后端：

//    文件下载功能
    @RequestMapping("/excel/download")
    public  void downexcel(HttpServletResponse res){
        System.out.println("文件下载功能==");
        String fileName = "日报表.xlsx";
        res.setHeader("content-type", "application/octet-stream");
        res.setContentType("application/octet-stream");
        res.setHeader("Content-Disposition", "attachment;filename=" + fileName);
        byte[] buff = new byte[1024];
        BufferedInputStream bis = null;
        OutputStream os = null;
        try {
            os = res.getOutputStream();
            bis = new BufferedInputStream(new FileInputStream(new File("d://"+fileName)));
            int i = bis.read(buff);
            while (i != -1) {
                os.write(buff, 0, buff.length);
                os.flush();
                i = bis.read(buff);
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (bis != null) {
                try {
                    bis.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
        System.out.println("success");
    }

前端（vue）:

<el-button style="width: 140px;" type="success"><a style="color: #ffffff;" class='download' :href='xxx/excel/download' download=""  title="excel模板下载">excel模板下载</a></el-button>

参考实现：https://blog.csdn.net/qq_37497275/article/details/80327661

补充：有时下载出现：

原因是：在HttpServletResponse Header中没有指定指定Content-Length：完整方法：

文件在resources目录下的static的excel目录下：

代码：

//    文件下载功能
    @RequestMapping("/excel/download")
    public  void downexcel(HttpServletResponse res){
        try {
            //获取要下载的模板名称
            String fileName = "xx.xlsx";
            //设置要下载的文件的名称
            res.setHeader("Content-disposition", "attachment;fileName=" + fileName);
            //通知客服文件的MIME类型
            res.setContentType("application/vnd.ms-excel;charset=UTF-8");
            //获取文件的路径
            //String filePath = getClass().getResource("/template/" + fileName).getPath();
            //excel模板路径
            File cfgFile = ResourceUtils.getFile(ResourceUtils.CLASSPATH_URL_PREFIX + "static/excel/xx.xlsx");
            FileInputStream input = new FileInputStream(cfgFile);
            //            FileInputStream input = new FileInputStream(new File("d://"+fileName));
            OutputStream out = res.getOutputStream();
            byte[] b = new byte[2048];
            int len;
            while ((len = input.read(b)) != -1) {
                out.write(b, 0, len);
            }
            //修正 Excel在“xxx.xlsx”中发现不可读取的内容。是否恢复此工作薄的内容？如果信任此工作簿的来源，请点击"是"
            res.setHeader("Content-Length", String.valueOf(input.getChannel().size()));
            input.close();
            System.out.println("应用导入模板下载完成");
        } catch (Exception ex) {
            System.out.println("应用导入模板下载失败！");
        }

}