code: public URL encodeURL(URL url) {
  		if(!isValid()) {
  			throw new IllegalStateException("SipApplicationSession already invalidated !");
  		}
  		String urlStr = url.toExternalForm();
  		try {
  			URL ret;
  			if (urlStr.contains("?")) {
  				ret = new URL(url + "&" + SIP_APPLICATION_KEY_PARAM_NAME + "="
  						+ getId());
  			} else {
  				ret = new URL(url + "?" + SIP_APPLICATION_KEY_PARAM_NAME + "="
  						+ getId());
  			}
  			return ret;
  		} catch (Exception e) {
  			throw new IllegalArgumentException("Failed encoding URL : " + url, e);
  		}
  	}
docs: {@inheritDoc}
  Adds a get parameter to the URL like this:
  http://hostname/link -> http://hostname/link?org.mobicents.servlet.sip.ApplicationSessionKey=0
  http://hostname/link?something=1 -> http://hostname/link?something=1&org.mobicents.servlet.sip.ApplicationSessionKey=0