从Springboot项目中下载文件

最近在做一个临时的项目，APP端在检测到程序有更新时，需要去后台下载新的安装包。具体过程如下:

controller层：

 /**
     * 下载app
     * @param response
     */
    @RequestMapping("downApp")
    @ResponseBody
    public void Download(HttpServletResponse response) {
        String fileName = "wuye.apk";
        String result = FileUtil.downloadFile(response, fileName);
        log.info("app包下载结果:",result);
    }

工具类：

public class FileUtil {

    public static String downloadFile(HttpServletResponse response, String fileName) {
        File path = null;
        response.setHeader("content-type", "application/octet-stream");
        response.setContentType("application/octet-stream");
        try {
            response.setHeader("Content-Disposition", "attachment;filename=" + java.net.URLEncoder.encode(fileName, "UTF-8"));
        } catch (UnsupportedEncodingException e2) {
            e2.printStackTrace();
        }
        byte[] buff = new byte[1024];
        BufferedInputStream bis = null;
        OutputStream os = null;
        try {
            path = new File(ResourceUtils.getURL("classpath:").getPath());
            os = response.getOutputStream();
            bis = new BufferedInputStream(new FileInputStream(new File(path + "/doc/" + fileName)));
            int i = bis.read(buff);
            while (i != -1) {
                os.write(buff, 0, buff.length);
                os.flush();
                i = bis.read(buff);
            }
        } catch (FileNotFoundException e1) {
            //e1.getMessage()+"系统找不到指定的文件";
            return "系统找不到指定的文件";
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (bis != null) {
                try {
                    bis.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
        return "success";
    }

访问：http://127.0.0.1:8081/ymd/downApp  文件就下载下来了，本方法借鉴了 网络上的一些文章