[hibernate-dev] Typing Help with JPA 2.1 impl

[Steve Ebersole]

Ah great point.  No I have been compiling with JDK 1.6

On Thu 14 Jun 2012 04:45:27 AM CDT, Hardy Ferentschik wrote:
> Hi,
>
> OOI, have you tried with the Java 7 compiler? I think there used to be a bug in the Java 6 compiler
> when it came to covariant return types.
>
> --Hardy
>
>
>
> On Jun 13, 2012, at 10:04 PM, Steve Ebersole wrote:
>
>> I realize I could split Join and Fetch into different hierarchies.
>> That is what I want to try to avoid though...
>>
>> On Wed 13 Jun 2012 02:55:03 PM CDT, Steve Ebersole wrote:
>>> I need some help with generic types in the JPA 2.1 API, specifically
>>> with regard to the new Join#on and Fetch#on methods. We ultimately
>>> unify those 2 interface hierarchies into a single hierarchy in out
>>> code using org.hibernate.ejb.criteria.JoinImplementor which extends
>>> from both Join and Fetch.
>>>
>>> The problem I am facing is in the return types. So, Join defines:
>>> public interface Join<Z,X>  {
>>> public Join<Z,X>  on(...);
>>> ...
>>> }
>>>
>>> Fetch defines:
>>> public interface Fetch<Z,X>  {
>>> public Fetch<Z,X>  on(...);
>>> ...
>>> }
>>>
>>>
>>> public interface JoinImplementor<Z,X>
>>> extends Join<Z,X>, Fetch<Z,X>, FromImplementor<Z,X>  {
>>> ...
>>> }
>>>
>>> The compiler does not at all like JoinImplementor as is, so I have to
>>> override the method:
>>>
>>> public interface JoinImplementor<Z,X>
>>> extends Join<Z,X>, Fetch<Z,X>, FromImplementor<Z,X>  {
>>> public JoinImplementor<Z,X>  on(...);
>>> ...
>>> }
>>>
>>> which should be fine as it is simple return type clarification. And
>>> actually that definition compiles fine.
>>>
>>> However, JPA also defines a whole hierarchy from Join such as.
>>> CollectionJoin, ListJoin, etc. So Hibernate has for example:
>>>
>>> public interface CollectionJoinImplementor<Z,X>  extends
>>> JoinImplementor<Z,X>, CollectionJoin<Z,X>  {
>>> @Override
>>> public CollectionJoinImplementor<Z, X>  on(...);
>>> ...
>>> }
>>>
>>> The IDE is fine with this type signature, however trying to compile
>>> this leads to the following error:
>>>
>>> types org.hibernate.ejb.criteria.JoinImplementor<Z,X>  and
>>> org.hibernate.ejb.criteria.JoinImplementor<Z,X>  are incompatible; both
>>> define on(javax.persistence.criteria.Predicate[]), but with unrelated
>>> return types
>>>
>>> I have no idea what I need to do here. Can anyone see the solution?
>>>
>>>
>>
>> --
>> steve at hibernate.org
>> http://hibernate.org
>> _______________________________________________
>> hibernate-dev mailing list
>> hibernate-dev at lists.jboss.org
>> https://lists.jboss.org/mailman/listinfo/hibernate-dev
>

--
steve at hibernate.org
http://hibernate.org