07 Spring Aop1

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2008 coreservlets.com

Part 1

Originals of Slides and Source Code for Examples:

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Topics in This Section

Aspect-oriented programming concepts

Introduction

Integration with Spring IoC

Program integration using pointcuts

Java EE trainin : htt ://courses.coreservlets.com4


spec - r en e



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Aspect-Oriented Programming

Addresses broad applicationresponsibilities

Logging

Transaction management

Error management

o u ar zes respons ye.g., logging

element


Aspect-Oriented Programming

Identifies program facets Uses mechanisms beyond traditional OO models

e.g., All POJO getter methods fromcom.company.persistence package class members

Target execution point is thejoin point e.g., constructor or method invocation

rogram component n ng t e execut on target s apointcut

An aspect is a single unit associating and applying an

advice to ointcuts


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Spring AOP

Programming modelMethod-only interceptors

AdvisorCaptures advice behavior using plain POJOs

AspectJ APIs nno a ons an rary s

Advice beans are well-formed

Conform to method conventions but not special interfaces

AOP Alliance APIs

Advice beans implement interfaces

Java EE trainin : htt ://courses.coreservlets.com

8

Spring AOP Continued

PointcutAspectJ API annotations mapped to bean methods

Spring AOP XML schema pointcut declarations

AspectAspectJ advice with advice and pointcut definitions

us ng spec anno a ons

Spring AOP XML schema aspect declarations


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General Spring IoC



Spring IoC Process Develop POJO library

. , . ,coreservlets.MockCustomerQuery

Register Spring JARs spring-core.jar, spring-context.jar , spring-beans.jar , commons-logging.jar

Create the bean definitions file classpath:/coreservletsContext.xml

Register beans" " =

class="coreservlets.MockCustomerQuery" />

Inject dependencies

Initialize the container BeanFactory beanFactory = new ClassPathXmlApplicationContext(

new String[]{"classpath:/ coreservletsContext.xml"});


CustomerQuery customerQuery =

(CustomerQuery) beanFactory.getBean("customerQuery");

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Develop POJO Library

public class Customer {

private String id;

private String name;

public Customer(String id, String name){

this.id = id;

this.name = name;

public String getId() {

return id;

}

public String getName() {

return name;

}


Develop POJO Librarypublic interface CustomerQuery {

public Customer getCustomerByName(String name);

}


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Develop POJO Library

public class MockCustomerQuery implements CustomerQuery {

private List customers;

public MockCustomerQuery(Listcustomers) {

this.customers = customers;

}

for(Customer c : customers){

if(c.getName().equals(name)){

return c;

}

}

return null;


}

Create Bean Definitions

Location classpath:/coreservletsContext.xml

< eans xm ns=" ttp: www.spr ng ramewor .org sc ema eans"

xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

xsi:schemaLocation="http://www.springframework.org/schema/beans

htt : www.s rin framework.or schema beans s rin -beans-2.5.xsd">


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Register Beans and


< ean>

Access and Use Beansimport org.springframework.context.support.*;

ublic class Main

public static void main(String[]args) {

BeanFactory beanFactory =

new ClassPathXmlApplicationContext(

"/coreservletsContext.xml");


Customer customer = query.getCustomerByName("Java Joe");

System.out.println(customer);

}


Standard output

Customer id=jjoe, name=Java Joe

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pr ng



Spring AOP JARs

spring-aop.jar

aopalliance.jar

aspectjweaver.jar

cglib.jar


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Spring AOP Hello World

Identify concern

e ec o n po n s All methods exposed by coreservlets.CustomerQuery

Create advice e.g., implement org.aopalliance.intercept.MethodInterceptor

Create AOP definitions file Create file classpath:/coreservletsAopContext.xml

Registerspring-aop NS

Register advice beans

Create pointcut definitions

Identifty join points


Define aspects

20

Select Join Points

All persistence methods coreservlets.CustomerQuerymethod

implementations

public interface CustomerQuery {


}


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Select Join Points





}



return c;

}

}

return null;


}

22

Create Adviceimport org.aopalliance.intercept.MethodInterceptor;

im ort or .ao alliance.interce t.MethodInvocation

import coreservlets.Customer;

public class HelloWorldAdvice implements MethodInterceptor {

public Object invoke(MethodInvocation invocation)

return new Customer(){

public String toString(){

return "Hello World!";

}

};


}

}23

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Create AOP Definitions File

Location classpath:/coreservletsAopContext.xml



xmlns:aop="http://www.springframework.org/schema/aop"

xsi:schemaLocation="htt : www.s rin framework.or schema beans

http://www.springframework.org/schema/beans/spring-beans-2.5.xsd

http://www.springframework.org/schema/aop

http://www.springframework.org/schema/aop/spring-aop-2.5.xsd">


Register Advice Beans

" "

class="coreservlets.aop.helloworld.HelloWorldAdvice" />


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Create Pointcut Definitions

" "



< eans>

26

Define Aspects

" "


27

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Domain Beans


< ean>

Initialize Spring IoC Containerimport org.springframework.context.support.*;

public class Main {




"/coreservletsContext.xml",

" ".

...

