通过简单demo了解Netty核心组件用法

Netty核心组件

• Bootstrap和ServerBootstrap：当需要连接客户端或者服务器绑定指定端口时需要使用Bootstrap，ServerBootstrap有两种类型，一种是用于客户端的Bootstrap，一种是用于服务端 的ServerBootstrap。
• Channel：相当于socket，与另一端进行通信的通道，具备bind、connect、read、write等IO操作的能力。
• EventLoop：事件循环，负责处理Channel的IO事件,一个EventLoopGroup包含多个EventLoop，一个EventLoop可被分配至多个Channel，一个Channel只能注册于一个EventLoop，一个EventLoop只能与一个Thread绑定。
• ChannelFuture：channel IO事件的异步操作结果。
• ChannelHandler：包含IO事件具体的业务逻辑。
• ChannelPipeline：ChannelHandler的管道容器。

DEMO
Netty服务端

public class NettyServer {
    public static void main(String[] args) throws InterruptedException {
        EventLoopGroup parentGroup = new NioEventLoopGroup();
        EventLoopGroup childGroup = new NioEventLoopGroup();
        try {
            //2.创建服务端启动引导/辅助类：ServerBootstrap
            ServerBootstrap bootstrap = new ServerBootstrap();
            //3.给引导类配置两大线程组,确定了线程模型
            bootstrap.group(parentGroup, childGroup)
                    // (非必备)打印日志
                    .handler(new LoggingHandler(LogLevel.INFO))
                    // 4.指定 IO 模型
                    .channel(NioServerSocketChannel.class)
                    .childHandler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel ch) throws Exception {
                            ChannelPipeline pipeline = ch.pipeline();
                            pipeline.addLast(new StringDecoder());
                            pipeline.addLast(new StringEncoder());
                            /**
                             *  服务端添加IdleStateHandler心跳检测处理器,添加自定义处理Handler类实现userEventTriggered()方法作为超时事件的逻辑处理.
                             *  IdleStateHandler心跳检测每十五秒进行一次读检测，如果十五秒内ChannelRead()方法未被调用则触发一次userEventTrigger()方法
                             *  服务端为读IDLE
                             *  pipeline.AddLast(new IdleStateHandler(15, 0, 0));//第一个参数为读，第二个为写，第三个为读写全部
                             */
                            pipeline.addLast(new IdleStateHandler(15, 0, 0, TimeUnit.SECONDS));
                            //5.可以自定义客户端消息的业务处理逻辑
                            pipeline.addLast(new DemoSocketServerHandler());
                        }
                    });

//            ChannelFuture future = bootstrap.bind(8888).sync().addListener(new ChannelFutureListener() {
//                @Override
//                public void operationComplete(ChannelFuture channelFuture) throws Exception {
//                    System.out.println("监听端口已经启动");
//                }
//            });
            ChannelFuture future = bootstrap.bind(8888).sync().addListener( future1 -> {
                if (future1.isSuccess()){
                    System.out.println("监听端口已经启动!");
                } else {
                    System.out.println("监听端口还未启动!");
                }
            } );
            System.out.println("服务器已启动。。。");
            future.channel().closeFuture().sync();
        } finally {
            parentGroup.shutdownGracefully();
            childGroup.shutdownGracefully();
        }
    }
}

Netty客户端

public class NettyClient {
    public static void main(String[] args) throws InterruptedException {
        NioEventLoopGroup eventLoopGroup = new NioEventLoopGroup();
        try {
            Bootstrap bootstrap = new Bootstrap();
            bootstrap.group(eventLoopGroup)
                    .channel(NioSocketChannel.class)
                    .handler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel ch) throws Exception {
                            ChannelPipeline pipeline = ch.pipeline();
                            pipeline.addLast(new StringDecoder(CharsetUtil.UTF_8));
                            pipeline.addLast(new StringEncoder(CharsetUtil.UTF_8));
                            pipeline.addLast(new DemoSocketClientHandler());
                        }
                    });

            ChannelFuture future = bootstrap.connect("localhost", 8888).sync();
            future.channel().closeFuture().sync();
        } finally {
            if(eventLoopGroup != null) {
                eventLoopGroup.shutdownGracefully();
            }
        }
    }
}

服务端处理handler

public class DemoSocketServerHandler extends ChannelInboundHandlerAdapter {

    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        InetSocketAddress inetSocketAddress = (InetSocketAddress) ctx.channel().remoteAddress();
        String ip = inetSocketAddress.getAddress().getHostAddress();
        int port = inetSocketAddress.getPort();
        super.channelActive(ctx);
        System.out.println(ip+":"+port+" 上线了");
    }

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        System.out.println(msg);
        System.out.println("Client Address ====== " + ctx.channel().remoteAddress());
        ctx.channel().writeAndFlush("from server:" + UUID.randomUUID());
        ctx.fireChannelActive();
        TimeUnit.MILLISECONDS.sleep(500);
    }
    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        cause.printStackTrace();
        ctx.close();
    }

    @Override
    public void userEventTriggered(ChannelHandlerContext ctx, Object evt) throws Exception {
        if (evt instanceof IdleStateEvent) {
            IdleStateEvent idleStateEvent = (IdleStateEvent) evt;
            if (idleStateEvent.state() == IdleState.READER_IDLE) {
                InetSocketAddress inetSocketAddress = (InetSocketAddress) ctx.channel().remoteAddress();
                String ip = inetSocketAddress.getAddress().getHostAddress();
                System.out.println((ip + ":" + inetSocketAddress.getPort() + "close"));
                ctx.channel().close();
            }
        }
    }
}

客户端处理handler

public class DemoSocketClientHandler extends ChannelInboundHandlerAdapter {
    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg)
            throws Exception {
        System.out.println(msg);
        ctx.channel().writeAndFlush("from client: " + System.currentTimeMillis());
        TimeUnit.MILLISECONDS.sleep(5000);
    }

    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        ctx.channel().writeAndFlush("from client：begin talking");
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        cause.printStackTrace();
        ctx.close();
    }
    //超时则关闭链路
    @Override
    public void userEventTriggered(ChannelHandlerContext ctx, Object evt) throws Exception {
        if (evt instanceof IdleStateEvent) {
            IdleStateEvent idleStateEvent = (IdleStateEvent) evt;
            if (idleStateEvent.state() == IdleState.READER_IDLE) {
                InetSocketAddress inetSocketAddress = (InetSocketAddress) ctx.channel().remoteAddress();
                String ip = inetSocketAddress.getAddress().getHostAddress();
                System.out.println((ip + ":" + inetSocketAddress.getPort() + "close"));
                ctx.channel().close();
            }
        }
    }
}