ProviderBase: JAX-WS controller http handler method returning a generic collection forces static type serialisation for that collection

[ylexus]

Example:

class Controller {
    @GET 
    public Collection<MyClass> getCollection {
        return Arrays.<MyClass>asList(new SubclassOfMyClass())
    }
}

class MyClass {
    public getA() {
       ...
    }
}
class SubclassOfMyClass extends MyClass {
    public getB() {
       ...
    }
}

When used with Jersey's JacksonFeature, JSON returned will only contain attribute A and not attribute B because static serialisation of the root type is forced and there is no way I can override that. If, however, I wrap the collection with some other non-generic type, then static serialisation will not be forced and I will get both attribute "a" and "b" in the JSON produced by this GET.

jackson-jaxrs-base version used is 2.5.4.

Issue originally reported against Jersey but they are inclined to blame jackson: https://java.net/jira/browse/JERSEY-2939.

[cowtowncoder]

This is a tricky problem, if I recall correctly, and I am not quite sure what to do with it.
My general advice at this point is to never use a generic type as root value, because of multiple related issues, with or without JAX-RS/JAX-WS. Beyond issue of static/dynamic content types, there is also the problem with polymorphism (for general case, hopefully not in your case).

But first things first: just to make sure, can this be reproduced with 2.6.1 as well?

[ylexus]

This is how we worked around it, having something else wrapping the collection as a root value was better design anyway. To be honest, our problem is solved and I do not think I can spend much more time on this. I just thought it's something you may want to fix, but since it's complicated maybe documentation could explicitly warn users from doing it.

[cowtowncoder]

@ylexus I appreciate your reporting this, and I agree that at very least it is worth commenting. It has been an on-going challenge as well, trying to balance sometimes conflicting needs. And finally, it is valuable to have issues filed for when others hit the same problem -- at least they can read more about problem itself, work-arounds and so forth.

I will keep this open for now, since there are some ideas for 2.7 that could help here.