Returns the keys of all the attributes stored under this session. If there are no
attributes, this returns an empty collection.
@return the keys of all attributes stored under this session, or an empty collection if
there are no session attributes.
@throws InvalidSessionException if this session has stopped or expired prior to calling this method.
Returns the keys of all the attributes stored under this session. If there are no attributes, this returns an empty collection.
@return the keys of all attributes stored under this session, or an empty collection if there are no session attributes. @throws InvalidSessionException if this session has stopped or expired prior to calling this method.