Standard Jetspeed-1 Group/Role/User resolver.
First looking for a group request parameter, then a role request parameter,
then a user request parameter. If none are found, then it uses the
current user's principal.
If it is null, it then falls back to a request parameter.
If it is null it gives up and returns null allowing subclasses
to continue processing.
Since there is no 1:1 value for a combination rule of group, the criterion's
value is ignored.
author: David Sean Taylor version: $Id: GroupRoleUserCriterionResolver.java 516448 2007-03-09 16:25:47Z ate $