1、"responseText”属性以字符串形式返回HTTP响应；“responseXML”属性以XML形式返回HTTP响应。
function getTel() { 
 var telText = document.getElementById("mantel");
 telText.value = "";
 if(xmlHttp.readyState == 4) {
  if (xmlHttp.status == 200) {  
   var message = xmlHttp.responseText;
   telText.value = message;
  }
 }
}
2、“responseXML”属性返回了一份XML文档对象，可以使用W3C DOM节点树方法和属性对该XML文档对象进行检查和解析。
function getUserInfo() {
 var peoplemobile=document.getElementById("_Peoplemobile"); 
 if(xmlHttp.readyState == 4) {
  if (xmlHttp.status == 200) {      
   var xmlDoc = xmlHttp.responseXML.documentElement; 
     var xSel = xmlDoc.getElementsByTagName("select");//得到xml文档中，节点为select的对象
     
     for (var i=0;i<xSel.length;i++){
      var xValue = xSel[i].childNodes[0].firstChild.nodeValue;//得到select节点下的第一个节点 
      var xText = xSel[i].childNodes[1].firstChild.nodeValue; //得到select节点下的第二个节点   
      if(xValue==‘peoplemobile‘){
      peoplemobile.value=xText;      
      }         
      
     }
  }
 }
}
二、java中的代码

/**
  * ajax获得用户电话号码，返回文本
  * @param mapping
  * @param form
  * @param request
  * @param response
  * @return
  * @throws DataAccessException
  * @throws IOException
  * @throws ParseException
  */
 public ActionForward toGetTelNumber(ActionMapping mapping, ActionForm form,
   HttpServletRequest request, HttpServletResponse response)
   throws DataAccessException, IOException, ParseException {
  String username = request.getParameter("person_id");
  String tel = releasePlanService.getTelByName(username);
  if (tel != null) {
   response.setContentType("text/html;charset=UTF-8");
   PrintWriter out = response.getWriter();
   out.print(tel);
   return null;
  } else {
   tel = "";
   response.setContentType("text/xml;charset=UTF-8");
   PrintWriter out = response.getWriter();
   out.print(tel);
   return null;
  }

 }
/**
  * ajax获得用户信息，返回xml
  * @param mapping
  * @param form
  * @param request
  * @param response
  * @return
  * @throws DataAccessException
  * @throws IOException
  * @throws ParseException
  */
 public ActionForward togetUserInfo(ActionMapping mapping, ActionForm form,
   HttpServletRequest request, HttpServletResponse response)
   throws DataAccessException, IOException, ParseException {
  String userid = request.getParameter("userid");
  
  response.setContentType("text/xml;charset=UTF-8");
  response.setHeader("Cache-Control", "no-cache");
  String xml_start = "<?xml version = \"1.0\" encoding = \"UTF-8\"?>";
  xml_start += "<selects>";
  String xml_end = "</selects>";
  String xml = "";
  String last_xml = "";
  try {
   UserInfoExtendBean userInfoExtendBean=userInfoService.select(userid);
   String mobile=userInfoExtendBean.getMobile()!=null?userInfoExtendBean.getMobile():"无";
   String tel=userInfoExtendBean.getTel()!=null?userInfoExtendBean.getTel():"无";
   String mail=userInfoExtendBean.getEmail()!=null?userInfoExtendBean.getEmail():"无";
   xml = xml + "<select><value>" + "peoplemobile"
   + "</value><text>" + mobile
   + "</text></select>"
   + "<select><value>" + "peopletel"
   + "</value><text>" + tel
   + "</text></select>"
   + "<select><value>" + "email"
   + "</value><text>" + mail
   + "</text></select>";;
   last_xml = xml_start + xml + xml_end;

   response.getWriter().print(last_xml);
  } catch (Exception e) {
   return mapping.findForward("error");
  }
  return null;

 }

ajax中responseText与responseXML区别