RE: Handling of database NULL - default value column to modeler?

From: Scott Anderson (sanderso..irvana.com)
Date: Wed Aug 20 2008 - 12:49:06 EDT

  • Next message: Scott Anderson: "RE: Handling of database NULL - default value column to modeler?"

    Sounds like you want to make the field NOT NULL with a default value in the database. That would transparently do what you've described, without any reliance on Cayenne.

    -----Original Message-----
    From: oyvindharbo..mail.com [mailto:oyvindharboe@gmail.com] On Behalf Of Øyvind Harboe
    Sent: Wednesday, August 20, 2008 5:47 AM
    To: cayenne-use..ncubator.apache.org
    Subject: Handling of database NULL - default value column to modeler?

    One way to handle database NULL (replace with default value)
    is to override the CayenneDataObject get/set methods.

    However, I was wondering if it would make sense to add a column
    to DbEntity in the modeler for this case.

    The idea is that this "documents" the behaviour in the modeler for
    what happens in this case for a column. It also saves a tad of
    Java boilerplate code.

    I would expect the default value to behave as follows:

    default value = null. Same as today.

    default value != null:

    - return default value upon getXxx() methods (readProperty()) when
    database column contains NULL
    - setProperty() w/default value upon column w/database NULL. Probably
    update the database upon commit. This would cause database NULL
    to be updated to default value when rewinding/submitting a form without
    actually making any changes to a form(using tapestry rewinding
    wording above...)
    - I'm not quite sure if I have decided what to expect from Expression's.
    If I search for a value in the database that is equal to the default value,
    would I then expect rows w/NULL to match? Probably not.

    -- 
    Øyvind Harboe
    http://www.zylin.com/zy1000.html
    ARM7 ARM9 XScale Cortex
    JTAG debugger and flash programmer
    



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