【一】设置字符唯一键(非自增)String uuid = UUID.randomUUID().toString().replace("-", “”);对象.setId(uuid);【二】重命名为唯一键:String fileName = FileUtil.renameToUUID(fname);【三】获取文件后缀:String fileType = fname.substring(fname.lastIndexOf(".") + 1, fname.length()).toLowerCase();