从单机到分布式 -> 分布式通信 ->最基本：二进制数据传输 TCP/IP

1、基本代码

package com.mashibing.rpc.common;

import java.io.Serializable;

public class User implements Serializable {
    private static final long serialVersionUID = 1L;

    private Integer id;
    private String name;

    public User(Integer id, String name) {
        this.id = id;
        this.name = name;
    }

    public Integer getId() {
        return id;
    }

    public String getName() {
        return name;
    }

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

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

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

package com.mashibing.rpc.common;

public interface IUserService {
    public User findUserById(Integer id);
}

package com.mashibing.rpc01;


import com.mashibing.rpc.common.IUserService;
import com.mashibing.rpc.common.User;

public class UserServiceImpl implements IUserService {
    @Override
    public User findUserById(Integer id) {
        return new User(id, "Alice");
    }
}

package com.mashibing.rpc01;

import com.mashibing.rpc.common.User;

import java.io.ByteArrayOutputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.net.Socket;

public class Client {
    public static void main(String[] args) throws Exception {
        Socket s = new Socket("127.0.0.1", 8888);
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        DataOutputStream dos = new DataOutputStream(baos);
        dos.writeInt(123);

        s.getOutputStream().write(baos.toByteArray());
        s.getOutputStream().flush();

        DataInputStream dis = new DataInputStream(s.getInputStream());
        int id = dis.readInt();
        String name = dis.readUTF();
        User user = new User(id, name);

        System.out.println(user);

        dos.close();
        s.close();
    }
}

2、增加stub，提供网络接口

package com.mashibing.rpc02;

import com.mashibing.rpc.common.User;

import java.io.ByteArrayOutputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.net.Socket;

public class Stub {
    public User findUserById(Integer id) throws Exception {
        Socket s = new Socket("127.0.0.1", 8888);
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        DataOutputStream dos = new DataOutputStream(baos);
        dos.writeInt(123);

        s.getOutputStream().write(baos.toByteArray());
        s.getOutputStream().flush();

        DataInputStream dis = new DataInputStream(s.getInputStream());
        int receivedId = dis.readInt();
        String name = dis.readUTF();
        User user = new User(id, name);

        dos.close();
        s.close();
        return user;
    }
}

3、动态代理

package com.mashibing.rpc03;

import com.mashibing.rpc.common.IUserService;
import com.mashibing.rpc.common.User;

import java.io.ByteArrayOutputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.net.Socket;

/**
 * 而且Client的调用显得不是很合理（Stub里只有findById的代码），如果有个findByName的新方法，那么就又得重新改进
 * 下面这种写法解决了方法增加的问题
 */

public class Stub {
    public static IUserService getStub() {
        InvocationHandler h = new InvocationHandler() {
            @Override
            public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
                Socket s = new Socket("127.0.0.1", 8888);

                ByteArrayOutputStream baos = new ByteArrayOutputStream();
                DataOutputStream dos = new DataOutputStream(baos);
                dos.writeInt(123);

                s.getOutputStream().write(baos.toByteArray());
                s.getOutputStream().flush();

                DataInputStream dis = new DataInputStream(s.getInputStream());
                int id = dis.readInt();
                String name = dis.readUTF();
                User user = new User(id, name);

                dos.close();
                s.close();
                return user;
            }
        };
        Object o = Proxy.newProxyInstance(IUserService.class.getClassLoader(), new Class[] {IUserService.class}, h);
        return (IUserService)o;
    }
}

4、方法代理再升级

package com.mashibing.rpc04;

import com.mashibing.rpc.common.IUserService;
import com.mashibing.rpc.common.User;

import java.io.ByteArrayOutputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.ObjectOutputStream;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.net.Socket;

/**
 * 但是这里仅仅实现了findByUserId的方法代理，如果要实现其他方法的代理该怎么做呢？
 * 这里就要从协议层做出改进
 *
 * 服务器端也要做出对应处理
 */

public class Stub {
    public static IUserService getStub() {
        InvocationHandler h = new InvocationHandler() {
            @Override
            public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
                Socket s = new Socket("127.0.0.1", 8888);

                ObjectOutputStream oos = new ObjectOutputStream(s.getOutputStream());

                String methodName = method.getName();
                Class[] parametersTypes = method.getParameterTypes();
                oos.writeUTF(methodName);
                oos.writeObject(parametersTypes);
                oos.writeObject(args);
                oos.flush();


                DataInputStream dis = new DataInputStream(s.getInputStream());
                int id = dis.readInt();
                String name = dis.readUTF();
                User user = new User(id, name);

                oos.close();
                s.close();
                return user;
            }
        };
        Object o = Proxy.newProxyInstance(IUserService.class.getClassLoader(), new Class[] {IUserService.class}, h);
        return (IUserService)o;
    }




}

package com.mashibing.rpc04;

import com.mashibing.rpc.common.IUserService;
import com.mashibing.rpc.common.User;

import java.io.*;
import java.lang.reflect.Method;
import java.net.ServerSocket;
import java.net.Socket;

public class Server {
    private static boolean running = true;
    public static void main(String[] args) throws Exception {
        ServerSocket ss = new ServerSocket(8888);
        while (running) {
            Socket s = ss.accept();
            process(s);
            s.close();
        }
        ss.close();
    }

    private static void process(Socket s) throws Exception {
        InputStream in = s.getInputStream();
        OutputStream out = s.getOutputStream();
        ObjectInputStream oos = new ObjectInputStream(in);
        DataOutputStream dos = new DataOutputStream(out);

        String methodName = oos.readUTF();
        Class[] parameterTypes = (Class[])oos.readObject();
        Object[] args = (Object[])oos.readObject();

        IUserService service = new UserServiceImpl();
        Method method = service.getClass().getMethod(methodName, parameterTypes);
        User user = (User)method.invoke(service, args);



        dos.writeInt(user.getId());
        dos.writeUTF(user.getName());
        dos.flush();
    }
}

5、Object 封装

返回值用Object封装，支持任意类型