Ajax基础实例

前端代码

 <script type="text/javascript">
    var xmlhttp;
    function go(url)
    {
    xmlhttp=null;
    if (window.XMLHttpRequest)
      {// code for IE7, Firefox, Opera, etc.
      xmlhttp=new XMLHttpRequest();
      }
    else if (window.ActiveXObject)
      {// code for IE6, IE5
      xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
      }
    ////////////////////////////////
    if (xmlhttp!=null)
      {
        //alert("123");
        xmlhttp.onreadystatechange=state_Change;
        xmlhttp.open("POST",url,true);
        xmlhttp.setRequestHeader("Content-type","application/x-www-form-urlencoded");
        xmlhttp.send("123="+"123");
      
      }
    else
      {
      alert("Your browser does not support XMLHTTP.");
      }
    }

    function state_Change()
    {
    if (xmlhttp.readyState==4)
      {// 4 = "loaded"
      if (xmlhttp.status==200)
        {// 200 = "OK"
       var v1=xmlhttp.status;
       var v2=xmlhttp.statusText;
       var v3=xmlhttp.responseText; 
       alert(v1+"    "+v2+"   "+v3);
        }
      else
        {
        alert("Problem retrieving XML data:" + xmlhttp.statusText);
        }
      }
    }
    </script>
  <body>
    This is my JSP page. <br>
     
     <input type="text" value="" name="123" />  
    <input type="button" value="提交" onclick="go('/Ajax.w3c/servlet/test');"/> 
  </body>

后端代码:

public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        
        System.out.println("jinru fangfa ");
        String name = request.getParameter("123");
        System.out.println(name); 
        
        response.setCharacterEncoding("utf-8");
        response.setContentType("text/html");
        response.setHeader("Cache-Control","no-cache");
        PrintWriter out = response.getWriter();
        out.println("yes");
        out.flush();
        out.close(); 
    }