Returning polymorphic objects from Google Cloud endpoints

I just tried to use polymorphism on objects to create classes with hierarchy using objectify. For example, I have a base Entity called Animal and there are subclasses for that name Mammal and Reptile, which are also entities.
And when I try to store data and retrieve it, it works great and I can convert from the base Animal class to Mammal or Reptile.

But when I try to return a list of animals in google endpoints, this inheritance is not preserved. And I could not convert from Animal class to Mammal or Reptile on the client side.

In fact, the google cloud endpoint creates a different model type that is actually returned as JSON at the endpoints for which it is different from our entities, and inheritance is not preserved in these model classes.

Basically, I need to query all animals and client-side depending on the type of object, regardless of whether a mammal or a reptile renders it the appropriate interface.

Here is some sample code,

I have two classes: Animals and Mammals. And the mammal is a subclass of Animal.

Animal annie = new Animal();
annie.name = "Annnnn";
ofy().save().entity(annie).now();

Mammal mam = new Mammal();
mam.name = "Mammmaaaal";
mam.longHair = true;
ofy().save().entity(mam).now();

// This will return the Cat
Animal fetched = ofy().load().type(Animal.class).id(mam.id).now();
return Animal;

      

        
        
        
      

    

I will return this animal object which can be a Mammal instance and I have to convert it to Mammal or any other Animal subclass based on its client side instance.

Does anyone have a solution or workaround for this problem?

Below is the json response for getting a list of animals. But I was unable to convert the animal object to Mammal on the Android client side.

{
 "items": [      
  {
   "id": "5631986051842048",
   "name": "mammm",
   "longHair": true,
   "kind": "animalApi#resourcesItem"
  },
  {
   "id": "5697423099822080",
   "name": "Animalll",
   "kind": "animalApi#resourcesItem"
  }
 ],
 "nextPageToken":     "CjwSNmofc35tb3ZpZWFkZGljdC12Mi1kZWJ1Zy1jb2RlaGFyZHITCxIGQW5pbWFsGICAgIDruI8KDBgAIAA",
 "kind": "animalApi#resources",
 "etag": "\"cZTcM4l5N_SjrKcEhGkKJEl9rU4/rs8BjIS52gHgN0B1UGEEi2DERwE\""
}