Allow ping handler to be set on ServerWebScoket

[trevorurquhart]

Describe the feature

Allow a ping handler to be specified on a ServerWebSocket (similar to pongHandler)

Use cases

Currently the ServerWebSocket responds to a ping with a pong:

// Echo back the content of the PING frame as PONG frame as specified in RFC 6455 Section 5.5.2
conn.writeToChannel(new PongWebSocketFrame(frame.getBinaryData().copy()));

We've had a use case where a user (either inadvertently or deliberately) flooded our websockets with 1000s of pings/sec. It would be nice to be able to monitor the number of pings a client web socket is sending.

We can get hold of this information if we add a framehandler to the websocket. The only issue with that is if you want to specify a text/binary message handler, the frame handler is overridden.

Contribution

Happy to supply a PR if required.

[vietj]

I think we could check in the frameHandler(...) method if the current frame handler is not null and is an instance of FrameAggregator and swap it to preserve the current frame handler. PR is welcome @trevorurquhart

[trevorurquhart]

Apologies, but I'm not totally following. Wouldn't I still lose my frame handler with this:

serverWebSocket
.frameHandler(myFrameHandler)
.textMessageHandler(myTextHandler) //Replaces my frame handler with FrameAggregator

The other issue with using a frame handler to monitor pings is that I have to re-implement FrameAggregator and attach text/binary handlers to my implementation.

Is there something I'm missing which makes this problematic?:

serverWebSocket
.textMessageHandler(myTextHandler)
.pingHandler(myPingHandler)

[vietj]

Actually it looks simpler to simply have a field FrameAggregator in addition of the frameHandler : #4799