Class FlowControlHandler

java.lang.Object
io.netty.channel.ChannelHandlerAdapter
io.netty.channel.ChannelInboundHandlerAdapter
io.netty.channel.ChannelDuplexHandler
io.netty.handler.flow.FlowControlHandler
All Implemented Interfaces:
ChannelHandler, ChannelInboundHandler, ChannelOutboundHandler
public class FlowControlHandler extends ChannelDuplexHandler
The FlowControlHandler ensures that only one message per read() is sent downstream.

Classes such as ByteToMessageDecoder or MessageToByteEncoder are free to emit as many events as they like for any given input. A channel's auto reading configuration doesn't usually apply in these scenarios. This is causing problems in downstream ChannelHandlers that would like to hold subsequent events while they're processing one event. It's a common problem with the HttpObjectDecoder that will very often fire an HttpRequest that is immediately followed by a LastHttpContent event. 

ChannelPipeline pipeline = ...;

pipeline.addLast(new HttpServerCodec());
pipeline.addLast(new FlowControlHandler());

pipeline.addLast(new MyExampleHandler());

class MyExampleHandler extends ChannelInboundHandlerAdapter {
  @Override
  public void channelRead(ChannelHandlerContext ctx, Object msg) {
    if (msg instanceof HttpRequest) {
      ctx.channel().config().setAutoRead(false);

      // The FlowControlHandler will hold any subsequent events that
      // were emitted by HttpObjectDecoder until auto reading is turned
      // back on or Channel#read() is being called.
    }
  }
}
See Also: