public static String calcSignature(String apiSecret, long ts) {

try {

Mac mac = Mac.getInstance("HmacSHA256");

SecretKeySpec key = new SecretKeySpec(apiSecret.getBytes(), "HmacSHA256");

mac.init(key);

return Base64.getEncoder()

.encodeToString(mac.doFinal(Long.toString(ts).getBytes()));

} catch (NoSuchAlgorithmException | InvalidKeyException e) {

throw new GatewayException(ErrorCodeConstant.SYSTEM_ERROR,

"sign api secret failed", e);

}