看着git 中的 wechatpay-apache-httpclient demo，写了图片上传，但是一直返回400 bad request，求帮忙看看啥情况？

下面是代码

PrivateKey merchantPrivateKey = PemUtil.loadPrivateKey(Files.newInputStream(Paths.get(PrivateKeyPath)));
//使用自动更新的签名验证器，不需要传入证书
verifier = new AutoUpdateCertificatesVerifier(
        new WechatPay2Credentials(tMerchantId, new PrivateKeySigner(MerchantSerialNumber, merchantPrivateKey)),
        ApiV3key.getBytes(StandardCharsets.UTF_8));
httpClient = WechatPayHttpClientBuilder.create()
        .withMerchant(MerchantId, MerchantSerialNumber, merchantPrivateKey)
        .withValidator(new WechatPay2Validator(verifier))
        .build();
URI uri = new URI("https://api.mch.weixin.qq.com/v3/merchant/media/upload");
byte[] bytes = file.getBytes();
try (InputStream byteArrayInputStream = new ByteArrayInputStream(bytes)) {
    String sha256 = DigestUtils.sha256Hex(byteArrayInputStream);
    WechatPayUploadHttpPost request = new WechatPayUploadHttpPost.Builder(uri)
            .withImage(file.getOriginalFilename(), sha256, byteArrayInputStream)
            .build();
    Header[] allHeaders = request.getAllHeaders();
    for (Header allHeader : allHeaders) {
        System.out.println(allHeader);
    }
    try (CloseableHttpResponse response = httpClient.execute(request)) {
        if (SC_OK == response.getStatusLine().getStatusCode()){
            HttpEntity entity = response.getEntity();
            // do something useful with the response body
            // and ensure it is fully consumed
            String s = EntityUtils.toString(entity);
            System.out.println(s);
            return success;
        }else {
            return error;
        }
    }
}