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Type casts in the HQL

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shl

Post subject: Type casts in the HQL

Posted: Tue Feb 24, 2004 6:26 am

Expert

Joined: Fri Feb 06, 2004 7:49 am
Posts: 255
Location: Moscow, Russia

Hi there!

I would like to ask if it is possible to use type casts in the Hibernate Query Language.

I mean the following query:

Code:

"from SomeClass obj where ((Child) (obj.parent)).someChildProperty=123"

where Child is subclass of Parent and SomeClass has reference to Child via member of Parent class:

Code:

public class Child extends Parent {
    int childProperty;
}

public class SomeClass {
    Parent parent;
}
...
SomeClass obj = new SomeClass();
obj.parent = new Child();

Thanks,
Leonid Shlyapnikov

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gavin

Post subject:

Posted: Tue Feb 24, 2004 12:05 pm

Hibernate Team

Joined: Tue Aug 26, 2003 12:50 pm
Posts: 5130
Location: Melbourne, Australia

It is not possible at this time. Instead, use:

select child.parents from Child child where child.someProperty=123

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shl

Post subject:

Posted: Tue Feb 24, 2004 2:14 pm

Expert

Joined: Fri Feb 06, 2004 7:49 am
Posts: 255
Location: Moscow, Russia

Pardon, but I did not get it.

Child is a subclass of Parent. I think I wrote not to good examle, it does not relate to "9. Parent/Child Relationships". Child class does not have any HAS-A assosiations with Parent, only IS-A relationship (Child IS-A Parent, but has not any references to Parent).

Gavin, is your example valid?

Code:

select child.parents from Child child where child.someProperty=123

Thanks,
Leonid Shlyapnikov

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tcollins

Post subject:

Posted: Tue Feb 24, 2004 2:59 pm

Beginner

Joined: Tue Jan 27, 2004 2:14 pm
Posts: 40
Location: Atlanta, GA, USA

If that's the case... you should be mapping this as a <subclass> or <joined-subclass>. Are you doing that? Then you will be able to query for it correctly and hibernate with cast it correctly for you. Which means you could get all the Parents and do an "instance of" to see if the object is an instance of your child or not. You could also just get all the children. So your mappings and I'll try to help you. Or someone from the team will help you.

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tcollins

Post subject:

Posted: Tue Feb 24, 2004 3:00 pm

Beginner

Joined: Tue Jan 27, 2004 2:14 pm
Posts: 40
Location: Atlanta, GA, USA

and check this out in the docs... http://www.hibernate.org/hib_docs/reference/html/inheritance.html

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shl

Post subject:

Posted: Wed Feb 25, 2004 4:27 am

Expert

Joined: Fri Feb 06, 2004 7:49 am
Posts: 255
Location: Moscow, Russia

Hi tcollins,

I mapped the inheritance properly. The question was if is it possible to use class casts in Hibernate Query Language. Gavin said that at this time is not possible and wrote some HQL example that I don't understand.

Now I have the aswer and junit test that said Gavin is right (no class casts in HQL:)

I found workaround for my query, question is closed.

Thanks for the help.

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moldoe

Post subject:

Posted: Mon Nov 22, 2004 1:00 pm

Newbie

Joined: Mon Nov 22, 2004 12:53 pm
Posts: 2

Is there something new about this topic? Is there a posibility to have dynamic cast in HQL? Something like "from Credetial as c where ((Badge) c).cardNumber=1234". Here Badge is a joined-subclass of Credential. Please let me know. Thanks!

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michael

Post subject:

Posted: Mon Nov 22, 2004 1:01 pm

Hibernate Team

Joined: Tue Sep 09, 2003 2:10 pm
Posts: 3246
Location: Passau, Germany

No, no such thing is implemented yet

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moldoe

Post subject:

Posted: Mon Nov 22, 2004 1:04 pm

Newbie

Joined: Mon Nov 22, 2004 12:53 pm
Posts: 2

Could you tell me if you planned this to implement and when I should expect it?
Thank again!

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