ZT

大跃进时代，菜鸟也能玩转EJB
曾在一个论坛上看到一个帖子“国内有些程序员拿着吓人的工资，使用吓人的技术，做着吓人的项目－－得出的结果也很吓人!”。对于J2EE开发而言，所谓的吓人的技术指的就是EJB。学会EJB就可以拿着吓人的工资，你是否也动心了呢？
EJB包括实体Bean、会话Bean、消息驱动Bean。实体Bean现在被称为ORM(对象关系映射)，是对象关系映射。会话Bean一般对应系统的一个功能模块，分为有状态Bean和无状态Bean两种；有状态bean是指在bean不同的调用方法中能保存bean状态，无状态bean不保存状态。现在一般非常建议使用无状态Bean，因为这样效率最高。
EJB的学习成本非常高，高得足以把很多人吓跑。所以会EJB的人可以拿吓人的工资，但随着Hibernate等轻量级的ORM技术的流行、Spring等轻量级的容器的兴起，这些情况正在悄悄的发生改变。特别是Spring的缔造者对EJB发表了猛烈的抨击后，EJB专家组终于被逼疯，于是吸取了Hibernate和Spring思想，制定了EJB3的规范。
如果你学过Hibernate，或懂得ORM，EntityBean就不难看懂；假如有XDoclet的基础，学EJB3真是小菜一碟。如果你是一个初学者也没关系，EJB3好简单，只要把开发环境搭建起来，你就可以进入EJB的殿堂里徜徉，欣赏其优美的ORM，慢慢地掉入沉思，也会有所悟。
环境搭建(Eclipse3.1M4+JBoss4)
1.下载并安装JDK5.0:http://java.sun.com.自己找并安装。(我安装在：C:Java)。
2.下载Eclipse3.1M4: [url]
http://www.eclipse.org/downloads/download.php?file=/eclipse/downloads/drops/S-3.1M4-200412162000/eclipse-SDK-3.1M4-win32.zip&url=ftp://gd.tuwien.ac.at/softeng/eclipse/S-3.1M4-200412162000/eclipse-SDK-3.1M4-win32.zip&mirror_id=7[/url]
。安装完JDK，Eclipse下载完解压缩就能用了。(我的是E:Eclipse)
3.下载JBoss4:http://optusnet.dl.sourceforge.net/sourceforge/jboss/jboss-4.0.0.zip。下载完解压缩就能用。(我安装在：d:JBoss4)
4.下载JBoss的EJB3插件：http://belnet.dl.sourceforge.net/sourceforge/jboss/jboss-EJB-3.0_Preview_2.zip。安装该插件的方法请参考：http://docs.jboss.org/ejb3/tutorial/installing.html。安装很简单的，把jboss-EJB-3.0_Preview_2.zip解压后，把lib下面的所有东西拷贝到{JBoss_Home}serveralldeploy下面就OK了。（我的是：D:JBoss4serveralldeploy）。
5.设置环境变量：JAVA_HOME和JBOSS_HOME。我的是：JAVA_HOME=C:Javajdk1.5.0和JBOSS_HOME=D:JBoss4
6.启动JBoss，从命令行运行：d:JBoss4binrun.bat -c all
7.打开Eclipse，新建一个project(我建的是ejb_test)，如果你看到工程下面的JRE System Library有jre1.5的字样，那就恭喜你，你的Eclipse能认出JDK5了。如果看不到，您还得按右键configure。
8.在你的工程下新建一个名为lib的目录，找到开发EJB所需要的jar，分别是：D:JBoss4lib的所有jar；D:JBoss4serveralllib的所有jar；D:JBoss4serveralldeployejb3.deployer的所有jar；把D:JBoss4serveralldeployjboss-aop.deployer这个文件用WinRAR打开解压后得的所有jar。把这些jar拷贝到新建的lib目录。
9.为了享受Eclipse自动编译的好处，你还需要把Eclipse编译java生成的class存放在如下指定的目录：在你的工程下创建一个名为build的目录，在该目录下创建名为classes的目录，然后右键选中你的工程，选中properties，把Default Output folder设置为：你的工程名字/build/classes
10.把我贴出来的ejb_test.rar解压，把所有的东东拷贝覆盖到你的工程，再刷新Eclipse。
11.环境配置完毕，为了照顾很多不会的人，配置是烦了点－－高手看了我写的东西肯定会笑死的^_^。
开发模板
EJB2下的开发我没经历过，只是看过几个EJB的Demo，我这里所贴出来的开发模板是我仿照我在Spring＋Hibernate＋XDoclet下的开发方法做的(对错否望指正)。
我贴出来的开发模板可以将其划分成三层：ORM层、Dao层、Service层。
ORM层是为对象关系映射层，是EntityBean的定义，和Hibernate差不了哪去，就是把XDoclet改成Annotation而已。
Dao层是Data Access Object层，Dao是对单个表(或Entity)的增删查改，按照惯例，使用了接口。
Service层是通过调用Dao层来对多个表(或Entity)的的负责操作。这一层我是从Spring+Hibernate移植过来的，感觉有好多问题－－总觉得通过调用Dao层这种方法的远程调用代价太高，而且怎样给SessionBean配置另一个SessionBean的实例我还没配置成功。
运行方法
1.先启动JBoss4，JBoss4的配置采用默认的设置.
2.本工程要用到junit，如果没有junit的包，你的工程出现了红色的错误提示信息。出现该错误信息时，把鼠标放在错误信息的那一行，按CTRL+1，eclipse会提示你把junit的包import进来的。保证无语法错误后，就可以运行junit测试了。
3.运行工程下的ant脚本build.xml：右键点击该文件->Run As->Ant Build。这样会打包和部署ejb到jboss服务器。
