 } catch(ServiceLocatorException se) {28 throw new EJBException(se);29 } catch (CreateException ce) {30 throw new EJBException(ce);31 }32 }33 public OrdersTO getOrdersByStatus(String status)34 throws OPCAdminFacadeException {35 OrdersTO.MutableOrdersTO retVal =36 new OrdersTO.MutableOrdersTO();37 PurchaseOrderLocal po;38 ProcessManagerLocal mgr = processManagerLocal;39 try {40 PurchaseOrderLocalHome pohome = poLocalHome;

41 Collection orders =42 mgr.getOrdersByStatus(status);43 Iterator it = orders.iterator();44 while((it!= null) && (it.hasNext())) {45 ManagerLocal mgrEjb =46 (ManagerLocal) it.next();47 po = pohome.48 findByPrimaryKey(mgrEjb.getOrderId());49 Date gotDate = new Date(po.getPoDate());50 String podate = (gotDate.getMonth()+1) +51 "/" + gotDate.getDate() + "/" +52 (gotDate.getYear()+1900);53 retVal.add(new OrderDetails(po.getPoId(),54 po.getPoUserId(), podate,55 po.getPoValue(), status));56 }57 } catch(FinderException fe) {58 System.err.println59 ("finder Ex while getOrdByStat :"60 + fe.getMessage());


lass

find "+



61 throw new OPCAdminFacadeException("Unable to62 "PurchaseOrders of given status : " +63 fe.getMessage());64 }65 return(retVal);66 }67 ...68 }


e enterprise



i-Patterns Java EE BluePrints Design Guidelines



Behavioral

Creational

Structural

Presentation Tier

Business Tier

Integration Tier


Summary

• The Java EE BluePrints designguidelines provide best practicesfor designing enterprise systemsusing Java EE platform technology

• The Java Pet Store demo softwareis a sample Web application thatillustrates these best practices

• By studying the Java Pet Storedemo software , you can see anexample of how the Java EEpatterns can be applied to create a largapplication

Ant

Java EE™ Patterns

Appendix A

Quick Reference for UML

There are no overheads associated with this appendix.

Appendix A

Quick Referencefor UML

associated with this appendix

Appendix A

Quick ReferenceFor UML

There are no overheadsassociated with this appendix

iew

Java EE™ Patterns

Appendix B

J2EE Technology RevAppendix B

ReviewJ2EE Technology

Appendix B

J2EE TechnologyReview

Appendix B

J2EE TechnologyReview

Appendix B, slide 2 of 91

J2EE platformon (Java RMI)

y Interface API

re


Objectives

• Describe the major technologies of the • Describe Java Remote Method Invocati• Describe Java IDL API• Describe the JAX-RPC API• Describe the Java Naming and Director• Describe the Java Servlet API• Describe JSP technology• Describe the Java Message Service API• Describe EJB technology• Describe JDBC technology• Describe the J2EE Connector Architectu


rm

and framework technology


Reviewing the J2EE Platfo

The J2EE platform is a development platformfor building component based enterprise Javaapplications

J2EE includes:

• Specification• The reference implementation server• J2EE BluePrints design guidelines• The Java Pet Store Demo application


rm

NDI) API

sare)

SAAJ)ftware



• Java Remote Method Invocation (RMI)• Java IDL API• Java Naming and Directory Interface (J• Java Servlet API• JavaServer Pages (JSP pages)• Enterprise JavaBeans (EJB) component• Java API for XML Parsing (JAXP) softw• Java API for XML-based RPC (JAX-RPC• SOAP with Attachments API for Java (• Java API for XML Registries (JAXR) so


rm

Service (JAAS)



• JDBC API• Java Message Service API (JMS)• JavaMail™ API• Java Transaction API (JTA)• Java Authentication and Authorization• J2EE connector architecture• J2EE management model


Basics

JavaMail

2SE

JND

IJM

S

JDB

C

JTA

JAF

ontainer

EJB

abase


Multi-Tier J2EE Architecture

J2SE

Web Container

<%

%>

J

JMX

JAX

RJA

CC

AppletServlet

JAX-RPC

SAAJ

JSP

EJB CApplet Container

J2SE

HTTPSSL

HTTPSSL

ApplicationClient Container

ApplicationClient

JAX-RPC

SAAJ JMXJAX

RJM

SJN

DI

JDB

C

DatJ2SE

JavaMail

JND

IJM

S

JMX

JAX

RJA

CC

JDB

C

JTA

JAF

JAX-RPC

SAAJ


ethod

n

I classes

Skeleton

emoteObject

Remote Java VM


Understanding Java Remote MInvocation

• Light-weight distributed communicatio• Uses stubs and skeletons• The java.rmi package contains the AP

