The only reason that I discovered this is because DataNucleus returns null
if the entity being examined inherits its identity from a mapped
superclass. Spring Data JPA assumes that the implementation should never
return null. I was left wondering whether the onus was on the
implementation (DN) or on the metamodel client (SD JPA) to navigate the
tree.
I agree that the methods parallel the java.lang.reflect methods, however, a
little clarity here certainly wouldn't hurt. The only difference in the
javadoc comments between the getId(Class) and getDeclaredId(Class) methods
are the words "declared by", which are very subtle. I just reread them and
had to read the comments twice even when looking for the difference! :)
-matthew
On Mon, Jul 23, 2012 at 12:41 PM, Linda DeMichiel <
linda.demichiel_at_oracle.com> wrote:
>
>
> On 7/23/2012 9:58 AM, Matthew Adams wrote:
>
>> Ok, so from your answer, I take it that it is the implementation's
>> responsibility to walk up the entity's metadata
>> hierarchy through any mapped superclasses until the class defining the
>> identity is found.
>>
>> Is that specified? The spec currently says:
>>
>> /**
>> * Return the attribute that corresponds to the id attribute of
>> * the entity or mapped superclass.
>> * @param type the type of the represented id attribute
>> * @return id attribute
>> * @throws IllegalArgumentException if id attribute of the given
>> * type is not present in the identifiable type or if
>> * the identifiable type has an id class
>> */
>> <Y> SingularAttribute<? super X, Y> getId(Class<Y> type);
>>
>> Potential javadoc clarification:
>>
>> "Return the attribute that corresponds to the id attribute of the entity,
>> mapped superclass, or the id of the entity's
>> or mapped superclasses' superclass(es). This method must not return
>> null."
>>
>> Better? Is there a TCK test for this?
>>
>>
> Not sure. I guess I don't understand the confusion, given that there is a
> getDeclaredId method.
>
> The method pairs getXXX, getDeclaredXXX mirror what java.lang.reflect
> does, so I really don't
> think this needs a change.
>
> Under what circumstances would you imagine that it would return null
> rather than throw an IAE?
>
> -Linda
>
> p.s. I'll let our TCK engineer respond to the test question.
>
>
>
> -matthew
>>
>>
>> On Mon, Jul 23, 2012 at 11:05 AM, Linda DeMichiel <
>> linda.demichiel_at_oracle.com <mailto:linda.demichiel@**oracle.com<linda.demichiel_at_oracle.com>>>
>> wrote:
>>
>> Hi Matthew,
>>
>>
>> On 7/23/2012 6:44 AM, Matthew Adams wrote:
>>
>> Hi all,
>>
>> Scenario: entity "app.domain.Profile" extends abstract mapped
>> superclass "app.domain.AbstractEntity". If
>> AbstractEntity defines a single string field as its @Id, should
>> the IdentifiableType instance corresponding to
>> app.domain.Profile guarantee that its getId(Class) method will
>> never return null?
>>
>> In other words, is it up to the client of the JPA metamodel to go
>> up the entity's type hierarchy until it finds the
>> SingularAttribute for the id field, or should the JPA
>> implementation do that?
>>
>>
>> I'm not sure I understand your question fully. However, it is the
>> responsibility of the metamodel implementation
>> to return the SingularAttribute that is the value of getId (this may
>> involve traversing the hierarchy if getId
>> were not defined in the IdentifiablyType itself).
>>
>> -Linda
>>
>>
>> Thanks,
>> Matthew
>>
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