John Dixon wrote:
> The App:
> I have a JSP page that collects data from a database and displays it in
> textfields. The user can change the data. click OK and the database is
> updated.
>
> The question: How do I lock the record in the database so that another user
> cannot change the data whilst this user is in the midst of changing the
> data. Using MSSQLServer.
_really_ bad plan. Use optimistic locking and when the user commits
check to see if the record has changed in between loading and trying to
save.
Why? Otherwise:
1. User locks record by starting to view.
2a. User goes to lunch and leaves record locked for one hour.
2b. User goes home and leaves locked overnight.
2c. User dies/machine turned off/ whatever and record never unlocked.
Basically, given the limitations of http and browsers, doing any form of
locking is IMHO a bad idea. You just have no way of knowing when the
next request is ever going to come in to unlock/commit changes to a
record.
Jari
--
Jari Worsley
Senior Programmer
Hyperlink plc
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