[OJB-developers] mapping abstract classes ?

[Jakob B. <jbr...@gm...>]

hi,

i have a question regarding the mapping of abstract classes.

given the following class hierarchy:

Project
..ITProject (abstract)
....SoftwareProject
....HardwareProject

using the tables PROJECT, SW_PROJECT, HW_PROJECT.

i can use the following mapping:=20

   <class-descriptor
   class=3D"org.apache.ojb.broker.Project"
   table=3D"PROJECT"
   >
      <extent-class class-ref=3D"org.apache.ojb.broker.SoftwareProject" =
/>
      <extent-class class-ref=3D"org.apache.ojb.broker.HardwareProject" =
/>
   ...

and class-descriptors for SoftwareProject and HardwareProject.
if i want to query ITProjects i'll have to define a class-descriptor:

   <class-descriptor
   class=3D"org.apache.ojb.broker.ITProject"
   >
      <extent-class class-ref=3D"org.apache.ojb.broker.SoftwareProject" =
/>
      <extent-class class-ref=3D"org.apache.ojb.broker.HardwareProject" =
/>
   </class-descriptor>

this all works fine. what irritates me is the duplicate definition of =
extents.=20
so i tried the following mapping, which reflects the class hierarchy:

   <class-descriptor
   class=3D"org.apache.ojb.broker.Project"
   table=3D"PROJECT"
   >
      <extent-class class-ref=3D"org.apache.ojb.broker.ITProject" />

   ...

   <class-descriptor
   class=3D"org.apache.ojb.broker.ITProject"
   >
      <extent-class class-ref=3D"org.apache.ojb.broker.SoftwareProject" =
/>
      <extent-class class-ref=3D"org.apache.ojb.broker.HardwareProject" =
/>
   </class-descriptor>

this mapping fails because ITProject has no table :(

so i came up with the following:=20
if the extent-class references an 'abstract' class (one without table), =
the search should continue with the extents-classes of the 'abstract' =
class.
the only drawback i see so far is performance caused by checking all =
extent-classes.

what do think of it ?

jakob