I use Ajax for subscribing/unsubscribing various things in CSNS, e.g. forums, topics, and mailing lists. They all share the same controller (SubscribeController/UnsubscribeController), but depending on the page on which the subscribe/unsubscribe link is displayed, the view returned by the controller could be different. So I used AjaxViewId to tell the controller which view (i.e. JSP) to return.