EJB 3.0 学习笔记——Entity Bean

EJB 3.0 学习笔记——Entity Bean

在EJB 3.0 学习笔记——准备工作中只是简单的搭好了EJB3.0开发的基本环境，之

后就可以开发最简单的Session Bean了，我感兴趣的还是Entity Bean，所以接下来

我想先试验一下Entity Bean。
 
一、在JBoss中配置好Data Source
我使用的是MySQL数据库，所以首先将MySQL的JDBC驱动复制到
jboss-4.0.3SP1\server\all\lib目录，然后将jboss-4.0.3SP1\docs\examples\jca

下的mysql-ds.xml作出适当修改后复制到jboss-4.0.3SP1\server\all\deploy目录

下，这是我修改后的mysql-ds.xml文件：

<? xml version="1.0" encoding="UTF-8" ?>

<!--  $Id: mysql-ds.xml,v 1.3.2.1 2004/12/01 11:46:00 schrouf Exp $  -->
<!--   Datasource config for MySQL using 3.0.9 available from:
http://www.mysql.com/downloads/api-jdbc-stable.html
-->

< datasources >
   < local-tx-datasource >
     < jndi-name > MySqlDS </ jndi-name >
     < connection-url > jdbc:mysql://localhost:3306/test </ connection-url >
     < driver-class > com.mysql.jdbc.Driver </ driver-class >
     < user-name > test </ user-name >
     < password ></ password >
     < exception-sorter-class-

name > org.jboss.resource.adapter.jdbc.vendor.MySQLExceptionSorter </ excepti

on-sorter-class-name >
     <!--  sql to call when connection is created
    <new-connection-sql>some arbitrary sql</new-connection-sql>
       -->
     <!--  sql to call on an existing pooled connection when it is obtained 

from pool 
    <check-valid-connection-sql>some arbitrary sql</check-valid-

connection-sql>
       -->

     <!--  corresponding type-mapping in the standardjbosscmp-jdbc.xml 

(optional)  -->
     < metadata >
        < type-mapping > mySQL </ type-mapping >
     </ metadata >
   </ local-tx-datasource >
</ datasources >

这样之后，JBoss下的MySQL Data Source配置完成。

二、创建数据库并编写Entity Bean代码

create table book(
id int not null auto_increment primary key,
title varchar(20) not null,
author varchar(40) not null
);
新建Java Project，导入User Library：EJB3_JBoss，以下是类代码。

// Book.java
package  ejb.bean.entity;

import  java.io.Serializable;

import  javax.persistence.Entity;
import  javax.persistence.GeneratedValue;
import  javax.persistence.GenerationType;
import  javax.persistence.Id;
import  javax.persistence.Table;

@Entity
@Table(name = " book " )
public   class  Book  implements  Serializable {
  /**
  * 
   */
  private   static   final   long  serialVersionUID  =   1L ;
  private  Integer id; 
  private  String title; 
  private  String author;
 
  public  Book() {  
   super (); 
 } 
  public  Book(Integer id, String title, String author) { 
   super ();  
   this .id  =  id;  
   this .title  =  title;  
   this .author  =  author; 
  }
 @Override
  public  String toString() { 
  
   return   " Book:  "   +  getId()  +   "  Title  "   +  getTitle()  +   "  

Author  "  + getAuthor(); 
 }
  public  String getAuthor() {
   return  author;
 }
 
 @Id @GeneratedValue(strategy = GenerationType.AUTO)
  public  Integer getId() {
   return  id;
 }
  public  String getTitle() {
   return  title;
 }
  public   void  setAuthor(String author) {
   this .author  =  author;
 }
  public   void  setId(Integer id) {
   this .id  =  id;
 }
  public   void  setTitle(String title) {
   this .title  =  title;
 }

}

三、编写一个简单的Stateless Session Bean 并进行测试

// BookTestLocal.java
package  ejb.bean.entity;

import  javax.ejb.Local;

@Local
public   interface  BookTestLocal {

  public   void  test();
}

// BookTestRemote.java
package  ejb.bean.entity;

import  javax.ejb.Remote;
@Remote
public   interface  BookTestRemote {
 
  public   void  test();

}

// BookTestBean.java
package  ejb.bean.entity;

import  javax.ejb.Stateless;
import  javax.persistence.EntityManager;
import  javax.persistence.PersistenceContext;

@Stateless
public   class  BookTestBean  implements  BookTestLocal, BookTestRemote {

 @PersistenceContext
 EntityManager em;
  public   void  test() {
   //  TODO Auto-generated method stub
  Book book  =   new  Book( null ,  " My first bean book " , 

" Sebastian " );
  em.persist(book);

 }

}

 

// Client.java
package  ejb.client.entity;

import  ejb.bean.entity. * ;


import  javax.naming.InitialContext;

/**
 * Comment
 *
 *  @author  <a href="mailto:[email protected]">Bill Burke</a>
 *  @version  $Revision: 1.1.6.7 $
  */
public   class  Client
{
    public   static   void  main(String[] args)  throws  Exception
   {
      InitialContext ctx  =   new  InitialContext();
      BookTestRemote book  =  (BookTestRemote) ctx.lookup

( " BookTestBean/remote " );

     

   
      book.test();
      
      System.out.println( " test successful!  " );

