private boolean isJson(String s) {
    try {
      Validator.validate(s);
      return true;
    } catch (JSONException e) {
      return false;
    }
  }
Tries to parse log event in json form using selected date format

@param s          log fragment
@param dateFormat instance of DateFormat
@return Optional of LogData if log event can be extracted, empty if not.
olv-core/src/main/java/pl/otros/logview/parser/json/JsonExtractor.java