R

Network transport layer (JRMP)

Caller Java VM

Caller

Server

bindlookup

StubRMI Registry

java.rmi.Naming

java.rmi.Naming

Functionality supplied by the Java RMI APIFunctionality generated by Java RMI compilerFunctionality written by the developer


ethod

va RMI

{oteException,



These are the basic steps to create and run a Jaapplication:

1. Define a remote interface:1 import java.rmi.*;2 public interface Borrowable extends java.rmi.Remote3 public boolean checkOut(String patron) throws Rem4 PatronException;5 public boolean checkIn() throws RemoteException;6 public boolean catalog() throws RemoteException;7 }


ethod



2. Define a remote class:1 import java.rmi.*;2 import java.rmi.server.*;34 public class Book extends UnicastRemoteObject5 implements Borrowable {6 String title;7 String author;8 String publisher;9 String callNo;1011 public Book(String t, String a, String p,12 String c) throws RemoteException {13 title = t;14 author = a;15 publisher = p;16 callNo = c;


ethod

ronException {



17 }1819 public boolean checkOut(String patron) throws Pat20 boolean result = false;21 if (checkOut == true)22 result = true;23 return result;24 }25 public boolean checkIn() {26 boolean result = false;27 if (checkIn == true)28 result = true;29 return result;30 }31 public boolean catalog() {32 boolean result = false;33 if (catalogued == true)34 result = true;


ethod



35 return result;36 }37 }


ethod

p, String c){

nce and a

);



3. Define a server class:1 public class BookLauncher {2 public boolean createBook(String t, String a, String3 Book bookRef = new Book(t, a, p, c);4 Naming.rebind("//libServer/Book", bookRef);5 // To put it in the RMI Registry, an object refere6 //logical name for use by callers is needed7 }8 public static void main(String args[]) {9 (new BookLauncher()).createBook(10 args[0], args[1], args[2], args[3]11 }12 }


ethod

p, String c){;

ect



4. Define a caller (client):1 import java.rmi.*;2 import library.*;34 public class BookUser {56 Borrowable b;7 public boolean createBook(String t, String a, String8 b = (Borrowable) Naming.lookup(“//libServer/Book”)9 // Need to know the name of the server10 // Need to know the logical name of the remote obj11 }1213 public boolean checkOut(String patron) {14 b.checkOut(patron);15 }16 // Other methods as necessary17 }


ethod

e stubs andver-side



5. Compile all the code:javac *.java

6. Use the rmic command to generate thskeletons which serve as caller and seproxies for the remote object:rmic Book.class

7. Start the Java RMI registry:rmiregistryRun the server program.java Booklauncher

8. Run the caller program:java BookUser


API

y

ins CORBAng Java

Java programming

stry

than CORBA

e Java 2 platform,on (Java SE™


Understanding the Java IDL

• The Java IDL API is the Java technologimplementation of CORBA

• The Object Management Group mainta• You can write CORBA applications usi

technology

Characteristic CORBA Java RMI

Programminglanguages

Java, C, C++, COBOL,Smalltalk, LISP, PL/I, andmore

Specific to the language

Naming service COS Naming Service Java RMI Regi

Complexity Quite complex Much simpler

Requiredsoftware

Must obtain an ORB Core API in thStandard Editiplatform)


API

I

ming service is

t, uses the Javaethod Protocol

one only using Javay


Understanding the Java IDL

Characteristic CORBA Java RM

Additionalservices

Other services often available,such as event processing andtransaction management

Only a naprovided

Networkprotocol

Uses Internet Inter-ORBProtocol (IIOP)

By defaulRemote M(JRMP)

Interfacedefinition

Definition of attributes andbehaviors in the languageneutral Interface DefinitionLanguage

Work is dtechnolog


API

s toodel,ironment usedk

service

is the most


Understanding the JAX-RPC

• Web services enable clients and servicecommunicate regardless of the object mprogramming language, or runtime envon either side of the communication lin

• XML based messages• HTTP is the most commonly used web

transport protocol• Simple Object Access Protocol (SOAP)

common format for the messages


API



Web ServiceInfrastructure

ApplicationFunctions

HeterogeneousClient Base

SwingClient

Other ClientTypes

Browser

ApplicationServer


API

-RPC) is ansed remote

ort HTTP 1.1 asmessagesX-RPC services



• The Java API for XML-based RPC (JAXextensible API for performing XML-baprocedure calls

• A JAX-RPC implementation must suppthe transport mechanism for SOAP 1.1

• The JAX-RPC specification describes JAaccording to the WSDL 1.1 specification

Java Objectsand

Data Types

SOAPMessage

JAX-RPC

InternetSOAP

Message

Marshall/Unmarshall

Transmit


API

l where servicepointervice messagethe method andn the message.lts, and stateless

ervice

gs



• JAX-RPC uses a service endpoint moderequests are directed to the service end

• The service endpoint unmarshalls the sand invokes the specified service usingparameter information contained withi

