code: @Override
      protected String getReadOnlyValue(final AbstractUIField _uiField)
          throws EFapsException
      {
          Object obj = _uiField.getValue().getReadOnlyValue(_uiField.getParent().getMode());
          if (obj != null && obj instanceof Collection) {
              obj = StringUtils.join(((Collection<?>) obj).iterator(), ", ");
          }
          return obj == null ? "" : String.valueOf(obj);
      }
docs: {@inheritDoc}