[Distributed-2] Custom RPC framework

The full name of RPC is remote procedure call , that is, remote procedure call. Implement calls to remote services, just like calling methods in your own services.

As shown in the figure above, what RPC needs to do is to encapsulate other steps except 1 and 6. 

In java, there are already ways to implement remote calls. It is java JMI. Its implementation depends on the Java virtual machine, because

Therefore it only supports calls from one JVM to another .

一：java RMI

Java RMI , Remote Method Invocation (Remote Method Invocation), a Java API (RPCRemote procedure call) used to implement remote procedure calls, can directly transmit serialized Java objects. Its implementation depends on the Java Virtual Machine, so it only supports calls from one JVM to another .

The code implements a method of checking users:

import com.lagou.edu.service.impl.UserServiceImpl;
import java.rmi.RemoteException;
import java.rmi.registry.LocateRegistry;
import java.rmi.registry.Registry;

/*** 服务端 */
public class RMIServer {

    public static void main(String[] args) {
        try {//1.注册Registry实例. 绑定端口
            Registry registry = LocateRegistry.createRegistry(9998);
            //2.创建远程对象
            IUserService userService = new UserServiceImpl();
            //3.将远程对象注册到RMI服务器上即(服务端注册表上)
            registry.rebind("userService", userService);
            System.out.println("---RMI服务端启动成功----");
        } catch (RemoteException e) {
            e.printStackTrace();
        }
    }
}

import com.lagou.edu.pojo.User;
import com.lagou.edu.service.IUserService;
import java.rmi.NotBoundException;
import java.rmi.RemoteException;
import java.rmi.registry.LocateRegistry;
import java.rmi.registry.Registry;

/*** 客户端 */
public class RMIClient {

    public static void main(String[] args)
        throws RemoteException, NotBoundException {
        //1.获取Registry实例
        Registry registry = LocateRegistry.getRegistry("127.0.0.1", 9998);
        //2.通过Registry实例查找远程对象
        IUserService userService = (IUserService) registry.lookup("userService");
        User user = userService.getById(2);
        System.out.println(user.getId() + "----" + user.getName());
    }
}

import com.lagou.edu.pojo.User;
import java.rmi.Remote;
import java.rmi.RemoteException;

public interface IUserService extends Remote {

    User getById(int id) throws RemoteException;
}

import com.lagou.edu.pojo.User;
import com.lagou.edu.service.IUserService;
import java.rmi.RemoteException;
import java.rmi.server.UnicastRemoteObject;
import java.util.HashMap;
import java.util.Map;

public class UserServiceImpl extends UnicastRemoteObject implements IUserService {

    Map<Object, User> userMap = new HashMap();

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

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

RMI will not be used in actual projects, because you will not really care about the ip and other information of other people's servers, and you will not maintain it yourself. The communication based on Netty is still used, such as the dubbo framework. The following simulates a custom one. 

Requirements : The client remotely calls the server to provide a method for querying the user object based on the ID .

1. Create an interface and define abstract methods. Used for contracts between consumers and providers ,

2. Create a provider that needs to listen to consumer requests and return data as agreed

3. Create a consumer, this class needs to transparently call methods that do not exist, and needs to use Netty for data communication internally

4. Provider and consumer data transmission uses json string data format

5. The provider uses netty to integrate the spring boot environment to achieve

1. Custom annotations:

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

/*** 对外暴露服务接口 */
@Target(ElementType.TYPE) // 用于接口和类上 
@Retention(RetentionPolicy.RUNTIME)// 在运行时可以获取到
public @interface RpcService {

}

2. Server implementation class:

import com.lagou.edu.annotation.RpcService;
import com.lagou.edu.pojo.User;
import com.lagou.edu.service.IUserService;
import java.util.HashMap;
import java.util.Map;
import org.springframework.stereotype.Service;

//该注解表示要注册到注册中心
@RpcService
@Service
public class UserServiceImpl implements IUserService {