• JAX-RPC supports two endpoint modeimplementation types, as well as servlesession beans

ServiceRequests

ServiceEndpoint

Web Container

JAX-RPC runtime

To ServiceSOAP

RPCRouterServlet Binding

Classes

EJB Container

To SStatelessSession

EJB BindinClasse


API

ality provided

.rmi.Remote

adata types

stants



• A service interface defines the functionby a web service

• A JAX-RPC interface must extend java

• All of the interface methods must throwjava.rmi.RemoteException and use supported by JAX-RPC

• The interface must not declare any con1 import java.rmi.Remote;2 import java.rmi.RemoteException;34 public interface InterfaceName extends Remote {5 // business method6 public ReturnType methodName(paramList)7 throws RemoteException;8 }


API

Java class thatice interface



A JAX-RPC service implementation class is a implements the methods declared on the serv

1 public class ClassName implements InterfaceName {2 // constructor3 public ClassName() {4 // do nothing5 }6 // the actual service7 public ReturnType methodName(paramList) {8 method body;9 }10 }


API

mplementation necessaryiles:

or deployment

cerovided with

(Java WSDP)nt build scripts

tionality in an



• Having created a service interface and iclass, a service developer generates theserver-side web service infrastructure f• The server tie files• The service properties file required f• Serializer and deserializer files• A WSDL file that describes the servi

• You can do these tasks using the tools pthe Java Web Services Developer Pack and automate them using one or more A

• Alternatively, you can rely on the funcIDE to perform this work for you


d Directory

ceshanging codek. It looks up

tions


Understanding the Java Naming anInterface™ (JNDI) API

• Allows access to multiple naming servi• Can change naming services without c• The naming service is like a phone boo

names and gets back objects

Java Application

Naming Manager

JNDI API

JNDI SPI

JNDIImplementa

PossibilitieLDAP DNS NIS NDS RMI CORBA


String jndiname){

teObject.narrowe.class);


JNDI API Class

1 public class CatalogManager {2 public CatalogQueryBeanHome findCatalogQueryBean(3 try {4 InitialContext ctx = new InitialContext();5 Object ref = ctx.lookup(jndiname);6 CatalogQUeryBeanHome home =7 (CatalogQueryBeanHome)javax.rmi.PortableRemo8 ("CatalogQueryBean", CatalogQUeryBeanHom9 }catch(Exception e) {10 e.printStackTrace();11 }12 }13 }


d Directory

e API classes

t to specify the

bject.narrow


Understanding the Java Naming anInterface™ API

• The javax.naming package contains th• Create an InitialContext object:

• Use a java.util.Properties objecURL and driver classes

• Call the lookup method• Use the javax.rmi.PortableRemoteO

method to narrow the results• Cast the results


the API classes

ataource


Understanding Servlets

• Server managed Web components• Servlets create dynamic Web content• Replace CGI and similar technologies• The javax.servlet package contains

Query

Result

Client BrowserHTTP(s)

HTML

DS

Servlet

Web Tier

Servlet retrieves user data from the data source.

Using the data, the servlet generates a personalized page.

User requests a Web page from the Web server.

2

3

1


nHome)

e.class);


Servlet Class

1 import java.io.*;2 import java.util.*;3 import javax.servlet.*;4 import javax.servlet.http.*;5 import libraryApp.*;67 public class CatalogServlet extends HttpServlet {8 private CatalogQueryBeanHome cqbh;9 public void init() throws ServletException {10 try {11 InitialContext ctx = new InitialContext();12 Object ref = ctx.lookup("CatalogQueryBean");13 CatalogQueryBeanHome cqbh = (CatalogQueryBea14 javax.rmi.PortableRemoteObject.narrow15 ("CatalogQueryBean", CatalogQUeryBeanHom16 }catch(Exception e) {17 e.printStackTrace();18 }19 }


tion {

chType");earchValue");

chValue);

.getMessage());

Writer


Servlet Class

2021 public void destroy() { }22 public void doGet (HttpServletRequest request,23 HttpServletResponse response)24 throws ServletException, IOExcep25 HttpSession session = request.getSession();26 try {27 String category = request.getParameter("Sear28 String searchValue = request.getParameter("S29 CatalogQueryBean cqb = cqbh.create();30 Collection titles = cqb.query(category, sear31 cqb.remove();32 }catch(CreateException crex) {33 System.out.println34 ("Error creating CatalogQueryBean " + crex35 }36 // Handle other exception types37 // set content-type header before accessing the


