如何在JSP上控制Servlet中的定时器～

JSP中根据条件循环产生radio  还有两个submit按钮：
<input type="submit" name="submit" value="Harvesting">
<input type="submit" name="submit" value="Stop"> ；
Servlet的主要代码：
String str_number=request.getParameter("Choose");//获得radio的value
String str=request.getParameter("submit");//获得submit的value
        System.out.println(str);
int number=Integer.parseInt(str_number);
File file=new File("C:/TEMP/Nodes.xml");//读取XML，并根据radio的value读取对应的节点信息
try{
Timer timer=new Timer();
if(str.length()==10){//如果submit按钮的value为harvesting，即执行
DocumentBuilderFactory factory=DocumentBuilderFactory.newInstance();
DocumentBuilder builder=factory.newDocumentBuilder();
Document doc=builder.parse(file);
NodeList NodeUrl=doc.getElementsByTagName("URL");
NodeList NodePort=doc.getElementsByTagName("Port");
    NodeList NodeTime=doc.getElementsByTagName("Interval");
    URL=NodeUrl.item(number).getTextContent();
    Time=NodeTime.item(number).getTextContent();
    Port=NodePort.item(number).getTextContent();
   
    timer.schedule(new HarvestTime(), 1000, 60000);
}
else if