On Aug 15, 2008, at 11:57 AM, Guido Neitzer wrote:
On 15.08.2008, at 11:13, Chuck Hill wrote:
NOW, the hard part! For every save you are going to have to trap
OptimisiticLocking exceptions and check if it failed on
OrderNumer. If it did, you are going to need to call
order.assignOrderNumber() again and repeat until the save
succeeds. This will be problematic if you have multiple Orders
being saved in one transaction.
Hmm, and there is one other rather serious problem: If another
order saves first, it will update the snapshot for OrderNumber and
you will not get the needed OptimisiticLocking exception. You
would need to catch the Object Changed In Store notification and
based on that updating OrderNumber, invalidate and re-assign the
number you had previously generated.
It's probably easier to wrap the same idea inside some simple direct
SQL statements.
If you are willing to be DB specific, an After Insert trigger might be
the best way to handle this. Just make sure the order number
attribute is not used for locking.
Chuck
--
Chuck Hill Senior Consultant / VP Development
Practical WebObjects - for developers who want to increase their
overall knowledge of WebObjects or who are trying to solve specific
problems.
http://www.global-village.net/products/practical_webobjects
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