[hibernate-dev] IdClass superclasses

[Gail Badner]

I've created https://hibernate.atlassian.net/browse/HHH-13776.

Thanks!
Gail


On Tue, Dec 10, 2019 at 1:30 PM Steve Ebersole <steve at hibernate.org> wrote:

> Actually I was thinking of @EmbeddedId, but you were asking about @IdClass.
>
> I think (2) sounds more natural.
>
>
> On Tue, Dec 10, 2019 at 3:12 PM Steve Ebersole <steve at hibernate.org>
> wrote:
>
>> To me this is perfectly consistent with how inheritance works in entity
>> hierarchies.  Unless a super type is marked with @Entity
>> or @MappedSuperclass, the "attributes" defined on that specific class are
>> not picked up.
>>
>> Maybe I'm misunderstanding you?
>>
>> On Mon, Dec 9, 2019 at 1:58 PM Gail Badner <gbadner at redhat.com> wrote:
>>
>>> Hi,
>>>
>>> Suppose we have the following:
>>>
>>> public class CompositeKey implements Serializable {
>>>
>>>   private Long id1;
>>>
>>>   private Long id2;
>>>
>>>   public CompositeKey(Long id1, Long id2) {
>>>     super();
>>>     this.id1 = id1;
>>>     this.id2 = id2;
>>>   }
>>> ...
>>> }
>>> public class InheritedKey extends CompositeKey {
>>>
>>>   private Long id3;
>>>
>>>   public InheritedKey(Long id1, Long id2, Long id3) {
>>>     super(id1, id2);
>>>     this.id3 = id3;
>>>   }
>>> ...
>>> }
>>>
>>> @Entity(name = "IKE")
>>> @IdClass(InheritedKey.class)public class InheritedKeyEntity {
>>>
>>>   @Id
>>>   private Long id1;
>>>
>>>   @Id
>>>   private Long id2;
>>>
>>>   @Id
>>>   private Long id3;
>>>
>>>   private String name;
>>> ...
>>> }
>>>
>>>
>>> Currently, Hibernate does not include InheritedKey#id3 in
>>> InheritedKeyEntity's composite key unless InheritedKey is annotated with
>>> @MappedSuperclass.
>>>
>>> I think there are some improvements that can be made.
>>>
>>> 1) As you can see, the entity, itself, has all of the ID fields
>>> annotated.
>>> An improvement would be for Hibernate to ensure that all mapped ID
>>> properties have been detected, and throw an exception if this is not the
>>> case.
>>>
>>> 2) A class used as an IdClass does not need any annotations (as opposed
>>> to
>>> a class used for an EmbeddedId class, which requires {{@Embeddable}}).
>>> Since the class used as an IdClass does not need to be annotated, it
>>> seems
>>> kind of strange that its superclass would need to be annotated with
>>> {{@MappedSuperclass}} in order for its fields/properties to be
>>> persistent.
>>> Since the field/property names must match what is annotated in an
>>> IdClass,
>>> it is clear that the field/property in a superclass is intended to be an
>>> ID. Perhaps we could make annotating the superclass with
>>> {{@MappedSuperclass}} optional?
>>>
>>> Opinions?
>>>
>>> Thanks,
>>> Gail
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>>> hibernate-dev at lists.jboss.org
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>>>
>>>