ajax进度条

最新推荐文章于 2025-07-07 12:18:45 发布

转载最新推荐文章于 2025-07-07 12:18:45 发布 · 3.1k 阅读

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#ajax #servlet #function #xmlhttprequest #table #border

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在最近的一个项目中，有一个上传功能：上传一个cvs文件，然后解析此文件并写入数据库
由于经常需要传很大的文件，客户完成此功能往往需要40分钟，在这个过程中，页面也没有任何提示，用户体验非常不好？
为何不用ajax作一个进度条呢？
分两步完成此需求：
一：写一个简单的ajax，实现最简单的进度条功能。
二：把此进度条改造为项目可用的进度条。

一：最简单的进度条
1。客户端每2秒发送一个createXMLHttpRequest请求给服务端.并得到服务端返回的进度数据.根据服务端返回的数据,用javascript更新一个table的width,
这样就模拟了一个进度条.
progressBar.html.内容如下：

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">

<html>

<head>

<title>Ajax Progress Bar</title>

var xmlHttp;

var key;

function createXMLHttpRequest() {

if (window.ActiveXObject) {

xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");

}

else if (window.XMLHttpRequest) {

xmlHttp = new XMLHttpRequest();

}

function go() {

createXMLHttpRequest();

clearBar();

var url = "ProgressBarServlet?task=create";

var button = document.getElementById("go");

button.disabled = true;

xmlHttp.open("GET", url, true);

xmlHttp.onreadystatechange = goCallback;

xmlHttp.send(null);

}

function goCallback() {

if (xmlHttp.readyState == 4) {

if (xmlHttp.status == 200) {

setTimeout("pollServer()", 2000);

}

function pollServer() {

createXMLHttpRequest();

var url = "ProgressBarServlet?task=poll&key=" + key;

xmlHttp.open("GET", url, true);

xmlHttp.onreadystatechange = pollCallback;

xmlHttp.send(null);

}

function pollCallback() {

if (xmlHttp.readyState == 4) {

if (xmlHttp.status == 200) {

var percent_complete = xmlHttp.responseXML.getElementsByTagName("percent")[0].firstChild.data;

var progress = document.getElementById("progress");

var progressPersent = document.getElementById("progressPersent");

progress.width = percent_complete + "%";

progressPersent.innerHTML = percent_complete + "%";

if (percent_complete < 100) {

setTimeout("pollServer()", 2000);

} else {

document.getElementById("complete").innerHTML = "Complete!";

//document.getElementById("go").disabled = false;

}

function clearBar() {

var progress_bar = document.getElementById("progressBar");

var progressPersent = document.getElementById("progressPersent");

var complete = document.getElementById("complete");

progress_bar.style.visibility = "visible"

progressPersent.innerHTML = " ";

complete.innerHTML = "Begin to upload this file...";

}

</script>

</head>

<body>

<tr>

</tr>

<tr >

<td>

<tr>

<td>

<tr>

</tr>

</table></td>

</tr>

</table>

</td>

</tr>

<tr>

<td align="center" id="complete">completed</td>

</tr>

</table>

</div>

</body>

</html>

2：一个模拟servlet：ProgressBarServlet1。java，内容如下：

package com.cyberobject.lcl.ajax;

import java.io.*;

import javax.servlet.*;
import javax.servlet.http.*;

/**
*
* @author nate
* @version
*/
public class ProgressBarServlet extends HttpServlet {
private int counter = 1;

/** Handles the HTTP <code>GET</code> method.
  * @param request servlet request
  * @param response servlet response
  */
protected 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();
}

/** Handles the HTTP <code>POST</code> method.
  * @param request servlet request
  * @param response servlet response
  */
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
  doGet(request, response);
}

/** Returns a short description of the servlet.
  */
public String getServletInfo() {
  return "Short description";
}
}
3：在web。xml中配置好servlet映射：
  
  <servlet>
   <servlet-name>ProgressBarServlet</servlet-name>
   <display-name>ProgressBarServlet</display-name>
   <servlet-class>com.cyberobject.lcl.ajax.ProgressBarServlet</servlet-class>
  </servlet>

    <servlet-mapping>
   <servlet-name>ProgressBarServlet</servlet-name>
   <url-pattern>/ProgressBarServlet</url-pattern>
  </servlet-mapping>

此时进度条已经可以运行了。接下来的工作就是把它移植到我们的系统。
  二：
  1：在写数据库的class DbOperater中，增加一个progress属性
  private int progress;

  2:在写数据库的class中，增加一个getProgress()方法:
  public int getProgress()
  {
return progress;
  }
  3: 在写库的for循环中, progress++;
  4:在调用DbOperater的servlet中调用DbOperater的getProgress()方法,这样就为进度条提供了实时数据.
  5:另外:servlet的doGet()用来获得进度数据,doPost()用来上传文件和写库操作.彼此分工明确.
  特此存档.

来自:http://blog.youkuaiyun.com/javatwt/archive/2007/03/02/1519117.aspx