public function validateRequired($only = [])
    {
        if (count($only) > 0) {
            return $this->validateSpecific($only);
        }

        /*
         * Go through each required attribute
         * and make sure they're not null
         */
        foreach ($this->required as $required) {
            if ($this->getAttribute($required) === null) {
                throw new AdldapException(sprintf($this->messages['required'], $required));
            }
        }

        return true;
    }