Implementation of the AbstractNonInteractiveCredentialsAction that looks for a user
principal that is set in the HttpServletRequest and attempts
to construct a Principal (and thus a PrincipalBearingCredential).
Implementation of the AbstractNonInteractiveCredentialsAction that looks for a user
principal that is set in the HttpServletRequest and attempts
to construct a Principal (and thus a PrincipalBearingCredential).