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從入門到超神進(jìn)階的Netty群聊系統(tǒng)

更新時間：2021年08月19日 15:35:56 作者：墨家巨子@俏如來

本篇文章基于Netty做一個聊天室案例加強(qiáng)Netty的熟練度，案例的效果是服務(wù)端可以廣播某客戶端的消息給所有客戶端。每個客戶端監(jiān)聽鍵盤輸入來獲取消息，然后發(fā)送給服務(wù)端

服務(wù)端

服務(wù)端一樣的需要創(chuàng)建BossGroup 和 WorkGroup , 然后使用ServerBootStrap 來配置Netty和啟動Netty。

public class NettyGroupChatServer {
    public static void main(String[] args) {
        new NettyGroupChatServer().start();
    }
    //監(jiān)聽
   public void start(){
        //循環(huán)組
       NioEventLoopGroup bossGroup = new NioEventLoopGroup();
       NioEventLoopGroup workGroup = new NioEventLoopGroup();
       //啟動引導(dǎo)
       ServerBootstrap bootstrap = new ServerBootstrap();
       //Netty配置
       bootstrap.group(bossGroup,workGroup)
               .option(ChannelOption.SO_BACKLOG,32)
               .childOption(ChannelOption.SO_KEEPALIVE,true)
               .channel(NioServerSocketChannel.class)
               .childHandler(new ChannelInitializer<SocketChannel>() {
                   @Override
                   protected void initChannel(SocketChannel channel) throws Exception {
                       //解碼器
                       channel.pipeline().addLast("decoder", new StringDecoder());
                       //編碼器
                       channel.pipeline().addLast("encoder",new StringEncoder());
                       //處理器
                       channel.pipeline().addLast("nettyGroupChatHandler",new NettyGroupChatServerHandler());
                   }
               });
       try {
           //啟動服務(wù)
           ChannelFuture future = bootstrap.bind(new InetSocketAddress("127.0.0.1", 8888)).sync();
           future.channel().closeFuture().sync();
       } catch (InterruptedException e) {
           e.printStackTrace();
       }finally {
           //關(guān)閉資源
           bossGroup.shutdownGracefully();
           workGroup.shutdownGracefully();
       }
   }
}

服務(wù)端處理器我們通過繼承 SimpleChannelInboundHandler 入站Handler來處理消息。

其中提供了幾個方法

channelRead0 ()：讀取消息
handlerRemoved ()：客戶端斷開
handlerAdded ()：客戶端建立連接
exceptionCaught ()：出現(xiàn)異常

具體代碼如下

public class NettyGroupChatServerHandler extends SimpleChannelInboundHandler<String> {
    //把所有客戶端的channel保存起來
    private static ChannelGroup channels = new DefaultChannelGroup(GlobalEventExecutor.INSTANCE);
    private static SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
    @Override
    protected void channelRead0(ChannelHandlerContext ctx, String msg) throws Exception {
        String message = dateFormat.format(new Date())+":%s:"+msg;
        //消息轉(zhuǎn)發(fā)給所有的客戶端
        channels.forEach(channel -> {
            if(channel == ctx.channel()){
                String sendMsg = String.format(message, "我");
                channel.writeAndFlush(sendMsg);
                System.out.println(sendMsg);

            }else{
                String sendMsg = String.format(message, ctx.channel().remoteAddress());
                channel.writeAndFlush(sendMsg);
                System.out.println(sendMsg);
            }
        });
    }
    //斷開連接 , 把消息廣播給其他客戶端
    @Override
    public void handlerRemoved(ChannelHandlerContext ctx) throws Exception {
        String message = dateFormat.format(new Date())+":"+ctx.channel().remoteAddress()+":斷開連接";
        channels.writeAndFlush(message);
        System.out.println(message);
    }
    //建立連接
    @Override
    public void handlerAdded(ChannelHandlerContext ctx) throws Exception {
        String message = dateFormat.format(new Date())+":"+ctx.channel().remoteAddress()+":加入聊天室";
        //自動把消息廣播給其客戶端
        channels.writeAndFlush(message);
        //客戶端加入組
        channels.add(ctx.channel());
        System.out.println(message);
    }
    //出現(xiàn)異常
    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        ctx.channel().close();
    }
    //客戶端退出
    @Override
    public void channelInactive(ChannelHandlerContext ctx) throws Exception {
        String message = dateFormat.format(new Date())+":"+ctx.channel().remoteAddress()+":退出聊天室";
        System.out.println(message);
    }
    //客戶端出于活動
    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        String message = dateFormat.format(new Date())+":"+ctx.channel().remoteAddress()+":上線啦";
        System.out.println(message);
    }
}

客戶端

客戶端需要創(chuàng)建一個循環(huán)事件組，然后通過BootStrap去啟動,然后掃描鍵盤輸入作為數(shù)據(jù)源來把信息發(fā)送給服務(wù)端

public class NettyGroupChatClient {
    public static void main(String[] args) {
        new NettyGroupChatClient().start();
    }
    public void start(){
        NioEventLoopGroup eventLoopGroup = new NioEventLoopGroup();
        Bootstrap bootstrap = new Bootstrap();
        bootstrap.group(eventLoopGroup)
                .channel(NioSocketChannel.class)
                .handler(new ChannelInitializer<SocketChannel>() {
                    @Override
                    protected void initChannel(SocketChannel channel) throws Exception {
                        //解碼器
                        channel.pipeline().addLast("decoder", new StringDecoder());
                        //編碼器
                        channel.pipeline().addLast("encoder",new StringEncoder());
                        //處理器
                        channel.pipeline().addLast("nettyGroupChatClientHandler",new NettyGroupChatClientHandler());
                    }
                });
        try {
            ChannelFuture future = bootstrap.connect(new InetSocketAddress("127.0.0.1", 8888)).sync();
            //通道
            Channel channel = future.channel();
            //掃描鍵盤輸入
            Scanner scanner = new Scanner(System.in);
            while(scanner.hasNextLine()){
                String message = scanner.nextLine();
                //發(fā)送數(shù)據(jù)
                channel.writeAndFlush(message);
            }
        } catch (InterruptedException e) {
        }finally {
            eventLoopGroup.shutdownGracefully();
        }
    }
}

對于處理器只需要接收服務(wù)端轉(zhuǎn)發(fā)過來的消息即可

public class NettyGroupChatClientHandler extends SimpleChannelInboundHandler<String> {
    @Override
    protected void channelRead0(ChannelHandlerContext ctx, String msg) throws Exception {
        System.out.println(msg);
    }
}

啟動服務(wù)端和多個客戶端，效果如下

在這里插入圖片描述