使用commons-fileupload实现单个和多个文件上传
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对于实现文件上传功能来说，Commons-fileupload组件是一个不错的选择，本文使用它实现了单个文件及多个文件上传，这里将实现过程写出来与大家共享。
1.单个文件上传。
页面代码：
....<div?id="content">
????????????<fieldset><legend>下列表</legend>
????????????????<ul>
????????????????<%
????????????????????List<String>?downloadList=(List<String>)request.getAttribute("downloadList");????
????????????????????
????????????????????if(downloadList!=null){
????????????????????????for(String?str:downloadList){????
????????????????????????????out.print("<li><a?href='DownloadFile?file="+str+"'>"+str+"</a></li>");
????????????????????????}
????????????????????}
????????????????%>
????????????????</ul>
????????????</fieldset>
????????
????????????<!--?enctype属性为表单定义了MIME编码方式，上传文件的表单enctype属性必须如此设置?-->
????????????<form?method="post"?action="UploadFile"?enctype="multipart/form-data"?>
????????????<p><input?type="text"?name="fileIntro"?value=""?/>文件介绍</p>
????????????<p><input?type="file"?name="myfile1"?value="浏览文件"?/></p>
????????????<p><input?type="submit"?value="上传"/></p>
????????????</form>
????????</div>....
在上传表单中，既有普通文本域也有文件上传域，注意在Servlet中取它们和平常的做法不同：
Servlet代码：
import?java.io.File;
import?java.util.ArrayList;
import?java.util.Iterator;
import?java.util.List;
import?javax.servlet.RequestDispatcher;
import?javax.servlet.ServletException;
import?javax.servlet.http.HttpServlet;
import?javax.servlet.http.HttpServletRequest;
import?javax.servlet.http.HttpServletResponse;
import?org.apache.commons.fileupload.FileItem;
import?org.apache.commons.fileupload.FileItemFactory;
import?org.apache.commons.fileupload.disk.DiskFileItemFactory;
import?org.apache.commons.fileupload.servlet.ServletFileUpload;
import?com.sitinspring.util.UploadUtil;
/**
?*?用于文件上传处理的Servlet
?*?@author?sitinspring
?*
?*?@date?2008-2-12
?*/
public?class?UploadFileServlet?extends?HttpServlet?{
????private?static?final?long?serialVersionUID?=?56890894234786L;
????@SuppressWarnings("unchecked")
????public?void?doPost(HttpServletRequest?request,?HttpServletResponse?response)
????????????throws?ServletException,?java.io.IOException?{
????????request.setCharacterEncoding("UTF-8");
????????//?文件上部分
????????boolean?isMultipart?=?ServletFileUpload.isMultipartContent(request);
????????
????????if?(isMultipart?==?true)?{
????????????try?{
????????????????FileItemFactory?factory?=?new?DiskFileItemFactory();
????????????????ServletFileUpload?upload?=?new?ServletFileUpload(factory);
????????????????
????????????????//?得到所有的表单域，它们目前都被当作FileItem
????????????????List<FileItem>?fileItems?=?upload.parseRequest(request);
????????????????Iterator<FileItem>?iter?=?fileItems.iterator();
????????????????
????????????????//?依次处理每个表单域
????????????????while?(iter.hasNext())?{
????????????????????FileItem?item?=?(FileItem)?iter.next();
????????????????????
????????????????????if(item.isFormField()){
????????????????????????//?如果item是正常的表单域
????????????????????????String?name?=?item.getFieldName();
????????????????????????String?value?=?item.getString();
????????????????????????System.out.print("表单域名为:"+name+"表单域值为:"+value);
????????????????????}
????????????????????else{
????????????????????????//?如果item是文件上传表单域
????????????????????????
????????????????????????//?获得文件名及路径
????????????????????????String?fileName?=?item.getName();
????????????????????????if?(fileName?!=?null)?{
????????????????????????????File?fullFile?=?new?File(item.getName());????????????????????????????
????????????????????????????????????????????????????????
????????????????????????????//?如果文件存在则上传
????????????????????????????if(fullFile.exists()){
????????????????????????????????File?fileOnServer?=?new?File(UploadUtil.getUploadPath(),
????????????????????????????????????????fullFile.getName());
????????????????????????????????item.write(fileOnServer);
????????????????????????????????
