Which is the default scope of a Spring 4 @Service?
The default scope is singleton
It is reasonable to design a Service implementation in order to store some info, related to the current logged user (according to the current HTTP session)
Yes. In that case, the service will have to have the scope “session”. See http://docs.spring.io/spring/docs/current/spring-framework-reference/html/beans.html#beans-factory-scopes-other