docs: public static String getClientIPByHeader(HttpServletRequest request, String... headerNames) {
  		String ip;
  		for (String header : headerNames) {
  			ip = request.getHeader(header);
  			if (false == isUnknow(ip)) {
  				return getMultistageReverseProxyIp(ip);
  			}
  		}
  
  		ip = request.getRemoteAddr();
  		return getMultistageReverseProxyIp(ip);
  	}