基于AJAX的文件上传显示进度条实现

基于Ajax的文件上传要实现的功能要求，要在用户提交了上传按钮请求后，客户端其页面要显示文件上传进度条。

其整个功能时序图如图所示。



简单的说，要实现在客户端显示进度条，需要做的是：当客户端提交上传文件请求后，服务器在上传文件的过程中，将上传进度情况保存到Session中，客户端周期性的发送请求来获取保存在Session中值，以获取上传文件的进度信息。

1. 新建web工程AjaxUpload。

2. 将commons-fileupload-1.2.1-bin.zip包中的commons-fileupload-1.2.1.jar文件和commons-io-1.4-bin.zip包中的commons-io-1.4.jar文件拷贝到web工程下的WEB-INF\lib目录下。

3. 由于本实例涉及到多个类，处理此类问题最好是给相应的类打包进行管理。在web工程src目录下新建一个包com.ncu.upload。

4. 服务器端实现。

首先要创建一个用来保存文件上传状态的类 FileUploadStatus。其源码如下：

package com.ncu.upload;

import java.util.*;

public class FileUploadStatus {
//上传总量
private long uploadTotalSize=0;
//读取上传总量
private long readTotalSize=0;
//当前上传文件号
private int currentUploadFileNum=0;
//成功读取上传文件数
private int successUploadFileCount=0;
//状态
private String status="";
//处理起始时间
private long processStartTime=0l;
//处理终止时间
private long processEndTime=0l;
//处理执行时间
private long processRunningTime=0l;
//上传文件URL列表
private List uploadFileUrlList=new ArrayList();
//取消上传
private boolean cancel=false;
//上传base目录
private String baseDir="";

public String getBaseDir() {
return baseDir;
}
public void setBaseDir(String baseDir) {
this.baseDir = baseDir;
}
public boolean getCancel() {
return cancel;
}
public void setCancel(boolean cancel) {
this.cancel = cancel;
}
public List getUploadFileUrlList() {
return uploadFileUrlList;
}
public void setUploadFileUrlList(List uploadFileUrlList) {
this.uploadFileUrlList = uploadFileUrlList;
}
public long getProcessRunningTime() {
return processRunningTime;
}
public void setProcessRunningTime(long processRunningTime) {
this.processRunningTime = processRunningTime;
}
public long getProcessEndTime() {
return processEndTime;
}
public void setProcessEndTime(long processEndTime) {
this.processEndTime = processEndTime;
}
public long getProcessStartTime() {
return processStartTime;
}
public void setProcessStartTime(long processStartTime) {
this.processStartTime = processStartTime;
}
public long getReadTotalSize() {
return readTotalSize;
}
public void setReadTotalSize(long readTotalSize) {
this.readTotalSize = readTotalSize;
}
public int getSuccessUploadFileCount() {
return successUploadFileCount;
}
public void setSuccessUploadFileCount(int successUploadFileCount) {
this.successUploadFileCount = successUploadFileCount;
}
public int getCurrentUploadFileNum() {
return currentUploadFileNum;
}
public void setCurrentUploadFileNum(int currentUploadFileNum) {
this.currentUploadFileNum = currentUploadFileNum;
}
public String getStatus() {
return status;
}
public void setStatus(String status) {
this.status = status;
}
public long getUploadTotalSize() {
return uploadTotalSize;
}
public void setUploadTotalSize(long uploadTotalSize) {
this.uploadTotalSize = uploadTotalSize;
}

}

由于要在客户端要显示进度条，所以在上传过程中服务器端需要监视和维护上传状态的信息，此过程需要处理的数据信息是：不断更新Session中保存的FileUploadStatus实例的信息，如：已经上传的字节数，上传文件的总大小等。FileUpload现在的1.2版本为监视上传进度提供了内建的支持，可以直接继承类ProgressListener，然后重载update()方法，在该方法中添加自己要处理的代码，最后在文件上传处理代码（后面会讲到）中通过为ServletFileUpload对象注册创建的监听类。监听类UploadListener的源代码如下：

package com.ncu.upload;

import javax.servlet.http.HttpSession;

import org.apache.commons.fileupload.ProgressListener;

public class UploadListener implements ProgressListener {

private HttpSession session=null;

