1.引入SpringBoot和hutool依赖

        <dependency>
            <groupId>cn.hutool</groupId>
            <artifactId>hutool-all</artifactId>
            <version>5.8.22</version>
        </dependency>

2.在项目resources目录下放入模版文件，结构如下：

3.定义文件下载接口

    @SneakyThrows(IOException.class)
    @ApiOperation(value = "下载模版文件", notes = "下载模版文件")
    @RequestMapping(value = "/down_template", method = RequestMethod.GET)
    public Response<Void> downTemplate(@RequestParam(required = false)String templateName, HttpServletResponse response) {
        if(StringUtils.isBlank(templateName)){
            return null;
        }
        response.setCharacterEncoding("utf-8");
        
        try (InputStream templateInputStream = this.getClass().getResourceAsStream("/template/" + templateName);
             OutputStream outputStream = response.getOutputStream()) {
            Asserts.notNull(templateInputStream, "templateInputStream is null");

            //获取文件字节数组
            byte[] bytes = IoUtil.readBytes(templateInputStream);
            //获取文件mimetype,也就是contenttype
            FileMagicNumber magicNumber = FileMagicNumber.getMagicNumber(bytes);
            if(magicNumber != FileMagicNumber.UNKNOWN){
                response.setContentType(magicNumber.getMimeType());
                String fileName = URLEncoder.encode("模版文件" + DateUtil.format(new Date(), "yyyyMMdd"), "UTF-8").replaceAll("\\+", "%20");
                response.setHeader("Content-disposition", "attachment; filename=" + fileName + "." + magicNumber.getExtension());
            }

            outputStream.write(bytes, 0, bytes.length);
        }
        return null;
    }

4.postman请求改接口，然后把文件流保存到本地目录，说明下载成功