    Map<Object, User> userMap = new HashMap();

    @Override
    public User getById(int id) {
        if (userMap.size() == 0) {
            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);
        }
        return userMap.get(id);
    }

}

Two: Netty simulates dubbo framework implementation

Core architecture diagram:

api layers:

Define the interface, output parameters and input parameters

IUserService:

import com.lagou.rpc.pojo.User;

/**
 * 用户服务
 */
public interface IUserService {

    /**
     * 根据ID查询用户
     *
     * @param id
     * @return
     */
    User getById(int id);
}

entity:

import lombok.Data;

@Data
public class User {
    private int id;
    private String name;
}

Enter:

/**
 * 封装的请求对象
 */
@Data
public class RpcRequest {

    /**
     * 请求对象的ID
     */
    private String requestId;
    /**
     * 类名
     */
    private String className;
    /**
     * 方法名
     */
    private String methodName;
    /**
     * 参数类型
     */
    private Class<?>[] parameterTypes;
    /**
     * 入参
     */
    private Object[] parameters;

}

 Out of parameters:

/**
 * 封装的响应对象
 */
@Data
public class RpcResponse {

    /**
     * 响应ID
     */
    private String requestId;

    /**
     * 错误信息
     */
    private String error;

    /**
     * 返回的结果
     */
    private Object result;

}

Server:

Annotate RpcService:

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

/**
 * 对外暴露服务接口
 */
@Target(ElementType.TYPE) // 用于接口和类上
@Retention(RetentionPolicy.RUNTIME)// 在运行时可以获取到
public @interface RpcService {
}

Interface implementation class:

import com.lagou.rpc.api.IUserService;
import com.lagou.rpc.pojo.User;
import com.lagou.rpc.provider.anno.RpcService;
import org.springframework.stereotype.Service;

import java.util.HashMap;
import java.util.Map;

@RpcService
@Service
public class UserServiceImpl implements IUserService {
    Map<Object, User> userMap = new HashMap();

    @Override
    public User getById(int id) {
        if (userMap.size() == 0) {
            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);
        }
        return userMap.get(id);
    }
}

 Server-side Netty startup class

package com.lagou.rpc.provider.server;

import com.lagou.rpc.provider.handler.RpcServerHandler;
import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import io.netty.handler.codec.string.StringDecoder;
import io.netty.handler.codec.string.StringEncoder;
import org.springframework.beans.factory.DisposableBean;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

/**
 * 启动类
 */
@Service
public class RpcServer implements DisposableBean {

    private NioEventLoopGroup bossGroup;

    private NioEventLoopGroup workerGroup;

    @Autowired
    RpcServerHandler rpcServerHandler;


    public void startServer(String ip, int port) {
        try {
            //1. 创建线程组
            bossGroup = new NioEventLoopGroup(1);
            workerGroup = new NioEventLoopGroup();
            //2. 创建服务端启动助手
            ServerBootstrap serverBootstrap = new ServerBootstrap();
            //3. 设置参数
            serverBootstrap.group(bossGroup, workerGroup)
                    .channel(NioServerSocketChannel.class)
                    .childHandler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel channel) throws Exception {
                            ChannelPipeline pipeline = channel.pipeline();
                            //添加String的编解码器
                            pipeline.addLast(new StringDecoder());
                            pipeline.addLast(new StringEncoder());
                            //业务处理类
                            pipeline.addLast(rpcServerHandler);
                        }
                    });
            //4.绑定端口(要同步阻塞等待)
            ChannelFuture sync = serverBootstrap.bind(ip, port).sync();
            System.out.println("==========服务端启动成功==========");
            //channel也要同步阻塞等待
            sync.channel().closeFuture().sync();
        } catch (InterruptedException e) {
            e.printStackTrace();
        } finally {
            if (bossGroup != null) {
                bossGroup.shutdownGracefully();
            }

            if (workerGroup != null) {
                workerGroup.shutdownGracefully();
            }
        }
    }