}

}


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Access and Use Beans

import org.springframework.context.support.*;

ublic class Main


BeanFactory beanFactory =new ClassPathXmlApplicationContext(new String[]{

"/coreservletsContext.xml"});

CustomerQuery query =

" "

Omitted

classpath:/coreservletsAopContext.xml

.



}

}


Standard output

Customer id=jjoe, name=Java Joe


ublic class Main



new ClassPathXmlApplicationContext(new String[]{


"/coreservletsAopContext.xml"});




}Output overridden

by bean advisor


Standard output

Hello World!

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n egra e rocess



Integrated Process ,

Develop POJO library e.g., coreservlets.Customer,

coreservlets.CustomerQuery,coreservlets.MockCustomerQuery

Register Spring IoC and AOP JARs spring-core.jar, spring-context.jar, spring-beans.jar, spring-aop.jar,

ao alliance. aras ect weaver. arc lib. ar commons-lo in . ar

Create the bean definitions file e.g., classpath:/coreservletsContext.xml

eg s er eans e.g.,


Inject dependencies e.g.,

e.g.,

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Integrated Process,

Identify concern









Define aspects

34


Initialize the container Specify both domain bean and Spring AOP definitions paths

e.g., BeanFactory beanFactory =new ClassPathXmlApplicationContext(

"classpath:/coreservletsContext.xml",

"classpath:/coreservletsAopContext.xml"});

e.g., CustomerQuery customerQuery = (CustomerQuery)

beanFactory.getBean("customerQuery");


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ress ng e



Pointcuts

Join point Identifies a program execution point

Pointcut

Defined by using general specifications about a class system

Enclosing class Supertype

Modifier

Name

Package namespace

Method

Name


Return type

Argument types

37

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Pointcut Definition (PCD)

Keywords execution

Method signature matching expression Matching includes supertypes

within

Package and class name matching expression

Matching does not include supertypes

this

Class or supertype matching expression

Matches on the rox bean

target

Class or supertype matching expression


38

Pointcut Definition (PCD)

Keywords continued

args

Method parameter matching expression

Includes runtime supertypes

e nes w en com ne w t anot er ; e.g. arge

Also maps join point parameters to advice bean parameters

beans Bean identfier pattern matching expression

Operators

Combines expression combinations using logical operators:AND, OR,

NOT

Context @or .as ect .lan .annotation.Pointcut content


Spring AOP XML expression attribute value

39

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Execution PCD



Execution PCD Details

PCD Expression

*.

()

Expression elements Access modifier*

Enclosing package and class name pattern *

Method name pattern

Method ar ument ex ression attern

Expression example execution(java.lang.String get*())


*optional

41

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Execution PCD Guidelines

Required/optional Optional elements can be fully omitted

Required elements must be represented explicitly or using aattern; e. ., execution(* *(..))

Pattern All expression elements can be replaced fully or partially

us ng a pa ern Root expression element such as enclosing package/class name

coreservlets.CustomerQuery

coreservlets.Customer

coreservlets.Customer*

Argument sub-expression


(*)

(coreservlets.Customer*)

42

Execution PCD Guidelines

Argument sub-expression optionsZero, one, or more arguments

()

. .

(java.lang.String,java.lang.String)

(java.lang.String,java.lang.String,*)Any argument set

(..)


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Integrated Process,




ao alliance. ar as ect weaver. ar c lib. ar commons-lo in . ar


eg s er eans e.g.,



e.g.,

Integrated Process , Identify concern



Create AOP definitions file

Create file classpath:/coreservletsAopContext.xml Registerspring-aop NS


Create pointcut definitions Identifty join points


Define aspects

45

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Integrated Process,








Execution PCD Process

classpath:/coreservletsContext.xml

- >

= =


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Select Join Points

All persistence methods coreservlets.CustomerQuerymethod

implementations



}


Select Join Pointspublic class MockCustomerQuery implements CustomerQuery {




}



return c;

}

}

return null;


}

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Create Advice

import org.aopalliance.intercept.*

public class SummarizingMethodAdvice

implements MethodInterceptor {

public Object invoke(MethodInvocation inv)

throws Throwable {

...

return inv.proceed();

...

}

}


Create Advice Continuedpublic Object invoke(MethodInvocation inv) throws Throwable {

Strin buffer = inv. etMethod().toGenericStrin ()

+ ". args=" + Arrays.toString(inv.getArguments());

try{

Object returnValue = inv.proceed();

buffer += ". exit=return[" + returnValue + "]";

return returnValue;

}

buffer += " - exit=error[" + t + "]";

throw t;

}

finally{

Logger log = Logger.getLogger(inv.getThis().getClass());

log.debug(">>>" + buffer);


}

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Create AOP Definitions










Register Advice Beans


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Define Pointcuts

Execution PCD expression

Method name

pattern

Return type Method parameter type

expression

Omitted access modifier

and package/class name


Define Aspects

Advisor

reference

Pointcut

reference


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Initialize Spring IoC Container


public class Main {





" ".

...

}

}



ublic class Main




m e

classpath:/coreservletsAopContext.xm

"/coreservletsContext.xml"});



" " .

