function sendRequestByGet(){
     //定義異步請求對象
    var xmlReq;
    //檢測瀏覽器是否直接支持ajax
    if(window.XMLHttpRequest){//直接支持ajax
      xmlReq=new XMLHttpRequest();
    }else{//不直接支持ajax
      xmlReq=new ActiveObject('Microsoft.XMLHTTP');
    }
    
     //設(shè)置回調(diào)函數(shù)
     xmlReq.onreadystatechange=function(){
       if (xmlReq.readyState==4&&xmlReq.status==200) {
         //獲取服務(wù)器的響應(yīng)值
        var result=xmlReq.responseText;
         //后續(xù)操作
         alert(result);
      }
     };
     
     //創(chuàng)建異步get請求
     var url="Hello?name=zhangsan";
     xmlReq.open("GET",url,true);
     //發(fā)送請求
     xmlReq.send(null);
   }

function sendRequestByPost(){
     //定義異步請求對象
    var xmlReq;
    //檢測瀏覽器是否直接支持ajax
    if(window.XMLHttpRequest){//直接支持ajax
      xmlReq=new XMLHttpRequest();
    }else{//不直接支持ajax
      xmlReq=new ActiveObject('Microsoft.XMLHTTP');
    }
    
     //設(shè)置回調(diào)函數(shù)
     xmlReq.onreadystatechange=function(){
       if (xmlReq.readyState==4&&xmlReq.status==200) {
         //獲取服務(wù)器的響應(yīng)值
        var result=xmlReq.responseText;
         //后續(xù)操作
         alert(result);
      }
     };
     
     //創(chuàng)建異步Post請求
     var url="Hello";
     xmlReq.open("POST",url,true);
     xmlReq.setRequestHeader("Content-Type","application/x-www-form-urlencoded");
     //發(fā)送請求
     var data="name=lisi";
     xmlReq.send(data);
   }

@Override
  protected void doPost(HttpServletRequest req, HttpServletResponse resp)
      throws ServletException, IOException {
    String name=req.getParameter("name");
    PrintWriter out = resp.getWriter();
    out.print(name);
  }