Hello Ziv,
In persisting the parent class OJB has to instantiate it (using log4j you
see the exact position if you set the logging to "DEBUG" in
theOJB.properties). Since this can't be done with an abstract class, the
described error occurs.
Working around the same error we decided to make the abstract class
concrete and have a log entry in the constructor, so we can check it`s
instantiations.
Another way would be to map each implementation to a different table, thus
treating the abstact class like an interface.
Perhaps there should be a warning in tutorial 3 ("Advanced O/R") about this
restriction.
Regards,
Birgitta
Ziv Yankowitz wrote:
Folks,
we need to map an abstract class and it's implementation to two different
tables we tried the following :
> abstract class A {
>
> private id
> private valueA
> protected ojbConcreteClass
> }
>
> class B extends A{
>
> private id2
> private valueB
> }
>
> the repository file:
>
> <class-descriptor
> class="A"
> table="A_TABLE">
>
>
> <field-descriptor
> name="id"
> column="ID"
> jdbc-type="INTEGER"
> primarykey="true"
> autoincrement="true"
> />
> <field-descriptor
> name="valueA"
> column="VALUE"
> jdbc-type="INTEGER"
> />
>
> </class-descriptor>
>
> <class-descriptor
> class="B"
> table="B_TABLE"
> >
>
> <field-descriptor
> name="id2"
> column="ID"
> jdbc-type="INTEGER"
> primarykey="true"
> autoincrement="true"
> />
>
>
> <field-descriptor
> name="valueB"
> column="VALUE"
> jdbc-type="INTEGER"
> />
>
> <field-descriptor>
> name="ojbConcreteClass">
> column="CLASS_NAME">
> jdbc-type="VARCHAR">
> />
>
> <reference-descriptor name="super"
> class-ref="A" auto-update="true">
> <foreignkey field-ref="id2"/>
> </reference-descriptor>
>
> </class-descriptor>
>
we encounter in the following error:
org.apache.ojb.broker.PersistenceBrokerException:
org.apache.ojb.broker.metadata.MetadataException: java.lang.Instantiat
ionException
what are we doing wrong ?
