Is there something similar to f:viewParam that can check if a given property is existent, and if not print a message?
For example I have a shopping cart site where the User gets redirected to. The cart resides in session scope. On a second site a extended cart should be shown where I would like to use this validation.
There are many use cases, for example if a user that would be stored in the session accesses the account site but is not logged in.