下面给大家分享下基于ajax实现文件上传并显示进度条。在jsp部分，需要设计一个表单，form的属性添加 enctype="multipart/form-data"，设计一个iframe，作为隐藏。form的target等于iframe的name;
在servlet部分：文件上传用的Commons-FileupLoad，需要两个Jar，commons-fileupload和commons-io,少了第二个会报出找不到类的异常；
第一个servlet处理上传，及把上传进度保存到session,第二个servlet处理ajax请求,回传session保存的进度值；
进度条：可以用ajax拿到回传的进度值，改变图片的width实现变化；
jsp代码：
立即学习“Java免费学习笔记（深入）”；
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>Insert title here
这是index.jsp里的代码：
提交后还在当前页显示进度，所以要用到iframe，提交后的返回放到隐藏的iframe里，不影响页面效果；
css代码：
复制代码 代码如下:
.pro{
height:15px;
width:500px;
background: #FFFFF0;
border: 1px solid #8FBC8F;
margin: 0;
padding: 0;
display:none;
position: relative;
left:25px;
float:left;
}
js代码
function go(){
f1.submit();
document.getElementById("pro").style.display="block";
document.getElementById("prop").style.display="";
timer=setInterval("getP()",50);
}
var xmlHttpRequest;
function getP(){
if(window.XmlHttpRequest){
xmlHttpRequest=new XmlHttpRequest();
}else{
xmlHttpRequest=new ActiveXObject("Microsoft.XMLHTTP");
}
xmlHttpRequest.onreadystatechange=callBack;
url="getProgressServlet";
xmlHttpRequest.open("post",url,true);
xmlHttpRequest.setRequestHeader("Content-type","application/x-www-form-urlencoded");
xmlHttpRequest.send("&timeStamp="+(new Date()).getTime());
}
//回调函数
function callBack(){
if(xmlHttpRequest.readyState==4 && xmlHttpRequest.status==200){
result=xmlHttpRequest.responseText;
var result=result.replace(/(^\s*)|(\s*$)/g, "");
var res=result.split(",");
var flag=res[1];
var per=parseInt(res[0]);
var err=res[2];
document.getElementById("imgpro").style.width=per*5+"px";
document.getElementById("prop").innerHTML=per+"%";
if(flag=="OK"){
window.clearInterval(timer);
alert("上传成功！");
document.getElementById("pro").style.display="none";
document.getElementById("prop").innerHTML="";
f1.reset();
}
if(err!=""||err.length>0){
window.clearInterval(timer);
alert(err);
}
if(flag==null){
window.clearInterval(timer);
}
}
}
flag为上传成功标记，err为出错标记；
servlet代码（UploadServlet）：
package com.ul.servlet;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.Iterator;
import java.util.List;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
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.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
public class UploadServlet extends HttpServlet {
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doPost(request, response);
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//设置编码格式为utf-8
request.setCharacterEncoding("utf-8");
response.setCharacterEncoding("utf-8");
//获取session，保存进度和上传结果，上传结果初始值为NOK，当为Ok表示上传完成
HttpSession session=request.getSession();
session.setAttribute("prog", "0");
session.setAttribute("result", "NOK");
session.setAttribute("error", "");
String error="";
//给上传的文件设一个最大值，这里是不得超过50MB
int maxSize=50*1024*1024;
//创建工厂对象和文件上传对象
DiskFileItemFactory factory=new DiskFileItemFactory();
ServletFileUpload upload=new ServletFileUpload(factory);
try {
//解析上传请求
List items=upload.parseRequest(request);
Iterator itr=items.iterator();
while(itr.hasNext()){
FileItem item=(FileItem)itr.next();
//判断是否为文件域
if(!item.isFormField()){
if(item.getName()!=null&&!item.getName().equals("")){
//获取上传文件大小和文件名称
long upFileSize=item.getSize();
String fileName=item.getName();
if(upFileSize>maxSize){
error="您上传的文件太大了，请选择不超过50MB的文件!";
break;
}
//此时文件暂存在服务器的内存中，构造临时对象
File tempFile=new File(fileName);
//指定文件上传服务器的目录及文件名称
File file=new File("f:\\temp",tempFile.getName());
//构造输入流读文件
InputStream is=item.getInputStream();
int length=0;
byte[] by=new byte[1024];
double persent=0;
FileOutputStream fos=new FileOutputStream(file);
PrintWriter out=response.getWriter();
while((length=is.read(by))!=-1){
//计算文件进度
persent+=length/(double)upFileSize*100D;
fos.write(by, 0, length);
session.setAttribute("prog", Math.round(persent)+"");
Thread.sleep(10);
}
fos.close();
Thread.sleep(1000);
}else{
error="没选择上传文件！";
}
}
}
} catch (Exception e) {
e.printStackTrace();
error="上传文件出现错误:"+e.getMessage();
}
if(!error.equals("")){
session.setAttribute("error", error);
}else{
session.setAttribute("result", "OK");
}
}
}
不要忘记commons-io包
servlet代码（getProgressServlet）：
package com.ul.servlet;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
public class getProgressServlet extends HttpServlet {
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doPost(request, response);
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
request.setCharacterEncoding("utf-8");
response.setCharacterEncoding("utf-8");
HttpSession sesson=request.getSession();
PrintWriter out=response.getWriter();
String str=(String)sesson.getAttribute("prog")+"";
String res=(String)sesson.getAttribute("result");
String err=(String)sesson.getAttribute("error");
System.out.println(str+","+res+","+err);
out.print(str+","+res+","+err);
out.flush();
out.close();
}
}
效果图如下：
以上就是本文的全部内容，希望对大家有所帮助。
