I have the following tables (pseudocode):

conversations
  id bigserial

subscribers
  id serial

asset_categories
  id smallserial

requirements
  id serial
  requireable_type text
  requireable_id bigint

For Hibernate I have a MappedSuperclass similar to this:

@MappedSuperclass
public abstract class BaseEntity<T extends Serializable> {
  private T id;

  @Id
  @GeneratedValue(strategy = GenerationType.IDENTITY)
  public T getId() {
    return id;
  }
}

And I have these entities:

Conversation<Long>
Subscriber<Integer>
AssetCategory<Short>
Requirement<Integer>

As you can see, requirements.requireable_type and requirements.requireable_id supports a polymorphic association to the three other types (and bigint of requireable_id covers the id types of the foreign keys).

But I haven’t been able to come up with the way to implement this in my Requirement entity.

I’ve tried an @Any like this in Requirement:

  @Any(fetch = FetchType.LAZY)
  @AnyDiscriminator(DiscriminatorType.STRING)
  @AnyDiscriminatorValues({
    @AnyDiscriminatorValue(discriminator = "subscriber", entity = Subscriber.class),
    @AnyDiscriminatorValue(discriminator = "conversation", entity = Conversation.class),
    @AnyDiscriminatorValue(discriminator = "asset_category", entity = AssetCategory.class)
  })
  @AnyKeyJavaClass(Long.class)
  @Column(name = "requireable_type")
  @JoinColumn(name = "requireable_id")
  public Requireable getRequireable() { return requireable; }  // I have an interface Requireable they all "implement"

But then only the Conversation can be associated and the Requirement persisted. The others fail with errors like java.lang.ClassCastException: class java.lang.Integer cannot be cast to class java.lang.Long (java.lang.Integer and java.lang.Long are in module java.base of loader 'bootstrap')

This seems like a normal-enough scenario where the polymorphic relationship is to various tables with different types of identifiers.

So… how do I support this relationship? Should I jettison the @Any annotations and create … something? A CompositeUserType?