</head>");


Servlet Class

38 response.setContentType("text/html");39 response.setBufferSize(8192);40 PrintWriter out = response.getWriter();41 // then write the data of the response42 out.println43 ("<html><head><title>Catalog Query Results</title>44 out.println("<body>");45 Iterator iter = titles.getItems();46 while (iter.hasNext()) {47 String title = (Book)iter.next();48 out.println(title);49 }50 out.println("</body>");51 out.println("</html>");52 out.close();53 }54 }


ET request:eeters for the

to set mime

HTML back to


Understanding Servlets

• Subclass of HttpServlet• doGet – Called when a client sends a G

• HttpServletRequest object; use thgetParameter method to get paramWeb page

• HttpServletResponse object:• Use the setContentType method

type• Use a PrintWriter object to send

the client


ges™

s

et classes


Understanding JavaServer PaTechnology

• Server managed Web components• Allows for separation of developer role• Improves application maintainability• Helps prevent cut-and-paste reuse• Automatic recompilation• Contains HTML with special tags• Get translated and compiled into Servl

JSP Page Flow

Init event

RequestResponse

Destroy event

jspInit()

jspService

jspDestroy

“JSP” Servlet


P Page


HTML Form Processed by a JS

1 <HTML>2 <HEAD>3 <TITLE>KDL University Library System</TITLE>4 </HEAD>5 <BODY>6 <FORM action="/Catalog.jsp" method="get">7 Search Type:8 <INPUT type=”text” name=”type”><BR>9 Search Text:10 <INPUT type=”text” name=”value”><BR>11 <INPUT type="submit" value="Submit">12 </FORM>13 </BODY>14 </HTML>


n" />>

%>

lt" />


JSP Page

1 <%@ include file="Header.jsp" %>2 <jsp:useBean id="Catalog" class="libraryApp.CatalogBea3 <% String searchType = request.getParameter("type"); %4 <jsp:setProperty name="Catalog"5 property="type" value="<%= searchType %>" />6 <% String searchValue = request.getParameter("value");7 <jsp:setProperty name="Catalog" property=8 "value" value="<%= searchValue %>" />9 <% try { %>10 <P>Account:11 <jsp:getProperty name="Catalog" property="searchResu12 </P>13 <% } catch (Exception e) { %>14 <P>Error retrieving item from library ctalog:15 <jsp:getProperty name="Catalog" property="value" />16 </P>17 <% } %>18 <%@ include file="Footer.jsp" %>

Technology

processor

*" %>

variables


Understanding JavaServer Pages

• Comments – Text ignored by JSP page 

• Directives – Compile-time instructions<%@ page language = "java" import = "java.util.

• Declarations – Declare Java technology<%! int x = 5 %>

• Expressions – Produce output<%= clock.getYear(); %>


Technology

ary" %>

xpression

>


Understanding JavaServer Pages

• Scriptlets<% int x = 5; out.println(x); %>

• JavaBeans components<jsp:useBean id="name" />

• Custom tags<%@ taglib uri="/tlds/library.tld" prefix="libr<P>New books in our collection</P><library:showNewBooks month="January" >

• Java Standard Tag Library (JSTL) and ELanguage (EL)<c:forEach var=”book” items=”${bookList.books}”<li> <c:out value=”book.name”/> </li></c:forEach>


e Service

rvices without

PI classesssaging


Understanding the Java Messag(JMS) API

• Allows access to multiple messaging serewriting code

• The javax.jms package contains the A• Provides a way to do asynchronous me

JMS Sender JMS ListenerJMS

Queue

JMS Publisher

JMS Subscriber

JMS Subscriber

JMSTopic


PI


Understanding the JMS A

1. Create a sender:1 import javax.jms.*;2 import javax.naming.*;3 public class PurchaseRequestSender {4 public static void main(String[] args) {5 Context context = null;6 QueueConnectionFactory qcFactory = null;7 QueueConnection queueConnection = null;8 QueueSession queueSession = null;9 Queue queue = null;10 QueueSender queueSender = null;11 TextMessage message = null;12 try {13 context = new InitialContext();14 } catch (NamingException ne) {15 System.out.println("Could not create “ +16 “JNDI context: " + ne.toString());17 System.exit(1);18 }


PI

e);



19 try {20 qcFactory = (QueueConnectionFactory)21 context.lookup("java:comp/env/jms/22 PurchasingQueueConnectionFactory");23 queue = (queue) context.lookup24 ("java:comp/env/jms/PurchaseQueue");25 } catch (NamingException e) {26 System.out.println27 ("JNDI lookup failed: " +e.toString());28 System.exit(1);29 }30 try {31 queueConnection =32 qcFactory.createQueueConnection();33 queueSession =34 queueConnection.createQueueSession(false,35 Session.AUTO_ACKNOWLEDGE);36 queueSender = queueSession.createSender(queu37 message = queueSession.createTextMessage();


PI



38 message.setText39 ("// Purchase request data goes here");40 queueSender.send(message);41 } catch (JMSException jmse) {42 System.out.println("Exception occurred: " +43 jmse.toString());44 } finally {45 if (queueConnection != null) {46 try {47 queueConnection.close();48 } catch (JMSException e) {49 System.out.println50 ("JMS error: " +e.getMessage());51 e.printStackTrace();52 }53 }54 }55 }56 }


PI

gs:

y.

ry.on.nd passing in

.



