Manages controller-specific session attributes declared via SessionAttributes @SessionAttributes. Ac
tual storage is delegated to a SessionAttributeStore instance.
When a controller annotated with @SessionAttributes adds attributes to its model, those attributes are checked against names and types specified via @SessionAttributes. Matching model attributes are saved in the HTTP session and remain there until the controller calls SessionStatus#setComplete(). @author Rossen Stoyanchev @author Juergen Hoeller @since 3.1