.map(String::trim)
                .filter(s -> !s.isEmpty())
                .collect(Collectors.toSet());
        final int scrollSize = fessConfig.getIndexExportScrollSizeAsInteger();

        final IndexExportFormatter resolvedFormatter =
                this.formatter != null ? this.formatter : createFormatter(fessConfig.getIndexExportFormat());

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

    /**
     * Get the value for the key 'index.export.format'. <br>
     * The value is, e.g. html <br>