public static function getInstance()
    {
        $configuration = Configuration::getConfig(self::CONFIG_FILE_NAME);
        $idpListServiceType = $configuration->getString(self::PROPNAME_IDP_LIST_SERVICE_TYPE, self::CSV);
        if ($idpListServiceType === self::CSV) {
            return new IdpListsServiceCsv();
        } elseif ($idpListServiceType === self::DB) {
            return new IdpListsServiceDB();
        } else {
            throw new Exception(
                'Unknown idpListService type. Hint: try ' . self::CSV . ' or ' . self::DB
            );
        }
    }