????????????????????????????????System.out.println("文件"+fileOnServer.getName()+"上传成功");
????????????????????????????}
????????????????????????}
????????????????????}
????????????????}????????????????
????????????}?catch?(Exception?e)?{
????????????????e.printStackTrace();
????????????}
????????}?else?{
????????????System.out.println("the?enctype?must?be?multipart/form-data");
????????}
????????
????????//?取得服务器中已有文件的下列表
????????List<String>?fileListInServer=new?ArrayList<String>();?
????????
????????File?dir?=?new?File(UploadUtil.getUploadPath());????????
????????String[]?children?=?dir.list();
????????if?(children?!=?null)?{
????????????for?(int?i=0;?i<children.length;?i++)?{
????????????????fileListInServer.add(children[i]);????????????????
????????????}
????????}
????????
????????request.setAttribute("downloadList",?fileListInServer);
????????//?跳回原面
????????RequestDispatcher?dispatcher?=?request
????????????????.getRequestDispatcher("/web/page/uploadtoserver.jsp");
????????dispatcher.forward(request,?response);
????????return;
????}
????public?void?doGet(HttpServletRequest?request,?HttpServletResponse?response)
????????????throws?ServletException,?java.io.IOException?{
????????doPost(request,?response);
????}
}
从上面的代码可以看出，无论是否文件上传表单域都被当成了FileItem来处理，要区别开来使用isFormField()方法即可，返回真是常规表单域，返回假则是文件上传表单域。
2.多个文件上传到服务器端。
这里采用JS动态生成几个文件上传表单域即可，Servlet无需改变。
多文件上传页面代码如下:
<%@page?language="java"?import="java.util.List"%>
<!DOCTYPE?HTML?PUBLIC?"-//W3C//DTD?HTML?4.0?Transitional//EN">
<html>
<head>
<title>上传多文件到服务器</title>
<meta?http-equiv="Content-Type"?content="text/html;?charset=UTF-8">
<link?rel="stylesheet"?rev="stylesheet"?href="web/css/style.css"
????type="text/css"?/>
</head>
<body>
????<div?id="bodyDiv">
????????<div?id="header">
????????????<jsp:include?page="/web/page/branch/header.jsp"/>
????????</div>
????????<div?id="sidebar">
????????????<jsp:include?page="/web/page/branch/sidebar.jsp"/>
????????</div>
????????<div?id="content">
????????????<fieldset><legend>下列表</legend>
????????????????<ul>
????????????????<%
????????????????????List<String>?downloadList=(List<String>)request.getAttribute("downloadList");????
????????????????????
????????????????????if(downloadList!=null){
????????????????????????for(String?str:downloadList){????
????????????????????????????out.print("<li><a?href='DownloadFile?file="+str+"'>"+str+"</a></li>");
????????????????????????}
????????????????????}
????????????????%>
????????????????</ul>
????????????</fieldset>
????????
????????????<!--?enctype属性为表单定义了MIME编码方式，上传文件的表单enctype属性必须如此设置?-->
????????????<form?name="uploadForm"?method="post"?action="UploadFile"?enctype="multipart/form-data"?>
????????????<p><input?type="button"?value="增加上传按钮"?onclick="addUploadButton()"/></p>
????????????<p><input?type="file"?name="myfile1"?value="浏览文件"?/></p>
????????????<p><input?type="submit"?value="上传"/></p>
????????????</form>
????????</div>
????????<div?id="footer">
????????????<jsp:include?page="/web/page/branch/footer.jsp"/>
????????</div>
????</div>
</body>
JS代码：
<!--
var?count=1;
function?addUploadButton(){????
????//?按ID找到FOrm
????var?uploadForm=document.getElementById("uploadForm");????
????
????//?创建P元素
????var?pNode=document.createElement("p");
????
????//?累加Count以观察次数
????count=count+1;
????
????pNode.innerHTML="<input?type='file'?name='myfile"+count+"'?value='浏览文件'/>";
????
????//?将P元素添加到body中
????uploadForm.appendChild(pNode);
}
//-->
</script>
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