Netty入门基础代码示例及简单描述

本文介绍了简单的Netty服务端和客户端的代码示例。简单描述了一下InboundHandler和OutboundHandler的关系。

NettyServer服务端代码模板

/**
 * netty服务端代码
 */
public class NettyServer {
    public static void main(String[] args) throws InterruptedException {
        EventLoopGroup bossGroup = new NioEventLoopGroup(1);
        EventLoopGroup workerGroup = new NioEventLoopGroup(5);
        try {
            ServerBootstrap bootstrap = new ServerBootstrap()
                    .group(bossGroup,workerGroup)
                    .channel(NioServerSocketChannel.class)
                    .option(ChannelOption.SO_BACKLOG,512)
                    .childHandler(new ChannelInitializer() {
                        @Override
                        protected void initChannel(SocketChannel socketChannel) throws Exception {
                            ChannelPipeline pipeline = socketChannel.pipeline();
                            //解码器
                            pipeline.addLast(new StringDecoder());
                            //编码器
                            pipeline.addLast(new StringEncoder());
                            //自定义处理的handler
                            pipeline.addLast(new NettyServerHandler());
                        }
                    });
            ChannelFuture cf = bootstrap.bind(9000).sync();
            //给cf注册监听器
            cf.addListener(new ChannelFutureListener() {
                @Override
                public void operationComplete(ChannelFuture channelFuture) throws Exception {
                    if (cf.isSuccess()){
                        //连接成功事件

                    }else {
                        //连接失败事件

                    }
                }
            });
            //对通道关闭进行监听，closeFuture是异步操作。监听通道关闭。。.sync()是同步等待通道关闭
            cf.channel().closeFuture().sync();
        }finally {
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }
}

NettyServer自定义handler

/**
 * 只重写了基础常用的功能
 */
public class NettyServerHandler extends ChannelInboundHandlerAdapter {

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

    /**
     * channel连接事件
     * @param ctx
     */
    @Override
    public void channelActive(ChannelHandlerContext ctx){
        Channel channel = ctx.channel();
        ctx.writeAndFlush(channel.remoteAddress()+"，已经连接");
    }

    /**
     * 读取客户端发送的数据
     * @param ctx
     * @param msg
     * @throws Exception
     */
    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg)  {
        System.out.println("服务读取线程："+Thread.currentThread().getName());
//        ByteBuf buf = (ByteBuf)msg;
        System.out.println("接收客户端消息："+msg.toString());
    }


    /**
     * 读取完毕的处理方法
     * @param ctx
     * @throws Exception
     */
    @Override
    public void channelReadComplete(ChannelHandlerContext ctx) {
        ByteBuf buf = Unpooled.copiedBuffer("helloClient",StandardCharsets.UTF_8);
        ctx.writeAndFlush(buf);

    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx,Throwable cause){
        ctx.close();
    }
}

NettyClient代码模板

/**
 * 客户端代码
 */
public class NettyClient {

    public static void main(String[] args) throws InterruptedException {
        EventLoopGroup group = new NioEventLoopGroup();
        try {
            Bootstrap bootstrap = new Bootstrap()
                    .group(group)
                    .channel(NioSocketChannel.class)
                    .handler(new ChannelInitializer() {
                        @Override
                        protected void initChannel(SocketChannel socketChannel) throws Exception {
                            ChannelPipeline pipeline = socketChannel.pipeline();
                            //解码器
                            pipeline.addLast(new StringDecoder());
                            //编码器
                            pipeline.addLast(new StringEncoder());
                            pipeline.addLast(new NettyClientHandler());
                        }
                    });

            ChannelFuture channelFuture = bootstrap.connect("127.0.0.1",9000).sync();

            channelFuture.channel().closeFuture().sync();

        }finally {
            group.shutdownGracefully();
        }
    }
}

NettyClientHandler代码示例

/**
 * 只重写了基础常用的功能
 */
public class NettyClientHandler extends ChannelInboundHandlerAdapter {


    /**
     * 客户端连接服务端完成时，会触发这个方法
     *
     * @param ctx
     */
    @Override
    public void channelActive(ChannelHandlerContext ctx) {
        ByteBuf buf = Unpooled.copiedBuffer("helloServer", Charsets.UTF_8);
        ctx.writeAndFlush(buf);

    }
    /**
     * 当通道有读取事件时，会触发。服务端发送数据给客户端时
     *
     * @param ctx
     * @param msg
     */
    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) {
//        ByteBuf buf = (ByteBuf)msg;
        System.out.println("收到服务端消息："+msg.toString());
    }
    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
        cause.printStackTrace();
        ctx.close();
    }
}

Handler有两种类型：InboundHandler和OutboundHandler

InboundHandler是输入的数据流向，是从上向下的。
OutboundHandler的输出的数据流量，是从下向上的。
当然，这个输入和输出都是相对来说的。
我们写netty程序也是遵循netty给我们固定的流程，来开发对应的数据处理handler。

本篇文章简单介绍了netty的服务端和客户端的基本写法。后面会补充拆包粘包的处理。