Re: Problems retrieving 1-N relationship

From: Craig Miskell (cmiskel..lbatross.co.nz)
Date: Thu Mar 06 2003 - 16:30:03 EST

  • Next message: Reinier (Linux 2.2.12): "Newbie: Tapestry 2.4 and cayenne1.0a6"

    The root cause of this appears to be that the relationship from
    Operation to Brainstorm involves two joins e.g. two attributes are
    involved in each table/entity. This would imply either a problem with
    your model, or that you are using compound keys. From your brief
    description (mentioning Brainstorm.OperationID=null), I'd hazard a guess
    that you aren't using compound keys, and that your model has something
    amiss with it.

    If you can't see anything obvious with it, feel free to send it to me
    (just the xml files), and I'll have a look.

    C
    On Fri, 2003-03-07 at 05:04, Eduardo Abinader wrote:
    > Hi,
    >
    > I'm having problem on the following scenario:
    >
    > got 3 entities:
    > - Brainstorm
    > - Operation
    > - Mission
    >
    > where,
    >
    > Mission(1) - (1..N) Operation (relationship: Operation_Collection)
    > Mission(1) - (N) Brainstorm (relationship: Brainstorm_Collection)
    > Operation(1) - (0..N) Brainstorm (relationship: Brainstorm_Collection)
    >
    > Here is an important detail: I may have brainstorms only related to
    > mission.In such situation Brainstorm.OperationID = NULL, ok?
    >
    > Well, when I execute:
    > ..
    > ..
    > ..
    > auxList = Operation.getBrainstorm_Collection();
    > System.out.println(auxList.size());
    > ..
    > ..
    > ..
    >
    >
    > I got the message below:
    >
    > "Caused by: org.objectstyle.cayenne.CayenneRuntimeException: OBJ_PATH
    > expressions are only supported for a single-join relationships. This
    > relationship has 2 joins"
    >
    >
    >
    > Please, what does that mean?
    >
    >
    > Thanks.
    >
    >
    >
    >
    >
    >
    >
    >



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