springboot下载apk解析包错误

springboot下载问题，我写了一个下载方法，如下：

public static String downloadFile(HttpServletResponse response, String fileName, String filePath) {
        File path =null;
        response.addHeader("Access-Contro1-A11ow-0rigin","*");
        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 e){
            e.printStackTrace();
        }
        byte[] buff =new byte[1024];
        BufferedInputStream bis =null;
        OutputStream os =null;
        try {
            path =new File(filePath);
            os = response.getOutputStream();
            bis =new BufferedInputStream(new FileInputStream(path));
            int i = bis.read(buff);
            while (i != -1) {
                os.write(buff,0, buff.length);
                os.flush();
                i = bis.read(buff);
            }
        } catch (FileNotFoundException  e){
            e.printStackTrace();
            System.out.println("系统找不到指定文件");
        } catch (IOException e){
            e.printStackTrace();
        } finally {
            if (bis !=null) {
                try {
                    bis.close();
                }catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
        return "success";
    }

但是当我访问这个接口的时候发现下载下来的apk无法进行安装，会提示解析包错误，但下载图片啥的又正常，我想知道我有什么地方搞错了？

但是不建议造轮子

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