参考地址

springboot：各种下载文件的方式_springboot下载文件-CSDN博客

开箱即用实战

 @GetMapping("/t1")
    public void down1(HttpServletResponse response) throws Exception {
        response.reset();
        response.setContentType("application/octet-stream;charset=utf-8");
        response.setHeader(
                "Content-disposition",
                "attachment; filename=test.png");
        try(
                BufferedInputStream bis = new BufferedInputStream(new FileInputStream("C:\\Users\\Harbor\\Pictures\\Camera Roll\\111.jpg"));
                // 输出流
                BufferedOutputStream bos = new BufferedOutputStream(response.getOutputStream());
        ){
            byte[] buff = new byte[1024];
            int len = 0;
            while ((len = bis.read(buff)) > 0) {
                bos.write(buff, 0, len);
            }
        }
    }