public UploadListener (HttpSession session){
this.session=session;
}
/**
* 更新状态
* @param pBytesRead 读取字节总数
* @param pContentLength 数据总长度
* @param pItems 当前正在被读取的field号
*/
public void update(long pBytesRead, long pContentLength, int pItems) {
FileUploadStatus fuploadStatus = UploadServlet.takeOutFileUploadStatusBean(this.session);
fuploadStatus.setUploadTotalSize(pContentLength);
//读取完成
if (pContentLength == -1) {
fuploadStatus.setStatus("完成对" + pItems + "个文件的读取：读取了 " + pBytesRead + "/"  + pContentLength+ " bytes.");
fuploadStatus.setReadTotalSize(pBytesRead);
fuploadStatus.setCurrentUploadFileNum(pItems);
fuploadStatus.setProcessEndTime(System.currentTimeMillis());
fuploadStatus.setProcessRunningTime(fuploadStatus.getProcessEndTime());
}else{//读取过程中
fuploadStatus.setStatus("当前正在处理第" + pItems+"个文件:已经读取了 " + pBytesRead + " / " + pContentLength+ " bytes.");
fuploadStatus.setReadTotalSize(pBytesRead);
fuploadStatus.setCurrentUploadFileNum(pItems);
fuploadStatus.setProcessRunningTime(System.currentTimeMillis());
}
//System.out.println("已经读取：" + pBytesRead);
UploadServlet.storeFileUploadStatusBean(this.session, fuploadStatus);
}

}

有了前面两个类的基础，下来我们可以动手去实现真正处理整个操作Servlet类。源代码如下。

package com.ncu.upload;

import java.io.*;
import java.util.List;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.FileUploadException;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.*;

/**
* Servlet implementation class for Servlet: UploadServlet
*
*/
public class UploadServlet extends javax.servlet.http.HttpServlet implements javax.servlet.Servlet {
static final long serialVersionUID = 1L;

public static final String UPLOAD_STATUS="UPLOAD_STATUS";
public static final String UPLOAD_DIR="/upload";

public UploadServlet() {
super();
}

/**
* 从文件路径中取出文件名
* @param filePath
* @return
*/
private String takeOutFileName(String filePath){
int pos=filePath.lastIndexOf(File.separator);
if (pos>0){
return filePath.substring(pos+1);
}
else{
return filePath;
}
}

/**
* 从request中取出FileUploadStatus Bean
* @param request
* @return
*/
public static FileUploadStatus takeOutFileUploadStatusBean(HttpSession session){
Object obj=session.getAttribute(UPLOAD_STATUS);
if (obj!=null){
return (FileUploadStatus)obj;
}
else{
return null;
}
}

/**
* 把FileUploadStatus Bean保存到session
* @param request
* @param uploadStatusBean
*/
public static void storeFileUploadStatusBean(
HttpSession session,
FileUploadStatus uploadStatusBean){
session.setAttribute(UPLOAD_STATUS,uploadStatusBean);
}

/**
* 删除已经上传的文件
* @param request
*/
private void deleteUploadedFile(HttpServletRequest request){
FileUploadStatus fUploadStatus=takeOutFileUploadStatusBean(request.getSession());
for(int i=0;i<fUploadStatus.getUploadFileUrlList().size();i++){
File uploadedFile = new File(request.getRealPath(UPLOAD_DIR)+
File.separator+fUploadStatus.getUploadFileUrlList().get(i));
uploadedFile.delete();
}
fUploadStatus.getUploadFileUrlList().clear();
fUploadStatus.setStatus("删除已上传的文件");
storeFileUploadStatusBean(request.getSession(),fUploadStatus);
}

/**
* 上传过程中出错处理
* @param request
* @param errMsg
* @throws IOException
* @throws ServletException
*/
private void uploadExceptionHandle(
HttpServletRequest request,
String errMsg) throws ServletException, IOException{
//首先删除已经上传的文件
deleteUploadedFile(request);
FileUploadStatus fUploadStatus=takeOutFileUploadStatusBean(request.getSession());
fUploadStatus.setStatus(errMsg);
storeFileUploadStatusBean(request.getSession(),fUploadStatus);
}

/**
* 初始化文件上传状态Bean
* @param request
* @return
*/
private FileUploadStatus initFileUploadStatusBean(HttpServletRequest request){
FileUploadStatus fUploadStatus=new FileUploadStatus();
fUploadStatus.setStatus("正在准备处理");
fUploadStatus.setUploadTotalSize(request.getContentLength());
fUploadStatus.setProcessStartTime(System.currentTimeMillis());
fUploadStatus.setBaseDir(request.getContextPath()+UPLOAD_DIR);
return fUploadStatus;
}

