Thanks Armin,
I'm starting to get a much better understanding re
persisting abstract classes. I have been able to
build some abstract and non-abstract test classes
that function correctly.
marcus
> [EMAIL PROTECTED] wrote:
>
> > 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?
> >
>
> yep, I wrote a test case (using "extent" and different tables, as
> described on my last post) on my local machine and it work without
> problems (store/delete graph of objects).
> Pay attention not to mix different mapping strategy, e.g. use "extent"
> and "super" for the same classes, this could cause side-effects.
>
> It should also be possible store the whole graph in one table using
> "ojbConcreteClass" feature.
>
> regards,
> Armin
>
> > 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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> >
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