I have, on the hibernate site, a description of the ThreadLocal Session but i don't understand the aim of this "pattern". Can someone explain to me how it works and the use of it?

Next, i'm working on a web site that uses Hibernate as O/R mapping layer and java technology ( jsp, servlets end JavaServer Faces).
There will be a lot a users connected at a time.
What is the best way to manage such connections at a time ( Thread Local Session or others patterns) ?

Thanks.

The Thread Local Session design pattern provides a way to bind each thread of execution with one Hibernate Session. This enables the Session to be propagated between different classes such as DAO (another common design pattern).
Say, for example, I have DAO1 and DAO2 used in the following code :


Using the Thread Local Session, I can open and close a single Hibernate Session which will be bound to the runnnig thread, and my two DAOs will share the same Session, thus benefiting from advanced mechanism such as concurrency checks and cache. This would give something like :



Laurent[/code]

Thanks for yours explanations and your example.
But in the doSomeThing() methods of DAO1 and DAO2, how to do to retrieve the session open by the ThreadLocalSession.openNewSession() call.
Is there a static method getSession() in the ThreadLocalSession class or something like that in order that the doSomeThing() methods get the opening session?

Thanks

In your ThreadLocalSession class, a static method will allow you to get the current session (see the design pattern section for implementation detail)

See below the DAO code

Effectively, what you're doing with a ThreadLocal Session is execute multiple data access operations (like DAO method invocations) within a kind of transaction. Note that a Hibernate Session keeps its own cache of persistent objects, therefore operations on a Session should get executed within a database transaction too, for data consistency - even read-only operations. session.beginTransaction on Session creation and a commit/rollback on Session closing would achieve that.

As noted at http://www.hibernate.org/42.html, the Spring Framework's transaction support includes special thread-local handling of Hibernate Sessions under the hood. You demarcate a transaction that spans multiple operations, be it with the Hibernate transaction strategy or JTA: Then each of your operations will receive the same Session instance, within a proper database transaction. The only programming pattern required is to look up a Session via Spring's SessionFactoryUtils.getSession(SessionFactory) method, or use Spring's HibernateTemplate helper class. See http://www.hibernate.org/110.html for details.

Juergen