protected function send($url)
    {
        $response = $this->httpAdapter->getContent($url);

        if ($response === null) {
            throw ServiceException::invalidServiceResult();
        }

        $statusCode = (string) $response->getStatusCode();

        if ($statusCode[0] === '4' || $statusCode[0] === '5') {
            throw ServiceException::invalidResponse($url, $statusCode);
        }

        return $response;
    }