public void setExtraHeader(String userAgent, String cookie) {
		if (EXTRA_HEADER == null && (!CommonUtils.isStringNullOrWhiteSpace(userAgent) || !CommonUtils.isStringNullOrWhiteSpace(cookie))) {
			EXTRA_HEADER = new HashMap<String, String>();
			EXTRA_HEADER.put(EXTRA_HEADER_USER_AGENT, userAgent);
			EXTRA_HEADER.put(EXTRA_HEADER_COOKIE, cookie);
		} else
			EXTRA_HEADER = null;
	}