Retrieve only the superclass from a class hierarchy

Question

I have an scenario as the following:

@Entity
@Table(name = "ANIMAL")
@Inheritance(strategy = InheritanceType.JOINED)

public class Animal implements Serializable {

    @Id
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "S_ANIMAL")
    @SequenceGenerator(name = "S_ANIMAL", sequenceName = "S_ANIMAL", allocationSize = 1)
    public int getNumero() {
        return numero;
    }

    public void setNumero(int numero) {
        this.numero = numero;
    }
        .
        .
        .
}

and as the subclass:

@Entity
@Table(name = "DOG")
public class Dog extends Animal {

    private static final long serialVersionUID = -7341592543130659641L;
        .
        .
        .
}

I have a JPA Select statement like this:

SELECT a FROM Animal a;

I'm using Hibernate 3.3.1

As I can see the framework retrieves instances of Animal and also of Dog using a left outer join.

Is there a way to Select only the "part" Animal? I mean, the previous Select will get all the Animals, those that are only Animals but not Dogs and those that are Dogs.

I want them all, but in the case of Dogs I want to only retrieve the "Animal part" of them.

I found the @org.hibernate.annotations.Entity(polymorphism = PolymorphismType.EXPLICIT) but as I could see this only works if Animal isn't an @Entity.

Thanks a lot.

Answer 1

Actually, there is a way to get just the superclass: you just need to use the native query from JPA. In my case, I am using JPA Repositories. Therefore, it would be something like that:

@Query(value = "SELECT * FROM animal", nativeQuery = true)
List<Resource> findAllAnimal();

The flag nativeQuery as true allow running the native SQL on database.

If you are using Entity Manager then check this out: https://www.thoughts-on-java.org/jpa-native-queries/