08 开箱即用：Netty 支持哪些常用的解码器？

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08 开箱即用：Netty 支持哪些常用的解码器？

固定长度解码器 FixedLengthFrameDecoder

通过构造函数设置固定长度的大小 frameLength，无论接收方一次获取多大的数据，都会严格按照 frameLength 进行解码。如果累积读取到长度大小为 frameLength 的消息，那么解码器认为已经获取到了一个完整的消息。如果消息长度小于 frameLength，FixedLengthFrameDecoder 解码器会一直等后续数据包的到达，直至获得完整的消息。

public class EchoServer {

    public void startEchoServer(int port) throws Exception {
    
        EventLoopGroup bossGroup = new NioEventLoopGroup();
        EventLoopGroup workerGroup = new NioEventLoopGroup();
        try {
            ServerBootstrap b = new ServerBootstrap();
            b.group(bossGroup, workerGroup)
                    .channel(NioServerSocketChannel.class)
                    .childHandler(new ChannelInitializer<SocketChannel>() {
                    
                        @Override
                        public void initChannel(SocketChannel ch) {
                            ch.pipeline().addLast(new FixedLengthFrameDecoder(10));
                            ch.pipeline().addLast(new EchoServerHandler());
                        }
                    });

            ChannelFuture f = b.bind(port).sync();
            f.channel().closeFuture().sync();
        } finally {
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }

    }

    public static void main(String[] args) throws Exception {
        new EchoServer().startEchoServer(8088);
    }

}

@Sharable
public class EchoServerHandler extends ChannelInboundHandlerAdapter {

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) {
        System.out.println("Receive client : [" + ((ByteBuf) msg).toString(CharsetUtil.UTF_8) + "]");
    }
}

…未完待续