AJAX问题:缺少对象

ronaldoliubing 2006-08-17 03:48:51

<Script language="javascript">
var xmlHttp;

function createXMLHttpRequest(){
if (window.ActiveXObject){
xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
}else if(window.XMLHttpRequest){
xmlHttp = new XMLHttpRequest();
}
}

function WhetherEntry(){
createXMLHttpRequest();
var useid = document.getElementById('useid');
var url = "/servlet/WhetherEntryServlet?useid=" + escape(useid.value);
alert(url);
xmlHttp.open("GET",url,true);
xmlHttp.onreadystatechange = callback;
xmlHttp.send(null);
}

function callback(){
if(xmlHttp.readyState == 4)
if(xmlHttp.status == 200)
outmessage();
}

function outmessage(){
var x = xmlHttp.responseXML.documentElement;
var mes = x.getElementsByTagName('message');
alert(mes);
if (mes[0].firstChild.nodeValue=="You not log on!"){
alert("你没有登录!");
}
var subs = xmlHttp.responseXML.getElementsByTagName("messsagedialog")[0].firstChild.nodeValue;
if (subs=="subscibe succeed!"){
alert("订阅成功!");
}

}
</Script>

Servlet代码如下:
package com.reekon.portlet.servlet;

import java.io.*;

import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.reekon.entity.*;
import com.reekon.portlet.healthsearch.service.healthsearchservice;

public class WhetherEntryServlet extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response)
throws IOException, ServletException {

response.setContentType("text/xml");

response.setHeader("Cache-Control", "no-cache");
String useid=request.getParameter("useid");//会员id
String userId =request.getRemoteUser();//用户登录id

//调试
PrintWriter out = response.getWriter();
System.out.println("useid: "+useid);
System.out.println("userId: "+userId);

//String xml = "<?xml version=\"1.0\" encoding=\"UTF-8\"?>";
String entrymessage = "You not log on!";
String subscibesucceed = "subscibe succeed!";

//将所得到参数set进去
NewsSubscribe ns = new NewsSubscribe();
ns.setUserid(userId);
ns.setOrganizationid(useid);

if (userId == null || userId == "" || userId.equals(null) || userId.equals("")){
out.println("<response>");
out.println("<message>" + entrymessage + "</message>");
out.println("</response>");
}else if (healthsearchservice.addNewsSubscribe(ns)){
out.println("<response>");
out.println("<messsagedialog>" + subscibesucceed + "</messsagedialog>");
out.println("</response>");
}
out.close();
}

public void doPost(HttpServletRequest request, HttpServletResponse response)
throws IOException, ServletException {
doGet(request, response);
}

public void init(ServletConfig config) throws ServletException {

}
}
这句中的:if (mes[0].firstChild.nodeValue=="You not log on!"){
alert("你没有登录!");
}
mes[0].firstChild.nodeValue报错:缺少对象

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