Bagaimana untuk memanggil java dari jauh berdasarkan RMI

package cn.hu.rmi.pojo;

import java.io.Serializable;

/**
 * @Author: hu.chen
 * @Description: 因为需要序列化和反序列化，所以需要实现Serializable接口
 * @DateTime: 2021/12/26 5:05 PM
 **/
public class User implements Serializable {
    private Integer id;

    private String name;

    public Integer getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

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

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", name='" + name + '\'' +
                '}';
    }
}

package cn.hu.rmi.service;

import cn.hu.rmi.pojo.User;

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

/**
 * @Author: hu.chen
 * @Description: 需要提供服务的接口需要继承 Remote 并且所有的方法都需要抛出 RemoteException 异常
 * @DateTime: 2021/12/26 5:06 PM
 **/
public interface UserService extends Remote {


    /**
     * 所有的方法都需要抛出 RemoteException 异常
     * @param id
     * @return
     * @throws RemoteException
     */
    User getUserById(Integer id) throws RemoteException;
}

创建userservice的实现类

package cn.hu.rmi.service.impl;

import cn.hu.rmi.pojo.User;
import cn.hu.rmi.service.UserService;

import java.rmi.RemoteException;
import java.rmi.server.UnicastRemoteObject;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

/**
 * @Author: hu.chen
 * @Description: 所有的实现类都需要继承 UnicastRemoteObject 这个类
 * @DateTime: 2021/12/26 5:07 PM
 **/
public class UserServiceImpl extends UnicastRemoteObject implements UserService {

    private static Map<Integer,User> userMap=new ConcurrentHashMap<>(8);

    static {
        User user1=new User();
        user1.setId(1);
        user1.setName("张三");
        User user2=new User();
        user2.setId(2);
        user2.setName("李四");
        userMap.put(user1.getId(),user1);
        userMap.put(user2.getId(),user2);
    }

    public UserServiceImpl() throws RemoteException {
        super();
    }


    @Override
    public User getUserById(Integer id) throws RemoteException  {
        return userMap.get(id);
    }
}

package cn.hu.rmi.server;

import cn.hu.rmi.service.UserService;
import cn.hu.rmi.service.impl.UserServiceImpl;

import java.rmi.RemoteException;
import java.rmi.registry.LocateRegistry;
import java.rmi.registry.Registry;

/**
 * @Author: hu.chen
 * @Description: 服务端（服务提供者）
 * @DateTime: 2021/12/26 5:11 PM
 **/
public class RmiServer {


    public static void main(String[] args) throws RemoteException {

        // 1: 创建注册表对象，之后服务提供者暴露的服务都需要注册到这个注册表中
        Registry registry = LocateRegistry.createRegistry(8089);

        UserService userService=new UserServiceImpl();

        // 将需要提供的service服务注册到注册表中
        registry.rebind("userService",userService);


        System.err.println("服务提供者启动成功");


    }
}

package cn.hu.rmi.client;

import cn.hu.rmi.pojo.User;
import cn.hu.rmi.service.UserService;

import java.rmi.NotBoundException;
import java.rmi.RemoteException;
import java.rmi.registry.LocateRegistry;
import java.rmi.registry.Registry;

/**
 * @Author: hu.chen
 * @Description: 客户端（服务消费者）
 * @DateTime: 2021/12/26 5:18 PM
 **/
public class RmiClient {
    public static void main(String[] args) throws RemoteException, NotBoundException {

        //1: 获取远程的注册表
        Registry registry = LocateRegistry.getRegistry("127.0.0.1", 8089);

        UserService userService= (UserService) registry.lookup("userService");

        User userById = userService.getUserById(1);

        System.err.println(userById);
    }
}