RMI是Java的一組擁護開發分布式應用程序的API。RMI使用Java語言接口定義了遠程對象，它集合了Java序列化和Java遠程方法協議(Java Remote Method Protocol)。簡單地說，這樣使原先的程序在同一操作系統的方法調用。變成了不同操作系統之間程序的方法調用。因為J2EE是分布式程序平臺。它以RMI機制實現程序組件在不同操作系統之間的通信。

比方，一個EJB能夠通過RMI調用Web上還有一臺機器上的EJB遠程方法。

用例server端結構大概如此

首先定義要傳送的實體類，由於要網絡傳輸。必須實現序列化

User.java

package com.yiyuwanglu.rmi.entity;

import java.io.Serializable;

public class User implements Serializable {
	/**
	 * 
	 */
	private static final long serialVersionUID = -8400949180923337013L;
	private String id;
	private String name;
	private int age;

	

	public String getId() {
		return id;
	}

	public void setId(String id) {
		this.id = id;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;

	}

	public int getAge() {
		return age;
	}

	public void setAge(int age) {
		this.age = age;
	}

}

UserService

package com.yiyuwanglu.rmi.service;

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

import com.yiyuwanglu.rmi.entity.User;

public interface UserService extends Remote {
	public User getUserById(String id)throws RemoteException;
}

UserServiceImpl

package com.yiyuwanglu.rmi.service.impl;

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

import com.yiyuwanglu.rmi.entity.User;
import com.yiyuwanglu.rmi.service.UserService;

public class UserServiceImpl extends UnicastRemoteObject  implements UserService {

	/**
	 * 
	 */
	private static final long serialVersionUID = 6222175854495075991L;

	public UserServiceImpl() throws RemoteException {
		super();
		// TODO Auto-generated constructor stub
	}

	@Override
	public User getUserById(String id) {
		User user=new User();
		user.setId(id);
		user.setAge(100);
		user.setName("測試");
		return user;
	}

}

Program.java

package com.yiyuwanglu.rmi.program;

import java.net.MalformedURLException;
import java.nio.channels.AlreadyBoundException;
import java.rmi.Naming;  
import java.rmi.RemoteException;
import java.rmi.registry.LocateRegistry;  

import com.yiyuwanglu.rmi.service.UserService;
import com.yiyuwanglu.rmi.service.impl.UserServiceImpl;
  
public class Program{  
    public static void main(String[] args) {  
        // TODO Auto-generated method stub  
        try {  
            UserService userService=new UserServiceImpl();  
            //註冊通訊端口  
            LocateRegistry.createRegistry(6600);  
            //註冊通訊路徑  
            Naming.rebind("rmi://127.0.0.1:6600/userService", userService);  
            System.out.println("Service Start!");  
        }  catch (RemoteException e) {
            System.out.println("創建遠程對象發生異常！
");
            e.printStackTrace();
        } catch (AlreadyBoundException e) {
            System.out.println("發生反復綁定對象異常！
");
            e.printStackTrace();
        } catch (MalformedURLException e) {
            System.out.println("發生URL畸形異常！");
            e.printStackTrace();
        } 
    }  
}  

比如：client的 UserService

package com.yiyuwanglu.rmi.service;

package com.yiyuwanglu.rmi.program;

import java.rmi.Naming;

import com.yiyuwanglu.rmi.entity.User;
import com.yiyuwanglu.rmi.service.UserService;

public class Client {
	 public static void main(String[] args){  
	        try{  
	            //調用遠程對象，註意RMI路徑與接口必須與server配置一致  
	        	UserService userService=(UserService)Naming.lookup("rmi://127.0.0.1:6600/userService");  
	            User user =userService.getUserById("1245");
	             System.out.println(user.getName());
	        }catch(Exception ex){  
	            ex.printStackTrace();  
	        }  
	    }  
}

先啟動server端
Program
然後啟動client
Client

Service Start!

client

測試

java遠程調用rmi入門實例