}
        } catch (final Exception e) {
            tempBuf.append("null");
        }
        buf.append(tempBuf.toString());
        return buf;
    }

    protected StringBuilder appendTimestamp(final StringBuilder buf) {
        final SystemHelper systemHelper = ComponentUtil.getSystemHelper();
        append(buf, "timestamp", () -> FessFunctions.formatDate(systemHelper.getCurrentTime()));
        return buf;
    }