使用Ajax实现简单的带百分比进度条实例

<table id="load" width="700" border="0" align="center" bgcolor="#FAFAFA" cellpadding="0" cellspacing="0" bordercolor="#000000" style="border-collapse:collapse;display:none ">
   <tr>
    <td><br><br>
    <table width="100%" border="1" cellspacing="0" cellpadding="0" bordercolor="#287BCE" style="border-collapse:collapse ">
      <tr bgcolor="#F7F7F6">
       <td width="20%" height="100" valign="middle">
        <table align=&#39;center&#39; width=&#39;500&#39;>
         <tr>
          <td colspan=&#39;2&#39; align=&#39;center&#39; id="progressPersent"><font size="2">
          正在进行保存，用时较长，请稍后...
          </font>
          </td>
         </tr>
         <tr>
          <td id=&#39;tdOne&#39; height=&#39;25&#39; width=1 bgcolor="blue"> </td>
          <td id=&#39;tdTwo&#39; height=&#39;25&#39; width=500 bgColor=&#39;#999999&#39;> </td>
         </tr>
        </table>
       </td>
      </tr>
    </table>
    </td>
   </tr>
  </table>　

/**添加带百分比的进度条*/
  var xmlHttp;
  //创建ajax引擎
  function createXMLHttpRequest() {
   if (window.XMLHttpRequest) {
     xmlHttp = new XMLHttpRequest();
    } else if (window.ActiveXObject) {
     try {
        xmlHttp = new ActiveXObject("Msxml2.XMLHTTP");
     } catch (e1) {
        try {
         xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
        } catch (e2) {
        }
     }
    }
  }
  function loading() {
    createXMLHttpRequest();
    clearLoad();
    var url = "elecCommonMsgAction_progressBar.do";
    xmlHttp.open("GET", url, true);
    xmlHttp.onreadystatechange = createCallback;
    xmlHttp.send(null);
  }
  function createCallback() {
    if (xmlHttp.readyState == 4) {
      if (xmlHttp.status == 200) {
        //每隔1秒钟执行一次percentServer()方法，直到当前访问结束
        setTimeout("percentServer()", 1000);
      }
    }
  }
  function percentServer() {
    createXMLHttpRequest();
    var url = "elecCommonMsgAction_progressBar.do";
    xmlHttp.open("GET", url, true);
    xmlHttp.onreadystatechange = updateCallback;
    xmlHttp.send(null);
  }
  function updateCallback() {
    if (xmlHttp.readyState == 4) {
      if (xmlHttp.status == 200) {
        //获取XML数据中的percent存放的百分比的值
        var percent_complete = xmlHttp.responseXML.getElementsByTagName("percent")[0].firstChild.data;
        var tdOne = document.getElementById("tdOne");
        var progressPersent = document.getElementById("progressPersent");
        //改变蓝色区域的宽度
        tdOne.width = percent_complete + "%";
        //将百分比的数值显示到页面上
        progressPersent.innerHTML = percent_complete + "%";
        //如果计算获取的百分比的数值没有达到100，则继续调用方法，直到操作结束为止
        if (percent_complete < 100) {
          setTimeout("percentServer()", 1000);
        }
      }
    }
  } 
  function clearLoad() {
    document.getElementById("load").style.display="";
    document.getElementById("opperate1").style.display="none";
    document.getElementById("opperate2").style.display="none";
  }

/** 
  * @throws Exception 
   * @Name: progressBar
  * @Description: 在页面执行保存后，使用ajax，计算执行的百分比情况，将结果显示到页面上
  * @Parameters: 无
  * @Return: ajax如果不需要跳转页面，返回null或者NONE
  */
  public String progressBar() throws Exception{
    //从session中获取操作方法中计算的百分比
    Double percent = (Double) request.getSession().getAttribute("percent");
    String res = "";
    //此时说明操作的业务方法仍然继续在执行
    if(percent!=null){
      //计算的小数，四舍五入取整
      int percentInt = (int) Math.rint(percent); 
      res = "<percent>" + percentInt + "</percent>";
    }
    //此时说明操作的业务方法已经执行完毕，session中的值已经被清空
    else{
      //存放百分比
      res = "<percent>" + 100 + "</percent>";
    }
    //定义ajax的返回结果是XML的形式
    PrintWriter out = response.getWriter();
    response.setContentType("text/xml");
    response.setHeader("Cache-Control", "no-cache");
    //存放结果数据，例如：<response><percent>88</percent></response>
    out.println("<response>");
    out.println(res);
    out.println("</response>");
    out.close();
    return null;
  }

/** 
  * @Name: save
  * @Description: 保存表单数据到数据库
  * @Parameters: 无
  * @Return: String：重定向到system/actingIndex.jsp再查询
  */
  public String save(){
    //模拟：循环保存150次，方便观察百分比变化
    for(int i=1;i<=150;i++){
      elecCommonMsgService.saveCommonMsg(elecCommonMsg);//保存数据
      request.getSession().setAttribute("percent", (double)i/150*100);
    }
    //线程结束，清空session
    request.getSession().removeAttribute("percent");
    return "save";
  }