Question

I know that Java EE’s session object can store complex objects, like a connection to a database.

I’m pondering how to implement a certain application for a programming practice, made with Java EE. My first option to use a connection pool, which is very easy with Java EE.

I’m wondering, out of curiosity, and also to properly justify the decision, what are the pros and cons of creating a connection to the database any time a client starts a session and storing it there, against the use of a connection pool.

Thanks a lot.

Answer 1

A resource pool will optimise the handling of the resource (your database connection) in a way your system can cope with it. Even though you can end up out of resources if you have a lot of opened connections.

That is more likely to happen if you store your database connection in the session context. Web applications don’t need to be connected all the time to a database, that connection can be stablished at the beginning of a new operation and closed at the end. Using a resource pool you return your connection back to the pool when you no longer need it, so a new user (session in the web paradigm) can use that resource you have already released instead of creating a new one.

The pool will also handle the scenario in which some resources have been idle for a long time (no one has used them in a specific amount of time) and then it will release those resources.

When storing a database connection in the session you are never releasing the resource but keeping a permanent reference to it that will last as long as the user session does. You may not face any issues in a short time with that, specially if there are really few users connected at the same time. But in real world applications you will definitively find them.

Thus, storing a database connection in the session context is considered as a bad practice.

EDIT: I forgot to mention that should only store Serializable objects in the session so, if the application server decides to passivate a session, it can be persisted and restored when the application server decides to reactivate it. A database connection is not a Serializable resource.