4.运行junit测试套件org.ggyy.test.AllTests.java，(右键->Run As->Junit Test)，如果能看到绿线，就恭喜你，测试通过。
调试EJB
不知道是我的孤陋寡闻，还是IDE技术本身的落后，我以前好像记得EJB无法调试的，也就是无法一步一步的调试跟踪，这是EJB饱受批评的地方。
今天我到JBoss的网站看一下，JBoss IDE 出来新版本（测试版），能够Debug EJB3.0！
JBoss IDE 的下载地址是：http://voxel.dl.sourceforge.net/sourceforge/jboss/JBossIDE-1.5-Preview-jre1.5-ALL.zip
下载后，解压，从Eclipse的Help->SoftWare Updates->Find and Update->Search New Features to install->New Local Site，然后选择刚才解压的目录进行安装，一直Next下去就OK了。[/url]

调试方法
我们使用Junit测试时，所能调试的都是远程的Bean，而远程Bean在部署的服务器的。为此，我们需要在Eclipse里面启动JBoss服务器。先把JBoss IDE面板显示出来：Windows->Show View->other..->JBoss IDE->Server Navigator。
在JBoss IDE 面板右键－>Configuration->JBoss4.0.x，按右键－>New，选择JBoss安装路径，进行其它设置就OK。
由于我们调试的都是远程程序，而我们编写的EJB的实现是经过服务器的所谓代理的，所以在Junit外面是无法单步跟踪到我们编写的EJB的实现的（这点和被Spring 拦截代理相似），所以我们必须在自己写的Bean的实现中设置断点才能调试我们的EJB。

简单看了一下 在   lomboz插件的目录下 加入 这个文件 

保存为 jboss400.server

<serverDefinition
  name="JBOSS 4.0.0"
  ejbModules="true"
  webModules="true"
  earModules="true">
<property id="serverRootDirectory"
 label="Application Server Directory:"
 type="directory"
 default="C:/java/jboss-4.0.0" />
<property id="serverAddress"
 label="Address:"
 type="string"
 default="127.0.0.1" />
<property id="serverPort"
 label="Port:"
 type="string"
 default="8080" />
<property id="serverConfig"
 label="Server Configuration (default/standard/all):"
 type="string"
 default="standard" />
<property id="classPathVariableName"
 label="Classpath Variable Name:"
 type="string"
 default="JBOSS400" />
<property id="classPath"
 label="Classpath Variable:"
 type="directory"
 default="C:/java/jboss-4.0.0" />
<serverHome>${serverRootDirectory}</serverHome>
<webModulesDeployDirectory>${serverRootDirectory}/server/${serverConfig}/deploy</webModulesDeployDirectory>
<ejbModulesDeployDirectory>${serverRootDirectory}/server/${serverConfig}/deploy</ejbModulesDeployDirectory>
<earModulesDeployDirectory>${serverRootDirectory}/server/${serverConfig}/deploy</earModulesDeployDirectory>
<jndiInitialContextFactory>org.jnp.interfaces.NamingContextFactory</jndiInitialContextFactory>
<jndiProviderUrl>jnp://${serverAddress}:1099</jndiProviderUrl>
<startClass>org.jboss.Main</startClass>
<startWorkingDirectory>${serverRootDirectory}/bin</startWorkingDirectory>
<startVmParameters></startVmParameters>
<startProgramArguments>-c ${serverConfig}</startProgramArguments>
<stopClass>org.jboss.Shutdown</stopClass>
<stopWorkingDirectory>${serverRootDirectory}/bin</stopWorkingDirectory>
<stopVmParameters></stopVmParameters>
<stopProgramArguments>-S</stopProgramArguments>
<serverClassPath>
 <jar type="variable">JDK_TOOLS</jar>
 <jar type="variable">${classPathVariableName}/bin/run.jar</jar>
