手写MQ框架（四）-使用netty改造梳理

一、背景

书接上文手写MQ框架（三）-客户端实现，前面通过web的形式实现了mq的服务端和客户端，现在计划使用netty来改造一下。前段时间学习了一下netty的使用。大概有一些想法。

netty封装了socket的使用，我们通过简单的调用即可构建高性能的网络应用。我计划采用以下例子来对gmq进行改造。

二、netty是什么

Netty是由JBOSS提供的一个java开源框架。Netty提供异步的、事件驱动的网络应用程序框架和工具，用以快速开发高性能、高可靠性的网络服务器和客户端程序。

netty是一个java框架，是网络编程框架，支持异步、事件驱动的特性，所以性能表现很好。

三、netty的简单实现

1、服务端

1）SimpleServerHandler

Handler是处理器，handler 是由 Netty 生成用来处理 I/O 事件的。

package me.lovegao.netty.learnw3c.mqdemo;

import io.netty.channel.Channel;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import io.netty.channel.group.ChannelGroup;
import io.netty.channel.group.DefaultChannelGroup;
import io.netty.util.concurrent.GlobalEventExecutor;

public class SimpleServerHandler extends SimpleChannelInboundHandler<String> {
    public static ChannelGroup channels = new DefaultChannelGroup(GlobalEventExecutor.INSTANCE);

    @Override
    public void handlerAdded(ChannelHandlerContext ctx) throws Exception {
        Channel incoming = ctx.channel();
        System.out.println("[SERVER] - " + incoming.remoteAddress() + " 加入\n");
        channels.add(ctx.channel());
    }

    @Override
    public void handlerRemoved(ChannelHandlerContext ctx) throws Exception {
        Channel incoming = ctx.channel();
        System.out.println("[SERVER] - " + incoming.remoteAddress() + " 离开\n");
        channels.remove(ctx.channel());
    }
    
    @Override
    protected void channelRead0(ChannelHandlerContext ctx, String s) throws Exception {
        Channel incoming = ctx.channel();
        System.out.println("[" + incoming.remoteAddress() + "]" + s);
        if(s == null || s.length() == 0) {
            incoming.writeAndFlush("消息是空的呀！\n");
        } else {
//            MqRouter<?> mqRouter = JSONObject.parseObject(s, MqRouter.class);
//            System.out.println(mqRouter.getUri());
            String responseMsg = "收到了，" + s + "\n";
            incoming.writeAndFlush(responseMsg);
        }
    }

    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        Channel incoming = ctx.channel();
        System.out.println("SimpleChatClient:"+incoming.remoteAddress()+"在线");
    }

    @Override
    public void channelInactive(ChannelHandlerContext ctx) throws Exception {
        Channel incoming = ctx.channel();
        System.out.println("SimpleChatClient:"+incoming.remoteAddress()+"掉线");
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        Channel incoming = ctx.channel();
        System.out.println("SimpleChatClient:"+incoming.remoteAddress()+"异常");
        
        cause.printStackTrace();
        ctx.close();
    }

}

2）SimpleServerInitializer

SimpleServerInitializer 用来增加多个的处理类到 ChannelPipeline 上，包括编码、解码、SimpleServerHandler 等。

package me.lovegao.netty.learnw3c.mqdemo;

import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.socket.SocketChannel;
import io.netty.handler.codec.DelimiterBasedFrameDecoder;
import io.netty.handler.codec.Delimiters;
import io.netty.handler.codec.string.StringDecoder;
import io.netty.handler.codec.string.StringEncoder;

public class SimpleServerInitializer extends ChannelInitializer<SocketChannel> {

    @Override
    protected void initChannel(SocketChannel ch) throws Exception {
        ChannelPipeline pipeline = ch.pipeline();
        pipeline.addLast("framer", new DelimiterBasedFrameDecoder(8192, Delimiters.lineDelimiter()));
        pipeline.addLast("decoder", new StringDecoder());
        pipeline.addLast("encoder", new StringEncoder());
        pipeline.addLast("handler", new SimpleServerHandler());
        
