基于Ajax技术实现文件上传带进度条

DiskFileItemFactory factory = new DiskFileItemFactory();
ServletFileUpload upload = new ServletFileUpload(factory); 

public List parseRequest(HttpServletRequest request) throws FileUploadException 

form enctype="multipart/form-data" method="post" action="UpLoad?action=uploadFile">

div id="progressBar" class="prog_border" align="left">
img src="images/progressBar.gif" width="0" height="13" id="imgProgress">/div>
span id="progressPercent" style="width:40px;display:none">0%/span>
input name="Submit" type="button" value="提交" onClick="deal(this.form)">
input name="Reset" type="reset" class="btn_grey" value="重置">/td>
/form> 

public void uploadFile(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=GBK");
request.setCharacterEncoding("GBK");
HttpSession session=request.getSession();
session.setAttribute("progressBar",0); //定义指定上传进度的Session变量
String error = "";
int maxSize=50*1024*1024; //单个上传文件大小的上限
DiskFileItemFactory factory = new DiskFileItemFactory(); //创建工厂对象
ServletFileUpload upload = new ServletFileUpload(factory); //创建一个新的文件上传对象
try {
List items = upload.parseRequest(request); // 解析上传请求
Iterator itr = items.iterator(); // 枚举方法
while (itr.hasNext()) {
FileItem item = (FileItem) itr.next(); //获取FileItem对象
if (!item.isFormField()) { // 判断是否为文件域
if (item.getName() != null  !item.getName().equals("")) {//是否选择了文件
long upFileSize=item.getSize(); //上传文件的大小
String fileName=item.getName(); //获取文件名
if(upFileSize>maxSize){
error="您上传的文件太大，请选择不超过50M的文件";
break;
}
// 此时文件暂存在服务器的内存中
File tempFile = new File(fileName); //构造文件目录临时对象
String uploadPath = this.getServletContext().getRealPath("/upload");
File file = new File(uploadPath,tempFile.getName()); 
InputStream is=item.getInputStream();
int buffer=1024; //定义缓冲区的大小
int length=0;
byte[] b=new byte[buffer];
double percent=0;
FileOutputStream fos=new FileOutputStream(file);
while((length=is.read(b))!=-1){
percent+=length/(double)upFileSize*100D; //计算上传文件的百分比
fos.write(b,0,length); //向文件输出流写读取的数据
session.setAttribute("progressBar",Math.round(percent)); 
}
fos.close();
Thread.sleep(1000); //线程休眠1秒
} else {
error="没有选择上传文件！";
}
}
}
} catch (Exception e) {
e.printStackTrace();
error = "上传文件出现错误：" + e.getMessage();
}
if (!"".equals(error)) {
request.setAttribute("error", error);
request.getRequestDispatcher("error.jsp").forward(request, response);
}else {
request.setAttribute("result", "文件上传成功！");
request.getRequestDispatcher("upFile_deal.jsp").forward(request, response);
}
} 

script language="javascript" src="js/request.js">/script>
script language="javascript">
var request = false;
function getProgress(){ 
var url="showProgress.jsp"; //服务器地址
var param ="nocache="+new Date().getTime(); //每次请求URL参数都不同 ，避免上传时进度条不动
request=httpRequest("post",url,true,callbackFunc,param); //调用请求方法 
}
//Ajax回调函数
function callbackFunc(){
if( request.readyState==4 ){ //判断响应是否完成 
if( request.status == 200 ){ //判断响应是否成功
var h = request.responseText; //获得返回的响应数据，该数据位上传进度百分比
h=h.replace(/\s/g,""); //去除字符串中的Unicode空白符
document.getElementById("progressPercent").style.display=""; //显示百分比 
progressPercent.innerHTML=h+"%"; //显示完成的百分比
document.getElementById("progressBar").style.display="block"; //显示进度条
document.getElementById("imgProgress").width=h*(235/100); //显示完成的进度
}
}
}
/script> 

%@page contentType="text/html" pageEncoding="GBK"%>
${progressBar} 

function deal(form){
form.submit(); //提交表单
timer=window.setInterval("getProgress()",500); //每隔500毫秒获取一次上传进度
}