You could write a function to handle unboxing objects for you. Something like this should help:
def unbox[A](t:Box[A])(a: A => JValue) = {
val msg = "You must be logged in to perform this operation."
t.map { u => a(u) }.getOrElse(JString(msg))
}
Then, you'd just call it like :
unbox(User.current){ u:User =>
//doing something
JString("Ready, all right.")
}