>3. you can use the PerBrokerCache so that changes to cached objects are
only visible within one thread.
I don't seem to be able to find PerBrokerCache. What is the consequence of
the cached objects being only visible within one thread ?
>By default OJB uses a global cache, so changes to any cached objects are
visible across the whole JVM.
What if I use the OJB in server mode with a multiuser environment ?
Regards,
Patrick Reyes
Thomas Mahler
<[EMAIL PROTECTED] To: OJB Users List <[EMAIL
PROTECTED]>
> cc: (bcc: Patrick Reyes/CDS/CG/CAPITAL)
Sent by: Subject: Re: Cache question
[EMAIL PROTECTED]
06/03/2003
10:51 AM
Please respond
to "OJB Users
List"
Hi Patrick,
[EMAIL PROTECTED] wrote:
> Hi guys, I am quite sure this is the right behavior of the cache, but I
> would like some clarifications.
>
> 1) I read the content of a table and store the corresponding objects in a
> Collection.
> 2) I update the content of the objects.
> 3) I re-read the content of the table without updating the modified
object.
> 4) Instead of replacing the content of the updated object with the
content
> stored in the database, the updated object is retrieved a such with its
> modifications.
>
> My questions are:
>
> 1) Is this due to the internal cache ?
Exactly! If you perform any OJB query, OJB will first check if a result
object is already cached. If so, the cached version is returned.
(even when the cached object is dirty (i.e. contains uncommitted changes))!
> 2) How can I ask OJB to retrieve only comitted changes from the database
?
1. you can call broker.clearCache() to empty the cache before performing
a query.
2. you can also set the class-descriptor attribute refresh="true" this
will advise OJB to always load instances of a given class from the db
and not from the cache.
3. you can use the PerBrokerCache so that changes to cached objects are
only visible within one thread.
> 3) If I use a muti-user environnment will each user get the same copy of
> the object (i.e. the updated one) even if I have still not store the
object
> ?
By default OJB uses a global cache, so changes to any cached objects are
visible across the whole JVM.
You should use the PerBrokerCache in a multi user / multi thread
environment to change this behaviour. See OJB.properties for details.
> 4) Does this behavior have anything to do with the optimistic caching ?
You mean Optimistic Locking? Not really. It's just Global vs. Local cache.
cheers,
Thomas
>
> Thanks and regards,
>
> Patrick Reyes
>
>
>
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