Netty 从LengthFieldBasedFrameDecoder返回的缓冲区太小 我目前正在评估NETY来处理java客户端的socket通信，以便与C++服务器集成。消息传递协议具有以下结构- 带大小的（类型）（子类型）（长度）（消息体） -长度包括标题

遵循Netty api I子类LengthFieldBasedFrameDecoder以接收有效的完整数据包，然后根据接收到的类型对每个数据包进行解码。从我使用的文档中-

• lengthFieldOffset=8
• lengthFieldLength=4
• 长度调整=-12（=HDR1+LEN的长度，负）
• initialBytesToStrip=0

它可以正常工作大约5分钟（我大约每5秒收到一条消息），然后解码事件包含一个远小于消息大小的ChannelBuffer。（我在坠机前多次收到此消息）。很明显，我的内部解码代码中出现了BufferUnderflowException。我做错什么了吗？使用LengthFieldBasedFrameDecoder时，是否应保证消息的缓冲区大小正确

LengthFieldBasedFrameDecoder类-

public class CisPacketDecoder extends LengthFieldBasedFrameDecoder
{
    public CisPacketDecoder(int maxFrameLength, int lengthFieldOffset,
            int lengthFieldLength, int lengthAdjustment, int initialBytesToStrip) {
        super(maxFrameLength, lengthFieldOffset, lengthFieldLength, lengthAdjustment,
                initialBytesToStrip);       
    }

    @Override
    protected Object decode(ChannelHandlerContext ctx, Channel channel, ChannelBuffer buf)
            throws Exception 
    {       
        CisMessage message = null;      
        int type = buf.getInt(0); //Type is always first int
        CisMessageType messageType = CisMessageType.fromIntToType(type);
        if(messageType != null)
        {
            message = messageType.getObject();
            if(message != null)
            {
                message.decode(buf.toByteBuffer());
            }
            else
            {
                System.out.println("Unable to create message for type " + type);
            }
        }

        //mark the Channel buf as read by moving reader index
        buf.readerIndex(buf.capacity());
        return message;
    }

}

并在这里实例化

public class PmcPipelineFactory implements ChannelPipelineFactory 
{

    @Override
    public ChannelPipeline getPipeline() throws Exception
    {
        ChannelPipeline pipeline = Channels.pipeline();

        pipeline.addLast("encoder", new CisPacketEncoder());
        pipeline.addLast("decoder", new CisPacketDecoder(1024, 8, 4, -12, 0));      
        pipeline.addLast("handler", new MsgClientHandler());
        return pipeline;
    }


} 

---

您需要调用super.decode（..）并在decode（..）方法中对返回的ChannelBuffer进行操作

就是这样,

public class CisPacketDecoder extends LengthFieldBasedFrameDecoder {
    public CisPacketDecoder(int maxFrameLength, int lengthFieldOffset,
            int lengthFieldLength, int lengthAdjustment, int initialBytesToStrip) {
        super(maxFrameLength, lengthFieldOffset, lengthFieldLength, lengthAdjustment,
            initialBytesToStrip);       
    }

    @Override
    protected Object decode(ChannelHandlerContext ctx, Channel channel, ChannelBuffer buf)
        throws Exception {

        // THIS IS IMPORTANT!!!!!
        ChannelBuffer decoded = (ChannelBuffer) super.decode(ctx, channel, buf);
        if (decoded == null) {
            return null;
        }

        // NOW ONLY OPERATE ON decoded 
        CisMessage message = null;      
        int type = decoded.getInt(0); //Type is always first int
        CisMessageType messageType = CisMessageType.fromIntToType(type);
        if(messageType != null) {
            message = messageType.getObject();
            if(message != null) {
                message.decode(decoded.toByteBuffer());
            } else {
                System.out.println("Unable to create message for type " + type);
            }
        }
        return message;
    }
}

---

请务必检查大写注释。

非常感谢，现在一切正常。别以为我一个人就能找到那个！