Java远程方法调用（RMI）

Java远程方法调用（Java Remote Method Invocation, RMI）支持一个JVM中的对象调用另一个JVM对象的方法，而这两个JVM可以分布在不同的主机上，为Java的分布式应用提供了支持。

 

1.首先，定义一个远程调用接口，该接口必须实现java.rmi.Remote接口，接口的方法声明要抛出java.rmi.RemoteException

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

public interface HelloRemote extends Remote {

    String sayHello(UserRemote user)throws RemoteException;

}

 

 

import java.io.Serializable;

public class User implements Serializable {

    private static final long serialVersionUID = 3553604278956856032L;

    private String name;

    public String getName() {
        return name;
    }

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

}

 2.实现接口并继承UnicastRemoteObject

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

public class HelloRemoteImpl extends UnicastRemoteObject implements HelloRemote {

    private static final long serialVersionUID = -6209023821784985143L;
    
    protected HelloRemoteImpl() throws RemoteException {
        super();
    }

    @Override
    public String sayHello(User user) throws RemoteException {
        return "Hello, " + user.getName();
    }

}

 3.注册该服务并启动

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

public class RemoteServer {

    public static void main(String[] args) {
        try {
//            System.setProperty("java.rmi.server.hostname", "10.0.0.249");
            LocateRegistry.createRegistry(5590);
            HelloRemoteImpl server = new HelloRemoteImpl();
            Naming.rebind("//10.0.0.249:5590/HelloRemote", server);
            System.out.println("server start……");
        } catch (RemoteException e) {
            e.printStackTrace();
        } catch (MalformedURLException e) {
            e.printStackTrace();
        }
    }

}

 

5.调用RMI服务

package com.lanhuidong.client;

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

public class RMIClient {
    
    public static void main(String[] args) {
        String url = "//10.0.0.249:5590/HelloRemote";
        try {
            HelloRemote helloRemote = (HelloRemote) Naming.lookup(url);
            User user = new User();
            user.setName("RMI");
            System.out.println(helloRemote.sayHello(user));
        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (RemoteException e) {
            e.printStackTrace();
        } catch (NotBoundException e) {
            e.printStackTrace();
        }

    }
}

 

 

在实际项目中，可能项目使用了Spring等框架，下面是spring的rmi服务

1定义接口（不用继承任何其它接口）

public interface UserRmiService {
    public String sayHello(User user);
}

 

import java.io.Serializable;

public class User implements Serializable{

    private static final long serialVersionUID = 8550373205815267923L;
    private String userName;

    public String getUserName() {
        return userName;
    }

    public void setUserName(String userName) {
        this.userName = userName;
    }

}

 2.实现该接口

public class UserRmiServiceImpl implements UserRmiService {

	@Override
	public String sayHello(User user) {
		return "Hello, " + user.getUserName();
	}

}

 

3.在applicationContext.xml中配置

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="
http://www.springframework.org/schema/beans 
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">

	<bean id="userRmiServiceImpl" class="com.darcy.rmi.service.impl.UserRmiServiceImpl"/>
	<bean id="userRmi" class="org.springframework.remoting.rmi.RmiServiceExporter">
		<property name="service" ref="userRmiServiceImpl" />
		<property name="serviceName" value="userRmi" />
		<property name="serviceInterface" value="com.darcy.rmi.service.UserRmiService" />
		<property name="registryPort" value="9999" />
	</bean>
</beans>

 4.启动服务

import org.springframework.context.support.ClassPathXmlApplicationContext;

public class ServerTest {

	public static void main(String[] args) {
                               System.setProperty("java.rmi.hostname", "10.0.0.249"); 
		new ClassPathXmlApplicationContext("applicationContext-Server.xml");
		System.out.println("server start......");
	}
}

 

5.调用服务

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class ClientTest {

    public static void main(String[] args) {
        ApplicationContext ctx = new ClassPathXmlApplicationContext("applicationContext-client.xml");
        UserRmiService ums = (UserRmiService) ctx.getBean("rmiProxy");
        User user = new User();
        user.setUserName("RMI");
        System.out.println(ums.sayHello(user));
    }
}

  applicationContext-client.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="
http://www.springframework.org/schema/beans 
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">

    <bean id="rmiProxy" class="org.springframework.remoting.rmi.RmiProxyFactoryBean">
        <property name="serviceUrl" value="rmi://127.0.0.1:9999/userRmi"/>
        <property name="ServiceInterface" value="com.darcy.rmi.service.UserRmiService" />
    </bean>
</beans>