servlet 调用 EJB 经典实例！

/*    文件结构：EJB端：    EJBFolderName          |          |------classes            |            |          |            |-------hello          |            |           |---------hello.class             //Remote           |            |           |---------helloHome.class    //Home          |            |           | ---------helloBean.class    //Bean           |            |          |            |--------META-INF          |                           |----------------ejb-jar.xml           //EJB配置文件            |                           |----------------MANIFEST.MF  //Manifest-Version: 1.0           Class-Path:           |            |            |-----------src                        |                       |-------hello                       |           |---------hello.java             //Remote                        |           |---------helloHome.java    //Home                       |           | ---------helloBean.java    //Bean                        |                       |--------META-INF                                     |----------------ejb-jar.xml           //servlet配置文件                                     |----------------MANIFEST.MF  //Manifest-Version: 1.0           Class-Path: servlete端：ServletFolderName          |          |----------src          |            |-------hello          |            |          |--------TestEJB.java  //被Servlet（只为目标清晰，也可直接写到Servlet内）          |            |          |            |-------TestEJBServlet.java  //一个Servlet  调用 包hello 中的方法。          |          |          |----------WebRoot                           |----------META-INF                           |                  |--------MANIFEST.MF    //Manifest-Version: 1.0       Class-Path:                            |                           |----------WEB-INF                                            |----------classes                                            |               |-----------TestEJBServlet.class                                            |               |                                             |               | -----------hello                                                |                               |----------TestEJB.class                                            |-----------lib                                                           |            |----------FirstEJB.jar   //EJB打好的一个Jar包！EJB2.0不可缺少                                               |                                                                        |------------web.xml   //Servlet配置文件              基本文件结构就是这样。结束！          */

下面是针对每个文件的详细说明：

//首先是Servlet端，Servlet有一个servlet文件，实现doGet方法和doPost方法，还有一个Servlet配置文件 web.xml//TestEJBServlet.java：import java.io.IOException;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import hello.TestEJB;public class TestEJBServlet extends HttpServlet {protected void doGet(HttpServletRequest arg0, HttpServletResponse arg1) throws ServletException, IOException {this.doPost(request,response);  //直接以页面的形式调用Servlet 调用的事doGet方法，                                                                                            //也可以直接在doGet方法中调用EJB}         public void doPost(HttpServletRequest request, HttpServletResponse response){         try{new TestEJB("iiop://localhost:2809/").test();  //调用 TestEJB.java 中的test()方法。} catch(Exception e){e.printStackTrace();}          }}
//TestEJB.java:
package hello;import javax.naming.Context;import java.util.Properties;import javax.naming.NamingException;import javax.naming.InitialContext;import javax.rmi.PortableRemoteObject;import java.rmi.RemoteException;import javax.ejb.CreateException;public class TestEJB {private static final String JNDI_NAME = "HelloEJB";  //EJB上传websphere时用的JNDI Nameprivate String url;private HelloHome home;public TestEJB(String url) throws NamingException{this.url = url;home = lookUpHome();}private Context getInitialContext() throws NamingException {Properties prop = new Properties();   prop.put(Context.INITIAL_CONTEXT_FACTORY,"com.ibm.websphere.naming.WsnInitialContextFactory");prop.put(Context.PROVIDER_URL, url);return new InitialContext(prop);}private HelloHome lookUpHome() throws NamingException{Context ctx = getInitialContext();Object home = ctx.lookup(JNDI_NAME);return (HelloHome)PortableRemoteObject.narrow(home,HelloHome.class);}public void test() throws RemoteException,CreateException,NamingException {Hello hello = (Hello)PortableRemoteObject.narrow(home.create(),Hello.class);System.out.println(hello.sayHello());}/*public static void main(String args[]) throws Exception{try{new TestEJB("iiop://localhost:2809/").test();}catch(Exception e){e.printStackTrace();}}*/}
//Servlet 配置文件 web.xml
<?xml version="1.0" encoding="UTF-8"?><web-app version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd"><servlet><servlet-name>TestEJB</servlet-name>   <servlet-class>TestEJBServlet</servlet-class> </servlet><servlet-mapping><servlet-name>TestEJBServlet</servlet-name>  //Servlet映射到web服务器上的名字<url-pattern>/servlet/TestEJBServlet</url-pattern>//Servlet映射到web服务器上的路径</servlet-mapping>  <welcome-file-list>    <welcome-file>index.jsp</welcome-file>//默认开始页面（可有可无）  </welcome-file-list></web-app>
 
接下来是EJB端：三个java文件（Home.java,Remote.java,Bean.java）和一个ejb-jar配置文件
helloHome.java(就是Home.java  本地接口)
package hello;import java.rmi.RemoteException;import javax.ejb.CreateException;import javax.ejb.EJBHome;public interface HelloHome extends EJBHome {public Hello create()throws CreateException,RemoteException;}
hello.java(就是Remote.java  远程接口)
package hello;import java.rmi.RemoteException;import javax.ejb.EJBObject;public interface Hello extends EJBObject {public String sayHello()throws RemoteException;}helloBean.java(就是Bean.java 实现类)
package hello;import java.rmi.RemoteException;import javax.ejb.EJBException;import javax.ejb.CreateException;import javax.ejb.SessionBean;import javax.ejb.SessionContext;public class HelloBean implements SessionBean {private SessionContext ctx;private String words ;public String sayHello(){System.out.println("i am in an EJB server."+words);return words;}public void ejbCreate() throws CreateException{this.words = "hello world";}public void ejbActivate() throws EJBException, RemoteException {// TODO Auto-generated method stub}public void ejbPassivate() throws EJBException, RemoteException {// TODO Auto-generated method stub}public void ejbRemove() throws EJBException, RemoteException {// TODO Auto-generated method stub}public void setSessionContext(SessionContext arg0) throws EJBException,RemoteException {this.ctx = arg0;}}
还有一个配置文件ejb-jar.xml
<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE ejb-jar PUBLIC "-//Sun Microsystems, Inc.//DTD Enterprise JavaBeans 2.0//EN" "http://java.sun.com/dtd/ejb-jar_2_0.dtd"><ejb-jar><display-name>HelloEjb</display-name><enterprise-beans><session><ejb-name>FirstEJB</ejb-name><home>hello.HelloHome</home><remote>hello.Hello</remote><ejb-class>hello.HelloBean</ejb-class><session-type>Stateless</session-type><transaction-type>Container</transaction-type></session></enterprise-beans><assembly-descriptor><container-transaction><method><ejb-name>FirstEJB</ejb-name><method-intf>Remote</method-intf><method-name>*</method-name></method><trans-attribute>Required</trans-attribute></container-transaction></assembly-descriptor></ejb-jar>
调用方法：Http://localhost:9080/Context(上下文节点)/servlet/TestEJBServlet