Re: Correctly implementing optimistic concurrency management in Cayenne for web-based computing

From: Andrus Adamchik (andru..bjectstyle.org)
Date: Fri May 05 2006 - 14:49:40 EDT

  • Next message: Eric Lazarus: "Re: Correctly implementing optimistic concurrency management in Cayenne for web-based computing"

    > Should I put a breakpoint in the data source delegate or what?

    Sure. You can also override CayenneDataObject.setPersistenceState(..)
    and catch when the state changes to PersistenceState.MODIFIED.

    Andrus

    On May 5, 2006, at 2:22 PM, Eric Lazarus wrote:
    > Andrus
    >
    > Objects are showing up in 'modifiedObjects' without
    > our seeing ANY update in 'writeProperty' so how can we
    > srceen for phantoms there. What else can cause objects
    > to show up as dirty when writeProperty is not called
    > for that object? Should I put a breakpoint in the data
    > source delegate or what?
    >
    > Eric
    > --- Andrus Adamchik <andru..bjectstyle.org> wrote:
    >
    >> Eric,
    >>
    >> I don't have time to go through all your code, but
    >> let me comment on
    >> possible pitfalls.
    >>
    >> Sometimes frontend frameworks cause "phantom"
    >> updates, when
    >> populating objects from the form values. By phantom
    >> I mean the
    >> equivalent of this: object.setX(object.getX()). They
    >> are cleared on
    >> commit and should not generate events for the peer
    >> context, however
    >> when you inspect an uncommitted DataContext, they
    >> will show up in
    >> "modifiedObjects" collection.
    >>
    >> We discussed various options to handle that, but
    >> decided to put off
    >> any solution till future releases [1]. Right now you
    >> can check for
    >> "phantoms" and discard them inside "writeProperty",
    >> but this has its
    >> own limitations as discussed in the Jira issue that
    >> I mentioned.
    >>
    >> Also there is a bug in the latest Beta, reported by
    >> Bryan [2]. This
    >> may or may not be related.
    >>
    >> Andrus
    >>
    >> [1] http://issues.apache.org/cayenne/browse/CAY-512
    >> [2]
    >>
    > http://objectstyle.org/cayenne/lists/cayenne-user/2006/04/0276.html
    >>
    >
    >
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