        System.out.println("SimpleChatClient:" + ch.remoteAddress() + "连接上");
    }

}

3）SimpleServer

package me.lovegao.netty.learnw3c.mqdemo;

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelOption;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioServerSocketChannel;

public class SimpleServer {
    private int port;

    public SimpleServer(int port) {
        this.port = port;
    }

    public void run() throws Exception {
        EventLoopGroup bossGroup = new NioEventLoopGroup();
        EventLoopGroup workerGroup = new NioEventLoopGroup();
        try {
            ServerBootstrap b = new ServerBootstrap();
            b.group(bossGroup, workerGroup).channel(NioServerSocketChannel.class)
                    .childHandler(new SimpleServerInitializer()).option(ChannelOption.SO_BACKLOG, 128)
                    .childOption(ChannelOption.SO_KEEPALIVE, true);

            System.out.println("SimpleChatServer 启动了");

            ChannelFuture f = b.bind(port).sync();

            f.channel().closeFuture().sync();
        } finally {
            workerGroup.shutdownGracefully();
            bossGroup.shutdownGracefully();

            System.out.println("SimpleChatServer 关闭了");
        }
    }

    public static void main(String[] args) throws Exception {
        int port;
        if (args.length > 0) {
            port = Integer.parseInt(args[0]);
        } else {
            port = 8080;
        }
        new SimpleServer(port).run();
    }
}

2、客户端

1）SimpleClientHandler

package me.lovegao.netty.learnw3c.mqdemo;

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

public class SimpleClientHandler extends SimpleChannelInboundHandler<String> {

    @Override
    protected void channelRead0(ChannelHandlerContext ctx, String s) throws Exception {
        System.out.println("收到的信息：" + s);
    }

}

2）SimpleClientInitializer

package me.lovegao.netty.learnw3c.mqdemo;

import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.socket.SocketChannel;
import io.netty.handler.codec.DelimiterBasedFrameDecoder;
import io.netty.handler.codec.Delimiters;
import io.netty.handler.codec.string.StringDecoder;
import io.netty.handler.codec.string.StringEncoder;

public class SimpleClientInitializer extends ChannelInitializer<SocketChannel> {

    @Override
    protected void initChannel(SocketChannel ch) throws Exception {
        ChannelPipeline pipeline = ch.pipeline();
        pipeline.addLast("framer", new DelimiterBasedFrameDecoder(8192, Delimiters.lineDelimiter()));
        pipeline.addLast("decoder", new StringDecoder());
        pipeline.addLast("encoder", new StringEncoder());
        pipeline.addLast("handler", new SimpleClientHandler());
    }

}

3）SimpleClient

package me.lovegao.netty.learnw3c.mqdemo;

import java.io.BufferedReader;
import java.io.InputStreamReader;

import io.netty.bootstrap.Bootstrap;
import io.netty.channel.Channel;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioSocketChannel;

public class SimpleClient {
    private final String host;
    private final int port;
    
    public SimpleClient(String host, int port) {
        this.host = host;
        this.port = port;
    }

    public static void main(String[] args) throws Exception {
        new SimpleClient("localhost", 8080).run();
    }
    
    public void run() throws Exception {
        EventLoopGroup group = new NioEventLoopGroup();
        try {
            Bootstrap bootstrap = new Bootstrap()
                    .group(group)
                    .channel(NioSocketChannel.class)
                    .handler(new SimpleClientInitializer());
            Channel channel = bootstrap.connect(host, port).sync().channel();
            BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
            while(true) {
                String line = in.readLine();
                if(line.equals("exit!")) {
                    break;
                }
                channel.writeAndFlush(line + "\r\n");
            }
        } catch(Exception e) {
            e.printStackTrace();
        } finally {
            group.shutdownGracefully();
        }
    }



}