文件的上传与下载

文件的上传和下载1.文件上传时继承HttpServlet类，实现里面的destroy(),doGet(),doPost(),init()方法文件上传时，可用doPost（）方法，用request.getParameter("")得不到参数值，因为上传时对信息的安全性要求特别高，所以我们借助第三方组件common-fileupload 来解决文件上传问题，首先用类DiskFileUpload产生一个对象，然后解析request，得到一个List集合，然后遍历这个集合，这时要分两种情况，一种是普通的表单控件，另一种是文件上传框，具体操作过程如下：（为了让上传的相同文件不相互覆盖，我们加了一个当前时间变量System.currentTimeMillis()）public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {//文件上传时，用request.getParameter("")得不到参数值，上传时对信息的安全性要求特别高// String username = request.getParameter("username");// System.out.println("username"+username);//利用第三方组件common-fileupload来解决文件上传问题//利用帮助类DiskFileUpload产生一个对象DiskFileUpload dfu = new DiskFileUpload();dfu.setHeaderEncoding("ISO8859-1");try {//解析request，得到一个LIST集合List list =dfu.parseRequest(request);for(Object obj:list){//一个FileItem对应一个组件FileItem fi = (FileItem) obj;//如果是普通的表单控件（非文件上传框）if(fi.isFormField()){String name = fi.getFieldName();//解决中文乱码String content = fi.getString("utf-8");System.out.println("name:"+name+" "+content);}else{//如果是文件上传框String name =new String(fi.getName().getBytes("ISO8859-1"),"utf-8");int index = stIndexOf("\\");name = name.substring(index+1);//解决要上传的文件中的中文问题//name =new String(name.getBytes("ISO8859-1"),"utf-8");System.out.println("name:"+name);//得到文件的内容//方法一// byte[] content = fi.get();// String path =this.getServletContext().getRealPath("/up");// File f = new File(path,name);// if(name!=null && !"".equals(name)){// OutputStream os = new FileOutputStream(f);// os.write(content);// os.close();// }//方法二,读浏览器上传的文件InputStream is = fi.getInputStream();String path =this.getServletContext().getRealPath("/up");if(name!=null && !"".equals(name)){File f =new File(path,System.currentTimeMillis()+"_"+name);OutputStream os = new FileOutputStream(f);int len = 0;byte[] buf = new byte[1024];while((len=is.read(buf))!=-1){os.write(buf,0,len);}is.close();os.close();}}}} catch (FileUploadException e) {e.printStackTrace();}}2.文件的下载a.文件下载时继承HttpServlet类，实现里面的destroy(),doGet(),doPost(),init()方法，此时doGet(),doPost()方法都可以使用，我们使用了doPost()方法，在doGet()方法中调用doPost()方法首先要获取用户的请求，然后到服务器源库去查找有没有该资源，如果有的话就读出来，这就是对流的操作，此时如果出现编码问题，加上response.setContentType("application/octet-stream; charset=" + "utf-8");对其进行修改，了了让浏览器打开附件提示框，我们再加上response.addHeader("content-disposition", "attachment; filename="+ response.encodeURL(f.getName())); 其中attachment表示附件，读完以后一定要注意关闭流下面是doGet()的完整方法：public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {doPost(request,response);}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {//获取用户的请求String fileName = request.getParameter("fileName");//到服务器源库String rootPath = this.getServletContext().getRealPath("/");System.out.println(rootPath);File f = new File(rootPath+"/download",fileName);if(f.exists()){response.setContentType("application/octet-stream; charset=" + "utf-8");// 让浏览器打开附件提示框response.addHeader("content-disposition", "attachment; filename="+ response.encodeURL(f.getName()));//attachment是附件response.setContentLength((int)f.length());InputStream is = new FileInputStream(f);OutputStream os = response.getOutputStream()；int len = 0;byte[] buf = new byte[1024];while((len=is.read(buf))!=-1){os.write(buf, 0, len);}is.close();os.close();}}b.批量下载，继承HttpServlet类，实现里面的destroy(),doGet(),doPost(),init()方法，批量下载用到文件数组，在doGet()方法中调用doPost()方法;public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {//解决响应的中文乱码response.setCharacterEncoding("utf-8");String path =this.getServletContext().getRealPath("/download");File f = new File(path);File[] fs = f.listFiles();PrintWriter pw = response.getWriter();for(int i=0;i<fs.length;i++){//System.out.println(fs[i]);Pw.println("<a href='download?fileName="+fs[i].getName()+"'>下载</a>");}}。