/**
  * @see org.eclipse.jetty.server.Authentication.Deferred#login(java.lang.String, java.lang.String)
  */
 public Authentication login(String username, Object password, ServletRequest request) {
   UserIdentity identity = _authenticator.login(username, password, request);
   if (identity != null) {
     IdentityService identity_service = _authenticator.getLoginService().getIdentityService();
     UserAuthentication authentication = new UserAuthentication("API", identity);
     if (identity_service != null) _previousAssociation = identity_service.associate(identity);
     return authentication;
   }
   return null;
 }