Add Projections to QuerydslPredicateExecutor

[membersound]

It would be great if the findBy() method of QuerydslPredicateExecutor could support projection interfaces.

The method currently only works with the real @Entity, like:

intercace MyEntityRepository extends JpaRepository<MyEntity, Long>, QuerydslPredicateExecutor<MyEntity> {
}

Usage:

Stream<MyEntity> stream = dao.findBy(predicate, FluentQuery.FetchableFluentQuery::stream);

But not this:

Stream<MyEntityView> stream = dao.findBy(predicate, FluentQuery.FetchableFluentQuery::stream)
interface MyEntityView {
     String getMyField1();
     String getMyField4();
}

[mp911de]

Have you seen that findBy accepts a functional callback that lets you specify the target type?

dao.findBy(predicate, q -> q.as(MyEntityView.class).stream())

[membersound]

I see, yes that's what I was looking for. Maybe this could be added to the docs? I could not find such an example.

[mp911de]

Take a look here: https://docs.spring.io/spring-data/jpa/docs/current/reference/html/#query-by-example.fluent

[membersound]

So as my ticket is about how to use projections, I think this is answered sufficient.

Anyways there seems to be a performance issue with this approach, for which I created a new issue for better tracking:
#3160