Netty4的可读字节太小

问题描述：

当使用Netty4解码时，我得到异常。该消息的长度只有640，但是这个只读的字节数是不够的。Netty4的可读字节太小

06-19 21:45:13.150 4192-4233/com.seewo.remote V/RemoteMassageDecoder: Decoder messageType == 1, messageLength: 640 
06-19 21:45:13.152 4192-4233/com.seewo.remote E/exceptionCaught: io.netty.handler.codec.DecoderException: java.lang.Exception: readableBytes is too small

1，首先，在ChannelInitializer

private static final int MAX_FRAME_LENGTH = 1024 * 1024; 
private static final int LENGTH_FIELD_LENGTH = 4; 
private static final int LENGTH_FIELD_OFFSET = 1; 
private static final int LENGTH_ADJUSTMENT = 2; 
private static final int INITIAL_BYTES_TO_STRIP = 0; 
channelPipeline.addLast("decoder", new RemoteMassageDecoder(MAX_FRAME_LENGTH, 
       LENGTH_FIELD_LENGTH, LENGTH_FIELD_OFFSET, LENGTH_ADJUSTMENT, INITIAL_BYTES_TO_STRIP)); 
channelPipeline.addLast("encoder", new RemoteMessageEncoder());

添加解码器

2，第二，从服务器解码器字节

@Override 
protected Object decode(ChannelHandlerContext ctx, ByteBuf in) throws Exception { 
    byte startCharacter = in.readByte(); 
    int messageLength = in.readInt(); 
    byte messageType = in.readByte(); 
    in.readByte(); 
    Log.v("RemoteMassageDecoder", "startCharacter == " + (startCharacter & 0xff)); 
    Log.v("RemoteMassageDecoder", "Decoder messageType == " + messageType + ", messageLength: " + messageLength); 
    if (messageLength < 0) { 
     throw new Exception("messageLength < 0"); 
    } 
    if (messageLength == 0 || messageType == 0) { 
     in.readByte(); 
     return null; 
    } 
    if (in.readableBytes() < messageLength) { 
     throw new Exception("readableBytes is too small"); 
    } 
    byte[] content = new byte[messageLength]; 
    in.readBytes(content); 
    byte stopCharacter = in.readByte(); 
    if (startCharacter != START_CHARACTER || stopCharacter != STOP_CHARACTER) { 
     return null; 
    } 
    return ProtocolPack.parseFrom(AESHelper.decryptContent(content)); 
}

可能重复的[Netty channelRead没有得到完整的消息]（https://stackoverflow.com/questions/31327443/netty-channelread-not-getting-full-message） – Ferrybig

答

原因这个问题很简单：你不能期望TCP流将始终同时返回足够的数据。

解决方案也很简单：您的ChannelHandler只需扩展ReplyingDecoder即可帮助您正确处理底层蒸汽。

Netty4的可读字节太小

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