EJB的存根和骨架的工作原理(1)
2009-01-25 00:29
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摘要:本文是作者对EJB工作原理的学习笔记,包括有RMI工作原理、Websphere实现、Weblogic实现和自己总结的理解体会,供大家参考!
一、RMI工作原理
RMI的本质就是实现在不同JVM之间的调用,它的实现方法就是在两个JVM中各开一个Stub和Skeleton,二者通过socket通信来实现参数和返回值的传递。
有关RMI的例子代码网上可以找到不少,但绝大部分都是通过extend the interface java.rmi.Remote实现,已经封装的很完善了,不免使人有雾里看花的感觉。下面的例子是我在《Enterprise JavaBeans》里看到的,虽然很粗糙,但很直观,利于很快了解它的工作原理。
1、定义一个Person的接口,其中有两个business method, getAge() 和getName()
代码:
2、Person的实现PersonServer类
代码:
3、好,我们现在要在Client机器上调用getAge()和getName()这两个business method,那么就得编写相应的Stub(Client端)和Skeleton(Server端)程序。这是Stub的实现:
代码:
注意,Person_Stub和PersonServer一样,都implements Person。它们都实现了getAge()和getName()两个business method,不同的是PersonServer是真的实现,Person_Stub是建立socket连接,并向Skeleton发请求,然后通过Skeleton调用PersonServer的方法,最后接收返回的结果。
4、骨架(Skeleton)的实现
代码:
Skeleton类extends from Thread,它长驻在后台运行,随时接收client发过来的request。并根据发送过来的key去调用相应的business method。
一、RMI工作原理
RMI的本质就是实现在不同JVM之间的调用,它的实现方法就是在两个JVM中各开一个Stub和Skeleton,二者通过socket通信来实现参数和返回值的传递。
有关RMI的例子代码网上可以找到不少,但绝大部分都是通过extend the interface java.rmi.Remote实现,已经封装的很完善了,不免使人有雾里看花的感觉。下面的例子是我在《Enterprise JavaBeans》里看到的,虽然很粗糙,但很直观,利于很快了解它的工作原理。
1、定义一个Person的接口,其中有两个business method, getAge() 和getName()
代码:
public interface Person { public int getAge() throws Throwable; public String getName() throws Throwable; } |
代码:
public class PersonServer implements Person { int age; String name; public PersonServer(String name, int age) { this.age = age; this.name = name; } public int getAge() { return age; } public String getName() { return name; } } |
代码:
//存根(stub)的实现 import java.io.ObjectOutputStream; import java.io.ObjectInputStream; import java.net.Socket; public class Person_Stub implements Person { Socket socket; public Person_Stub() throws Throwable { // connect to skeleton socket = new Socket("computer_name", 9000); } public int getAge() throws Throwable { // pass method name to skeleton ObjectOutputStream outStream = new ObjectOutputStream(socket.getOutputStream()); outStream.writeObject("age"); outStream.flush(); ObjectInputStream inStream = new ObjectInputStream(socket.getInputStream()); return inStream.readInt(); } public String getName() throws Throwable { // pass method name to skeleton ObjectOutputStream outStream = new ObjectOutputStream(socket.getOutputStream()); outStream.writeObject("name"); outStream.flush(); ObjectInputStream inStream = new ObjectInputStream(socket.getInputStream()); return (String)inStream.readObject(); } } |
4、骨架(Skeleton)的实现
代码:
import java.io.ObjectOutputStream; import java.io.ObjectInputStream; import java.net.Socket; import java.net.ServerSocket; public class Person_Skeleton extends Thread { PersonServer myServer; public Person_Skeleton(PersonServer server) { // get reference of object server this.myServer = server; } public void run() { try { // new socket at port 9000 ServerSocket serverSocket = new ServerSocket(9000); // accept stub's request Socket socket = serverSocket.accept(); while (socket != null) { // get stub's request ObjectInputStream inStream = new ObjectInputStream(socket.getInputStream()); String method = (String)inStream.readObject(); // check method name if (method.equals("age")) { // execute object server's business method int age = myServer.getAge(); ObjectOutputStream outStream = new ObjectOutputStream(socket.getOutputStream()); // return result to stub outStream.writeInt(age); outStream.flush(); } if(method.equals("name")) { // execute object server's business method String name = myServer.getName(); ObjectOutputStream outStream = new ObjectOutputStream(socket.getOutputStream()); // return result to stub outStream.writeObject(name); outStream.flush(); } } } catch(Throwable t) { t.printStackTrace(); System.exit(0); } } public static void main(String args []) { // new object server PersonServer person = new PersonServer("Richard", 34); Person_Skeleton skel = new Person_Skeleton(person); skel.start(); } } |