ejb-core.htm

写给JSP初级程序员的书

              }</p>
            <p>public void ejbPassivate() {<br>
              if (verbose)<br>
              System.out.println(&quot;ejbPassivate called&quot;);<br>
              }</p>
            <p>/**<br>
              * Sets the session context.<br>
              *<br>
              * @param SessionContext<br>
              */<br>
              public void setSessionContext(SessionContext ctx) { <br>
              if (verbose)<br>
              System.out.println(&quot;setSessionContext called&quot;);<br>
              this.ctx = ctx;<br>
              }</p>
            <p>/**<br>
              * This method corresponds to the create method in<br>
              * the home interface HelloHome.java. <br>
              * The parameter sets of the two methods are <br>
              * identical. When the client calls <br>
              * HelloHome.create(), the container allocates an <br>
              * instance of the EJBean and calls ejbCreate(). <br>
              */ <br>
              public void ejbCreate () {<br>
              if (verbose)<br>
              System.out.println(&quot;ejbCreate called&quot;);<br>
              }<br>
              /**<br>
              * **** HERE IS THE BUSINESS LOGIC *****<br>
              * the getHello just return a &quot;Hello World&quot; string.<br>
              */<br>
              public String getHello()<br>
              throws RemoteException<br>
              {<br>
              return(&quot;Hello World&quot;);<br>
              }<br>
              }</p>
            <p>5、创建ejb-jar.xml文件<br>
              　　ejb-jar.xml文件是EJB的部署描述文件，包含EJB的各种配置信息，如是有状态Bean(Stateful Bean) 
              还是无状态Bean(Stateless Bean)，交易类型等。ejb-jar.xml文件的详细信息请参阅EJB规范。以下是HelloBean的配置文件：<br>
              &lt;?xml version=&quot;1.0&quot;?&gt;<br>
              &lt;!DOCTYPE ejb-jar PUBLIC &quot;-//Sun Microsystems Inc.//DTD 
              Enterprise JavaBeans 1.2//EN&quot; &quot;http://java.sun.com/j2ee/dtds/ejb-jar_1_2.dtd&quot;&gt;<br>
              &lt;ejb-jar&gt;<br>
              &lt;enterprise-beans&gt;<br>
              &lt;session&gt;<br>
              &lt;ejb-name&gt;Hello&lt;/ejb-name&gt;<br>
              &lt;home&gt;ejb.hello.HelloHome&lt;/home&gt;<br>
              &lt;remote&gt;ejb.hello.Hello&lt;/remote&gt;<br>
              &lt;ejb-class&gt;ejb.hello.HelloBean&lt;/ejb-class&gt;<br>
              &lt;session-type&gt;Stateless&lt;/session-type&gt;<br>
              &lt;transaction-type&gt;Container&lt;/transaction-type&gt;<br>
              &lt;/session&gt; <br>
              &lt;/enterprise-beans&gt;<br>
              &lt;assembly-descriptor&gt;<br>
              &lt;container-transaction&gt;<br>
              &lt;method&gt;<br>
              &lt;ejb-name&gt;Hello&lt;/ejb-name&gt;<br>
              &lt;method-name&gt;*&lt;/method-name&gt;<br>
              &lt;/method&gt;<br>
              &lt;trans-attribute&gt;Required&lt;/trans-attribute&gt;<br>
              &lt;/container-transaction&gt; <br>
              &lt;/assembly-descriptor&gt;<br>
              &lt;/ejb-jar&gt;</p>
            <p>6、编译和部署<br>
              编译Java源文件并将编译后class和ejb-jar.xml打包到Hello.jar <br>
              mkdir build<br>
              mkdir build/META-INF<br>
              cp ejb-jar.xml build/META-INF<br>
              javac -d build *.java<br>
              cd build<br>
              jar cvf Hello.jar META-INF ejb<br>
              cd .. <br>
              用EJB工具生成可部署到Apusic Application Server中运行的jar文件: <br>
              java com.apusic.ejb.utils.EJBGen -d /usr/apusic/classes/Hello.jar 
              build/Hello.jar <br>
              增加/usr/apusic/classes/Hello.jar到CLASSPATH中 <br>
              将Hello.jar加入到Apusic Application Server配置文件中。在/usr/apusic/config/server.xml 
              加入以下几行： <br>
              &lt;module&gt;<br>
              &lt;ejb&gt;<br>
              &lt;ejb-uri&gt;classes/Hello.jar&lt;/ejb-uri&gt;<br>
              &lt;bean&gt;<br>
              &lt;ejb-name&gt;Hello&lt;/ejb-name&gt;<br>
              &lt;jndi-name&gt;HelloHome&lt;/jndi-name&gt;<br>
              &lt;/bean&gt;<br>
              &lt;/ejb&gt;<br>
              &lt;/module&gt;<br>
              启动服务器 <br>
              java -Xms64m com.apusic.server.Main -root /usr/apusic</p>
            <p>7、写客户端调用程序<br>
              　　您可以从Java Client，JSP，Servlet或别的EJB调用HelloBean。 <br>
              　　调用EJB有以下几个步骤： <br>
              　　通过JNDI(Java Naming Directory Interface)得到EJB Home Interface <br>
              　　通过EJB Home Interface 创建EJB对象，并得到其Remote Interface <br>
              　　通过Remote Interface调用EJB方法 </p>
            <p>以下是一个从Java Client中调用HelloBean的例子： <br>
              package ejb.hello;</p>
            <p>import javax.naming.Context;<br>
              import javax.naming.InitialContext;<br>
              import java.util.Hashtable;<br>
              import javax.ejb.*;<br>
              import java.rmi.RemoteException;</p>
            <p>/**<br>
              * @author Copyright (c) 2000 by Apusic, Inc. All Rights Reserved.<br>
              */<br>
              public class HelloClient{<br>
              public static void main(String args[]){<br>
              String url = &quot;rmi://localhost:6888&quot;;<br>
              Context initCtx = null;<br>
              HelloHome hellohome = null;<br>
              try{<br>
              Hashtable env = new Hashtable();<br>
              env.put(Context.INITIAL_CONTEXT_FACTORY,<br>
              &quot;com.apusic.jndi.InitialContextFactory&quot;); <br>
              env.put(Context.PROVIDER_URL, url); <br>
              initCtx = new InitialContext(env);<br>
              }catch(Exception e){<br>
              System.out.println(&quot;Cannot get initial context: &quot; + e.getMessage());<br>
              System.exit(1);<br>
              }<br>
              try{<br>
              hellohome = (HelloHome)initCtx.lookup(&quot;HelloHome&quot;); <br>
              Hello hello = hellohome.create();<br>
              String s = hello.getHello();<br>
              System.out.println(s); <br>
              }catch(Exception e){<br>
              System.out.println(e.getMessage());<br>
              System.exit(1);<br>
              } <br>
              }</p>
            <p>}<br>
              运行HelloClient，可得到以下输出： <br>
              Hello World <br>
            </p>
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