AJAX 进度条实现代码

!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
html>
head>
title>Ajax Progress Bar/title>
script type="text/javascript">
var xmlHttp;
var key;
var bar_color = 'gray';//进度条的颜色
var span_id = "block";
var clear = "nbsp;nbsp;nbsp;";
function createXMLHttpRequest()//创建XMLHttpRequest对象
{
if(window.ActiveXObject)
{
xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
}
else if(window.XMLHttpRequest)
{
xmlHttp = new XMLHttpRequest();
}
}
function go()
{
createXMLHttpRequest();//创建XMLHttpRequest对象
checkDiv();//显示滚动条
xmlHttp.onreadystatechange = callBack;//设置回调函数
var url = "/AjaxDemo/servlet/ProgressBarServlet?task=create";//请求的地址
var button = document.getElementById("go");
button.disabled = true;//设置按钮不可用
xmlHttp.open("get",url,true);//打开对服务器的连接
xmlHttp.send();//发送请求
}
function callBack()
{
if(xmlHttp.readyState == 4)
{
if(xmlHttp.status == 200)
{
setTimeout("pollServer()",500);//定时调用
}
}
}
function pollServer()
{
createXMLHttpRequest();
var url="/AjaxDemo/servlet/ProgressBarServlet?task=pollkey="+key;
xmlHttp.onreadystatechange = pollCallBack;
xmlHttp.open("GET",url,true);
xmlHttp.send();
}
function pollCallBack()
{
if(xmlHttp.readyState == 4)
{
if(xmlHttp.status == 200)
{
var percent_complete = xmlHttp.responseXML.getElementsByTagName("percent")[0]
.firstChild.data;//从服务器端获得响应信息
var index = processResult(percent_complete);
for(var i = 1; i=index; i++)
{
var elem = document.getElementById("block"+i);
elem.innerHTML = clear;
elem.style.backgroundColor = bar_color;
var next_cell = i+1;
if(next_cell > index next_cell = 9)
{
document.getElementById("block"+next_cell).innerHTML = percent_complete + "%";
}
}
if(index 9 )
{
setTimeout("pollServer()",500);
}
else
{
document.getElementById("complete").innerHTML = "Complete!";
document.getElementById("go").disabled = false;
}
}
}
}
function processResult(percent_complete)
{
var ind;
if(percent_complete.length == 1)
{
ind = 1;
}
else if(percent_complete.length == 2)
{
ind = percent_complete.substring(0,1);
}
else
{
ind = 9;
}
return ind;
}
function checkDiv()
{
var progress_bar = document.getElementById("progressBar");
if(progress_bar.style.visibility == "visible")
{
clearBar();
document.getElementById("complete").innerHTML = "";
}
else
{
progress_bar.style.visibility = "visible";
}
}
function clearBar()
{
for(var i =1; i10; i++)
{
var elem = document.getElementById("block"+i);
elem.innerHTML = clear;
elem.style.backgroundColor = "white";
}
}
/script>
/head>
body>
h1>Ajax Progress Bar Example/h1>
Launch long-running process:
input type="button" value="Launch" id="go" onclick="go()"/>
p>
table align="center">
tbody>
tr>
td>
div id="progressBar" style="padding:2px;border:solid black 2px;visibility:hidden">
span id="block1">nbsp;nbsp;nbsp;/span>
span id="block2">nbsp;nbsp;nbsp;/span>
span id="block3">nbsp;nbsp;nbsp;/span>
span id="block4">nbsp;nbsp;nbsp;/span>
span id="block5">nbsp;nbsp;nbsp;/span>
span id="block6">nbsp;nbsp;nbsp;/span>
span id="block7">nbsp;nbsp;nbsp;/span>
span id="block8">nbsp;nbsp;nbsp;/span>
span id="block9">nbsp;nbsp;nbsp;/span>
/div>
/td>
/tr>
tr>td align="center" id="complete">/td>/tr>
/tbody>
/table>
/body>
/html>

package cn.Ajax.test;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
@SuppressWarnings("serial")
public class ProgressBarServlet extends HttpServlet {
private int counter = 1;
/**
* The doGet method of the servlet. br>
*
* This method is called when a form has its tag value method equals to get.
*
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws ServletException if an error occurred
* @throws IOException if an error occurred
*/
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
String task = request.getParameter("task");
String res="";
if(task.equals("create")){
res = "key>1/key>";
counter = 1;
}
else{
String percent = "";
switch (counter) {
case 1: percent = "10";break;
case 2: percent = "23";break;
case 3: percent = "35";break;
case 4: percent = "51";break;
case 5: percent = "64";break;
case 6: percent = "73";break;
case 7: percent = "89";break;
case 8: percent = "100";break;
}
counter++;
res ="percent>"+percent+"/percent>";
}
PrintWriter out = response.getWriter();
response.setContentType("text/xml");
response.setHeader("Cache-Control", "no-cache");
out.println("response>");
out.println(res);
out.println("/response>");
out.close();
}
/**
* The doPost method of the servlet. br>
*
* This method is called when a form has its tag value method equals to post.
*
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws ServletException if an error occurred
* @throws IOException if an error occurred
*/
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}