RMI初探

　　RMI(Remote Method Invocation)，远程方法调用，即本地调用远程主机的服务，使用RMI能实现如同在调用本地方法似的效果，也就是说能够实现分布式应用。

 

　　一。Chat　远程方法接口需要继承Remote接口，并且远程接口的所有方法必须抛出RemoteException

 

package com.template.rmi;

import java.rmi.Remote;
import java.rmi.RemoteException;

/**
 * Created by IntelliJ IDEA.
 * User: Zhong Gang
 * Date: 11-8-4
 * Time: 下午9:04
 */
public interface Chat extends Remote {

    void send(String message) throws RemoteException;

    String receive() throws RemoteException;
}

 

　　二。ChatImpl　远程接口的实现类　需要继承UnicastRemoteObject类，并实现Chat接口

 

package com.template.rmi;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.rmi.RemoteException;
import java.rmi.server.UnicastRemoteObject;

/**
 * Created by IntelliJ IDEA.
 * User: Zhong Gang
 * Date: 11-8-4
 * Time: 下午9:05
 */
public class ChatImpl extends UnicastRemoteObject implements Chat {

    private Logger logger = LoggerFactory.getLogger(ChatImpl.class);

    protected ChatImpl() throws RemoteException {
        super();
    }

    @Override
    public void send(String message) throws RemoteException {
        logger.info("Sending a message!");
        logger.info(message);
        logger.info("Sended a message!");
    }

    @Override
    public String receive() throws RemoteException {
        logger.info("Received a message!");
        return "This is a received message content!";
    }
}

 

　　三。ChatServer　远程服务注册

 

package com.template.rmi;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.net.MalformedURLException;
import java.rmi.Naming;
import java.rmi.RemoteException;

/**
 * Created by IntelliJ IDEA.
 * User: Zhong Gang
 * Date: 11-8-4
 * Time: 下午9:10
 */
public class ChatServer implements Runnable {

    private Logger logger = LoggerFactory.getLogger(ChatServer.class);

    @Override
    public void run() {
        try {
            logger.info("Server start!");
            logger.info("Initialize chat service!");
            ChatImpl chat = new ChatImpl();
            logger.info("Bind the chat service to  the server!");
            Naming.rebind("chat", chat);
            logger.info("Server has started the chat service!");
        } catch (RemoteException e) {
            logger.error(e.getMessage());
        } catch (MalformedURLException e) {
            logger.error(e.getMessage());
        }
    }
}

 

　　四。ChatClient　本地调用远程服务

 

package com.template.rmi;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.net.MalformedURLException;
import java.rmi.Naming;
import java.rmi.NotBoundException;
import java.rmi.RemoteException;

/**
 * Created by IntelliJ IDEA.
 * User: Zhong Gang
 * Date: 11-8-4
 * Time: 下午9:10
 */
public class ChatClient implements Runnable {

    private Logger logger = LoggerFactory.getLogger(ChatClient.class);

    @Override
    public void run() {
        try {
            logger.info("Find chat service from server!");
            Chat chat = (Chat) Naming.lookup("//127.0.0.1/chat");
            logger.info("Sending a message to the server!");
            chat.send("This is a message from client to server!");
            logger.info("Sended a message to the server!");

            logger.info("Receive a message from server!");
            String message = chat.receive();
            logger.info("The message received from server is : ");
            logger.info(message);
        } catch (NotBoundException e) {
            logger.error(e.getMessage());
        } catch (MalformedURLException e) {
            logger.error(e.getMessage());
        } catch (RemoteException e) {
            logger.error(e.getMessage());
        }
    }
}

 

 

　　五。Main

 

package com.template.rmi;

/**
 * Created by IntelliJ IDEA.
 * User: Zhong Gang
 * Date: 11-8-4
 * Time: 下午10:48
 */
public class Main {

    public static void main(String[] args) {

        Runnable chatServer = new ChatServer();
        Thread server = new Thread(chatServer);
        server.run();

        Runnable chatClient = new ChatClient();
        Thread client = new Thread(chatClient);
        client.run();

    }
}

 

　　六。启动rmiregistry服务器

 

　　七。运行Main主类

 

　　八。实现效果

　　

 

　　附：如果想要正确启动远程服务，需要对ChatImpl类进行远程方法调用的编译，即使用rmic命令，生成ChatImpl的Stub，即存根。当然，如果使用的IDE，那IDE会帮我们做这一步的。其次，为了正确使用远程服务，需要确保远程方法调用服务器在正确的位置启动，即能够找到Stub存根的目录下。启动远程方法调用，需要使用rmiregistry命令。