This JMS sender code does the following thin

a. Looks up a queue connection factorb. Looks up a queue.c. Creates a connection using the factod. Creates a session using the connectie. Creates a sender using the session a

the queue.f. Creates a message using the senderg. Sends the message.h. Closes the connection.


PI



2. Create a message receiver:1 import javax.jms.*;2 import javax.naming.*;3 public class PurchaseOrderReceiver {4 public static void main(String[] args) {5 Context context = null;6 QueueConnectionFactory qcFactory = null;7 QueueConnection queueConnection = null;8 QueueSession queueSession = null;9 Queue queue = null;10 QueueReceiver queueReceiver = null;11 TextMessage message = null;12 try {13 context = new InitialContext();14 } catch (NamingException e) {15 System.out.println("Could not create16 InitiialContext: " + e.toString());17 System.exit(1);


PI



18 }19 try {20 qcFactory = (QueueConnectionFactory)21 context.lookup("java:comp/env/jms22 PurchasingQueueConnectionFactory");23 queue = (Queue)context.lookup24 ("java:comp/env/jms/PurchaseQueue");25 } catch (NamingException e) {26 System.out.println27 ("JNDI lookup failed: " + e.toString());28 System.exit(1);


PI



29 }30 try {31 queueConnection =32 qcFactory.createQueueConnection();33 queueSession =34 queueConnection.createQueueSession(35 false,Session.AUTO_ACKNOWLEDGE);36 queueReceiver = queueSession37 .createReceiver(queue);38 queueConnection.start();39 while (true) {40 Message m = queueReceiver.receive(1);41 if (m != null) {42 if (m instanceof TextMessage) {43 message = (TextMessage) m;44 System.out.println("Reading “ +45 “message: " + message.getText());46 } else {47 break;


PI



48 }49 }50 }51 } catch (JMSException e) {52 System.out.println("Exception occurred: "53 + e.toString());54 } finally {55 queueConnection.close();56 ...


PI

ngs:

..d passing in



This JMS receiver code does the following thi

1. Looks up a queue connection factory.2. Looks up a queue.3. Creates a connection using the factory4. Creates a session using the connection5. Creates a receiver using the session an

the queue.6. Starts the connection.7. Receives the message.8. Closes the connection.


Beans™s

nts


Understanding Enterprise JavaTechnology Component

• Container managed business compone• Components for business logic• Container provides these services:

• Security• Transactions• Concurrency• Resource management• Persistence


chitecture

rity

es

0


Overall Enterprise JavaBeans Ar

Secu

Client

Server B

JNDIJNDI

Server A

Container

createfind remove

HomeObject

Services

Naming Transaction Persistence

HomeInterface

EJBObject

RemoteInterface

Bean

Environmental Properti

2

3

4

8

5

91

6

1


chitecture:nt

stroys beans

nds the


Overall Enterprise JavaBeans ArParts of an EJB Compone

Home Object:

• Is a factory that creates, locates, and de• Provided by the container• Implements the Home interface that exte

javax.ejb.EJBHome interface


chitecture:nt

the bean

at extends the



EJB Object:

• A proxy that forwards business calls to• Provided by the container• Implements the component interface th

javax.ejb.EJBObject interface


chitecture:nt

the

r



Deployment Descriptor:

• Is an XML document• Contains structural information about • EJB component• Is used for deployment by the containe


chitecture:es

omponent

omponents

EE platform


Overall Enterprise JavaBeans ArRemote and Local Interfac

• Developer can choose the Home and Cinterfaces to be remote or local

• Remote interfaces allow access to EJB cacross the network

• Local interfaces are more efficient for J2components on the same physical host


ents

essage-Drivenean

odelingsynchronoususiness logic

essageDrivenBean

tateless. Notccessible by thelient except throughhe JMS API


Three Types of EJB Compon

Session Bean Entity BeanMB

PrimaryPurpose

Modelingsynchronousbusiness logic

Modeling entities,especially tables inan RDBMS or objectsin an ODBMS

Mab

Interface SessionBean EntityBean M

Client State Can beconversational(stateful or stateless)

Models persistentstate

Sact


ss Session Bean

s

lly no

accept parametersialization

ng one-shots logic, such asg a catalog or

ing a credit cardr. Sometimes moret than a stateful bean


Session Beans

Stateful Session Bean Statele

Conversational State Stateful Stateles

Instance owned byclient?

