if ( a == null ) {
            return null;
        }
        synchronized ( a ) {
            a.url = url;
            a.sae = sae;
            return a.getNtlmPasswordAuthentication();
        }
    }


    /**
     * An application extending this class must provide an implementation for this method that returns new user

        if( auth == null ) {
            return null;
        }
        synchronized( auth ) {
            auth.url = url;
            auth.sae = sae;
            return auth.getNtlmPasswordAuthentication();
        }
    }
/**