Netty实战《RPC调用》

Netty实现RPC
常见的 RPC 框架有: 比较知名的如阿里的Dubbo、google的gRPC、Go语言的rpcx、Apache的thrift， Spring 旗下的 Spring Cloud

RPC调用流程图

说明：
1） client以本地方式调用服务
2）client stub接受调用负责将方法，参数等封装成能够进行网络传输的消息体
3） client stub将消息进行编码并发送到客户端
4）server stub收到消息后进行解码
5）server stub根据解码的消息调用本地服务
6） 本地服务执行并将结果返回给server stub
7）server stub将返回的结果编码，并发送至消费方
8）client stub收到消息后进行解码
9）client得到结果
RPC的目标就是将2-8步骤封装起来，用户无需关系这些细节，用本地方法就可以完成远程服务调用。

客户端启动类

/**
 * @author gusteu
 * @date 2022/04/17 08:09:11
 */
public class ClientBootstrap {



    public static void main(String[] args) throws InterruptedException {
        NettyClient nettyClient = new NettyClient();


        UserService userService = (UserService) nettyClient.getBean(UserService.class, InterfaceConstant.PROVIDER_NAME);

        for (int i = 0; i < 6; i++) {
            Thread.sleep(3000);
            System.out.println(userService.getUserNameById("20132230310" + i));
        }
    }

}

客户端

import io.netty.bootstrap.Bootstrap;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelOption;
import io.netty.channel.ChannelPipeline;
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.lang.reflect.Proxy;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

/**
 * @author gusteu
 * @date 2022/04/17 08:11:33
 */
public class NettyClient {


    private static ExecutorService executorService = Executors.newFixedThreadPool(Runtime.getRuntime().availableProcessors());

    private static ClientHandler clientHandler;


    /**
     * 创建一个代理对象
     */
    public Object getBean(final Class<?> serviceClass,
                          final String providerName) {
        return Proxy.newProxyInstance(Thread.currentThread().getContextClassLoader(),
                new Class<?>[]{serviceClass}, (proxy, method, args) -> {
                    if (clientHandler == null) {
                        initClient();
                    }
                    // 设置参数
                    clientHandler.setPara(providerName + args[0]);
                    return executorService.submit(clientHandler).get();
                });
    }


    private static void initClient() throws InterruptedException {
        clientHandler = new ClientHandler();
        NioEventLoopGroup nioEventLoopGroup = new NioEventLoopGroup();
        Bootstrap bootstrap = new Bootstrap();
        bootstrap.group(nioEventLoopGroup)
                .channel(NioSocketChannel.class)
                .option(ChannelOption.TCP_NODELAY, true)
                .handler(new ChannelInitializer<SocketChannel>() {
                    @Override
                    protected void initChannel(SocketChannel socketChannel) throws Exception {
                        ChannelPipeline pipeline = socketChannel.pipeline();
                        pipeline.addLast(new StringDecoder());
                        pipeline.addLast(new StringEncoder());
                        pipeline.addLast(clientHandler);
                    }
                });
        bootstrap.connect("127.0.0.1", 8001).sync();

    }
}

客户端处理器

import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;

import java.util.concurrent.Callable;

/**
 * @author gusteu
 * @date 2022/04/17 08:13:31
 */
public class ClientHandler extends ChannelInboundHandlerAdapter implements Callable {
    private ChannelHandlerContext context;

    private String result;

    private String para;

    /**
     * 与服务器的连接已经及建立之后将被调用
     * @param ctx
     */
    @Override
    public void channelActive(ChannelHandlerContext ctx) {
        context = ctx;
    }

    /**
     * 收到服务端数据，唤醒等待线程
     */
    @Override
    public synchronized void channelRead(ChannelHandlerContext ctx, Object msg) {
        result = msg.toString();
        notify();
    }

    /**
     * 写出数据，开始等待唤醒
     */
    @Override
    public synchronized Object call() throws InterruptedException {
        context.writeAndFlush(para);
        wait();
        return result;
    }

    void setPara(String para) {
        this.para = para;
    }
}

接口常量类

public class InterfaceConstant {
    public static final String PROVIDER_NAME = "UserService#getUserNameById#";
}

服务端启动类

/**
 * @author gusteu
 * @date 2022/04/17 08:34:39
 */
public class ServerBootstrap {

    public static void main(String[] args) {
        NettyServer.startServer("127.0.0.1", 8001);

    }

}

服务端初始化

import io.netty.bootstrap.ServerBootstrap;
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;

/**
 * @author gusteu
 * @date 2022/04/17 08:29:51
 */
public class NettyServer {

    /**
     * 启动客户端
     */
    public static void startServer(String hostName, int port) {
        startServer0(hostName, port);
    }

    private static void startServer0(String hostName, int port) {
        try {
            ServerBootstrap bootstrap = new ServerBootstrap();
            NioEventLoopGroup eventLoopGroup = new NioEventLoopGroup();
            bootstrap.group(eventLoopGroup)
                    .channel(NioServerSocketChannel.class)
                    .childHandler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel ch) throws Exception {
                            ChannelPipeline p = ch.pipeline();
                            p.addLast(new StringDecoder());
                            p.addLast(new StringEncoder());
                            p.addLast(new ServerHandler());
                        }
                    });

            bootstrap.bind(hostName, port).sync();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

服务端handler

import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;

/**
 * @author gusteu
 * @date 2022/04/17 08:30:46
 */
public class ServerHandler extends ChannelInboundHandlerAdapter {
    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {

        // 如何符合约定，则调用本地方法，返回数据
        if (msg.toString().startsWith(InterfaceConstant.PROVIDER_NAME)) {
            String result = new UserServiceImpl()
                    .getUserNameById(msg.toString().substring(msg.toString().lastIndexOf("#") + 1));
            ctx.writeAndFlush(result);
        }
    }
}

业务接口和实现类

/**
 * @author gusteu
 * @date 2022/04/17 08:25:17
 */
public interface UserService {

    String getUserNameById(String id);
}

import java.util.UUID;

/**
 * @author gusteu
 * @date 2022/04/17 08:32:42
 */
public class UserServiceImpl implements UserService {
    @Override
    public String getUserNameById(String id) {
        return UUID.randomUUID().toString();
    }
}