Generally yes Genera

create methodparameters

Can take parameters forinitialization

Cannotfor init

Use Modeling conversationalbusiness logic, such asneeded for a shopping cart

Modelibusinesqueryinvalidatnumbeefficiensession


ace

.EJBHome {


Session Bean Home Interf

1 import javax.ebj.*;2 import java.rmi.*;34 public interface ShoppingCartHome extends javax.ejb5 public ShoppingCart create() throws6 CreateException, RemoteException;7 public ShoppingCart create(String custID) throws8 CreateException, RemoteException;9 }


erface

Object {xception;

qty)


Session Bean Component Int

1 import java.rmi.*;2 import javax.ejb.*;3 public interface ShoppingCart extends javax.ejb.EJB4 public Collection getItemsInCart() throws RemoteE5 public boolean addToCart(String itemID, int qty)6 throws RemoteException;7 public boolean removeFromCart(String itemID, int 8 throws RemoteException;9 public checkOut(String custID)10 throws RemoteException, CustomerException;11 }


SessionBean {

s

r

s{


Session Bean Class

1 import javax.ejb.*;2 import java.util.*;34 public class ShoppingCartBean implements javax.ejb.5 private SessionContext context;6 private String customerID;7 private LinkedList items;8 // Initialize the bean instance with no parameter9 public void ejbCreate() {}10 // Initialize the bean instance with one paramete11 public void ejbCreate(String custID) {12 customerID = custID;13 }14 // Save object which provides environmental acces15 public void setSessionContext(SessionContext sc) 16 context = sc;17 }


{

qty) {


Session Bean Class

18 // Destroy bean instance19 public void ejbRemove() { }20 // The next two methods are container callbacks21 // for resource management22 public void ejbPassivate() { }23 public void ejbActivate() { }24 // Remote interface methods25 public Collection getItemsInCart() {26 return items;27 }28 public boolean addToCart(String itemID, int qty) 29 // Add item logic30 }31 public boolean removeFromCart(String itemID, int 32 // Remove item logic33 }34 public checkOut(String custID) {35 // Perform order check out operations36 }}


thod for every

od in then classthods


Session Bean Class

Must contain:

• A codeless, no argument constructor• Home related methods; ejbCreate me

create method in the Home interface• Business methods; every business meth

component interface must be in the bea• javax.ejb.SessionBean interface me


container

the containerary storagethe containercondary storage


Session Bean Class

Session Bean Methods:

• ejbCreate – Initialization code• ejbRemove – Clean up code before the

destroys the instance• ejbPassivate – Clean up code before

writes a stateful session bean to second• ejbActivate – Regain resources after

rebuilds a stateful session bean from se


ions (CMT)

P) or container-

code code


Entity Beans

• Represent a persistent business entity• Persisted in a data store• Must have container-managed transact• Are pooled• Can be bean-managed persistence (BM

managed persistence (CMP):• BMP – Developer writes data access• CMP – Container writes data access


rface

{,


BMP Entity Bean Home Inte

1 import javax.ejb.*;2 import java.rmi.*;3 import java.util.*;4 public interface BookHome extends javax.ejb.EJBHome5 public Book create(String anAuthor, String aTitle6 String aCallNo, String aSubject)7 throws CreateException, RemoteException;8 public String findByPrimaryKey(String theCallNo)9 throws FinderException, RemoteException;10 }


nterface

oteException;


BMP Entity Bean Component I

1 import javax.ejb.*;2 import java.rmi.*;3 import java.util.*;4 public interface Book extends EJBObject {5 public boolean checkOut(String cardID) throws Rem6 public String getAuthor() throws RemoteException;7 public String getTitle() throws RemoteException;8 public String getStatus() throws RemoteException;9 }

BMP Entity Bean Class

1 import javax.ejb.*;2 import java.util.*;3 public class BookBean4 implements javax.ejb.EntityBean {5 private String author;6 private String title;7 private String callNo;8 private String subject;9 private String status;10 private EntityContext context;1112 public String ejbCreate(String anAuthor,13 String aTitle, String aCallNo,14 String aSubject) {15 author = anAuthor;16 title = aTitle;17 callNo = aCallNo;18 subject = aSubject;19 // Do an insert into the database


20 // Return the primary key21 return aCallNo;22 }23 public String ejbPostCreate(String anAuthor,24 String aTitle, String aCallNo,25 String aSubject) {26 // There must be an ejbPostCreate() method for27 // every ejbCreate() method which uses the28 // same parameters, even if it does nothing.29 }


