Hi,
i dont get why you manually want to modify the JPAVERSION attribute.
If you dont want to keep the detached object in the session (thats
what we do), you
must at least remember the OID (object id) of the Document, find it
again from the
persistenceManager and then do the changes on the object and
persist/merge again.
Manually setting the version attribute makes no sense at all because
you really want the
ORM layer to manage the version attribute and only he knows best when
someone
modified your data and throws an OptimisticException when this happened.
Regarding the bloated HTTPSession. We just speak of a CRUD based
application where
you are just on the way modifying a record dont you? How big can the
object model
for that specific GUI can be? After that you can easily remove the
detached entities
from the session.
---
regards
Marc Logemann
http://www.logemann.org
http://www.logentis.de
Am 14.11.2009 um 09:38 schrieb Nikhil Patwardhan:
Hi,
I'm new to OpenJPA and I have been trying to create a small prototype
demonstrating how I can use it as a JPA compliant persistence
provider in a
J2EE web applications. In one of my use cases, I do the following:
1) Look up an entity(Class name:Document, for instance) using em.find
() in
the service layer. The entity has a version field.
2) Detach the entity by closing the em.
3) Pass the detached entity to the presentation layer (a JSP) which
shows a
screen to update various fields of the entity. The UI also has a
field for
the version attribute which is sent back on submit.
4) Submit the data back, create a new Document object, set the
fields and
call em.merge(document) inside a transaction.
This code fails in step 4 with the following exception when I try to
set the
version attribute on the Document object before calling merge().
---
org.apache.openjpa.persistence.InvalidStateException: Detected
attempt to
modify field core.persistence.Document.docVer with value strategy
restrict.
Am I missing something here? My approach here is to set the version
attribute obtained from the UI on the entity to be merged so that
optimistic
concurrency control would come into play to find out
if the entity has been updated since the last read. If version
attribute
cannot be set on an entity, I might have to keep the detached entity
obtained from find() in HttpSession and then use it when the updated
data is
submitted. But I'm wondering if keeping entities in session is a
good idea,
as it can make the session bloated with entities.
--
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