Enthuware

If it was a @Stateless Session bean ?

Can I assume that the quantity of instances depends on the container ? Or what?

I have tested with @Stateless, only one instance was created but I dont know if this will always happen or it is by chance

The specification does not say anywhere that there can be only one instance of a stateless session bean. If you want exactly one instance, then you can use a Singleton stateless bean.

HTH,
Paul.