This is not a bug. This is a question.

I would like to know if it's possible to have, for example. Different "Configuration" objects for two or more users that access the system. They would be made on the fly by changing the Configuration object (I can set parameters such as name and password, right?).

The question is: if I have multiple users do I lose the caching? The fact that there will be many different Configurations will imply that I can't have caching shared through different users (Configurations, really)?

If we use Ehcache as a caching strategy, than not.
Ehcache is thread safe.