}

}Standard output


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Access and Use Beans


ublic class Main


BeanFactory beanFactory =new ClassPathXmlApplicationContext(new String[]{




" ".


}

}

Standard output

>>> public java.lang.String coreservlets.Customer.getName().

args=[]. exit=return[Java Joe]

>>> public java.lang.String coreservlets.Customer.toString().

args=[]. exit=return[Customer id=jjoe, name=Java Joe]


>>> public abstract coreservlets.Customer

coreservlets.CustomerQuery.getCustomerByName(java.lang.String).

args=[Java Joe]. exit=return[Customer id=jjoe, name=Java Joe]

Execution PCD Match Origins>>> public java.lang.String coreservlets.Customer.getName().




>>> ublic abstract coreservlets.Customer




...

public Customer getCustomerByName(String name) {

for(Customer customer : customers){

f(customer.getName().equals(name)){

return customer;

} execution(* *(..))


return null;

}

}59

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Execution PCD Match Origins










throws Throwable {

...


execution(* *(..))


u er += ". ex t=return " + returnVa ue + " ";

...

}60

Execution PCD Match Origins>>> public java.lang.String coreservlets.Customer.getName().













execution(* *(..))


CustomerQuery eanFactory.getBean "customerQuery" ;


}61

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More Execution PCD Examples

Drop access modifier aop:po n cu

expression="execution(coreservlets.Customer

coreservlets.CustomerQuery.getCustomerByName(

". .

Any access modifier and return type

ny access mo er, re urn ype an coreserv e spackage 62

More Execution PCD Examples

Any access modifier, return type, package, class, and

ny pu c ean proper y ge er me o

Any public bean property setter method


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Within PCD



Within PCD Details

PCD Expression

Expression elements Enclosing package and class name pattern

xpress on examp e within(coreservlets.MockCustomerQuery)


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Within PCD Guidelines

Match target Matches on the instantiated/concrete bean type

Does not match on target bean supertypes e.g., coreservlets.CustomerQuerywill not match on an

instantiation ofcoreservlets.MockCustomerQuery

Does not match on method signature elements

Expression supports partial or full replacement using

wildcard(s)






ao alliance. ar as ect weaver. ar c lib. ar commons-lo in . ar


eg s er eans e.g.,



e.g.,

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Integrated Process,

Identify concern









Define aspects

68









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- >

= =


Select Join Points

General coreservlets library methods coreservletspackage members

All class member methods ex ression="within(coreservlets.*)"

coreservlets.Customer

coreservlets.CustomerQuerycoreservlets.MockCustomerQuery

coreservlets.jdbc.JdbcCustomerQuery


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Create Advice

import org.aopalliance.intercept.*




throws Throwable {

...

return inv.proceed();

...

}

}


Create Advice Continuedpublic Object invoke(MethodInvocation inv) throws Throwable {



try{



return returnValue;

}


throw t;

}

finally{




}

73

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Register Advisor Beans


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Define Pointcuts

Execution PCD expression Package namespace

Class wildcard

Does not match on sub-packages

PCD expression keyword


Define Aspects

Advisor

reference

Pointcut

reference


77

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public class Main {





" ".

...

}

}



ublic class Main







" ".


}

}

Standard output






>>> public abstract coreservlets.Customer



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More Within PCD Examples

Fully-qualified classname on gura on s oun o e mp emen a on ype

- y Quietly fails to match

Interface-type Name must be within the coreservlets package and include the term

CustomerQuery


More Within PCD Examples

General package name pattern a c es on y on e mme a e mem ers o e coreserv e spac age

What's the point?


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Target PCD



Target PCD Details

PCD Expression

Expression elements Enclosing package and class name pattern

xpress on examp e target(coreservlets.CustomerQuery)

Match target Matches on the instantiated/concrete bean type

Matches on target bean supertypes

Does not match on method signature elements

Pattern support NONE

Wildcards will generate errors


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Target PCD Guidelines

Assists s av ng we - e ne nter ace types

Many concrete POJOs implementing marker interfaces Hinders Concrete types sharing no general interfaces




- >

= =


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Select Join Points

General coreservlets.CustomerQueryimplementors and methods

package coreservlets;



}


Create Adviceimport org.aopalliance.intercept.*




throws Throwable {

...return inv.proceed();

...

}

}


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Create Advice Continued

public Object invoke(MethodInvocation inv) throws Throwable {



try{Object returnValue = inv.proceed();


return returnValue;

}


throw t;

}

finally{




}

88











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Define Pointcuts

Execution PCD expression

> Fully-qualified interface typePCD expression keyword


Define Aspects

Advisor

reference

Pointcut

reference

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public class Main {





" ".

...

}

}



ublic class Main









}

} Standard output


oc us omer uery pu c a s rac coreserv e s. us omer



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More Target PCD Examples

Concrete type on gura on s oun o a par cu ar concre e ype

u y y



Wrap-up



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Summary

Manage AOP code and definitions separately


rea e e n ons e Create file classpath:/coreservletsAopContext.xml



Create pointcut definitions Identifty join points

Define as ects


Merge AOP code and definitions with domain productsat runtime96


ues ons

07 Spring Aop1

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