* Sends a NotificationAcknowledgment with the given serial number.
* @throws Exception if the acknowledgment could not be sent.
*/
protected void sendNotificationAcknowledgment(String serialNumber, HttpServletResponse response,
Notification notification, HttpServletRequest request) throws Exception {
NotificationAcknowledgment ack = new NotificationAcknowledgment();
ack.setSerialNumber(serialNumber);
Utils.toXML(ack.toJAXB(), response.getOutputStream());
logger.log(Level.INFO,
"Sent response ack:\n" + Utils.SEND_AND_RECEIVE_DEBUGGING_STRING,
new Object[]{200, request.getRemoteAddr(), notification, ack});
}