Netty学习笔记——一个简单的多人聊天Demo

上篇博客使用Nio实现了一个多人聊天Demo，可以发现，Nio主要有三大核心部分：Channel、Buffer和Selector，但Nio编程比较复杂，而Netty是一个基于NIO的网络编程框架，可以帮助我们快速简单的开发一个网络应用。使用Netty实现多人聊天Demo的代码如下：

pom文件如下：

<dependency>
     <groupId>io.netty</groupId>
     <artifactId>netty-all</artifactId>
     <version>4.1.50.Final</version>
</dependency>

服务端代码如下：

package com.netty.chat;

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.*;
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;

public class ChatServer {
    private int port;

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

    public void run(){
        // 每个 EventLoop 维护着一个 Selector 实例
        EventLoopGroup bossGroup = new NioEventLoopGroup();
        EventLoopGroup workerGroup = new NioEventLoopGroup();

        try {
            // 服务器端启动助手
            ServerBootstrap sb = new ServerBootstrap();
            sb.group(bossGroup, workerGroup)
                    .channel(NioServerSocketChannel.class)
                    .option(ChannelOption.SO_BACKLOG, 128)
                    .childOption(ChannelOption.SO_KEEPALIVE, true) // 设置长连接
                    .childHandler(new ChannelInitializer<SocketChannel>() { // 添加自定义业务处理类
                        @Override
                        protected void initChannel(SocketChannel socketChannel) throws Exception {
                            ChannelPipeline pipeline = socketChannel.pipeline();
                            // 添加解码器
                            pipeline.addLast("decoder", new StringDecoder());

                            // 添加编码器
                            pipeline.addLast("encoder", new StringEncoder());

                            // 添加自定义处理类 一定要添加在编码器和解码器之后
                            pipeline.addLast(new ChatServerHandler());
                        }
                    });
            System.out.println("Netty chat Server启动.....");
            ChannelFuture sync = sb.bind(port).sync();
            sync.channel().closeFuture().sync();
        } catch (InterruptedException e) {
            e.printStackTrace();
        } finally {
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
            System.out.println("Netty chat Server关闭");
        }

    }

    public static void main(String[] args) {
        ChatServer chatServer = new ChatServer(9999);
        chatServer.run();
    }
}

服务端业务处理代码如下：

package com.netty.chat;

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

import java.util.ArrayList;
import java.util.List;

/**
 * SimpleChannelInboundHandler 可以避免消息类型转换
 */
public class ChatServerHandler extends SimpleChannelInboundHandler<String> {
    // 该集合存储所有channel，用于广播消息
    public static List<Channel> channels = new ArrayList<>();

    /**
     * 通道断开后执行该方法
     * @param ctx
     * @throws Exception
     */
    @Override
    public void channelInactive(ChannelHandlerContext ctx) throws Exception {
        Channel inChannel = ctx.channel();
        channels.remove(inChannel);
        System.out.println("[Server:]" + inChannel.remoteAddress().toString() + "下线");
    }

    /**
     * 通道就绪执行该方法
     * @param ctx
     * @throws Exception
     */
    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        Channel inChannel = ctx.channel();
        channels.add(inChannel);
        System.out.println("[Server:]" + inChannel.remoteAddress().toString() + "上线");
    }

    /**
     * 服务器端读取消息
     * @param ctx
     * @param s
     * @throws Exception
     */
    @Override
    protected void channelRead0(ChannelHandlerContext ctx, String s) throws Exception {
        Channel inChannel = ctx.channel();
        for (Channel channel : channels) {
            if (channel != inChannel){
                channel.writeAndFlush("[" + inChannel.remoteAddress().toString() + "] 说：" + s + "\n");
            }
        }
    }
}

客户端代码如下：

package com.netty.chat;

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.Scanner;

public class ChatClient {
    private int port;
    private String host;

    public ChatClient(int port, String host) {
        this.port = port;
        this.host = host;
    }

    public void run(){
        EventLoopGroup group = new NioEventLoopGroup();

        try {
            Bootstrap bt = new Bootstrap();
            bt.group(group)
                    .channel(NioSocketChannel.class)
                    .option(ChannelOption.SO_BACKLOG, 128)
                    .handler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel socketChannel) throws Exception {
                            ChannelPipeline pipeline = socketChannel.pipeline();
                            // 添加解码器
                            pipeline.addLast("decoder", new StringDecoder());

                            // 添加编码器
                            pipeline.addLast("encoder", new StringEncoder());

                            // 添加自定义处理类 一定要添加在编码器和解码器之后
                            pipeline.addLast(new ChatClientHandler());

                        } // 添加自定义业务处理类
                    });
            ChannelFuture connect = bt.connect(host, port).sync();
            Channel channel = connect.channel();
            System.out.println("--------" + channel.localAddress().toString() + "---------");

            Scanner sc = new Scanner(System.in);
            while (sc.hasNextLine()){
                String msg = sc.nextLine();
                channel.writeAndFlush(msg + "\r\n");

            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            group.shutdownGracefully();
            System.out.println("Netty chat Client关闭");
        }

    }

    public static void main(String[] args) {
        ChatClient chatClient = new ChatClient(9999, "127.0.0.1");

        chatClient.run();
    }
}

客户端业务处理代码如下：

package com.netty.chat;

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

//SimpleChannelInboundHandler 可以避免消息类型转换
public class ChatClientHandler extends SimpleChannelInboundHandler<String> {
    /**
     * 接受服务器端广播发送过了的消息
     * @param ctx
     * @param s
     * @throws Exception
     */
    @Override
    protected void channelRead0(ChannelHandlerContext ctx, String s) throws Exception {
        System.out.println(s);
    }
}