使用Java 调用https://api.weixin.qq.com/wxa/getwxacodeun 获取微信二维码时，生成的二维码图片破损如何解决？

public static void generateQrcode(String scene, String page, String filePath) {
    HttpURLConnection connection = null;
    try {
        String accessToken = getAccessToken();
        URL url = new URL(WXACODE_URL+"?access_token=" + accessToken);
        connection = (HttpURLConnection) url.openConnection();
        connection.setRequestMethod("POST");
        connection.setDoOutput(true);
        connection.setRequestProperty("Content-Type", "application/json");
        JSONObject requestBody = new JSONObject();
        requestBody.put("scene", scene);
        requestBody.put("page", page);
        try (OutputStream os = connection.getOutputStream()) {
            byte[] input = requestBody.toString().getBytes("utf-8");
            os.write(input, 0, input.length);
        }
        int responseCode = connection.getResponseCode();
        if (responseCode == HttpURLConnection.HTTP_OK) {
            // 读取响应流
            try (InputStream is = connection.getInputStream();
                 FileOutputStream fos = new FileOutputStream(filePath)) {
                byte[] buffer = new byte[4096];
                int bytesRead;
                while ((bytesRead = is.read(buffer)) != -1) {
                    fos.write(buffer, 0, bytesRead);
                }
                System.out.println("二维码生成成功，保存路径：" + filePath);
            }
        } else {
            System.out.println("请求失败，响应状态码：" + responseCode);
        }
    } catch (IOException e) {
        System.err.println("发生 IO 异常: " + e.getMessage());
    } catch (JSONException e) {
        throw new RuntimeException(e);
    } finally {
        if (connection != null) {
            connection.disconnect();
        }
    }
}