参见 Netty的 LengthFieldBasedFrameDecoder

    1. public class TestLengthDecoder {
    2.     public static void main(String[] args) {
    3.         EmbeddedChannel channel = new EmbeddedChannel(
    4.                 new LengthFieldBasedFrameDecoder(1024,0,4,0,4),
    5.                 new LoggingHandler(LogLevel.DEBUG),
    6.                 new ChannelInboundHandlerAdapter(){
    7.                     @Override
    8.                     public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
    9.                         ByteBuf buf = (ByteBuf) msg;
    10.                         System.out.println(buf.toString(Charset.defaultCharset()));
    11.                     }
    12.                 }
    13.         );
    15.         ByteBuf buf = ByteBufAllocator.DEFAULT.buffer();
    16.         buf.writeInt(12);
    17.         buf.writeBytes("hello, world".getBytes());
    18.         buf.writeInt(6);
    19.         buf.writeBytes("你好".getBytes());
    20.         channel.writeInbound(buf);
    21.     }
    22. }