Hi Armin,
yes - I tried defining an extent and the appropriate
class-descriptor's - I also experimented with
"super". I assume that I am correct in assuming
that it "is" possible to build such a structure with
an abstract class?
regards,
Marcus
> Hi Marcus,
>
> did you try to declare class-descriptor's for B and C (including all
> fields and references) and define an extent for class A:
>
> <class-descriptor class="A">
> <extent-class class-ref="B" />
> <extent-class class-ref="C" />
> </class-descriptor>
>
> regards,
> Armin
>
> Marcus Young wrote:
>
> > Hi,
> >
> > I have just been working an issue related to mapping abstract classes.
> > I've read quite a lot about it but I'm still unclear. The structure I
> > have is as follows:
> >
> > Abstract Class A which can hold a collection of 'A' objects.
> > Classes B and C which extend A
> > Each class is mapped to a separate table.
> >
> > I am hoping to be able to retreive records in such a way as to 'build'
> > an 'A' class object including the objects collection which may include
> > objects of class B and C. So far I have been working with 'super' and
> > 'extents' - but to be honest I'm not really sure how to get it working.
> > Most commonly I'm getting exceptions of "InstantiationException". -
> > this appears to be related to the abstract 'A' class? I can resolve
> > this particular exception by using a concrete class, however I
> > particularly wanted to use an abstract class. Any assistance would be
> > greatly appreciated.
> >
> > I end up with something like this:
> >
> > public abstract class A extends TransferObject
> > { protected Long _id;
> > }
> >
> > public class B extends A
> > {
> > private String _name;
> > private String _description;
> > *}
> >
> > *public class C extends A
> > {
> > private String _name;
> > private String _description;
> > *}
> >
> > * <class-descriptor
> > class="com.eclipsej.permission.A" table="A">
> > <field-descriptor
> > name="_id"
> > column="ID"
> > jdbc-type="BIGINT"
> > primarykey="true"
> > autoincrement="true"
> > />
> > <!-- extent-class class-ref="com.eclipsej.user.B" / -->
> > </class-descriptor>
> > <!-- Defnitions for com.eclipsej.user.B -->
> > <class-descriptor class="com.eclipsej.user.B" table="roles">
> > <field-descriptor name="_id" column="ID" jdbc-type="BIGINT"
> > primarykey="true" autoincrement="true"/>
> > <field-descriptor name="_name" column="NAME" jdbc-type="VARCHAR"/>
> > <field-descriptor name="_description" column="DESCRIPTION"
> > jdbc-type="VARCHAR"/> <reference-descriptor name="super"
> > class-ref="com.eclipsej.permission.A"
> > auto-retreive="true" auto-update="true" auto-delete="true">
> > <foreignkey field-ref="_id"/>
> > </reference-descriptor> </class-descriptor>*
> > *
> >
> >
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> >
> >
>
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