文件上传过程中，如果我们能看到进度条会更好，实现思路是服务器端用监听器实时监听进度并存入session，客户端异步请求服务器端获得上传进度，并进行效果渲染。
效果图：
服务器端servlet：
public class UploadServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
//取出监听器MyProgress在session中保存的进度信息
String progress=(String) req.getSession().getAttribute("progress");
//响应
resp.getWriter().print(progress);
//清除session中保存的数据
// req.getSession().removeAttribute("progress");
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
req.setCharacterEncoding("UTF-8");
DiskFileItemFactory factory=new DiskFileItemFactory();
ServletFileUpload upload=new ServletFileUpload(factory);
upload.setProgressListener(new MyProgressListener(req));
try {
List<FileItem> list = upload.parseRequest(req);
for (FileItem fileItem : list) {
if (fileItem.isFormField()) {//普通表单
}else{//上传文件
String path=req.getRealPath("uploads");
String fileName=fileItem.getName();
File file=new File(path, fileName);
fileItem.write(file);
System.out.println("成功上传文件："+fileName);
}
}
} catch (Exception e) {
System.out.println("文件上传发生错误！");
e.printStackTrace();
}
}
}
服务器端监听器：
public class MyProgressListener implements ProgressListener {
private HttpSession session;
public MyProgressListener(HttpServletRequest request){
session = request.getSession();
}
@Override
public void update(long pBytesRead, long pContentLength, int pItems) {
//将数据进行格式化
//已读取数据由字节转换为M
double readM=pBytesRead/1024.0/1024.0;
//已读取数据由字节转换为M
double totalM=pContentLength/1024.0/1024.0;
//已读取百分百
double percent=readM/totalM;
//格式化数据
//已读取
String readf=dataFormat(pBytesRead);
//总大小
String totalf=dataFormat(pContentLength);
//进度百分百
NumberFormat format=NumberFormat.getPercentInstance();
String progress=format.format(percent);
//将信息存入session
session.setAttribute("progress", progress);
//打印消息到控制台
System.out.println("pBytesRead===>"+pBytesRead);
System.out.println("pContentLength==>"+pContentLength);
System.out.println("pItems===>"+pItems);
System.out.println("readf--->"+readf);
System.out.println("totalf--->"+totalf);
System.out.println("progress--->"+progress);
}
/**
* 格式化读取数据的显示
* @param data要格式化的数据 单位byte
* @return 格式化后的数据，如果小于1M显示单位为KB，如果大于1M显示单位为M
*/
public String dataFormat(double data){
String formdata="";
if (data>=1024*1024) {//大于等于1M
formdata=Double.toString(data/1024/1024)+"M";
}else if(data>=1024){//大于等于1KB
formdata=Double.toString(data/1024)+"KB";
}else{//小于1KB
formdata=Double.toString(data)+"byte";
}
return formdata.substring(0, formdata.indexOf(".")+2);
}
}
客户端：
<html>
<head>
<base href="https://www.atool.online/article/<%=basePath%>" rel="external nofollow" >
<title>带进度条的文件上传效果</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<style type="text/css">
#progressBar{width: 300px;height: 20px;border: 1px #EEE solid;}
#progress{width: 0%;height: 20px;background-color: lime;}
</style>
<script type="text/javascript" src="https://www.atool.online/article/js/jquery-1.4.2.js"></script>
<script type="text/javascript">
function upload(){
$("#f1").submit();
var pro=null;
pro=setInterval(function(){
$.get("UploadServlet","",function(data){
if(data=='100%'){
clearInterval(pro);
$("#proInfo").text("上传进度：100%");
//更新进度条
$("#progress").width("100%");
}else{//正在上传
//更新进度信息
$("#proInfo").text("上传进度："+data);
//更新进度条
$("#progress").width(data);
}
});
},200);
}
</script>
</head>
<body>
<iframe name="aa" style="display: none;"></iframe>
<h2>带进度条的文件上传效果</h2>
<form target="aa" id="f1" action="UploadServlet" method="post" enctype="multipart/form-data">
文件：<input name="file" type="file">
<input type="button" value="上传" onclick="upload();">
<div id="progressBar">
<div id="progress"></div>
</div>
<span id="proInfo">上传进度：0%</span>
</form>
</body>
</html>
说明：为了让上传后该页面不跳转，我们可以让表单跳转至一个隐藏的iframe。
以上这篇基于fileUpload文件上传带进度条效果的实例(必看)就是小编分享给大家的全部内容了，希望能给大家一个参考，也希望大家多多支持阿兔在线工具。
