}

        final File thumbnailFile = thumbnailManager.getThumbnailFile(doc);
        if (thumbnailFile == null) {
            if (fessConfig.isThumbnailEnabled()) {
                thumbnailManager.offer(doc);
            }
            // 404
            throw responseManager.new404("Thumbnail for " + form.docId + " is under generating.");
        }

    }

    default void setThumbnailEnabled(final boolean value) {
        setSystemPropertyAsBoolean(Constants.THUMBNAIL_ENALBED_PROPERTY, value);
    }

    default boolean isThumbnailEnabled() {
        return getSystemPropertyAsBoolean(Constants.THUMBNAIL_ENALBED_PROPERTY, false);
    }

    default void setIncrementalCrawling(final boolean value) {

        searchLogSupport = fessConfig.isSearchLog();
        favoriteSupport = fessConfig.isUserFavorite();
        thumbnailSupport = fessConfig.isThumbnailEnabled();
        runtime.registerData("searchLogSupport", searchLogSupport);
        runtime.registerData("favoriteSupport", favoriteSupport);
        runtime.registerData("thumbnailSupport", thumbnailSupport);

        form.resultCollapsed = fessConfig.isResultCollapsed() ? Constants.TRUE : Constants.FALSE;
        form.loginLink = fessConfig.isLoginLinkEnabled() ? Constants.TRUE : Constants.FALSE;
        form.thumbnail = fessConfig.isThumbnailEnabled() ? Constants.TRUE : Constants.FALSE;
        form.incrementalCrawling = fessConfig.isIncrementalCrawling() ? Constants.TRUE : Constants.FALSE;
        form.dayForCleanup = fessConfig.getDayForCleanup();