3031 public void setEntityContext(EntityContext ctx)32 {33 context = ctx;34 }35 public void unsetEntityContext() { }36 public void ejbRemove() {37 // Delete the row from the database38 }39 public void ejbActivate() {40 callNo = (String) context.getPrimaryKey();41 }42 public void ejbPassivate() {43 author = null;44 title = null;45 callNo = null;46 subject = null;47 status = null;48 }


49 public void ejbLoad() {50 callNo = (String) context.getPrimaryKey();51 // Do a database select and initialize the data52 // members of the bean with the data53 }5455 public void ejbStore() {56 // Do a database update based on the content57 // of the data members58 }


59 public String findByPrimaryKey60 (String theCallNo) throws FinderException {61 boolean found = true;62 // Do query using theCallNo.63 // if unsuccessful, set found to false.64 if(found == false)65 throw new FinderException66 (theCallNo + "not found in database");67 else68 return theCallNo;69 }70 public boolean checkOut(String cardID) {71 boolean result = false;72 // Process check out request73 return result;74 }75 public String getAuthor() {76 return author;77 }


78 public String getTitle() {79 return title;80 }81 public String getStatus() {82 return status;83 }84 }


dte method in

ery findXXX in

thod in then class.


Entity Beans

A BMP bean must contain:

• A codeless no argument constructor.• The persistent fields.• Home related methods – ejbCreate an

ejbPostCreate method for every creathe Home interface. ejbFindXXX for evthe Home interface.

• Business methods – Every business mecomponent interface must be in the bea

• One or more javax.ejb.EntityBeaninterface methods.


containerary storage containercondary storage


Entity Beans

Entity Bean Methods:

• ejbCreate – Inserts a row• ejbRemove – Deletes a row• ejbPassivate – Clean up code before

writes a stateful session bean to second• ejbActivate – Regain resources after

rebuilds a stateful session bean from se


efore container

beanatabase


Entity Beans

Entity Bean Methods:

• setEntityContext – Constructor code• unsetEntityContext– Cleanup code b

destroys instance• ejbLoad – Puts data from database into• ejbStore – Puts data from bean into d


rface

ring cardID)


CMP Entity Bean Home Inte

1 import javax.ejb.*;2 import java.rmi.*;34 public interface PatronHome extends EJBHome {5 public Patron create(String name, String addr, St6 throws RemoteException, CreateException;7 public String findByPrimaryKey(String cardID)8 throws RemoteException, FinderException;9 }


nterface

ption;


CMP Entity Bean Component I

1 import javax.ejb.*;2 import java.util.*;3 import java.rmi.*;45 public interface Patron extends EJBObject {6 public String getName() throws RemoteException;7 public Collection getHoldings() throws RemoteExce8 public float getFines() throws RemoteException;9 }


ean {


CMP Entity Bean Class

1 import javax.ejb.*;2 import java.util.*;3 import java.rmi.*;45 public abstract class PatronBean implements EntityB6 private EntityContext context;7 public String ejbCreate(String name,8 String addr, String cardID) {9 setName(name);10 setAddress(addr);11 setLibCardNo(cardID);12 return getLibCardNo();13 }14 public void ejbPostCreate(String name,15 String addr, String cardID) {16 }17 public void setEntityContext(EntityContext ctx) {18 context = ctx;19 }

CMP Entity Bean Class

20 public void unsetEntityContext() { }21 public void ejbRemove() { }22 public void ejbActivate() {}23 public void ejbPassivate() {}24 public void ejbLoad() {}25 public void ejbStore() {}26 public abstract String getName();27 public abstract void setName(String name);28 public abstract String getLibCardNo();29 public abstract void setLibCardNo(String lcn);30 public abstract String getAddress();31 public abstract void setAddress(String addr);32 }


persistent fieldsdte method in

thod in then classhods


Entity Beans

A CMP bean must contain:

• A codeless no argument constructor• Abstract getters and setters in place of • Home related methods – ejbCreate an

ejbPostCreate method for every creathe Home interface.