    @Override
    public void destroy() throws Exception {
        if (bossGroup != null) {
            bossGroup.shutdownGracefully();
        }

        if (workerGroup != null) {
            workerGroup.shutdownGracefully();
        }
    }
}

Business processing class RpcServerHandler:

The role of this class is:

1. Cache all custom-annotated classes to the map, and the key is the name of the interface

2. Find the specific implementation class in the map according to the interface name of the requester parameter, and then call the method reflectively according to other parameters.

package com.lagou.rpc.provider.handler;

import com.alibaba.fastjson.JSON;
import com.lagou.rpc.common.RpcRequest;
import com.lagou.rpc.common.RpcResponse;
import com.lagou.rpc.provider.anno.RpcService;
import io.netty.channel.ChannelHandler;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import org.springframework.beans.BeansException;
import org.springframework.cglib.reflect.FastClass;
import org.springframework.cglib.reflect.FastMethod;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.stereotype.Component;

import java.lang.reflect.InvocationTargetException;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;

/**
 * 服务端业务处理类
 * 1.将标有@RpcService注解的bean缓存
 * 2.接收客户端请求
 * 3.根据传递过来的beanName从缓存中查找到对应的bean
 * 4.解析请求中的方法名称. 参数类型 参数信息
 * 5.反射调用bean的方法
 * 6.给客户端进行响应
 */
@Component
@ChannelHandler.Sharable
public class RpcServerHandler extends SimpleChannelInboundHandler<String> implements ApplicationContextAware {

    private static final Map SERVICE_INSTANCE_MAP = new ConcurrentHashMap();

    /**
     * 1.将标有@RpcService注解的bean缓存
     *
     * @param applicationContext
     * @throws BeansException
     */
    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        Map<String, Object> serviceMap = applicationContext.getBeansWithAnnotation(RpcService.class);
        if (serviceMap != null && serviceMap.size() > 0) {
            Set<Map.Entry<String, Object>> entries = serviceMap.entrySet();
            for (Map.Entry<String, Object> item : entries) {
                Object serviceBean = item.getValue();
                if (serviceBean.getClass().getInterfaces().length == 0) {
                    throw new RuntimeException("服务必须实现接口");
                }
                //默认取第一个接口作为缓存bean的名称
                String name = serviceBean.getClass().getInterfaces()[0].getName();
                SERVICE_INSTANCE_MAP.put(name, serviceBean);
            }
        }
    }

    /**
     * 通道读取就绪事件
     *
     * @param channelHandlerContext
     * @param msg
     * @throws Exception
     */
    @Override
    protected void channelRead0(ChannelHandlerContext channelHandlerContext, String msg) throws Exception {
        //1.接收客户端请求- 将msg转化RpcRequest对象
        RpcRequest rpcRequest = JSON.parseObject(msg, RpcRequest.class);
        RpcResponse rpcResponse = new RpcResponse();
        rpcResponse.setRequestId(rpcRequest.getRequestId());
        try {
            //业务处理
            rpcResponse.setResult(handler(rpcRequest));
        } catch (Exception exception) {
            exception.printStackTrace();
            rpcResponse.setError(exception.getMessage());
        }
        //6.给客户端进行响应
        channelHandlerContext.writeAndFlush(JSON.toJSONString(rpcResponse));

    }

    /**
     * 业务处理逻辑
     *
     * @return
     */
    public Object handler(RpcRequest rpcRequest) throws InvocationTargetException {
        // 3.根据传递过来的beanName从缓存中查找到对应的bean
        Object serviceBean = SERVICE_INSTANCE_MAP.get(rpcRequest.getClassName());
        if (serviceBean == null) {
            throw new RuntimeException("根据beanName找不到服务,beanName:" + rpcRequest.getClassName());
        }
        //4.解析请求中的方法名称. 参数类型 参数信息
        Class<?> serviceBeanClass = serviceBean.getClass();
        String methodName = rpcRequest.getMethodName();
        Class<?>[] parameterTypes = rpcRequest.getParameterTypes();
        Object[] parameters = rpcRequest.getParameters();
        //5.反射调用bean的方法- CGLIB反射调用
        FastClass fastClass = FastClass.create(serviceBeanClass);
        FastMethod method = fastClass.getMethod(methodName, parameterTypes);
        return method.invoke(serviceBean, parameters);
    }


