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From "Erik Bengtson" <e...@jpox.org>
Subject RE: Query by interface
Date Sat, 01 Sep 2007 15:53:29 GMT

I think you have to use the Implements annotation. Something like:

	public class MyPerson implements Person {}

-----Message d'origine-----
De : cbeams [mailto:cbeams@gmail.com] 
Envoyé : samedi 1 septembre 2007 9:14
À : jdo-user@db.apache.org
Objet : Query by interface

As a user, here's what I would expect to work:

	public interface Person {}

	public class MyPerson implements Person {}

	public class Main {
		public static void main(String... args) {
			PersistenceManagerFactory pmf =  
			PersistenceManager pm = pmf.getPersistenceManager();
			pm.makePersistent(new MyPerson());  // persist the
concrete type

			Query query = pm.newQuery(Person.class);  // query
by the interface
			Person person = (Person)query.execute();

			assert person instanceof MyPerson == true;

This does not work, however (at least with JPOX).  My instanceof  
assertion at bottom fails, because person is actually a type  
generated by the implementation (PersonImpl in the case of JPOX).   
While I understand that this class generation approach may have some  
uses, I'm actually dealing with I believe is a much simpler use case  
that doesn't seem to be supported:  I simply want to be able to  
persist an instance of a concrete type and subsequently query for  
that object by it's interface.

Am I missing something?  Note that I'm not looking for any JPOX- 
specific tips here; just some guidance on usage per the spec.


- Chris

Chris Beams

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