一、需求说明

1、dubbo底层使用了netty作为网络通讯框架，要求使用netty实现一个简单的RPC框架。

2、模仿dubbo，消费者和提供者约定接口和协议，消费者远程调用提供者的服务，提供者返回一个字符串，消费者打印提供者返回的数据。底层网络通信使用netty4.x。

二、设计说明

1、创建一个接口，定义抽象方法。用于消费者和提供者之间的约定。

2、创建一个提供者，该类需要监听消费者的请求，并按照约定返回数据。

3、创建一个消费者，该类需要透明的调用自己不存在的方法，内部需要使用netty请求提供者返回数据。

三、代码

1、接口
HelloService.java

package netty.dubborpc.publicinterface;/*** 接口，服务提供方和服务消费方都需要* @author user**/
public interface HelloService {public String hello(String msg);
}

2、netty服务端
NettyServer.java

package netty.dubborpc.netty;import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.EventLoopGroup;
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 io.netty.handler.logging.LogLevel;
import io.netty.handler.logging.LoggingHandler;public class NettyServer {public static void startServer(String hostname, int port) {startServer0(hostname, port);}private static void startServer0(String hostname, int port) {EventLoopGroup bossGroup = new NioEventLoopGroup(1);EventLoopGroup workerGroup = new NioEventLoopGroup(8);try {ServerBootstrap bootstrap = new ServerBootstrap();bootstrap.group(bossGroup, workerGroup).channel(NioServerSocketChannel.class).handler(new LoggingHandler(LogLevel.DEBUG)).childHandler(new ChannelInitializer() {@Overrideprotected void initChannel(SocketChannel ch) throws Exception {ChannelPipeline pipeline = ch.pipeline();pipeline.addLast(new StringDecoder());pipeline.addLast(new StringEncoder());pipeline.addLast(new NettyServerHandler()); //业务处理类}}); //自定义一个初始化类ChannelFuture cf = bootstrap.bind(7000).sync();System.out.println("服务提供方启动，开始监听了......");cf.channel().closeFuture().sync();} catch (Exception e) {e.printStackTrace();} finally {bossGroup.shutdownGracefully();workerGroup.shutdownGracefully();}}
}

NettyServerHandler.java

package netty.dubborpc.netty;import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
import netty.dubborpc.provider.HelloServiceImpl;public class NettyServerHandler extends ChannelInboundHandlerAdapter {@Overridepublic void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {cause.printStackTrace();ctx.channel().close();}@Overridepublic void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {//获取客户端发送的消息，并调用服务System.out.println("msg=" + msg);//客户端在调用服务器的api时，我们需要定义一个协议//比如我们要求，每次发消息时，都必须以某个字符串开头 "HelloService#hello#"if (msg.toString().startsWith("HelloService#hello#")) {//去除协议头//这里可以用反射生成处理类//还要考虑粘包拆包问题String result = new HelloServiceImpl().hello(msg.toString().substring(19));ctx.writeAndFlush(result);}}
}

3、netty客户端
NettyClient.java

package netty.dubborpc.netty;import java.lang.reflect.Proxy;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;import io.netty.bootstrap.Bootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelOption;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.EventLoopGroup;
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 io.netty.handler.logging.LogLevel;
import io.netty.handler.logging.LoggingHandler;public class NettyClient {//创建线程池private static ExecutorService executor = Executors.newFixedThreadPool(10);private static NettyClientHandler client;//编写方法，使用代理模式获取代理对象public Object getBean(final Class serviceClass, final String protocolHeader) {return Proxy.newProxyInstance(Thread.currentThread().getContextClassLoader(), new Class[] {serviceClass}, //lambel表达式就是实现的接口InvocationHangler的invoke方法(proxy, method, args) -> {//这部分代码，客户端每调用一次hello，就会进入该代码块if (client == null) {initClient();initConnect();}//设置要发给服务器的信息//protocolHeader协议头，args[0]就是客户端调用api hello()里传的参数client.setParam(protocolHeader + args[0]);return executor.submit(client).get();});}//初始化客户端private static void initClient() {client = new NettyClientHandler();}//初始化连接private static void initConnect() {EventLoopGroup group = new NioEventLoopGroup();try {Bootstrap bootstrap = new Bootstrap();bootstrap.group(group) //设置线程组.channel(NioSocketChannel.class).option(ChannelOption.TCP_NODELAY, true).handler(new LoggingHandler(LogLevel.DEBUG)).handler(new ChannelInitializer() {@Overrideprotected void initChannel(SocketChannel ch) throws Exception {ChannelPipeline pipeline = ch.pipeline();pipeline.addLast(new StringDecoder());pipeline.addLast(new StringEncoder());pipeline.addLast(client);}}); //自定义一个初始化对象ChannelFuture cf = bootstrap.connect("127.0.0.1", 7000).sync();//这里不能阻塞必须返回，因为后续代理还要调用call方法，所以不能closeFuture sync，但可以对closeFuture加一个listener回调//cf.channel().closeFuture().sync();} catch (Exception e) {e.printStackTrace();} finally {//这里也不能shutdown//group.shutdownGracefully();}}
}

NettyClientHandler.java

package netty.dubborpc.netty;import java.util.concurrent.Callable;import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;public class NettyClientHandler extends ChannelInboundHandlerAdapter implements Callable