Netty ReplayingDecoder 源码分析与特性解读以及其他编解码器介绍

转自：https://blog.csdn.net/wzq6578702/article/details/78826494

在介绍ReplayingDecoder之前 想看一下它的用法，构建一个服务端和客户端的模型：

服务端：

public class MyServer {
    public static void main(String[] args) throws InterruptedException {
        EventLoopGroup bossGroup = new NioEventLoopGroup(1);
        EventLoopGroup workerGroup = new NioEventLoopGroup();
        try{
            ServerBootstrap serverBootstrap = new ServerBootstrap();
            serverBootstrap.group(bossGroup,workerGroup).channel(NioServerSocketChannel.class)
                    .childHandler(new MyServerInitializer());
            ChannelFuture channelFuture = serverBootstrap.bind(8899).sync();
            channelFuture.channel().closeFuture().sync();
        }finally{
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }
}

服务端initializer：

public class MyServerInitializer extends ChannelInitializer {
    @Override
    protected void initChannel(SocketChannel ch) throws Exception {
        ChannelPipeline pipline = ch.pipeline();
        pipline.addLast(new MyReplayingDecoder());//使用ReplayingDecoder
        pipline.addLast(new MyLongToByteEncoder());
        pipline.addLast(new MyServerHandler());
    }
}

ServerHandler:

public class MyServerHandler extends SimpleChannelInboundHandler {
    @Override
    protected void channelRead0(ChannelHandlerContext ctx, Long msg) throws Exception {
        System.out.println(ctx.channel().remoteAddress()+" --> "+msg);
        ctx.writeAndFlush(654321L);
    }

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

MyReplayingDecoder:

public class MyReplayingDecoder extends ReplayingDecoder {

    @Override
    protected void decode(ChannelHandlerContext ctx, ByteBuf in, List