   }
}

三、其他文件
将jboss-EJB-3.0_RC5-PFD\docs\tutorial中的找到的jndi.properties、log4j.xml、builder.xml等复制到当前工程中，其中builder.xml需要修改。
//builder.xml

<? xml version="1.0" ?>

<!--  

======================================================================= 

-->
<!--  JBoss build file                                                     

   -->
<!--  

======================================================================= 

-->

< project  name ="JBoss"  default ="ejbjar"  basedir ="." >

    < property  file ="../local.properties"   />
    < property  environment ="env" />
    < property  name ="src.dir"  value ="${basedir}/src" />
    < property  name ="jboss.home"  value ="E:/Programming/Servers/jboss-

4.0.3SP1/" />
    < property  name ="jboss.server.config"  value ="all" />
    < property  name ="build.dir"  value ="${basedir}/build" />
    < property  name ="build.classes.dir"  value ="${build.dir}/classes" />

    <!--  Build classpath  -->
    < path  id ="classpath" >
       <!--  So that we can get jndi.properties for InitialContext  -->
       < pathelement  location ="${basedir}" />
       < fileset  dir ="${jboss.home}/lib" >
          < include  name ="**/*.jar" />
       </ fileset >
       < fileset  dir ="${jboss.home}/server/${jboss.server.config}/lib" >
          < include  name ="**/*.jar" />
       </ fileset >
       < fileset  dir ="${jboss.home}/server/

${jboss.server.config}/deploy/ejb3.deployer" >
          < include  name ="*.jar" />
       </ fileset >
       < fileset  dir ="${jboss.home}/server/

${jboss.server.config}/deploy/jboss-aop-jdk50.deployer" >
          < include  name ="*.jar" />
       </ fileset >
       < pathelement  location ="${build.classes.dir}" />
    </ path >

    < property  name ="build.classpath"  refid ="classpath" />

    <!--  

===================================================================  -->
    <!--  Prepares the build directory                                      

   -->
    <!--  

===================================================================  -->
    < target  name ="prepare" >
       < mkdir  dir ="${build.dir}" />
       < mkdir  dir ="${build.classes.dir}" />
    </ target >

    <!--  

===================================================================  -->
    <!--  Compiles the source code                                          

   -->
    <!--  

===================================================================  -->
    < target  name ="compile"  depends ="prepare" >
       < javac  srcdir ="${src.dir}"
         destdir ="${build.classes.dir}"
         debug ="on"
         deprecation ="on"
         optimize ="off"
         includes ="**" >
          < classpath  refid ="classpath" />
       </ javac >
    </ target >

    < target  name ="ejbjar"  depends ="compile" >
       < jar  jarfile ="build/tutorial.jar" >
          < fileset  dir ="${build.classes.dir}" >
             < include  name ="**/*.class" />
          </ fileset >
         < fileset  dir ="." >
            < include  name ="META-INF/persistence.xml" />
         </ fileset >
       </ jar >
       < copy  file ="build/tutorial.jar"  todir ="${jboss.home}/server/

${jboss.server.config}/deploy" />
    </ target >

    < target  name ="run.stateless"  depends ="ejbjar" >
       < java  classname ="ejb.client.stateless.Client"  fork ="yes"  dir ="." >
          < classpath  refid ="classpath" />
       </ java >
    </ target >
 
  < target  name ="run.stateful"  depends ="ejbjar" >
        < java  classname ="ejb.client.stateful.Client"  fork ="yes"  

dir ="." >
           < classpath  refid ="classpath" />
        </ java >
  </ target >
 
  < target  name ="run.timer"  depends ="ejbjar" >
        < java  classname ="ejb.client.timer.Client"  fork ="yes"  

dir ="." >
           < classpath  refid ="classpath" />
        </ java >
  </ target >
 
  < target  name ="run.entity"  depends ="ejbjar" >
         < java  classname ="ejb.client.entity.Client"  

fork ="yes"  dir ="." >
            < classpath  refid ="classpath" />
         </ java >
   </ target >
 

    <!--  

===================================================================  -->
    <!--  Cleans up generated stuff                                         

   -->
    <!--  

===================================================================  -->
    < target  name ="clean.db" >
       < delete  dir ="${jboss.home}/server/

${jboss.server.config}/data/hypersonic" />
    </ target >

    < target  name ="clean" >
       < delete  dir ="${build.dir}" />
       < delete  file ="${jboss.home}/server/

${jboss.server.config}/deploy/tutorial.jar" />
    </ target >


</ project >

最后，在工程目录下新建目录META-INF，在目录META-INF新建persistence.xml文件，以下是文件内容：

<? xml version="1.0" encoding="UTF-8" ?>
< persistence >
    < persistence-unit  name ="test" >
       < jta-data-source > java:/MySqlDS </ jta-data-source >
       < properties >
        < property  name ="hibernate.dialect"  

value ="org.hibernate.dialect.MySQLDialect" />        
         < property  name ="hibernate.hbm2ddl.auto"  value ="update" />
       </ properties >
    </ persistence-unit >
</ persistence >

四、运行测试
run as->ant build后，选择运行目标为run.entity->run。
运行结果：

Buildfile: D:\Programs\Java\EclipseWork\EJB3\build.xml
prepare:
compile:
ejbjar:
run.entity:
      [ java ]  test successful!
BUILD SUCCESSFUL
Total time:  9  seconds

MySQL中

select   *   from  book;

id        title                     author
1         My first bean book         Sebastian

已经成功写入。