static private function getDriver() {
        if (self::$_driver != null) return self::$_driver;
        
        $driver = Utils::spare(Config::get('cache.driver'), 'file');

        switch (strtolower($driver)) {
            case 'memcached':
                self::$_driver = new \Lollipop\Cache\MemcachedAdapter();
                break;
                
            case 'file':
            default:
                self::$_driver = new \Lollipop\Cache\FileAdapter();
                break;
        }
        
        return self::$_driver;
    }