public void init() {
        final FessConfig fessConfig = ComponentUtil.getFessConfig();
        final int maxPageSize = fessConfig.getPagingSearchPageMaxSizeAsInteger();
        final int windowSize = fessConfig.getRankFusionWindowSizeAsInteger();
        if (maxPageSize * 2 < windowSize) {
            logger.warn("rank.fusion.window_size is lower than paging.search.page.max.size. "

     * @return The value of found property. (NotNull: if not found, exception but basically no way)
     * @throws NumberFormatException When the property is not integer.
     */
    Integer getRankFusionWindowSizeAsInteger();

    /**
     * Get the value for the key 'rank.fusion.rank_constant'. <br>
     * The value is, e.g. 20 <br>
     * comment: Rank constant for rank fusion.