Include sub-classes with generated Google Cloud Endpoint client library

Question

I am currently working on an Android project that stores data using Google Datastore and is accessible via the Cloud Endpoints with the Objectify library. The objectify library does a decent job explaining polymorphism using the "@Subclass" annotation however the problem I'm having is that when I generate the client library for use in the Android code the sub-classes are not included. Is there a way to force the compiler to include these classes?

Here is a basic example of what I'm doing. Lets take the polymorphism example from the Objectify documentation:

@Entity
public class Animal {
    @Id Long id;
    String name;
}

@Subclass(index=true)
public class Mammal extends Animal {
    boolean longHair;
}

@Subclass(index=true)
public class Cat extends Mammal {
    boolean hypoallergenic;
}

It's worth mentioning that all three of these classes have been registered with "ObjectifyService.factory().register()." Using the classes above I have a method in my api that looks similar to this:

@ApiMethod(
            name = "getAnimals", path = "zoo/getAnimals", httpMethod = ApiMethod.HttpMethod.GET
)
public Collection<Animal> getAnimals(final User user, @Named("IdList") Collection<Long> idList)
        throws UnauthorizedException {
    // If the user is not logged in, throw an UnauthorizedException
    if (user == null) {
        throw new UnauthorizedException("Authorization required");
    }

    Map<Long,Animal> animalMap = ofy().load().type(Animal.class).ids(idList);

    ArrayList<Animal> animals= new ArrayList<>();
    for (Long animalId:idList) {
        animals.add(animalMap.get(animalId));
    }
    return animals;
}

As you can see the final ArrayList "animals" could contain Animals, Mammals, or Cats however the generated library only gives me access to the Animal class. I need to make sure that the sub-classes are available to the Android code. How does the compiler know which classes to include and is there a way to force a class to be added? Does the polymorphism even carry over to the client side or is that only supported server side?

Answer 1

This is not a great answer but you could expose a no-op API which returns those types (in reality just return null;). This should force the class generation. If there's a more formal way to do this, feel free to correct me.