JBoss Netty的ReplayingDecoder问题
这个类非常好用，但是有个问题：
decode
protected abstract Object decode(ChannelHandlerContext ctx,
Channel channel,
ChannelBuffer buffer,
T state)
throws ExceptionDecodes the received packets so far into a frame.
Parameters:
ctx - the context of this handler
channel - the current channel
buffer - the cumulative buffer of received packets so far. Note that the buffer might be empty, which means you should not make an assumption that the buffer contains at least one byte in your decoder implementation.
state - the current decoder state (null if unused)
Returns:
the decoded frame
Throws:
Exception
