问java调用腾讯会议API总是报400？

public static String createUsers() throws IOException, InvalidKeyException, NoSuchAlgorithmException {
    String uri="/v1/users";
    String SecretId="";
    String SecretKey="";
    String appId="";
    String url="https://api.meeting.qq.com/v1/users";
    int num = 95279280;
    String  timestamp = Long.toString(System.currentTimeMillis()/1000L);
    //body参数
    String req_body=
                "{\n"+
                "\t\"username\": \"bX9280\", \n"+
                "\t\"phone\" : \"13343411234\", \n"+
                "\t\"userId\": \"bu9280\", \n" +
                "\t\"email\": \"7392615@qq.com\n" +
                "}";
    //生成签名
    String signature = sign(SecretId, SecretKey, "POST", Integer.toString(num), timestamp, uri, req_body);
    String Content_Type="application/json";
    String code = doPost(url,Content_Type,SecretId,timestamp,num,appId,signature, req_body);
    return code;
}

public static void main(String[] args) throws NoSuchAlgorithmException, InvalidKeyException, IOException {
    String code = createUsers();
}

private static String doPost(String urlPath,String Content_Type,String SecretId,String createTime,int num,String appId,String signature,String datas) throws IOException {
    StringBuilder sub = new StringBuilder();
    // 建立连接
    try {
        URL url = new URL(urlPath);
        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
        // 设置连接请求属性post
        conn.setDoOutput(true);
        conn.setDoInput(true);
        // 忽略缓存
        conn.setUseCaches(false);
        conn.setRequestMethod("POST");
        conn.setRequestProperty("Content-Type", Content_Type);
        conn.setRequestProperty("X-TC-Key", SecretId);
        conn.setRequestProperty("X-TC-Timestamp", createTime);
        conn.setRequestProperty("X-TC-Nonce", String.valueOf(num));
        conn.setRequestProperty("AppId", appId);
        conn.setRequestProperty("X-TC-Signature", signature);
        DataOutputStream out = new DataOutputStream(conn.getOutputStream());
        out.write(datas.getBytes(StandardCharsets.UTF_8));
        out.flush();
        out.close();
        // 定义BufferedReader输入流来读取URL的响应
        int code = conn.getResponseCode();
        System.out.println("====="+conn.getResponseMessage()+"-"+conn.getResponseCode());
        if (HttpURLConnection.HTTP_OK == code) {
            BufferedReader in = new BufferedReader(new InputStreamReader(
                    conn.getInputStream(), StandardCharsets.UTF_8));
            String line;
            while ((line = in.readLine()) != null) {
                sub.append(line);
            }
            in.close();
        }
        return sub.toString();
    } catch (IOException e) {
        e.printStackTrace();
        sub = new StringBuilder();
        System.out.println("调用kettle服务失败:"+";urlPath="+urlPath+";data:"+urlPath+"Message:"+e.getMessage());
    }
    return sub.toString();
}
private static String HMAC_ALGORITHM = "HmacSHA256";
private static char[] HEX_CHAR = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'};
static String bytesToHex(byte[] bytes) {

    char[] buf = new char[bytes.length * 2];
    int index = 0;
    for (byte b : bytes) {
        buf[index++] = HEX_CHAR[b >>> 4 & 0xf];
        buf[index++] = HEX_CHAR[b & 0xf];
    }
    return new String(buf);
}

/**
 * 生成签名，开发版本oracle jdk 1.8.0_221
 *
 * @param secretId        邮件下发的secret_id
 * @param secretKey       邮件下发的secret_key
 * @param httpMethod      http请求方法 GET/POST/PUT等
 * @param headerNonce     X-TC-Nonce请求头，随机数
 * @param headerTimestamp X-TC-Timestamp请求头，当前时间的秒级时间戳
 * @param requestUri      请求uri，eg：/v1/meetings
 * @param requestBody     请求体，没有的设为空串
 * @return 签名，需要设置在请求头X-TC-Signature中
 * @throws NoSuchAlgorithmException e
 * @throws InvalidKeyException      e
 */
static String sign(String secretId, String secretKey, String httpMethod, String headerNonce, String headerTimestamp, String requestUri, String requestBody)
        throws NoSuchAlgorithmException, InvalidKeyException {
    String tobeSig =
            httpMethod + "\nX-TC-Key=" + secretId + "&X-TC-Nonce=" + headerNonce + "&X-TC-Timestamp=" + headerTimestamp + "\n" + requestUri + "\n" + requestBody;
    Mac mac = Mac.getInstance(HMAC_ALGORITHM);
    SecretKeySpec secretKeySpec = new SecretKeySpec(secretKey.getBytes(StandardCharsets.UTF_8), mac.getAlgorithm());
    mac.init(secretKeySpec);
    byte[] hash = mac.doFinal(tobeSig.getBytes(StandardCharsets.UTF_8));
    String hexHash = bytesToHex(hash);
    return new String(Base64.getEncoder().encode(hexHash.getBytes(StandardCharsets.UTF_8)));
}