Java JPA Polymorphic Many-to-One Mapping

I am trying to map JPA (now using Hibernate). Many-to-one relationship with polymorphic type, but I had no luck. I don't understand why this is not possible, or why I would be forced to declare a specific type in the display. Here's an example:

@MappedSuperclass
class BaseClass {
    @Id
    long id;
}
class ClassWithList extends BaseClass {
    String attribute;

    @OneToMany(mappedBy="backPointer")
    List<ListClass> list;
}
class ListClass extends BaseClass {
    String listItemData;

    @ManyToOne
    @JoinColumns({
       @JoinColumn(name="baseId"),
       @JoinColumn(name="baseType"),
    })
    BaseClass backPointer;
}

      

        
        
        
      

    

Thanks for any advice you can give.