*
     * @param date the date to format
     * @return formatted date string, or empty string if date is null
     */
    public static String formatDate(final Date date) {
        if (date == null) {
            return StringUtil.EMPTY;
        }
        final SimpleDateFormat sdf = new SimpleDateFormat(Constants.ISO_DATETIME_FORMAT);

                                final Date dt = FessFunctions.parseDate(values[0], dateFormat);
                                if (dt != null) {
                                    dataMap.put(mapping.getValue1(), FessFunctions.formatDate(dt));
                                } else {
                                    logger.warn("Failed to parse date mapping: {}", mapping);
                                }
                            } else {

                    value = list.stream().collect(Collectors.joining("\n"));
                }
            } else if (dateFieldSet.contains(key)) {
                value = FessFunctions.formatDate((Date) value);
            } else if (integerFieldSet.contains(key) || longFieldSet.contains(key) || floatFieldSet.contains(key)
                    || doubleFieldSet.contains(key)) {
                value = value.toString();