Hi Hibernate community,

I'm relatively new to Hibernate but I'm facing "non standard" problem. A lot of blogs, books and tutorials speak about Hibernate-Spring-[Insert your Web framework here]. But my concern is a bit different, my web framework can simulate a "connected Mode" with Ajax and Reverse Ajax. Like googleDoc, this allows to build "nearly realtime" application : a user modification on an element is immediately seen by another user.

Like an heavy client in a Client/Server architecture, I'm searching patterns, advices and tips to make use of Hibernate in this situation.

Actually I'm using the classic 3-Tiers pattern : DAO - Service - Presentation, with an open Session in view pattern and some helper classes to perform automatic reassociations.
My first idea is to add a fourth layer between Service and Presentation to make another "Entity" cache shared by all users (actually we have the Hibernate Session cache wich is associated to a single HTTPsession ). The first user which select an element add it in this cache where the second user can retreive the *same* reference so modifications made by the two users will be shared...

I am right ? Where Can I find further informations ? Is there an option to make an application scoped cache instead of session scoped ?

Thanks in advance,
See you soon

EventListener might be interesting to have a hook on objects which have
changed.

The design pattern is probably a Observer calling back all applications and informing them about the changed objects.

Hi, thanks for your reply. Yes Event Listener with Observer Pattern is a nice Pattern for that. However what do you suggest ?

On entity change do I have to force all users to reload their entity version with a lock(entity,LockMode.READ) ?
Or either do I have to maintain a global cache manually because Hibernate does'nt "merge" between Hib Sessions ?

And what about manually synchronizing entites : the first user loads an entity which will be shared between all futures user (with something that force entity injection on Hibernate Sessions without DB call ) ?

Ouch a good soul have an idea ?