添加hutool依赖

<dependency>     <groupId>cn.hutool</groupId>     <artifactId>hutool-all</artifactId>     <version>5.7.20</version> </dependency> <dependency>     <groupId>org.apache.poi</groupId>     <artifactId>poi-ooxml</artifactId>     <version>4.1.2</version> </dependency> 

 /**      * 导入      * @param file      * @return      * @throws IOException      */     @PostMapping("import")     public boolean imp(MultipartFile file) throws IOException {         InputStream inputStream = file.getInputStream();         ExcelReader reader = ExcelUtil.getReader(inputStream);         List<User> list = reader.readAll(User.class);         return userService.saveBatch(list);     }      /**      * 导出      * @param response      * @throws IOException      */     @GetMapping("export")     public void export(HttpServletResponse response) throws IOException {         List<User> list = userService.list();         ExcelWriter writer = ExcelUtil.getWriter(true); //        writer.addHeaderAlias("username","用户名"); //        writer.addHeaderAlias("password", "密码"); //        writer.addHeaderAlias("nickname", "昵称"); //        writer.addHeaderAlias("email", "邮箱"); //        writer.addHeaderAlias("phone", "电话"); //        writer.addHeaderAlias("address", "地址"); //        writer.addHeaderAlias("createTime", "创建时间"); //        writer.addHeaderAlias("avatarUrl", "头像");          // 一次性写出list内的对象到excel，使用默认样式，强制输出标题         writer.write(list, true);          // 设置浏览器响应的格式         response.setContentType("application/vnd.openxmlformats-officedocument.spreadsheetml.sheet;charset=utf-8");         String fileName = URLEncoder.encode("用户信息", "UTF-8");         response.setHeader("Content-Disposition", "attachment;filename=" + fileName + ".xlsx");          ServletOutputStream out = response.getOutputStream();         writer.flush(out, true);         out.close();         writer.close();  }