/**
* 处理文件上传
* @param request
* @param response
* @throws IOException
* @throws ServletException
*/
private void processFileUpload(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException{
DiskFileItemFactory factory = new DiskFileItemFactory();
//设置内存阀值，超过后写入临时文件
//factory.setSizeThreshold(10240000*5);
//设置临时文件存储位置
//factory.setRepository(new File(request.getRealPath("/upload/temp")));
ServletFileUpload upload = new ServletFileUpload(factory);
//设置单个文件的最大上传size
//upload.setFileSizeMax(10240000*5);
//设置整个request的最大size
//upload.setSizeMax(10240000*5);
//注册监听类
upload.setProgressListener(new UploadListener(request.getSession()));
//保存初始化后的FileUploadStatus Bean
storeFileUploadStatusBean(request.getSession(),initFileUploadStatusBean(request));

try {
List items = upload.parseRequest(request);
//处理文件上传
for(int i=0;i<items.size();i++){
FileItem item=(FileItem)items.get(i);

//取消上传
if (takeOutFileUploadStatusBean(request.getSession()).getCancel()){
deleteUploadedFile(request);
break;
}
//保存文件
else if (!item.isFormField() && item.getName().length()>0){
String fileName=takeOutFileName(item.getName());
File uploadedFile = new File(request.getRealPath(UPLOAD_DIR)+File.separator+fileName);
item.write(uploadedFile);
//更新上传文件列表
FileUploadStatus fUploadStatus=takeOutFileUploadStatusBean(request.getSession());
fUploadStatus.getUploadFileUrlList().add(fileName);
storeFileUploadStatusBean(request.getSession(),fUploadStatus);
Thread.sleep(500);
}
}

} catch (FileUploadException e) {
e.printStackTrace();
//uploadExceptionHandle(request,"上传文件时发生错误:"+e.getMessage());
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
//uploadExceptionHandle(request,"保存上传文件时发生错误:"+e.getMessage());
}
}

/**
* 回应上传状态查询
* @param request
* @param response
* @throws IOException
*/
private void responseFileUploadStatusPoll(HttpServletRequest request,HttpServletResponse response) throws IOException{
FileUploadStatus fUploadStatus=(FileUploadStatus)request.getSession().getAttribute(UPLOAD_STATUS);
//计算上传完成的百分比
long percentComplete = (long)Math.floor(((double) fUploadStatus.getReadTotalSize()/(double) fUploadStatus.getUploadTotalSize())*100.0);
System.out.println("com:"+percentComplete);
response.setContentType("text/xml");
response.setCharacterEncoding("UTF-8");
response.setHeader("Cache-Control", "no-cache");
if ( ((long)fUploadStatus.getReadTotalSize() == (long)fUploadStatus.getUploadTotalSize()) || (fUploadStatus.getCancel() == true)){
response.getWriter().write(fUploadStatus.getStatus().toString()+"success");
}else{
response.getWriter().write(fUploadStatus.getStatus().toString()+"<div class=\"prog-border\"><div class=\"prog-bar\" style=\"width: "
+ percentComplete + "%;\"></div></div>");
}
}
/**
* 处理取消文件上传
* @param request
* @param response
* @throws IOException
*/
private void processCancelFileUpload(HttpServletRequest request,HttpServletResponse response) throws IOException{
FileUploadStatus fUploadStatus=(FileUploadStatus)request.getSession().getAttribute(UPLOAD_STATUS);
fUploadStatus.setCancel(true);
request.getSession().setAttribute(UPLOAD_STATUS, fUploadStatus);
responseFileUploadStatusPoll(request,response);

}

/**
* 在上传文件列表中查找与文件名相关的id
* @param request
* @param fileName 文件名
* @return　找到返回id,否则返回-1
*/
private int findFileIdInFileUploadedList(HttpServletRequest request,String fileName){
FileUploadStatus fileUploadStatus=takeOutFileUploadStatusBean(request.getSession());
for(int i=0;i<fileUploadStatus.getUploadFileUrlList().size();i++){
if (fileName.equals((String)fileUploadStatus.getUploadFileUrlList().get(i))){
return i;
}
}
return -1;
}

