When a http decoding exception like TooLongFrameException is thrown by the HttpObjectDecoder (process method), RestEasy is not checking it and processes an incompletely parsed request. The exception is not bubbling up the stack but is accessible in the message object that the request contains.

As an example, if the header size goes beyond the limit set in NettyJaxrsServer's HttpRequestDecoder instance, it will process the headers under the limit but ignore the headers above the limit.

I am not sure how other frameworks working on top of Netty do it, but I think Resteasy might need to check the value of request.getDecoderResult().isFailure() in RestEasyHttpRequestDecoder's decode method.