• Business methods – Every business mecomponent interface must be in the bea

• javax.ejb.EntityBean interface met


he JMS API

ts

B

B


Message-Driven Beans

• Are asynchronously invoked through t• Have no home or component interface• Are similar to stateless session beans:

• Hold no conversational state• Pooled• Handle requests from multiple clien

JMS ClientJMS

MessageTopic

MD

MD


ss


Message-Driven Bean Cla

1 import java.io.Serializable;2 import java.rmi.*;3 import javax.ejb.*;4 import javax.naming.*;5 import javax.jms.*;6 public class PurchaseOrderMakerBean7 implements MessageDrivenBean, MessageListener {8 private MessageDrivenContext mdContext;9 public void setMessageDrivenContext(10 MessageDrivenContext mdc) {11 mdContext = mdc;12 }13 public void ejbCreate() { }14 public void onMessage(Message inMessage) {15 try {16 if (inMessage instanceof TextMessage) {17 TextMessage msg =(TextMessage) inMessage;18 // Extract data from msg and create order19 } else {


ss


Message-Driven Bean Cla

20 System.out.println("Wrong message type “21 + inMessage.getClass().getName());22 }23 } catch (Exception e) {24 e.printStackTrace();25 mdContext.setRollbackOnly();26 }27 }28 public void ejbRemove() { }29 }


face methods:

nally save a

face method:ss a message

dard JMS client


Message-Driven Beans

Must contain:

• A codeless no argument constructor• javax.ejb.MessageDrivenBean inter

• ejbCreate – Initialization code• setMessageDrivenContext – Optio

reference to the context• A javax.jms.MessageListener inter

onMessage – Code for how to proce

There are no interfaces, and the client is a stan


nology

thout rewriting

JNDI.


Understanding JDBC™ Tech

• Allows access to multiple databases wicode

• Steps for database access:1. Look up the DataSource object using2. Get a connection.3. Create a statement.4. Execute a query.5. Process the results.6. Close the connection.


ons on the

2ee/jcbs/ds1")

Connection

ce


JDBC Technology Class InteractiJ2EE Platform

lookup("java:/j2ee/jcbs/ds1") lookup("java:/j

JNDI

DataSource

Connection

StatementStatement Statement

ResultSet ResultSet

Connection

Statement

ResultSet

DataSour


taSource


JDBC Technology Using the DaClass

1 import java.sql.*;2 import javax.sql.*;3 import java.util.*;4 import javax.naming.*;56 public class CatalogSearcher {7 DataSource ds;8 Connection conn;9 PreparedStatement stmt;10 ResultSet rs;11 InitialContext context;12 public static void main(String[] args) {13 CatalogSearcher cs = new CatalogSearcher();14 cs.search("Lewis, C. S.");15 }16 public CatalogSearcher() {17 try {18 context = new InitialContext();


taSource



19 ds = (DataSource)context.lookup20 ("java:comp/env/jdbc/catalog");21 } catch(NamingException ne) {22 System.out.println23 ("JNDI failure: " + ne.getMessage());24 System.exit(1);25 }26 }27 public Collection search(String authorName) {28 ArrayList al = new ArrayList();29 try {30 conn = ds.getConnection();31 stmt = conn.prepareStatement(32 "select * from Catalog where author = ?");33 stmt.setString(1, authorName);34 ResultSet rs = stmt.executeQuery();35 int x = 0;36 while(rs.next() == true) {


taSource



37 String title = rs.getString("Title");38 String pub = rs.getString("Publisher");39 String date = rs.getString("Date");40 String callNo = rs.getString("CallNo");41 Material m = new Material42 (title, pub, date, callNo);43 al.add(x, m); // Add item from44 }45 stmt.close();46 conn.close();47 } catch(SQLException sqle) {48 System.out.println49 ("SQL Error: " + sqle.getMessage());50 sqle.printStackTrace();51 }52 return al;53 }54 }


rchitecture

a wide variety

the ability toerver(RAR) package, Architecture


Understanding J2EE Connector A

• J2EE applications might need to accessof enterprise information systems (EIS)

• EIS integration components might needintegrate with the services of the J2EE s

• The vendor supplies a resource archivewhich conforms to the J2EE Connector(J2EE CA) specification.

• Benefits:• Fewer restrictions on the code• Full integration with the J2EE server• Can support CCI


rchitecture

y services of the



Resource adapters can integrate with these keapplication server:

• Transaction management• Resource pooling• Security

EIS

Enterprise Bean

Managers:TransactionConnectionSecurity

System Contract Resource Adapter

Web Component

Application Contract

Application Contract

J2EE Technology Server


rchitecture

the JDBC APIis API to

raged to

pplication

ire CCI.

some API calls



• CCI is a set of interfaces that resemble interfaces. The J2EE components use thcommunicate with the EIS.

• CCI support is not compulsory:• Resource adapter vendors are encou

implement CCI.• Vendors can provide an alternative a

contract.• Some resource adapters do not requ

The use of CCI does not completely eliminatethat are specific to the legacy system.


ing enterprise

2EE include:


Summary

• J2EE platform is a framework for buildapplications using Java technology

• The major technologies supported by J• Java RMI• Java IDL• JNDI API• Java Servlet API• JavaServer Pages• JMS API• EJB technology• JDBC technology

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