RMI流程简述

RMI通过proxy和socket实现了远程的方法调用。让我们能方便的想调用本地方法一样调用远程的方法。

调用流程

公共包

服务端和客户端必须都有，并且包名一致

/**
 * 消息接口
 */
package core.rmi.common;
import java.rmi.Remote;
import java.rmi.RemoteException;
// Remote 接口用于标识其方法可以从非本地虚拟机上调用的接口
public interface MessageService extends Remote {

    MessageDto getMessage() throws RemoteException;
}


/**
 * 消息类，需要序列化
 */
package core.rmi.common;
import java.io.Serializable;

public class MessageDto implements Serializable {

    private static final long serialVersionUID = 1L;

    private String content;
    private String sender;
    private String receiver;

    public String getReceiver() {
        return receiver;
    }

    public void setReceiver(String receiver) {
        this.receiver = receiver;
    }

    public String getSender() {
        return sender;
    }

    public void setSender(String sender) {
        this.sender = sender;
    }

    public String getContent() {
        return content;
    }

    public void setContent(String content) {
        this.content = content;
    }
}

服务端

/**
 * 消息实现类
 */
package core.rmi.server;
import core.rmi.common.MessageDto;
import core.rmi.common.MessageService;
import java.rmi.RemoteException;
import java.rmi.server.UnicastRemoteObject;

public class MessageServiceImp extends UnicastRemoteObject implements MessageService {

    protected MessageServiceImp() throws RemoteException {
    }

    @Override
    public MessageDto getMessage() throws RemoteException {  // 网络不稳定，需要抛出异常
        MessageDto dto = new MessageDto();
        dto.setSender("server");
        dto.setReceiver("client");
        dto.setContent("this is message.");
        System.out.println("send message ... ");
        return dto;
    }
}


/**
 * 测试类
 */
package core.rmi.server;
import core.rmi.common.MessageService;
import java.rmi.Naming;
import java.rmi.registry.LocateRegistry;
import java.rmi.registry.Registry;

public class Test {

    public static void main(String[] args) {
        new Test().test();
    }

    private void test() {
        try {
            Registry registry = LocateRegistry.createRegistry(8888);
            MessageService service = new MessageServiceImp();
            Naming.rebind("rmi://127.0.0.1:8888/messageService", service);
            System.out.println("server is running ... ");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

客户端

/**
 * 测试类
 */
package core.rmi.client;
import core.rmi.common.MessageDto;
import core.rmi.common.MessageService;
import java.rmi.Naming;

public class Test {

    public static void main(String[] args) {
        new Test().test();
    }

    private void test() {
        try {
            MessageService service = (MessageService) Naming.lookup("rmi://127.0.0.1:8888/messageService");
            MessageDto message = service.getMessage();
            showMessage(message);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private void showMessage(MessageDto dto) {
        StringBuilder builder = new StringBuilder();
        builder.append("sender=").append(dto.getSender()).append(", receiver=").append(dto.getReceiver()).append(", content=").append(dto.getContent());
        System.out.println(builder.toString());
    }
}

注：

客户端、服务端、注册服务，可以在运行在三台机器上。示例中注册服务和服务端放在一起运行。
个人懒得码字，比较喜欢画图和代码搞定，如果想看详细版本可参考java RMI原理详解