public Pattern getFieldNamePattern() {
      if (StringUtil.isEmpty(fieldName)) {
        return null;
      }
      if (fieldNamePattern == null) {
        try {
          fieldNamePattern = Pattern.compile(fieldName);
        } catch (PatternSyntaxException e) {
          fieldName = null;
          LOG.warn(e.getMessage());
        }
      }
      return fieldNamePattern;
    }
public Pattern getFieldNamePattern()