String path = request.getServletContext().getRealPath("upload") + File.separator;
                  //形成年月日的文件夹， 下面每天一个文件夹
                  Calendar calendar = Calendar.getInstance();
                  int year  = calendar.get(Calendar.YEAR);
                  int month = calendar.get(Calendar.MONTH) + 1;
                  int day   = calendar.get(Calendar.DAY_OF_MONTH);
                  String uploadDir = year + "" + month + File.separator + day;
                 
                  File uploads = new File(path + uploadDir);
                  if (!uploads.exists()) {uploads.mkdirs();} //注意这里是mkdirs,不是mkdir
                  //生成目录结束