实例要求编写一个 Netty 群聊系统，实现服务器端和客户端之间的数据简单通讯（非阻塞）实现多人群聊服务器端：可以监测用户上线，离线，并实现消息转发功能客户端：通过channel 可以无阻塞发送消息给其它所有用户，同时可以接受其它用户发送的消息(有服务器转发得到)

目的：进一步理解Netty非阻塞网络编程机制

服务端

编写GroupChatServer类

GroupChatServerHandler

private static ChannelGroup channelGroup = new DefaultChannelGroup(GlobalEventExecutor.INSTANCE);

java复制代码public class GroupChatServer {    private int port;//监听端口    public GroupChatServer(int port) {        this.port = port;    }    //编写run方法，处理客户端端请求    public void run() throws InterruptedException {        //创建两个线程组        NioEventLoopGroup bossGroup = new NioEventLoopGroup(1);        NioEventLoopGroup workerGroup = new NioEventLoopGroup(8);        try {            ServerBootstrap bootstrap = new ServerBootstrap();            bootstrap.group(bossGroup, workerGroup)                    .channel(NioServerSocketChannel.class)                    .option(ChannelOption.SO_BACKLOG, 128)                    .childOption(ChannelOption.SO_KEEPALIVE, true)                    .childHandler(new ChannelInitializer<SocketChannel>() {                        @Override                        protected void initChannel(SocketChannel ch) throws Exception {                            //获取到pipelineå                            ChannelPipeline pipeline = ch.pipeline();                            //向pipeline加入解码器                            pipeline.addLast("decoder", new StringDecoder());                            //向pipeline加入编码器                            pipeline.addLast("encoder", new StringEncoder());                            //加入自己到业务处理handler                            pipeline.addLast(new GroupChatServerHandler());                        }                    });            System.out.println("Netty 服务器启动");            ChannelFuture channelFuture = bootstrap.bind(port).sync();            //监听关闭            channelFuture.channel().closeFuture().sync();        } finally {            bossGroup.shutdownGracefully();            workerGroup.shutdownGracefully();        }    }    public static void main(String[] args) throws InterruptedException {        new GroupChatServer(7000).run();    }}

java复制代码public class GroupChatServerHandler extends SimpleChannelInboundHandler<String> {    //定义一个channel组，管理所以到channel    //GlobalEventExecutor.INSTANCE 是全局的事件执行器，单例    private static ChannelGroup channelGroup = new DefaultChannelGroup(GlobalEventExecutor.INSTANCE);    SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");    //handlerAdded表示连接建立，一旦连接，第一个被执行该方法    //将当前channel加入到channelGroup    @Override    public void handlerAdded(ChannelHandlerContext ctx) throws Exception {        Channel channel = ctx.channel();        //将该客户端加入聊天端信息推送给其他在线端客户端。该方法会将channelGroup中所有端channel遍历，并发送信息。因此不需要自己遍历        channelGroup.writeAndFlush("[客户端]" + channel.remoteAddress() + " 加入聊天" + sdf.format(new Date()) + "\n");        channelGroup.add(channel);    }    //断开连接，将xx客户离开信息推送哥当前在线的客户    @Override    public void handlerRemoved(ChannelHandlerContext ctx) throws Exception {        Channel channel = ctx.channel();        channelGroup.writeAndFlush("[客户端]" + channel.remoteAddress() + " 离开了\n");        System.out.println("当前channelGroup大小：" + channelGroup.size());    }    //表示channel处于活动的状态 提示xxx上线    @Override    public void channelActive(ChannelHandlerContext ctx) throws Exception {        System.out.println(ctx.channel().remoteAddress() + " 上线了～"+sdf.format(new Date()) + "\n");    }    //表示channel处于不活动的状态 提示xxx下线    @Override    public void channelInactive(ChannelHandlerContext ctx) throws Exception {        System.out.println(ctx.channel().remoteAddress() + " 离线了～"+sdf.format(new Date()) + "\n");    }    @Override    protected void channelRead0(ChannelHandlerContext ctx, String msg) throws Exception {        //获取当前channel        Channel channel = ctx.channel();        //遍历channelGroup，根据不同的情况，推送不同的消息 （排除自身）        channelGroup.forEach(ch -> {            if (channel != ch) {//不是当前channel，转发消息                ch.writeAndFlush("[客户]" + channel.remoteAddress() + " 发送了消息：" + msg + sdf.format(new Date()) + "\n");            } else {//自己发送的信息，在自己上如何显示                ch.writeAndFlush("[自己]" + " 发送了消息：" + msg + "\n");            }        });    }}

GroupChatClient

cdn.jsdelivr.net/gh/kylincw/…

java复制代码public class GroupChatClient {    //属性    private final String host;    private final int port;    public GroupChatClient(String host, int port) {        this.host = host;        this.port = port;    }    public void run() throws InterruptedException {        NioEventLoopGroup group = new NioEventLoopGroup();        Bootstrap bootstrap = new Bootstrap();        try {            bootstrap.group(group)                    .channel(NioSocketChannel.class)                    .handler(new ChannelInitializer<SocketChannel>() {                        @Override                        protected void initChannel(SocketChannel ch) throws Exception {                            //得到pipeline                            ChannelPipeline pipeline = ch.pipeline();                            //加入相关handler                            pipeline.addLast("decoder", new StringDecoder());                            pipeline.addLast("encoder", new StringEncoder());                            //自定义handler                            pipeline.addLast(new GroupChatClientHandler());                        }                    });            ChannelFuture channelFuture = bootstrap.connect(host, port).sync();            //得到channel            Channel channel = channelFuture.channel();            System.out.println("--------" + channel.localAddress() + "--------");            //客户端需要输入信息，创建一个扫描器            Scanner scanner = new Scanner(System.in);            while (scanner.hasNextLine()){                String msg = scanner.nextLine();                //通过channel发送大服务器端                channel.writeAndFlush(msg+"\r\n");            }        } finally {            group.shutdownGracefully();        }    }    public static void main(String[] args) throws InterruptedException {        new GroupChatClient("127.0.0.1",7000).run();    }}

java复制代码public class GroupChatClientHandler extends SimpleChannelInboundHandler<String> {    @Override    protected void channelRead0(ChannelHandlerContext ctx, String msg) throws Exception {        System.out.println(msg.trim());//取掉两端空格    }}

作者：以范特西之名

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