}

Server startup class:

package com.lagou.rpc.provider;

import com.lagou.rpc.provider.server.RpcServer;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class ServerBootstrapApplication implements CommandLineRunner {


    @Autowired
    RpcServer rpcServer;

    public static void main(String[] args) {
        SpringApplication.run(ServerBootstrapApplication.class, args);
    }

    @Override
    public void run(String... args) throws Exception {
        new Thread(new Runnable() {
            @Override
            public void run() {
                rpcServer.startServer("127.0.01", 8899);
            }
        }).start();
    }
}

Note: CommandLineRunner is provided by springboot and is executed after spring initialization is completed. For specific usage, please refer to: https://www.cnblogs.com/yanxiaoguo/p/16167221.html

client: 

Netty startup class:

package com.lagou.rpc.consumer.client;

import com.lagou.rpc.consumer.handler.RpcClientHandler;
import io.netty.bootstrap.Bootstrap;
import io.netty.channel.*;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;
import io.netty.handler.codec.string.StringDecoder;
import io.netty.handler.codec.string.StringEncoder;

import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;

/**
 * 客户端
 * 1.连接Netty服务端
 * 2.提供给调用者主动关闭资源的方法
 * 3.提供消息发送的方法
 */
public class RpcClient {

    private EventLoopGroup group;

    private Channel channel;

    private String ip;

    private int port;

    private RpcClientHandler rpcClientHandler = new RpcClientHandler();

    private ExecutorService executorService = Executors.newCachedThreadPool();

    public RpcClient(String ip, int port) {
        this.ip = ip;
        this.port = port;
        initClient();
    }

    /**
     * 初始化方法-连接Netty服务端
     */
    public void initClient() {
        try {
            //1.创建线程组
            group = new NioEventLoopGroup();
            //2.创建启动助手
            Bootstrap bootstrap = new Bootstrap();
            //3.设置参数
            bootstrap.group(group)
                    .channel(NioSocketChannel.class)
                    .option(ChannelOption.SO_KEEPALIVE, Boolean.TRUE)
                    .option(ChannelOption.CONNECT_TIMEOUT_MILLIS, 3000)
                    .handler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel channel) throws Exception {
                            ChannelPipeline pipeline = channel.pipeline();
                            //String类型编解码器
                            pipeline.addLast(new StringDecoder());
                            pipeline.addLast(new StringEncoder());
                            //添加客户端处理类
                            pipeline.addLast(rpcClientHandler);
                        }
                    });
            //4.连接Netty服务端
            channel = bootstrap.connect(ip, port).sync().channel();
        } catch (Exception exception) {
            exception.printStackTrace();
            if (channel != null) {
                channel.close();
            }
            if (group != null) {
                group.shutdownGracefully();
            }
        }
    }

    /**
     * 提供给调用者主动关闭资源的方法
     */
    public void close() {
        if (channel != null) {
            channel.close();
        }
        if (group != null) {
            group.shutdownGracefully();
        }
    }

    /**
     * 提供消息发送的方法
     */
    public Object send(String msg) throws ExecutionException, InterruptedException {
        rpcClientHandler.setRequestMsg(msg);
        Future submit = executorService.submit(rpcClientHandler);
        return submit.get();
    }
}

 Business processing class RpcClientHandler:

package com.lagou.rpc.consumer.handler;

import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;

import java.util.concurrent.Callable;

/**
 * 客户端处理类
 * 1.发送消息
 * 2.接收消息
 */
public class RpcClientHandler extends SimpleChannelInboundHandler<String> implements Callable {

