Generic JAX-RS service class and generic type resolution

[Thibaut Robert]

Hi!

I would like to share a strange behaviour I have with cxf JAX-RS
frontend. I am writing a generic JAX-RS service class like this:

public class AbstractRestController<T extends RestResource> {
    @POST
    public Response add(final T resource) { ... }
}

where RestResource is an interface.

Then I use a concrete implementation:
public class ConcreteRestController exends
AbstractRestController<ConcreteRestResource> { ... }

I have an error when a post a request, caused by the way the generic
type T is resolved:
org.codehaus.jackson.map.JsonMappingException: Can not construct
instance of cxfjaxrs.RestResource, problem: abstract types can only be
instantiated with additional type information

T is resolved as RestResource instead of ConcreteRestResource.

I found out that in the method InjectionUtils.getSuperType(), it
prefers using the type parameter bound when present, instead of
calculating the real type argument. Is there any motivation beyond
this ? In this case, the actual argument type can be determined at
runtime, and is better that the parameter bound.

I got things working by using this trick: public class
AbstractRestController<T extends Object & RestResource> (because in
this case it only considers the first bound, and thus go beyond to
find a type more precise than Object)

Is there any way to fix this ?

I tested with 2.7.7-SNAPSHOT and 3.0.0-SNAPSHOT. Things works out of
the box with Jersey.

BR,
Thibaut