a rmi simple demo

     这个例子模拟了一个远程请求对象属性的过程。有一个远程对象Dog在网络上，现在要得到它的名字（strName）属性。程序在客户端设一个存根（Dog_Stub）类，在服务器端启动一个骨架（dog_Skeleton）类，这两个类都实现了Dog接口，Dog_Stub与 Dog_Skeleton通过Socket进行远程通信。当客户程序DogClient向Dog_Stub发出获取名字属性的请求时，Dog_Stub对象把方法名“getName()”作为一个字符串通过Socket发给远程的Dog_Skeleton对象，Dog_Skeleton对象收到这个字符串后再根据字符串的内容执行DogServer对象的getName()方法，得到Dog的名字，然后又通过Socket返回给DogStub对象。整个流程通过网络实现，但对于客户程序DogClient来讲，它并不知道真正的Dog对象在哪里，甚至也不知道这个过程通过了网络，它只知道发出的获取名字属性的请求得到了满意的结果而已。

Dog.java
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package rmi.dog;

public interface Dog {

    String getName() throws Exception;

}

DogSkeleton.java
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package rmi.dog;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.net.ServerSocket;
import java.net.Socket;

public class DogSkeleton extends Thread {
   
    public static final int PORT = 8123;
   
    public static final String GET_NAME = "getName()";
   
    static ServerSocket ss;
   
    private DogServer dogServer;
   
    DogSkeleton (final DogServer dogServer) {
        try {
            this.dogServer = dogServer;
            if (ss == null) {
                ss = new ServerSocket(PORT);
                System.out.println("Server started in port" + PORT);
                this.start();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
   
    public synchronized void run() {
        try {
            while (ss != null) {
                System.out.println("Waiting for request...");
                Socket socket = ss.accept();
                // oos must be locate before ois. remember!!!
                ObjectOutputStream oos = new ObjectOutputStream(socket.getOutputStream());
                ObjectInputStream ois = new ObjectInputStream(socket.getInputStream());
                String methodName = (String)ois.readObject();
                System.out.println("Request method name: " + methodName);
                
                if (methodName.equals(GET_NAME)) {
                    oos.writeObject(dogServer.getName());
                    oos.flush();
                    System.out.println("Wrote dog name: " + dogServer.getName() + " to client.");
                    ois.close();
                    oos.close();
                }
            }
            sleep(1000);
        } catch (IOException e) {
            e.printStackTrace();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

DogStub.java
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package rmi.dog;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.net.Socket;
import java.net.UnknownHostException;

public class DogStub implements Dog {

    public static final String SERVER_URL = "localhost";
   
    public static final int PORT = 8123;
   
    public static final String EMPTY = "";
   
    Socket socket;
   
    ObjectInputStream ois;
   
    ObjectOutputStream oos;
   
    DogStub () {
        try {
            socket = new Socket(SERVER_URL, PORT);
             // oos must be locate before ois. remember!!!
            oos = new ObjectOutputStream(socket.getOutputStream());
            ois = new ObjectInputStream(socket.getInputStream());
        } catch (UnknownHostException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
   
   
    }

    public String getName() throws Exception {
        final String GET_NAME = "getName()";
        String dogName = EMPTY;

        oos.writeObject(GET_NAME);
        oos.flush();

        dogName = (String) ois.readObject();

        return dogName;
    }

}

DogServer.java
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package rmi.dog;

public class DogServer implements Dog {

    private String name;

    DogServer(final String name) {
        this.name = name;
    }
   
    public String getName() throws Exception {
        return this.name;
    }
   
    /**
     * @param args
     */
    public static void main(String[] args) {
        new DogSkeleton(new DogServer("Tomcat"));
    }
}
 
DogClient.java
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package rmi.dog;

public class DogClient {

    /**
     * @param args
     */
    public static void main(String[] args) {
        DogStub dogStub = new DogStub();
        try {
            String dogName = dogStub.getName();
            System.out.println("The dog name is " + dogName);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

}