Netty重写SimpleChannelInboundHandler后的ChannelRead0方法从未被调用？

Question

Netty重写SimpleChannelInboundHandler后的ChannelRead0方法从未被调用？

public class RequestHandler extends SimpleChannelInboundHandler<MessageProtocol<MessageRequest>> {
@Override
    protected void channelRead0(ChannelHandlerContext channelHandlerContext, MessageProtocol<MessageRequest> protocol)
            throws Exception {
// 请求过来这里的代码从未被调用
// 业务代码....
}
}

// .........
.childHandler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel socketChannel) {
                            socketChannel.pipeline()
                                    // 协议编码
                                    .addLast(new StringEncoder())
                                    // 协议解码
                                    .addLast(new StringDecoder())
                                    // 请求处理器
                                    .addLast(new RequestHandler());
                        }
                    }).childOption(ChannelOption.SO_KEEPALIVE, true);

// .........

希望结果：重写后的方法【RpcRequestHandler#channelRead0】每次有新请求都被调用