TimerListener在Sip Servlets中出现问题

Question

为了使用servlet定时器，我必须使用TimerListener接口。当我部署我的应用程序时，我收到此错误：

java.lang.IllegalStateException: No TimerListener is configured. 

我已在Sip部署描述符（sip.xml）的侦听器元素中声明了我的实现类：

<?xml version="1.0" encoding="UTF-8"?>
<sip-app  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
      xsi:schemaLocation="http://www.jcp.org/xml/ns/sipservlet http://www.jcp.org/xml/ns/sipservlet/sip-app_1_1.xsd"
      version="1.1">
  <listener>
     <listener-class>net.sip.psngn.NaerumPoliceSipServlet</listener-class>
  </listener>
</sip-app>

错误发生在我创建servlet计时器时。有谁知道如何解决这个问题？提前致谢。

package net.sip.psngn;

import javax.servlet.sip.*;
import javax.servlet.ServletContext;
import java.sql.Time;
import javax.annotation.Resource;
import javax.persistence.*;
import javax.transaction.UserTransaction;
import javax.servlet.sip.annotation.SipListener;


@javax.servlet.sip.annotation.SipServlet
@SipListener
public class NaerumPoliceSipServlet extends SipServlet implements TimerListener  {


private static final long serialVersionUID = 3978425801979081269L;

public String CSeq;

@PersistenceUnit
private EntityManagerFactory emf;

@Resource
private UserTransaction utx;

@Resource
TimerService timerservice;

/*
 * Demonstrates extension with a new "REPUBLISH" method
 */
@Override
protected void doRequest(SipServletRequest reqfromclient) throws javax.servlet.ServletException, java.io.IOException {
    if( reqfromclient.getMethod().equals("MESSAGE") ) {
        String MsgContent = reqfromclient.getContent().toString();
        System.out.println("The arrived message is " + MsgContent);



        // Assign the callee URI
        String URICallee = reqfromclient.getTo().getURI().toString();


        String reqDomain = ((SipURI)reqfromclient.getTo().getURI()).getHost();

         //Assign the caller URI
        String URICaller = reqfromclient.getFrom().getURI().toString();

        //Get the sequence of arriving MESSAGE
        CSeq = reqfromclient.getHeader("CSeq");
        System.out.println("Sequence number of the message "+CSeq);

        // Get the application session of the message
        SipApplicationSession sas = reqfromclient.getApplicationSession();

        System.out.println("The app session is: " + sas);



        // Create the timer with a timeout after 20 seconds
        ServletTimer servlettimer = timerservice.createTimer(sas, 20000, false, "enough");

        System.out.println("The Servlet Timer is created and delay is set to 20 seconds");

       //Store the ID of the timer as an attribute of the SipApplicationSession
        sas.setAttribute("TimerID", servlettimer.getId());


        System.out.println("TimerID: " + servlettimer.getId());

        // Access the stopwatch from the other class
        StopwatchClass stwclass = new StopwatchClass();
        //Get the message arrival time
        Time time = new Time(System.currentTimeMillis());
      }
    }

    public void timeout(ServletTimer servlettimer) {
       if ("enough".equals(servlettimer.getInfo())) {
         System.out.println(servlettimer.getApplicationSession()); 
       }
    }



}