Hello,
Another option would be to make your detachable model aware of the
version aswell as the id which will allow you to catch this case.
Process:
Cache the version aswell as the object id.
Then either do a query to make sure the cached version is still valid or
wait until after the object is materialized and then check the version like:
Object dbBackedObject = loadFromDataBase (objectId);
if (!dbBackedObject.getVersion().equals (cachedVersion))
throw new RuntimeException("stale version excetption");
I'm not sure if you can catch the exception within the form processing
or if it will bubble up to the request cycle exception handling logic
(where you can redirect to another page).
Regards,
Mike
Hi all. I'm new to wicket. I was reading in the Wicket In Action book on
LoadableDetachedModels...particularly how when the model is detached, just
the id of the actual database persistent object is stored. Then, in the
load method, you retrieve the persistent object from the database. That all
makes sense.
However, I then read one use case for this, at
http://stronglytypedblog.blogspot.com/2009/03/wicket-patterns-and-pitfalls-1.html.
The idea is that you retrieve the object from the database to present
in
a form, and then when a person submits the form, you retrieve the object
from the database again, apply any needed changes, and then persist the
object.
Isn't there a problem here related to versioning of objects? Specifically,
the first time I retrieve an object, it could be at version 1. The next
time I retrieve the object, to apply the values from the form, I could be
retrieving version 4. I would then apply the changes from the form, and
hibernate would happily persist the object, because version 4 is the most
current.
Yes, Hibernate's automatic optimistic locking fails in this scenario.
You can add your own validator onto the form (with a hidden field for
the version) if you want.
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