apollo-core/src/main/java/com/ctrip/framework/apollo/core/signature/HmacSha1Utils.java/HmacSha1Utils/signString
class HmacSha1Utils:  public static String signString(String stringToSign, String accessKeySecret) {
    try {
      Mac mac = Mac.getInstance(ALGORITHM_NAME);
      mac.init(new SecretKeySpec(
          accessKeySecret.getBytes(ENCODING),
          ALGORITHM_NAME
      ));
      byte[] signData = mac.doFinal(stringToSign.getBytes(ENCODING));
      return BaseEncoding.base64().encode(signData);
    } catch (NoSuchAlgorithmException | UnsupportedEncodingException | InvalidKeyException e) {
      throw new IllegalArgumentException(e.toString());
    }
  }