@Override
    public ResponseData doHead(final String url) {
        HttpUriRequest httpHead;
        try {
            httpHead = new HttpHead(url);
        } catch (final IllegalArgumentException e) {
            throw new CrawlingAccessException("The url may not be valid: " + url, e);
        }
        return doHttpMethod(url, httpHead);
    }

    /**
     * Executes an HTTP method for the given URL and request.