java 文件上传后下载

public String downFile()throws Exception{
??System.out.println(fId+"========="+mailId);
??MailAttach mailAttach = this.mailAttachManager.get(fId);

? String filePath = ZbwtFileUploadUtil.getBigFileUpload()+mailAttach.getAttachFilePath();? //文件路径
??File file = new File(filePath);
??if (file.exists()) {
???HttpServletResponse response = Struts2Utils.getResponse();
???HttpServletRequest request = Struts2Utils.getRequest();
???response.setHeader("Pragma", "No-Cache");
???response.setHeader("Cache-Control", "No-Cache");
???response.setDateHeader("Expires", 0);
???response.setHeader("Accept-Ranges", "bytes");
???response.setContentType("application/octet-stream");
???OutputStream out = response.getOutputStream();
???response.setHeader("Content-Type", "application/x-msdownload");
???String agent = (String)request.getHeader("USER-AGENT");??
???if(agent != null && agent.indexOf("MSIE") == -1) {?? //用于中间有空格时 空格后名称无法出现
????// FF???
????String enableFileName = "=?UTF-8?B?" + (new String(Base64.encodeBase64(mailAttach.getAttachSolidName().getBytes("UTF-8")))) + "?=";??
????response.setHeader("Content-Disposition", "attachment; filename=" + enableFileName); }?
???else {??
????// IE???
????String enableFileName = new String(mailAttach.getAttachSolidName().getBytes("GBK"), "ISO-8859-1");??? response.setHeader("Content-Disposition", "attachment; filename=" + enableFileName);
????response.setHeader("Content-Disposition", "attachment; filename=" + enableFileName);??
???}
???FileInputStream input = new FileInputStream(file);
???int line = 0;
???byte[] bytes = new byte[2048];
???while ((line = input.read(bytes)) != -1) {
????out.write(bytes, 0, line);
???}
???input.close();
???out.close();
??}
??return null;
?}