apollo-configservice/src/main/java/com/ctrip/framework/apollo/configservice/util/AccessKeyUtil.java/AccessKeyUtil/buildSignature
class AccessKeyUtil:  public String buildSignature(String path, String query, String timestampString, String secret) {
    String pathWithQuery = path;
    if (!Strings.isNullOrEmpty(query)) {
      pathWithQuery += "?" + query;
    }

    return Signature.signature(timestampString, pathWithQuery, secret);
  }