CXF continuation enhancement

[Willem Jiang]

Hi

I just did some work to let the camel-cxf leverage the CXF continuation 
framework which you did. I just found current CXF continuation which 
suspend is implemented by throw the runtime exception. This 
implementation has a shortcoming which cannot call the other framework's 
async API after continuation suspend is called as Jetty7 does.

This will introduce a situation that continuation resume will be called 
before the continuation suspend is called if the famework's async API is 
finally using the thread to do the job.

So I'm thinking of some enhancement could be possible to let CXF 
continuation leverage Jetty 7 new continuation API.

Any idea?

Willem