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(这条文章已经被阅读了 138 次) 时间：2001-04-10 00:32:34 来源：szxyz (zjxyz) 原创-IT

这里不会讨论EJB的概念，只讨论如何编写一个简单EJB，部署EJB，Weblogic与JBuilder的整合，本文先把介绍仅用文本编辑器编写一个最简单的EJB所需要的一切，以让大家一览EJB的概貌，然后才介绍如何把Weblogic与JBuilder整合起来，使用JBuilder开发Weblogic的EJB，我相信这样会得到很好的学习效果，因为这是我学习的路径，当然我会把我遇到的问题告诉大家，以免大家走弯路。

下面是一个最简单的EJB所需要的代码及XML说明，手工制作EJB的JAR包比较麻烦，在WIN2000下，我仿照例子制作了一个 build.cmd 批处理文件

weblogic-ejb-jar.xml

HelloWorldBean

100

hello.HelloWorld

HelloWorldBean
hello.HelloWorldHome
hello.HelloWorld
hello.HelloWorldBean
Stateless
Container

HelloWorldBean
*

Required

——————————————————————————–
package hello;
import java.rmi.*;
import javax.ejb.*;

public class HelloWorldBean implements SessionBean {
private SessionContext sessionContext;
public void ejbCreate() {
}
public void ejbRemove() {
}
public void ejbActivate() {
}
public void ejbPassivate() {
}
public void setSessionContext(SessionContext context) {
sessionContext = context;
}
public String getHelloWorld(){
return “Hello World!”;
}
}

——————————————————————————–
HelloWorld.java
package hello;
import java.rmi.*;
import javax.ejb.*;

public interface HelloWorld extends EJBObject {
public java.lang.String getHelloWorld() throws RemoteException;
}

——————————————————————————–
HelloWorldHome.java
package hello;
import java.rmi.*;
import javax.ejb.*;

public interface HelloWorldHome extends EJBHome {
public HelloWorld create() throws RemoteException, CreateException;
}

——————————————————————————–

HelloWorldBean.java
package hello;
import java.rmi.*;
import javax.ejb.*;

——————————————————————————–

HelloWorldBeanClient1.java
package hello;

import javax.naming.*;
import javax.rmi.PortableRemoteObject;

public class HelloWorldBeanClient1 {
private static final String ERROR_NULL_REMOTE = “Remote interface reference is null. It must be created by calling one of the Home interface methods first.”;
private static final int MAX_OUTPUT_LINE_LENGTH = 50;
private boolean logging = true;
private HelloWorldHome helloWorldHome = null;
private HelloWorld helloWorld = null;

/**Construct the EJB test client*/
public HelloWorldBeanClient1() {
long startTime = 0;
if (logging) {
log(“Initializing bean access.”);
startTime = System.currentTimeMillis();
}

try {
//get naming context
Context ctx = new InitialContext();

//look up jndi name
Object ref = ctx.lookup(“HelloWorld”);

//cast to Home interface
helloWorldHome = (HelloWorldHome) PortableRemoteObject.narrow(ref, HelloWorldHome.class);
if (logging) {
long endTime = System.currentTimeMillis();
log(“Succeeded initializing bean access.”);
log(“Execution time: ” + (endTime – startTime) + ” ms.”);
}

HelloWorld hello=helloWorldHome.create();
String str=hello.getHelloWorld();
System.out.println(str);
}
catch(Exception e) {
if (logging) {
log(“Failed initializing bean access.”);
}
e.printStackTrace();
}
}

//—————————————————————————-
// Methods that use Home interface methods to generate a Remote interface reference
//—————————————————————————-

public HelloWorld create() {
long startTime = 0;
if (logging) {
log(“Calling create()”);
startTime = System.currentTimeMillis();
}
try {
helloWorld = helloWorldHome.create();
if (logging) {
long endTime = System.currentTimeMillis();
log(“Succeeded: create()”);
log(“Execution time: ” + (endTime – startTime) + ” ms.”);
}
}
catch(Exception e) {
if (logging) {
log(“Failed: create()”);
}
e.printStackTrace();
}

if (logging) {
log(“Return value from create(): ” + helloWorld + “.”);
}
return helloWorld;
}

//—————————————————————————-
// Methods that use Remote interface methods to access data through the bean
//—————————————————————————-

public String getHelloWorld() {
String returnValue = “”;
if (helloWorld == null) {
System.out.println(“Error in getHelloWorld(): ” + ERROR_NULL_REMOTE);
return returnValue;
}
long startTime = 0;
if (logging) {
log(“Calling getHelloWorld()”);
startTime = System.currentTimeMillis();
}

try {
returnValue = helloWorld.getHelloWorld();
if (logging) {
long endTime = System.currentTimeMillis();
log(“Succeeded: getHelloWorld()”);
log(“Execution time: ” + (endTime – startTime) + ” ms.”);
}
}
catch(Exception e) {
if (logging) {
log(“Failed: getHelloWorld()”);
}
e.printStackTrace();
}

if (logging) {
log(“Return value from getHelloWorld(): ” + returnValue + “.”);
}
return returnValue;
}

//—————————————————————————-
// Utility Methods
//—————————————————————————-

private void log(String message) {
if (message.length() > MAX_OUTPUT_LINE_LENGTH) {
System.out.println(“– ” + message.substring(0, MAX_OUTPUT_LINE_LENGTH) + ” …”);
}
else {
System.out.println(“– ” + message);
}
}
/**Main method*/

public static void main(String[] args) {
HelloWorldBeanClient1 client = new HelloWorldBeanClient1();
// Use the client object to call one of the Home interface wrappers
// above, to create a Remote interface reference to the bean.
// If the return value is of the Remote interface type, you can use it
// to access the remote interface methods. You can also just use the
// client object to call the Remote interface wrappers.
}
}

——————————————————————————–

build.cmd

if “” == “%JAVA_HOME%” set JAVA_HOME=java
if “” == “%WL_HOME%” set WL_HOME=weblogic
set MYSERVER=%WL_HOME%myserver
set MYCLASSPATH=%JAVA_HOME%libclasses.zip;%WL_HOME%classes;%WL_HOME%libweblogicaux.jar;%MYSERVER%clientclasses

@REM Create the build directory, and copy the deployment descriptors into it
mkdir build buildMETA-INF
copy *.xml buildMETA-INF

@REM Compile ejb classes into the build directory (jar preparation)
javac -d build -classpath %MYCLASSPATH% HelloWorld.java HelloWorldHome.java HelloWorldBean.java

@REM Make a standard ejb jar file, including XML deployment descriptors
cd build
jar cv0f std_ejb_HelloWorld.jar META-INF hello
cd ..

@REM Run ejbc to create the deployable jar file
java -classpath %MYCLASSPATH% -Dweblogic.home=%WL_HOME% weblogic.ejbc -compiler javac buildstd_ejb_HelloWorld.jar %MYSERVER%ejb_Hello.jar

@REM Compile ejb interfaces & client app into the clientclasses directory
javac -d %MYSERVER%clientclasses -classpath %MYCLASSPATH% HelloWorld.java HelloWorldHome.java HelloWorldBeanClient1.java