Having read the document over layered architecture and session handling, I am still quite unsure how to use Hibernate in my web application.

At the moment I disconnect the session which has the effect that I am having a new session for each web request. I expect to get memory problems under traffic, when I do not properly close the session.

At the moment, I see two choices (please correct me, if I am wrong)
1)
Saving the hibernate session in the session
a) disconnection and reconnection
b) keeping it alive
and reusing it by this procedure
2)
Closing the session
This means that in each request I copy the Data from a Hibernate List to a Normal java.util List to decouple it from the database.
3)
Learning and understanding the stuff with the detached objects. (Here I do not understand how to detach a Hibernate List).

At the moment I think to use number 1 as I expect it to be faster as number 2. Am i right with the alternatives? What do you consider to be the best way?
Thank you for all ideas.

Sebastian

"2)" (session/transaction per request) is the right way, but you do not need to copy any lists. If you need cache then use JVM level cache for this optimization. "Fat" objects in httpsession produce many problems : synchronization and memory leaks, random data from different caches (sessions), it will complicate load balancing too.

What do you mean with:
"If you need cache then use JVM level cache for this optimization" ?

Coping data from lists seems to be necessary.
What is the best way for solve this problem ?

What about lazy fatching of associations ?
If I close the session, when I try to access a associated class, hibernate throw an Exception (it says that the connection is closed).

Thank you.

The way I understand this (I've been trying to understand how to do some of this for a while, too) is that you need to fully initialize whatever you want to send to the client side before closing the session. This would commonly be done by using fetching strategies in the Query (part of the HQL itself)/Criteria APIs or by simply "walking" the object graph before you send it.

What I am unsure about is whether the retrieved entities (after the session is closed they "become" detached entities) are Serializable. If I understand all of this, if they are serializable as POJOs (when used outside of hibernate, that is), then the proxies that hibernate generates will also be Serializable. Of course, if the client calls a getter on a lazy-loaded property that is not initialized, you will get a LazyInitializationException, but this is why you have to make sure you've initialized everything you want to use before closing the session.