java远程调用rmi入门实例

      RMI是Java的一组拥护开发分布式应用程序的API。RMI使用Java语言接口定义了远程对象，它集合了Java序列化和Java远程方法协议(Java Remote Method Protocol)。简单地说，这样使原先的程序在同一操作系统的方法调用。变成了不同操作系统之间程序的方法调用。因为J2EE是分布式程序平台。它以RMI机制实现程序组件在不同操作系统之间的通信。

比方，一个EJB能够通过RMI调用Web上还有一台机器上的EJB远程方法。

    用例server端结构大概如此

    

首先定义要传送的实体类，由于要网络传输。必须实现序列化

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;
}

}

第二定义实体接口,必须继承 java.rmi.Remote

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;
}

第三，实现接口 记得继承UnicastRemoteObject

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("測试");
return user;
}

}

server端启动

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();
//注冊通讯端口
LocateRegistry.createRegistry(6600);
//注冊通讯路径
Naming.rebind("rmi://127.0.0.1:6600/userService", userService);
System.out.println("Service Start!");
}  catch (RemoteException e) {
System.out.println("创建远程对象发生异常！
");
e.printStackTrace();
} catch (AlreadyBoundException e) {
System.out.println("发生反复绑定对象异常！
");
e.printStackTrace();
} catch (MalformedURLException e) {
System.out.println("发生URL畸形异常！");
e.printStackTrace();
}
}
}

client測试，最好找还有一台机子（当然同一台机子或许，只是为了模拟真实情况，还是还有一台机子，记得iP要换）创建client。切记：相关的类的包的路径要跟server一样

比如：client的 UserService

package com.yiyuwanglu.rmi.service;

最后client调用

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{
//调用远程对象，注意RMI路径与接口必须与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();
}
}
}

先启动server端
Program
然后启动client
Client

显示结果各自是

Service Start!

client

測试