1 Reply Latest reply on Jul 19, 2004 2:06 AM by Alexey Loubyansky

    how to implement bidirectional NxM CMR within subclassed ent

    microbiotic Newbie

      Hi!

      I'm trying to use inheritance within entity beans. The superclass defines a set of CMR methods which should be used in the subclass without the need to declare them in the subclasses again. 1xN relations don't make any trouble i think, but NxM relations will do.

      To make my problem a little more concrete:

      I have a entity bean called "DeviceBean" and to subclasses "FTPDeviceBean" and "FTAMDeviceBean". Each subclass has a set of additional attributes. All entity beans are mapped in different tables. All entries have a unique id (Integer) which is unique within all device tables.

      Next, the "DeviceBean" defines a bidirectional relation to a "PollingCycleBean" which will be mapped in a relation table.

      (I hope may bad "ASCII arts" makes my problem clear :)

      DeviceBean n<------------------>m PolingCycleBean
      |-- FTPDeviceBean -------------------^ should also use relation
      |-- FTAMDeviceBean -----------------^ should also use relation


      Relation table:
      ______________________
      |device_id (pk)| pc_id (pk)|
      ______________________


      To use the relation in my subclasses I have to declare the relation in the ejb-jar.xml for each subclass with a unique name.

      But next step will make trouble i think. Associating a FTP-device with a new polling cycle will add an entry to the relation table. But can the container make an inverse lookup and return the associated devices (FTP- and FTAM-devices) which are stored in different tables ?

      Can I use bidirectional NxM CMR in subclasses with JBoss 3.2 ?

      Thanks a lot for bringing some more light in my understanding of the abilities of CMR.

      Regards,
      Marcel