I've just reread the REST and SOAP United blog entry I did back in July 2008, more than 2 years ago.
This theme is as active as ever in CXF; as I've mentioned on this blog quite a few times we've been trying to provide the environment for SOAP developers to experiment with JAX-RS with as few changes as possible and indeed, quite a few CXF SOAP developers do use JAX-RS today while continuing running their SOAP services. Some developers are choosing to annotate the same service interface or implementation class with both JAX-WS and JAX-RS annotations, while some of those, preferring to do the WSDL-first approach, have tried to apply an external CXF JAX-RS user model, something that is demonstrated now in one of the Talend SF demos, and thus avoiding having to modify the (generated) code altogether.
There have been some new improvements recently in the integration between JAX-WS and JAX-RS runtimes.
First, many of the custom CXF annotations are now supported by the JAX-RS frontend. So one can easily do a combined JAX-WS and JAX-RS service which for example supports a FastInfoset feature by using CXF FastInfoset, Feature or In/OutInterceptors annotations, possibly also relying on say a DataBinding annotation enabling the CXF SDO DataBinding.
It was possible to wrap CXF DataBindings as JAX-RS MessageBodyReaders and MessageBodyWriters for a while, with XmlBeans being the latest DataBinding supported, thus effectively reusing the same provider instance between JAX-WS and JAX-RS endpoints.
But just a couple of weeks ago a CXF user asked about having JAX-RS MessageBodyWriters being used by SOAP JAX-WS endpoints. Does it sound a bit hairy to you :-), irrespectively of whether you are a JAX-WS or JAX-RS developer ?
It might sound so initially but I think it is just the next natural step in the way both frontends can get integrated.
A user who asked a question had developed an optimized XML Stax provider and did not want to rely on JAXB while working with JAX-WS services. So I just went ahead and added a utility JAX-RS DataBinding which can be plugged in into JAX-WS endpoints and which will delegate to custom JAX-RS writers and readers. I used a JAXBElementProvider shipped with the JAX-RS frontend to test this feature. Thus, even though most SOAP developers will unlikely use the feature due to a number of limitations, some of them might go ahead and see if some of the existing JAX-RS XML-aware providers can do something useful for their SOAP applications.
I've just thought about doing SOAP-Atom with Atom payloads being transmitted inside SOAP envelopes and handled by CXF JAX-RS Atom providers. But no, I won't advocate doing the double enveloping (soap:Envelope plus atom:feed) at all even though this feature makes it possible now :-).
Have fun :-)