Modeling heterogeneous entities (inheritance issue)

From: ihawk ihawker (ihawkmai..mail.com)
Date: Thu Jul 10 2008 - 10:38:01 EDT

  • Next message: Mike Kienenberger: "Re: Modeling heterogeneous entities (inheritance issue)"

    Thank you for the answer. As I understand I follow Composition Design, but
    still have problems with implementing inheritance...

    It seems my first message was badly formatted.
    So I'll copy it in this message again:

    -----------------
    Hello!

    I am trying to model a list of heterogeneous entities by having a
    ListItem table where the list item entity is able to point to an
    arbitrary entity (Person, Computer, URL, Movie, etc).

    I don't want to use single-table inheritance natively supported by
    Cayenne because of big database size overheads (the entities are
    drastically different from one another). In fact I don't necessarily
    want to use inheritance at all (PersonListItem, ComputerListItem,
    etc), but this seems to be the only option in Cayenne to model such a
    list.

    I've read Mike Kienenberger's article
    (http://cwiki.apache.org/CAY/compositeverticalinheritance.html) about
    simulation of vertical inheritance in Cayenne and found that it might
    be acceptable for my case.

    But I am having problems generating classes from the velocity template
     given in the article, although I've used code generator parameters
    recommended in article.

    It seems the parser fails to parse ${objEntity.getClientSuperClassName()},
    ${anObjEntity.getClientClassName()}, although other methods/attributes
    of "objEntity", "entityUtils", "stringUtils", "importUtils" are parsed
    correctly.

    I've tried with Cayenne 2.0.4, Cayenne 3.0M4.

    Thank you,

    Andrey Strib.

    This archive was generated by hypermail 2.0.0 : Thu Jul 10 2008 - 10:38:35 EDT