public static function init($with_cache = true)
{
if (!WITHOUT_CACHE && $with_cache && defined('CACHE_STORAGE') && constant('CACHE_STORAGE')) {
self::$_instance_name = CACHE_STORAGE;
} else {
self::$_instance_name = 'base_cache_nocache';
//todo：增加无cache类，提高无cache情况下程序的整体性能
}
self::$_instance = null;
}