void authenticate(UserRealm realm, HttpRequest request) {
_userPrincipal = realm.authenticate(_jUserName, _jPassword, request);
if (_userPrincipal != null) _realm = realm;
}
void authenticate(UserRealm realm, String user, String password, HttpRequest request) {
_jUserName = user;
_jPassword = password;
_userPrincipal = realm.authenticate(user, password, request);
if (_userPrincipal != null) _realm = realm;
}