    ChannelHandlerContext context;
    //发送的消息
    String requestMsg;

    //服务端的消息
    String responseMsg;

    public void setRequestMsg(String requestMsg) {
        this.requestMsg = requestMsg;
    }

    /**
     * 通道连接就绪事件
     *
     * @param ctx
     * @throws Exception
     */
    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        context = ctx;
    }

    /**
     * 通道读取就绪事件
     *
     * @param channelHandlerContext
     * @param msg
     * @throws Exception
     */
    @Override
    protected synchronized void channelRead0(ChannelHandlerContext channelHandlerContext, String msg) throws Exception {
        responseMsg = msg;
        //唤醒等待的线程
        notify();
    }

    /**
     * 发送消息到服务端
     *
     * @return
     * @throws Exception
     */
    @Override
    public synchronized Object call() throws Exception {
        //消息发送
        context.writeAndFlush(requestMsg);
        //线程等待
        wait();
        return responseMsg;
    }
}

Proxy class: When the client actually calls the interface, each client is actually the proxy object of the interface used.

When the proxy class executes the invoke method, the RpcClient object is actually created to connect to the server for communication.

package com.lagou.rpc.consumer.proxy;

import com.alibaba.fastjson.JSON;
import com.lagou.rpc.common.RpcRequest;
import com.lagou.rpc.common.RpcResponse;
import com.lagou.rpc.consumer.client.RpcClient;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.util.UUID;

/**
 * 客户端代理类-创建代理对象
 * 1.封装request请求对象
 * 2.创建RpcClient对象
 * 3.发送消息
 * 4.返回结果
 */
public class RpcClientProxy {

    public static Object createProxy(Class serviceClass) {
        return Proxy.newProxyInstance(Thread.currentThread().getContextClassLoader(),
                new Class[]{serviceClass}, new InvocationHandler() {
                    @Override
                    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
                        //1.封装request请求对象
                        RpcRequest rpcRequest = new RpcRequest();
                        rpcRequest.setRequestId(UUID.randomUUID().toString());
                        rpcRequest.setClassName(method.getDeclaringClass().getName());
                        rpcRequest.setMethodName(method.getName());
                        rpcRequest.setParameterTypes(method.getParameterTypes());
                        rpcRequest.setParameters(args);
                        //2.创建RpcClient对象
                        RpcClient rpcClient = new RpcClient("127.0.0.1", 8899);
                        try {
                            //3.发送消息
                            Object responseMsg = rpcClient.send(JSON.toJSONString(rpcRequest));
                            RpcResponse rpcResponse = JSON.parseObject(responseMsg.toString(), RpcResponse.class);
                            if (rpcResponse.getError() != null) {
                                throw new RuntimeException(rpcResponse.getError());
                            }
                            //4.返回结果
                            Object result = rpcResponse.getResult();
                            return JSON.parseObject(result.toString(), method.getReturnType());
                        } catch (Exception e) {
                            throw e;
                        } finally {
                            rpcClient.close();
                        }

                    }
                });
    }
}

Test class:

package com.lagou.rpc.consumer;

import com.lagou.rpc.api.IUserService;
import com.lagou.rpc.consumer.proxy.RpcClientProxy;
import com.lagou.rpc.pojo.User;

/**
 * 测试类
 */
public class ClientBootStrap {
    public static void main(String[] args) {
        IUserService userService = (IUserService) RpcClientProxy.createProxy(IUserService.class);
        User user = userService.getById(1);
        System.out.println(user);
    }
}

Client process summary:

1. Create an interface proxy object.

2. When the proxy object calls invoke, it creates an RpcClient object. In the RpcClient construction method, the Netty information connection server will be initialized.

3. To call the send method in RpcClient is actually to execute the call method of the rpcClientHandler thread.

4. The call method of rpcClientHandler will send and receive server messages.

The above is a simple implementation of custom RPC, Netty-related things, you need to review the previous chapters.