[hibernate-dev] dynamic instantiation queries

[andrea boriero]

I think attempting to dynamically infer what to do using the existing ctr
would be great

On 24 October 2016 at 21:49, Steve Ebersole <steve at hibernate.org> wrote:

> I'm not sure what you are getting at. This is a feature Hibernate has had
> for close to 15 years.  It's not a "new feature", I'm just proposing a new
> behavior to be more consistent with what people generally expect.
>
> On Mon, Oct 24, 2016, 3:30 PM Sanne Grinovero <sanne at hibernate.org> wrote:
>
> > Option 2# looks very nice indeed, I'd like that as it would be useful
> > to be able to create immutable DTOs directly from a query; but I'm
> > wondering what kind of difficulties this might pose, for example I'd
> > assume the DTO constructor would be able to trigger lazy loading of
> > any property of Person?
> >
> > Also wondering, if we expose query results as streams in the future,
> > would such a feature not become obsolete?
> >
> >
> > On 24 October 2016 at 20:38, Steve Ebersole <steve at hibernate.org> wrote:
> > > So Person is your entity, e.g.:
> > >
> > > @Entity
> > > class Person {
> > >     @Id
> > >     Long id;
> > >     ...
> > > }
> > >
> > > For a query like `select new DTO( p ) from Person p` Hibernate expects
> a
> > > DTO like:
> > >
> > > class DTO {
> > >     public DTO(Long id) {
> > >         ...
> > >     }
> > > }
> > >
> > > in fact a DTO like:
> > >
> > > class DTO {
> > >     public DTO(Person person) {
> > >         ...
> > >     }
> > > }
> > >
> > > will not work with Hibernate.
> > >
> > > What I was proposing was for adding some support for that in 6.0 based
> on
> > > the SQM work.  "Support" here could mean either:
> > > 1) add a flag that says whether to support legacy behavior, or this new
> > > behavior
> > > 2) attempt to dynamically infer what to do (looks at available ctors)
> > >
> > > (2) would be awesome I think.  We'd still have to know how to handle
> > cases
> > > where the "DTO" defined ctors matching both cases and which to prefer.
> > >
> > >
> > > On Mon, Oct 24, 2016 at 2:31 PM Vlad Mihalcea <mihalcea.vlad at gmail.com
> >
> > > wrote:
> > >
> > >> Do you mean we should allow the dynamic instantiation to resolve
> > entities
> > >> when we pass the entity identifier?
> > >>
> > >> I think I saw this request on StackOverflow once.
> > >>
> > >> Did I understand the question properly?
> > >>
> > >> Vlad
> > >> ------------------------------
> > >> From: Steve Ebersole <steve at hibernate.org>
> > >> Sent: ‎10/‎24/‎2016 22:21
> > >> To: hibernate-dev <hibernate-dev at lists.jboss.org>
> > >> Subject: [hibernate-dev] dynamic instantiation queries
> > >>
> > >> Historically (well before JPA) HIbernate would handle dynamic
> > instantiation
> > >> queries in cases where one of the arguments being an entity-reference
> by
> > >> passing just the entity's identifier rather than a complete reference
> to
> > >> the entity.  To be clear, I am talking about a query like:
> > >>
> > >>     select new DTO( p ) from Person p
> > >>
> > >> Hibernate implicitly treats this like:
> > >>
> > >>     select new DTO( p.id ) from Person p
> > >>
> > >> and expects DTO to have a ctor taking the appropriate ID type.
> > >>
> > >> JPA came along and also defines support for dynamic instantiation
> > queries,
> > >> but does not specify one way or the other how this case should be
> > handled.
> > >> I have been told other providers interpret this the opposite way.
> Makes
> > >> sense.  I think it is time we at least allow that as an option.  Or
> > maybe a
> > >> nicer implementation that looks for both and picks the available one
> (if
> > >> that's not too much effort).
> > >>
> > >> What do y'all think?
> > >> _______________________________________________
> > >> hibernate-dev mailing list
> > >> hibernate-dev at lists.jboss.org
> > >> https://lists.jboss.org/mailman/listinfo/hibernate-dev
> > >>
> > > _______________________________________________
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> > > hibernate-dev at lists.jboss.org
> > > https://lists.jboss.org/mailman/listinfo/hibernate-dev
> >
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