从Jersey资源返回超类

Question

I'm doing a very simple thing that should just work, IMO. I've got a resource like:

@GET
@Produces(MediaType.APPLICATION_JSON)
@Path("{nodeType}/{uuid}")
public Object getResourceInfo(@PathParam("nodeType") String nodeType,
                              @PathParam("uuid") String uuid,
                              @Context SecurityContext authority) { ...

Note I'm returning type Object. This is because depending on the call (here depending on the nodeType argument) I want to return a different concrete class (which will always be @XmlRootElement) and have that get marshalled out into the response.

However, this does not work. I get exception like:

Exception Description: A descriptor for class com.mycompany.XmlElementTypeInstance was not found in the project.  For JAXB, if the JAXBContext was bootstrapped using TypeMappingInfo[] you must call a marshal method that accepts TypeMappingInfo as an input parameter.

If I change Object to a single subclass, it works. But I want it to be able to handle any subclass, XmlElementTypeInstance, XmlElementTypeInstance2, etcetc.

I tried making a common interface from which all of the XmlElementTypeInstance subclasses derive, but then I only get those properties in the interface, not the extra properties in the subclasses. Playing with @XmlElementRef and adding all possible properties to the common interface is extremely ugly and can't work quite correctly to generate the JSON I want, so please don't suggest that. =)

Is there any way to do this? It seems like simple, basic, necessary functionality... any other REST framework I've used, no problem...

Answer 1

The solution it turns out is simple (had to read the JSR instead of the actual Jersey docs, however!)

Instead of returning Object, returning Response (section 3.3.3 of JSR 339) with the object set as the entity forces the implementation to pick an appropriate MessageBody{Writer,Reader} at runtime.

return Response.ok().entity(<the object>).build();

Lost way too much time on this. Hope it helps someone later. =/