java使用ajax实现进度条_java使用ajax实现进度条
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：
Ajax Progress Barvar 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...";
}
| 86% | ||
|
||
| completed |
2：一个模拟servlet：ProgressBarServlet.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 GET 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 = "1";
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 + "";
}
PrintWriter out = response.getWriter();
response.setContentType("text/xml");
response.setHeader("Cache-Control", "no-cache");
out.println("");
out.println(res);
out.println("");
out.close();
}
/** Handles the HTTP POST 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：
ProgressBarServlet
ProgressBarServlet
com.cyberobject.lcl.ajax.ProgressBarServlet
ProgressBarServlet
/ProgressBarServlet
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.