[hibernate-dev] DTO Projection support for native queries?

[Arnold Gálovics]

Hey Steve,

Thanks for the answer.

I was aware of these two solutions but there are definitely projects which
want to use DTO projections and cannot (don't) want to utilize neither the
annotation nor the native Hibernate API.

I think using the approach I mentioned would be beneficial, at least I see
the potential.

Do you think if we implement this it would violate some contract or do you
see anything which prevents us from supporting this?

Thanks.

Best,
Arnold

On 18 Aug 2017 17:16, "Steve Ebersole" <steve at hibernate.org> wrote:

That error might be the manifestation of the problem, but its just a
symptom of the fact that this is not supported.  The type passed in to type
the query must match what is selected (your "...").

And in fact JPA and Hibernate *do* support this, just not the way you do
it.  You have to use a ResultSet mapping (see
@javax.persistence.SqlResultSetMapping).
You'd specify a javax.persistence.ConstructorResult.

Hibernate has an alternative means to support this using
a org.hibernate.transform.ResultTransformer

On Fri, Aug 18, 2017 at 9:47 AM Arnold Gálovics <galovicsarnold at gmail.com>
wrote:

> Hi all,
>
> I'm particularly interested in the usecase when you want to have a DTO
> projection from a native query. Currently as far as I know this is not
> supported through the JPA API.
>
> If I say entityManager.createNativeQuery("...", SomeDTO.class) Hibernate
> says SomeDTO is not an entity, at least that's what I remember.
>
> Now I implemented the support for the Tuple type for native queries, so
> implementing the support for DTO projections shouldn't be an issue.
>
> Is there any reason why this is not supported yet?
>
> Thanks in advance!
>
> Best,
> Arnold
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