基本的Netty echo服务器-字符串编码器错误?

This is my first time using Netty and I'm having trouble making a simple echo server! I looked at docs and it says to use the string encoder and decoder, which I am not using properly apparently. For the framedecoder, I'd like to use the header messages with one byte length, but that doesn't seem to be working either due to the string issue. I assume my implementation of the PipelineFactory is messed up.This is my first time using Netty and I'm havin