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From "Antonio Gallardo" <agalla...@agsoftware.dnsalias.com>
Subject RE: [RT] Direct Form-&gt;SQL mapping through OJB and DynaBeans
Date Fri, 31 Oct 2003 22:04:42 GMT
Hunsberger, Peter dijo:
> Ugo Cei <u.cei@cbim.it> writes:
>
>> Hunsberger, Peter wrote:
>> > In general, this moves the responsibility for locking up a
>> level which
>> > isn't something I'd care to code, but if you're going to use JDO I
>> believe you'll just get a last change wins result anyways, which is
>> how you could manage this...
>>
>> If you implement this strategy, pretty soon you're going to
>> end up with
>> lost updates: Bob reads a record, Alice reads the same record, makes
>> some changes and commits them, Bob makes some changes and
>> commits them,
>> overriding all of Alice's changes.
>>
>> To solve this problem, you need to implement an optimistic locking
>> strategy using version fields. Bob would not be able to commit his
>> changes because the version number he retrieved does not
>> match the one
>> stored in the database because Alice incremented it.
>
> Exactly my point about having to take responsibility for locking....
>
>> I know Hibernate handles this, don't know about JDO
>
> Don't know, sooner or later you're always in a position where you either
> have to trash an update or dead lock waiting for manual resolution, or
> you have to implement versioning...
>
> For us, last update wins, we're not update intensive, but I'm waiting
> for the day when someone forces us to wade through the audit log to
> determine why there update didn't take.

The "last update wins" is the most used approaching in this cases. You can
implement this using JDO.

Best Regards,

Antonio Gallardo



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