 <jar type="variable">${classPathVariableName}/bin/shutdown.jar</jar>
 <jar type="variable">${classPathVariableName}/client/jboss-j2ee.jar</jar>
 <jar type="variable">${classPathVariableName}/lib/jboss-common.jar</jar>
 <jar type="variable">${classPathVariableName}/lib/namespace.jar</jar>
 <jar type="variable">${classPathVariableName}/lib/commons-httpclient.jar</jar>
 <jar type="variable">${classPathVariableName}/lib/commons-logging.jar</jar>
 <jar type="variable">${classPathVariableName}/lib/webdavlib.jar</jar>
 <jar type="variable">${classPathVariableName}/lib/concurrent.jar</jar>
 <jar type="variable">${classPathVariableName}/lib/dom4j.jar</jar>
 <jar type="variable">${classPathVariableName}/lib/jboss-jmx.jar</jar>
 <jar type="variable">${classPathVariableName}/lib/getopt.jar</jar>
 <jar type="variable">${classPathVariableName}/lib/gnu-regexp.jar</jar>
 <jar type="variable">${classPathVariableName}/lib/jboss-system.jar</jar>
 <jar type="variable">${classPathVariableName}/lib/log4j-boot.jar</jar>
 <jar type="variable">${classPathVariableName}/server/${serverConfig}/lib/activation.jar</jar>
 <jar type="variable">${classPathVariableName}/server/${serverConfig}/lib/bcel.jar</jar>
 <jar type="variable">${classPathVariableName}/server/${serverConfig}/lib/bsh-deployer.jar</jar>
 <jar type="variable">${classPathVariableName}/server/${serverConfig}/lib/cglib-full-2.0.1.jar</jar>
 <jar type="variable">${classPathVariableName}/server/${serverConfig}/lib/hibernate2.jar</jar>
 <jar type="variable">${classPathVariableName}/server/${serverConfig}/lib/hsqldb.jar</jar>
 <jar type="variable">${classPathVariableName}/server/${serverConfig}/lib/hsqldb-plugin.jar</jar>
 <jar type="variable">${classPathVariableName}/server/${serverConfig}/lib/javax.servlet.jar</jar>
 <jar type="variable">${classPathVariableName}/server/${serverConfig}/lib/javax.servlet.jsp.jar</jar>
 <jar type="variable">${classPathVariableName}/server/${serverConfig}/lib/jboss.jar</jar>
 <jar type="variable">${classPathVariableName}/server/${serverConfig}/lib/jboss-common-jdbc-wrapper.jar</jar>
 <jar type="variable">${classPathVariableName}/server/${serverConfig}/lib/jboss-hibernate.jar</jar>
 <jar type="variable">${classPathVariableName}/server/${serverConfig}/lib/jboss-j2ee.jar</jar>
 <jar type="variable">${classPathVariableName}/server/${serverConfig}/lib/jboss-jaxrpc.jar</jar>
 <jar type="variable">${classPathVariableName}/server/${serverConfig}/lib/jboss-jca.jar</jar>
 <jar type="variable">${classPathVariableName}/server/${serverConfig}/lib/jboss-jsr77.jar</jar>
 <jar type="variable">${classPathVariableName}/server/${serverConfig}/lib/jboss-management.jar</jar>
 <jar type="variable">${classPathVariableName}/server/${serverConfig}/lib/jboss-monitoring.jar</jar>
