Heim > Artikel > Web-Frontend > Implementieren Sie das Hochladen von Dateien und zeigen Sie den Fortschrittsbalken basierend auf Ajax_Javascript-Kenntnissen an

Implementieren Sie das Hochladen von Dateien und zeigen Sie den Fortschrittsbalken basierend auf Ajax_Javascript-Kenntnissen an

WBOYOriginal: 2016-05-16 15:47:311379Durchsuche

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：

<%@ page language="java" contentType="text/html; charset=UTF-8"
 pageEncoding="UTF-8"%>
<!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>Insert title here</title>
<link rel="stylesheet" type="text/css" href="css/progress.css">
<script type="text/javascript" src="js/ul.js" charset="gbk"></script>
</head>
<body>
<form action="UploadServlet" name="f1" id="f1" method="post" enctype="multipart/form-data" target="if">
 <input type="file" name="file1" /><br><br>
 <input type="reset" name="res1" value="重置"/>
 <input type="button" name="but1" value="提交" onclick="go();"/>
</form><br>
<div id="pro" class="pro" align="left">
 <img alt="" src="photo/progress.png" width="0" height="15" id="imgpro">
</div>
  <span id="prop" style="width:15px;height:15px;display: none;">0%</span>
<iframe id="if" name="if" src="" style="display: none"></iframe>
</body>
</html>

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。

Stellungnahme：

Der Inhalt dieses Artikels wird freiwillig von Internetnutzern beigesteuert und das Urheberrecht liegt beim ursprünglichen Autor. Diese Website übernimmt keine entsprechende rechtliche Verantwortung. Wenn Sie Inhalte finden, bei denen der Verdacht eines Plagiats oder einer Rechtsverletzung besteht, wenden Sie sich bitte an admin@php.cn

Vorheriger Artikel：Implementieren Sie die Formularvalidierung basierend auf Jquery_jqueryNächster Artikel：Implementieren Sie die Formularvalidierung basierend auf Jquery_jquery

In Verbindung stehende Artikel

Mehr sehen