code: @Override
    public final String fromString(final Map<String, Object> pAddParam,
      final String pStrVal) throws Exception {
      if (pStrVal == null || "".equals(pStrVal)) {
        return null;
      }
      return pStrVal;
    }
docs: <p>Convert from string.</p>
  @param pAddParam additional params, e.g. IRequestData
  to fill owner itsVersion.
  @param pStrVal string representation
  @return string value
  @throws Exception - an exception