JPA instantiate in query

Question

I use JPA2 and Hibernate 3.6 as provider.

I have some code like this:

final List<Object[]> result = entityManager.createQuery("SELECT qt, tt FROM ...").getResultList();

I have a converter who transform the list of Object[] to list of SimpleClass, which contains my qt and tt entity.

Is is possible to do something like this in JPA 2 ? (In C# with linq, it's possible)

final List<SimpleClass> result = entityManager.createQuery("SELECT new SimpleClass(qt, tt) FROM ...").getResultList();

Thanks.

You can look at this related answer http://stackoverflow.com/questions/2355728/jpql-create-new-object-in-select-statement-avoid-or-embrace — landal79, Mar 14 '12 at 15:34
Hmm, interesting question. I first thought using @MappedSuperclass as a wrapper, but it looks like you cannot query against it. I think good old composition will work as a backdoor. — d1e, Mar 14 '12 at 20:49
@landal79 this is exactly what i search, i will try and make a feedback. Thanks you. — La Chamelle, Mar 19 '12 at 13:31
Ok this is the good answer but sadly i use some fetch in my query and jpa complains : `query specified join fetching, but the owner of the fetched association was not present in the select list` — La Chamelle, Mar 19 '12 at 13:47

score 0 · Answer 1 · answered Mar 14 '12 at 13:15

0

If you have mapped your entities, you should be able to do:

List<SimpleClass> result = entityManager
    .createQuery("select s from SimpleClass s", SimpleClass.class)
    .getResultList();

answered Mar 14 '12 at 13:15

beerbajay

SimpleClass is not an Entity, its just a wrapper who contains the two other entities. – La Chamelle Mar 14 '12 at 13:29
`.__.` Perhaps you should be running two `JPQL` queries and combining the results in `SimpleClass` instances. You'd get the OR mapping for free in that case. – beerbajay Mar 14 '12 at 14:07
This is a related question/answer : http://stackoverflow.com/questions/2355728/jpql-create-new-object-in-select-statement-avoid-or-embrace – La Chamelle Mar 19 '12 at 13:51

1 Answers1