 <jar type="variable">${classPathVariableName}/server/${serverConfig}/lib/jbossmq.jar</jar>
 <jar type="variable">${classPathVariableName}/server/${serverConfig}/lib/jboss-saaj.jar</jar>
 <jar type="variable">${classPathVariableName}/server/${serverConfig}/lib/jbosssx.jar</jar>
 <jar type="variable">${classPathVariableName}/server/${serverConfig}/lib/jboss-transaction.jar</jar>
 <jar type="variable">${classPathVariableName}/server/${serverConfig}/lib/jmx-adaptor-plugin.jar</jar>
 <jar type="variable">${classPathVariableName}/server/${serverConfig}/lib/jnpserver.jar</jar>
 <jar type="variable">${classPathVariableName}/server/${serverConfig}/lib/jpl-pattern.jar</jar>
 <jar type="variable">${classPathVariableName}/server/${serverConfig}/lib/jpl-util.jar</jar>
 <jar type="variable">${classPathVariableName}/server/${serverConfig}/lib/log4j.jar</jar>
 <jar type="variable">${classPathVariableName}/server/${serverConfig}/lib/mail.jar</jar>
 <jar type="variable">${classPathVariableName}/server/${serverConfig}/lib/mail-plugin.jar</jar>
 <jar type="variable">${classPathVariableName}/server/${serverConfig}/lib/odmg-3.0.jar</jar>
 <jar type="variable">${classPathVariableName}/server/${serverConfig}/lib/properties-plugin.jar</jar>
 <jar type="variable">${classPathVariableName}/server/${serverConfig}/lib/scheduler-plugin.jar</jar>
 <jar type="variable">${classPathVariableName}/client/wsdl4j.jar</jar>
</serverClassPath>
<clientClassPath>
 <jar type="variable">${classPathVariableName}/client/avalon-framework.jar</jar>
 <jar type="variable">${classPathVariableName}/client/axis-ws4ee.jar</jar>
 <jar type="variable">${classPathVariableName}/client/commons-discovery.jar</jar>
 <jar type="variable">${classPathVariableName}/client/commons-logging.jar</jar>
 <jar type="variable">${classPathVariableName}/client/concurrent.jar</jar>
 <jar type="variable">${classPathVariableName}/client/getopt.jar</jar>
 <jar type="variable">${classPathVariableName}/client/jacorb.jar</jar>
 <jar type="variable">${classPathVariableName}/client/jaxr-client.jar</jar>
 <jar type="variable">${classPathVariableName}/client/jbossall-client.jar</jar>
 <jar type="variable">${classPathVariableName}/client/jboss-client.jar</jar>
 <jar type="variable">${classPathVariableName}/client/jboss-common-client.jar</jar>
 <jar type="variable">${classPathVariableName}/client/jbosscx-client.jar</jar>
 <jar type="variable">${classPathVariableName}/client/jboss-deployment.jar</jar>
 <jar type="variable">${classPathVariableName}/client/jbossha-client.jar</jar>
 <jar type="variable">${classPathVariableName}/client/jboss-iiop-client.jar</jar>
 <jar type="variable">${classPathVariableName}/client/jboss-j2ee.jar</jar>
