Netty学习——实战篇8 Handler链调用、TCP粘包和拆包 备份

 1 Handler链调用-需求

        使用自定义的编码器和解码器来说明Netty的Handler调用机制。客户端发送long类型数据到服务端；服务端发送long到客户端。

2 Handler链调用-实战

2.1  NettyServer.java

public class NettyServer {
    public static void main(String[] args) {
        NioEventLoopGroup bossGroup = new NioEventLoopGroup(1);
        NioEventLoopGroup workerGroup = new NioEventLoopGroup();
        try {
            ServerBootstrap serverBootstrap = new ServerBootstrap();
            serverBootstrap.group(bossGroup,workerGroup)
                    .channel(NioServerSocketChannel.class)
                    .childHandler(new MyServerInitializer());//自定义一个初始化类
            ChannelFuture sync = serverBootstrap.bind(8000).sync();
            sync.channel().closeFuture().sync();
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }
}

2.2 MyServerInitializer.java

public class MyServerInitializer extends ChannelInitializer<SocketChannel> {
    @Override
    protected void initChannel(SocketChannel ch) throws Exception {
        ChannelPipeline pipeline = ch.pipeline();
        //对入站的Hadler进行解码
        pipeline.addLast(new MyByteToLongDecoder2());
        //对出站的Handler进行解码
        pipeline.addLast(new MyLongToByteEncoder());
        //自定义Handler
        pipeline.addLast(new MyServerHandler());
    }
}

2.3 MyByteToLongDecoder2.java

public class MyByteToLongDecoder2 extends ReplayingDecoder<Void> {
    @Override
    protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception {
        System.out.println("MyByteToLongDecoder2 被调用");
        out.add(in.readLong());
    }
}

 2.4 MyLongToByteEncoder.java

public class MyLongToByteEncoder extends MessageToByteEncoder<Long> {
    @Override
    protected void encode(ChannelHandlerContext ctx, Long msg, ByteBuf out) throws Exception {
        System.out.println("MyLongToByteEncoder 被调用");
        System.out.println("msg = " + msg);
        out.writeLong(msg);
    }
}

2.5 MyServerHandler.java

public class MyServerHandler extends SimpleChannelInboundHandler<Long> {
    @Override
    protected void channelRead0(ChannelHandlerContext ctx, Long msg) throws Exception {
        System.out.println("从客户端:"+ctx.channel().remoteAddress() + "读取到long类型数据："+msg);
        //向客户端发送一个long类型数据
        ctx.writeAndFlush(123456L);
    }

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

2.6 NettyClient.java

public class NettyClient {
    public static void main(String[] args) {
        NioEventLoopGroup g = new NioEventLoopGroup();
        try {
            Bootstrap bootstrap = new Bootstrap();
            bootstrap.group(g)
                    .channel(NioSocketChannel.class)
                    .handler(new MyClientInitializer());
            ChannelFuture sync = bootstrap.connect("127.0.0.1",