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interfaces [message #390038]

Thu, 09 July 2009 16:47

Andreas Leue
Messages: 6
Registered: July 2009

Junior Member

Hi,

JPA standard says

"An enum or interface should not be designated as an entity"

I googled a bit around and it seems
http://stackoverflow.com/questions/281503/jpa-mapping-interf aces
it might work somewhere else.

Anyway - how do you do it?

Assuming I have interface Person and implementing classes
Programmer and Manager. Somewhere else, I have an attribute
List<Person>, or a plain attribute Person.

I've read the suggestion to make the interface an abstract class.
Is that the only workaround?

What do you do in case of multiple interfaces? Are you lost then?

Thanks for help,
Andreas

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Re: interfaces [message #390050 is a reply to message #390038]

Mon, 13 July 2009 10:16

James Sutherland
Messages: 1834
Registered: July 2009

Senior Member

JPA does not have support for mapping interfaces, but EclipseLink does
have support for interface descriptor and variable 1-1 mappings.

You can define a OneToOne relationship to an interface using the
@VariableOneToOne EclipseLink annotation.

There is currently no annotation for interface descriptors, but you can
define them using a SessionCustomizer and create a RelationalDescriptor of
interface type (setJavaInterface()).

You could also make it an abstract class, or define an abstract class in
addition to the interface.

---
James
http://www.nabble.com/EclipseLink---Users-f26658.html

James : Wiki : Book : Blog

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Re: interfaces [message #390289 is a reply to message #390050]

Tue, 14 July 2009 16:34

Andreas Leue
Messages: 6
Registered: July 2009

Junior Member

Dear James,

thank you for the clarification.

> You can define a OneToOne relationship to an interface using the
> @VariableOneToOne EclipseLink annotation.

Is there a notation to do this inside xml mappings?

> There is currently no annotation for interface descriptors, but you
> can define them using a SessionCustomizer and create a
> RelationalDescriptor of interface type (setJavaInterface()).

I tried defining a mapping for an interface in xml, but get a null pointer
exception at
org.eclipse.persistence.internal.jpa.metadata.accessors.clas ses.EntityAccessor
line 190:

EntityAccessor parentAccessor =
getProject().getEntityAccessor(parent.getName());

I guess that "parent" is null, since interfaces do not habe a superclass.
Is this supposed to work, or am I on the wrong track by trying this?

Besides - I'm just curious: am I the only one missing this feature in JPA?
To me it seems rather natural to map interfaces.

Andreas

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Re: interfaces [message #390297 is a reply to message #390289]

Thu, 16 July 2009 10:15

James Sutherland
Messages: 1834
Registered: July 2009

Senior Member

The EclipseLink orm.xml support mirrors the EclipseLink annotations, its
schema is in the eclipselink.jar and on the wiki.

Please include your mappings and the full exception stack trace.

James : Wiki : Book : Blog

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Re: interfaces [message #390512 is a reply to message #390289]

Tue, 21 July 2009 05:48

Ana Oleski
Messages: 22
Registered: July 2009

Junior Member

Hi Andreas,

I miss it too, I logged an enhancement request

http://bugs.eclipse.org/275836

You can vote for it :-)

Ana

Andreas Leue wrote:

> Besides - I'm just curious: am I the only one missing this feature in JPA?
> To me it seems rather natural to map interfaces.

> Andreas

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