 <jar type="variable">${classPathVariableName}/client/jboss-jaxrpc.jar</jar>
 <jar type="variable">${classPathVariableName}/client/jbossjmx-ant.jar</jar>
 <jar type="variable">${classPathVariableName}/client/jboss-jsr77-client.jar</jar>
 <jar type="variable">${classPathVariableName}/client/jbossmq-client.jar</jar>
 <jar type="variable">${classPathVariableName}/client/jboss-saaj.jar</jar>
 <jar type="variable">${classPathVariableName}/client/jbosssx-client.jar</jar>
 <jar type="variable">${classPathVariableName}/client/jboss-system-client.jar</jar>
 <jar type="variable">${classPathVariableName}/client/jboss-transaction-client.jar</jar>
 <jar type="variable">${classPathVariableName}/client/jboss-ws4ee-client.jar</jar>
 <jar type="variable">${classPathVariableName}/client/jmx-client.jar</jar>
 <jar type="variable">${classPathVariableName}/client/jmx-invoker-adaptor-client.jar</jar>
 <jar type="variable">${classPathVariableName}/client/jnp-client.jar</jar>
 <jar type="variable">${classPathVariableName}/client/log4j.jar</jar>
 <jar type="variable">${classPathVariableName}/client/logkit.jar</jar>
 <jar type="variable">${classPathVariableName}/client/namespace.jar</jar>
 <jar type="variable">${classPathVariableName}/client/wsdl4j.jar</jar>
</clientClassPath>
<projectClassPath>
 <jar type="variable">JDK_TOOLS</jar>
 <jar type="variable">${classPathVariableName}/bin/run.jar</jar>
 <jar type="variable">${classPathVariableName}/bin/shutdown.jar</jar>
 <jar type="variable">${classPathVariableName}/client/jboss-j2ee.jar</jar>
 <jar type="variable">${classPathVariableName}/lib/concurrent.jar</jar>
 <jar type="variable">${classPathVariableName}/lib/jboss-system.jar</jar>
 <jar type="variable">${classPathVariableName}/server/${serverConfig}/lib/bcel.jar</jar>
 <jar type="variable">${classPathVariableName}/server/${serverConfig}/lib/jboss.jar</jar>
 <jar type="variable">${classPathVariableName}/server/${serverConfig}/lib/jboss-transaction.jar</jar>
 <jar type="variable">${classPathVariableName}/server/${serverConfig}/lib/jnpserver.jar</jar>
 <jar type="variable">${classPathVariableName}/server/${serverConfig}/lib/jpl-pattern.jar</jar>
 <jar type="variable">${classPathVariableName}/server/${serverConfig}/lib/jpl-util.jar</jar>
</projectClassPath>
<adminTool>
 <web><deploy /><undeploy />
 </web>
 <ejb><deploy /><undeploy />
 </ejb>
 <ear><deploy /><undeploy />
  <webModule><deploy /><undeploy />
  </webModule>
  <ejbModule><deploy /><undeploy />
  </ejbModule>
 </ear>
</adminTool>
<adminToolPath>
</adminToolPath>
</serverDefinition>

然后lomboz的服务器选项里就会有 jboss400, 默认配置除了改 两个路径为 jboss的路径以外，还有把 standard改为 default.  当然也可以 把jbossserver目录下的 default目录复制为一个standard目录。（据 jboss的文档介绍，这里完全可以用自己的配置，不过我是不懂的啦）