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Hibernate & Design PatternsA Practical Overview

BSc. Thiago OliveiraTechnical ManagerGalileo TeamCoimbra, April 14th, 2009

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Agenda

•Design Patterns

–Transfer Objects

–Data Transfer Objects

–Factories

•Hibernate Framework

•Connecting the pieces

PART IDesign Patterns & Hibernate

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What Are Design Patterns?

•In the simplest term, it’s a solution to a

design problem in particular field

•It’s define the problem, the solution, when

apply it and what are the consequences

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Transfer Objects

•Application need to exchange data with Beans/Persistence Layer trough a networkContext

•The Client invoke multiples times a get method to retrieve all necessary data•Such approach generates a network overheadProblem•Use a Transfer Object (TO) to encapsulate all the Business dataSolution

•Simplifies Entity Beans and Remote Interfaces•Transfer more Data in Fewer Remotes Calls•Reduces Network Traffic …

Consequences

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Transfer Objects

• A Transfer Object is just

a Serializable POJO

(Plain Old Java Object)

• Also called Persistent

POJO or Valuable Object

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Indentify Class “Version”.

Calculated Hash using the attributes

names and methods

signatures. It’s not a random number!

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Updatable Transfer Object Strategy

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Data Access Objects

•Access to data varies depending on the source of the data. Depends on the kind of storage (databases, flat file, so on) and vendor Implementation Context•Potential creation of dependency between the application code and the data access codeProblem

•Use a Data Access Object (DAO) to abstract and encapsulate all access to the data source. The DAO Manages the connection with the data source to obtain and store the dataSolution•Enables Transparency•Enables Easier Migration•Reduces Code Complexity in the Business Objects …

Consequences

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Data Access Objects

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Data Access Objects

•Implement the CRUD operations:

–public int insertResource(…)

–public boolean deleteResource(…)

–public ResourceTO findResource(…)

–public boolean updateResource(…)

…

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DAO – We want more flexibility

Concrete Factory

DAO – Implements the operation for a specific

Entity

Abstract Factory

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Hibernate Framework

• Hibernate is a object/relational mapping (ORM) tool for

Java

• Hibernates goal is to relieve the developer from 95% of

common data persistence related programming task

• Last Release: 3.3.1 GA

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Hibernate Framework

• It provides:

– Mapping from Java Objects to Relational Tables

– Automatic conversion from Java Types to SQL Types

– Data Query and retrieve facilities that can reduce the time

effort of development

– Sophisticated Query Options you can use pure SQL or HQL

(Hibernate Query Language )

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Hibernate Framework

• It provides:

– Transparent Persistence

– SQL generation

– Support for Transaction

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How this magic became true?

Through XML Configuration Files and

powerful API

–Hibernate Conf File (hibernate.cfg.xml)

–Mapping Files (myClass.hbm.xml)

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A connection configuration filehibernate.cfg.xml

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We don’t want to write any single configuration file by hand…

• JBoss Tools is a set of

plugins for Eclipse for

support JBoss and

related technology, like

Hibernate

•The actual stable

release is the JBoss Tools

3.0.0.GA, requires Eclipse

Ganymede 3.4.2

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Hibernate Tools for Hibernate 3.0

•Key Features

–Code Generation

–Wizards for creation of common Hibernate

files

–Support auto-completion and syntax

highlighting

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PART IIConnecting the Pieces

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Just Remembering

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A Simple ER

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A Employee Hibernate Mapping FileEmployeeTO.hbm.xml

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Yes, I Know… You want to see code…DepartmentDAO - Interface

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Yes, I Know… You want to see code…EmployeeDAO - Interface

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Yes, I Know… You want to see code…HbmDepartmentDAO – A concrete DAO

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Yes, I Know… You want to see code…HbmDAOFactory – A Concrete Factory

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Yes, I Know… You want to see code…DAOFactory – An Abstract Factory

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So we got a workspace structure like this…

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Ok, That’s beautiful… How do I use it?

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A deeper look attestInsertDepartment()

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A deeper look attestFindDepartmentById()

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A deeper look attestListDepartments()

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A deeper look attestFindDepartmentByName()

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A deeper look attestUpdateDepartment()

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A deeper look attestDeleteDepartment()

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Further Reading

•More about Hibernate & HSQL

–Hibernate Reference Document (

http://www.hibernate.org/hib_docs/v3/reference/en/pdf/hibernate_reference.p

df )

–BAUER, Christian; KING, Gavin. Java Persistence with Hibernate. Manning

Publications Co: New York, 2007

•More about Data Access Objects

–Core J2EE Patterns - Data Access Objects (

http://java.sun.com/blueprints/corej2eepatterns/Patterns/DataAccessObject.htm

l )

•More about Transfer Objects

–Core J2EE Patterns - Transfer Objects (

http://java.sun.com/blueprints/corej2eepatterns/Patterns/TransferObject.html )

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Further Reading

•More about Junit

–Unit testing with JUnit 4.x and EasyMock in Eclipse (

http://www.vogella.de/articles/JUnit/article.html )

–Junit 4.x How to (

http://pub.admc.com/howtos/junit4x/junit4x.pdf)

•More about Hibernate Tools

–Hibernate Tools Reference Guide (

http://docs.jboss.org/tools/3.0.0.GA/en/hibernatetools/pdf/Hibernatetools_Reference_

Guide.pdf

)

http://www.assembla.com/wiki/show/gps/

BSc. Thiago OliveiraTechnical Manager

thiagosilvaoliveira@gmail.com

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