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doPost(request,response);
}

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
boolean isMultipart = ServletFileUpload.isMultipartContent(request);

if (isMultipart) {
processFileUpload(request,response);
}else{
request.setCharacterEncoding("UTF-8");

if (request.getParameter("uploadStatus")!=null){
responseFileUploadStatusPoll(request,response);
}
if (request.getParameter("cancelUpload")!=null){
processCancelFileUpload(request,response);
}
}

}
}

至此，服务器端的代码已经基本完成。

5. 客户端实现

由于在上传文件时需要在同一页面显示对应的进度条控件，因此，在提交表单时当前页面不能被刷新。我们可以通过将表单提交至一个隐藏的 iframe 中来实现。关于Ajax的技术前面讲过，这里就不再细说，直接给出源代码如下：

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>基于Ajax的上传文件显示进度条</title>
<style>
.prog-border {
height: 15px;
width: 205px;
background: #fff;
border: 1px solid #000;
margin: 0;
padding: 0;
}
.prog-bar {
height: 11px;
margin: 2px;
padding: 0px;
background: #178399;
font-size: 10pt;
}
body{
font-family: Arial, Helvetica, sans-serif;
font-size: 10pt;
}
</style>
<script language="javascript" type="text/javascript">
<!--
//var userName=document.getElementById("userName").value;
//创建跨浏览器的XMLHttpRequest对象
var timer;
function startListener(){
var xmlhttp;
try{
//IE 5.0
xmlhttp = new ActiveXObject('Msxm12.XMLHTTP');
}catch(e){
try{
//IE 5.5 及更高版本
xmlhttp = new ActiveXObject('Microsoft.XMLHTTP');
}catch(e){
try{
//其他浏览器
xmlhttp = new XMLHttpRequest();
}catch(e){}
}
}
var progressStatusText = document.getElementById("progressBar");
xmlhttp.open("get","UploadServlet?uploadStatus=true",true);
/**此处Header设置非常重要，必须设置Content-type类型，负责会报错误
*/
xmlhttp.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
xmlhttp.onreadystatechange = function(){
if(xmlhttp.readyState == 4){
if(xmlhttp.status == 200){
progressStatusText.innerHTML = "";
progressStatusText.innerHTML = xmlhttp.responseText;
var temp = xmlhttp.responseText.indexOf("success");
if (  temp > 0 ){
window.clearTimeout(timer);
}else{
timer = window.setTimeout(startListener,1000);
}
}
}
}
xmlhttp.send(null);
}
function startUpload(){
timer = window.setTimeout(startListener,1000);
return true;
}
function cancelUpload(){
var xmlhttp;
try{
//IE 5.0
xmlhttp = new ActiveXObject('Msxm12.XMLHTTP');
}catch(e){
try{
//IE 5.5 及更高版本
xmlhttp = new ActiveXObject('Microsoft.XMLHTTP');
}catch(e){
try{
//其他浏览器
xmlhttp = new XMLHttpRequest();
}catch(e){}
}
}
var progressStatusText = document.getElementById("progressBar");
xmlhttp.open("get","UploadServlet?cancelUpload=true",true);
xmlhttp.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
//xmlhttp.setRequestHeader("Content-type", "multipart/form-data");
xmlhttp.onreadystatechange = function(){
if(xmlhttp.readyState == 4){
if(xmlhttp.status == 200){
progressStatusText.innerHTML = "";
progressStatusText.innerHTML = xmlhttp.responseText;
}
}
}
xmlhttp.send(null);
return false;
}
//-->
</script>
</head>
<body>
<div id="controlPanel">
<!-- 这个是隐藏的<iframe>作为表单提交后处理的后台目标
通过表单form的target属性指定该<iframe>将返回信息显示在<iframe>框架中
-->
<iframe id='target_upload' name='target_upload' src='' style='display: none'></iframe>
<form id="fileUploadForm" name="fileUploadForm" action="UploadServlet"
enctype="multipart/form-data" method="post" onsubmit="return startUpload();" target="target_upload">
<input type="file" name="file" id="file" size="40"/><br>
<input type="submit" name="uploadButton" id="uploadButton" value="开始上传"/>
<input type="button" name="cancelUploadButton" id="cancelUploadButton" value="取消上传" onclick="return cancelUpload();"/><br>
</form>
<div id="progressBar">
</div>
</div>
</body>
</html>

至此，整个文件上传的实现到此完成，读者可以在此基础上，发挥自己的创新能力，去完善此实例。

Good Luck!
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