public static function loadMetadataClass($className, $packageName = '')
    {
        if (class_exists($className, false)) {
            return true;
        }
        if (isset(self::$_classNameCache[$packageName . $className])) {
            return true;
        }
        $filePath = self::getLibFileWithPath($className, $packageName);
        if ($filePath) {
            include_once($filePath);
            self::$_classNameCache[$packageName . $className] = 1;
            return true;
        }
        return false;
    }