} catch (final IllegalArgumentException e) {
            throw new CrawlingAccessException("The url may not be valid: " + url, e);
        }
        return doHttpMethod(url, httpHead);
    }

    public ResponseData doHttpMethod(final String url, final HttpUriRequest httpRequest) {
        if (httpClient == null) {
            init();
        }

        if (logger.isDebugEnabled()) {