servlet中文件的上传与下载

文件的上传与下载，有三个前提：关于表单的type属性为File       其提交方式为post      enctype="multipart/form-data "     多部件上传

关于文件格式及大小的限制的JS代码如下所示：

<script type="text/javascript">function fileChange(target) {//检测上传文件的类型 var imgName = document.all.up_file.value;var ext, idx;if(imgName == '') {document.all.submit_upload.disabled = true;alert("请选择需要上传的文件!");return;} else {idx = imgName.lastIndexOf(".");if(idx != -1) {ext = imgName.substr(idx + 1).toUpperCase();ext = ext.toLowerCase();// alert("ext="+ext);if(ext != 'zip' && ext != 'rar') {document.all.submit_upload.disabled = true;alert("只能上传.zip  .rar 类型的文件!");return;}} else {document.all.submit_upload.disabled = true;alert("只能上传.zip  .rar 类型的文件!");return;}}//检测上传文件的大小        var isIE = /msie/i.test(navigator.userAgent) && !window.opera;var fileSize = 0;if(isIE && !target.files) {var filePath = target.value;var fileSystem = new ActiveXObject("Scripting.FileSystemObject");var file = fileSystem.GetFile(filePath);fileSize = file.Size;} else {fileSize = target.files[0].size;}var size = fileSize / 1024 * 1024;if(size > (10*1024*1024)) {document.all.submit_upload.disabled = true;alert("文件大小不能超过10M");} else {document.all.submit_upload.disabled = false;}}</script>

下面部分为servlet中的代码，其代码如下

package com.itqf.servlet;import java.io.File;import java.io.FileOutputStream;import java.io.IOException;import java.io.InputStream;import java.io.PrintWriter;import java.text.SimpleDateFormat;import java.util.Date;import java.util.List;import java.util.UUID;import javax.servlet.ServletContext;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.FileUploadException;import org.apache.commons.fileupload.ProgressListener;import org.apache.commons.fileupload.disk.DiskFileItemFactory;import org.apache.commons.fileupload.servlet.ServletFileUpload;import org.apache.commons.io.FilenameUtils;public class DealServlet extends HttpServlet {private static final long serialVersionUID = 1L;public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {//浏览器  -- 服务器  --> 本地磁盘//1.判断类型boolean is = ServletFileUpload.isMultipartContent(request);if (is) {//2.创建本地磁盘工厂DiskFileItemFactory factory = new DiskFileItemFactory();File file = new File("c:\\workspace");//设置缓存路径factory.setRepository(file);//3.创建解析核心类ServletFileUpload upload = new ServletFileUpload(factory);upload.setProgressListener(new ProgressListener() {@Overridepublic void update(long arg0, long arg1, int arg2) {// TODO Auto-generated method stubSystem.out.println(arg0+"  -- "+arg1+" -- "+arg2);}});//解决上传中文文件名乱码问题upload.setHeaderEncoding("UTF-8");        //upload.setFileSizeMax();  //限制单个input 的大小//upload.setSizeMax(1024*1024*10);  //限制表单中文件的总大小    1024*1024*1024 GB//在正常情况下，在HTML中利用JS设置上传文件格式及大小的限制//4.解析请求try {List<FileItem>  items = upload.parseRequest(request);//FileItem就是每一个input  //普通的文本input 还有一个 文件 inputfor (FileItem fileItem : items) {if (fileItem.isFormField()) {//ture 普通的文本//name  value String name = fileItem.getFieldName();String value = fileItem.getString("UTF-8");System.out.println(name+"  ---  "+ value);}else{//文件dealFile(fileItem);}}} catch (FileUploadException e) {// TODO Auto-generated catch blocke.printStackTrace();}}}/** * 处理文件input的 * @param fileItem */private void dealFile(FileItem fileItem) {//1.获取文件的名字 String filename = fileItem.getName(); if (filename != null) {filename = FilenameUtils.getName(filename); //c://xx/xx/i.jpg   = i.jpg  0    //filename= filename.substring(filename.lastIndexOf(File.separator)+1);}//2.文件保存的位置   //1. 指定磁盘  //2. 保存本项目下 ServletContext servletContext = getServletContext();  //获取时间 SimpleDateFormat format = new SimpleDateFormat("yyyyMMdd");  String time = format.format(new Date());  //根据相对路径获取绝对路径 String path = servletContext.getRealPath("/WEB-INF/filedir/"+time);  System.out.println("文件夹的路径:"+path); //创建保存的文件夹 Filedir = new File(path);  if (!dir.exists()) {dir.mkdirs(); //创建文件夹 }  //保证文件不重复 filename = UUID.randomUUID()+filename; // filename = System.currentTimeMillis()+filename;  //创建具体的文件 File file = new File(dir,filename);  try { //写到指定的文件中//fileItem.write(file); write(fileItem);} catch (Exception e) {// TODO Auto-generated catch blocke.printStackTrace();} }public void  write(FileItem fileItem) throws IOException{  String filename = fileItem.getName(); ServletContext servletContext = getServletContext(); //获取时间 SimpleDateFormat format = new SimpleDateFormat("yyyyMMdd");  String time = format.format(new Date());  //根据相对路径获取绝对路径 String path = servletContext.getRealPath("/WEB-INF/filedir/"+time);  System.out.println("文件夹的路径:"+path); //创建保存的文件夹 Filedir = new File(path);  if (!dir.exists()) {dir.mkdirs(); //创建文件夹 }  //保证文件不重复 filename = UUID.randomUUID()+filename; // filename = System.currentTimeMillis()+filename;  //创建具体的文件 File file = new File(dir,filename);//得到文件内容的流InputStream inputStream = fileItem.getInputStream();FileOutputStream fileOutputStream  =  new  FileOutputStream(file);byte [] buffer = new byte[1024];int len = -1;while((len = inputStream.read(buffer))!=-1){fileOutputStream.write(buffer, 0, len);}fileOutputStream.close();inputStream.close();fileItem.delete();}public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {  doGet(request, response);}}