Ajax 访问 servlet 是没法获得xmlhttprequest！用高分求解！

Ajax 访问 servlet 是无法获得xmlhttprequest！！！！！急用高分求解！！！
function getXmlHttp()
{
alert("getXmlHttp");

      var xmlhttp=null;
      alert("di yi ge if zhiqian ");
     //运行到这里就不运行了  if也没进去  感觉是windows.XMLHttpRequest有问题！
      if(windows.XMLHttpRequest){
          alert("xmlhttprequest");  
          xmlhttp=new XMLHttpRequest();
      }else{
      alert("else");
        try{alert("activeobject");
           xmlhttp=new ActiveXObject("Msxml12.XMLHTTP");
           }catch(e){
                     try{alert("activeobject111");
                         xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
                        }catch(e){
                        alert("null");
                                 return null;
                                 }
                    }
      }
      alert("return");
     
      return xmlhttp;
}
function updateToDo(todo)
{         
          alert("updateToDo()");
          var state=encodeURIComponent(todo.toString());
          alert(state);
          var url="updateToDoRequest";
          qry='state='+state;
          //获取request
          alert("获取request"); 
          var xmlhttp=getXmlHttp();
          if(!xmlhttp){ 
          alert("xmlhttp获取失败");
          return;
          }
          alert("open");
          xmlhttp.open("POST",url,true);
          alert("onready");
          xmlhttp.onreadystatechange=getResult;
          alert("setHeader");

          xmlhttp.setRequestHeader("Content-Type","application/x-www-from-urlencoded");
          xmlhttp.setRequestHeader("Content-type","application/x-www-form-urlencoded");
          alert("准备发送请求");
          xmlhttp.send(qry);
}
function getResult()
{
    if (xmlhttp.readyState==4 && xmlhttp.status==200)
    {
       //服务器处理完成
       //处理服务器回应的结果
       
    }
         
}
 

用myeclipse写的 js没有代码检测  所以写了好多alert（）来检测错误  新手求喷！ Ajax Servlet XMLHttpRequest 服务器 函数
[解决办法]

      //if(windows.XMLHttpRequest){//多了一个s
      if(window.XMLHttpRequest){