Re: Optimistic locking

From: Michael Gentry (blacknex..mail.com)
Date: Tue Apr 10 2007 - 11:37:02 EDT

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    In a lot of web applications (JSP, Struts, Tapestry, ...) the session is
    usually stored as a cookie in the browser, so opening a new browser window
    and re-connecting to the application won't give you a new session and
    therefore you'd be connected to the original session (and DataContext -- I'm
    assuming you are storing the DC in the session) with the updated values.
    Try your test using different concurrent browsers, such as Firefox and
    IE/Safari (for example) and see if you get the same results. I use
    optimistic locking on pretty much everything and haven't noticed a problem.
    I wrote this a long time ago, too, which may or may not help:

    http://cwiki.apache.org/CAY/optimistic-locking-explained.html

    I'll be out-of-touch for most of the rest of the day, but if you still have
    problems, perhaps someone else on the list can help.

    Thanks,

    /dev/mrg

    On 4/10/07, Marc Gabriel-Willem <marc.gabriel-wille..ide-international.com>
    wrote:
    >
    > Hi,
    >
    >
    >
    > I have some trouble with the optimistic locking function.
    >
    > I set the 'optimistic locking' option to an ObjEntity and moreover I set
    > an attribute as "used for locking".
    >
    >
    >
    > I'm in a web environment.
    >
    >
    >
    > When I do some modification in a DataObject, the 'log' displayed by
    > Cayenne displays properly the query using the attribute for locking
    > check.
    >
    > But, when a concurrent client modifies the 'same' DataObject, no error
    > is detected ... because the new value for the optimistic check is used.
    >
    >
    >
    > It is important to note that the DataObject is modified by different
    > browser (so different session data context) and by different child data
    > context !
    >
    >
    >
    > Scenario:
    >
    >
    >
    > My original record > attr1=MyAttr1, attr2=10:15:10
    >
    > My record modified by client #1> attr1=MyAttr2,
    > attr2(UseForLock)=10:18:15 [ attrSpecifiedInWhereClause: 10:15:10 ]
    >
    > My record modified by client #2> attr1=MyAttr3,
    > attr2(UseForLock)=10:19:40 [ attrSpecifiedInWhereClause: 10:18:15 ]
    >
    >
    >
    > The value of the attribute used for optimistic locking seems to be
    > refreshed...
    >
    >
    >
    > Thank you,
    >
    > Marc
    >
    >

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