A Camel-CXF's provider endpoint returns an HTTP 200 with an empty SOAP message when it should be returning an HTTP 202 with no content.
This is analogue to the jaxws's Provider behavior implemented in:
CXF-3926 Supporting JAXWS Provider's null response handling (the provider's invoke may return a null to indicate no response should be sent back)
where property jaxws.provider.interpretNullAsOneway at the endpoint determines whether a null is interpreted as a oneway call (i.e. no response).
Concretely, Jaxws 2.2 section 5.1.1 states:
"When an invoke method returns null, it is considered that no response needs to be sent by service."
This use case assumes there is no information about the operation's MEP (no wsdl, no java annotation).
This offers an option of using a provider endpoint to dynamically change its response behavior based on the retern value.
Namely, if the service returns a non-null value, the response is a normal HTTP 200 with the corresponding payload. In contrast, if the service returns a null, the response becomes an HTTP 202 with no content.
I think it makes sense to align the Camel-CXF Provider's endpoint to support this behavior.
I am proposing a fix in DefaultCxfBinding to provide this behavior.
Additionally, to simplify the configuration of a provider endpoint, I think it is practical to introduce a default payload provider SEI so that the provider SEI does not explicitly configured in the endpoint configuration.
I am attaching a patch file including these changes and test cases to illustrate these points.
Could you have a look at this?