final FessConfig fessConfig = ComponentUtil.getFessConfig();
        if (fessConfig.getIndexFieldUrl().equals(key) || !dataMap.containsKey(key) || !getFessConfig().isCrawlerDocumentAppendData()) {
            dataMap.put(key, value);
        } else {
            final Object oldValue = dataMap.get(key);
            final Object[] oldValues;
            if (oldValue instanceof Object[]) {

     * The value is, e.g. true <br>
     * comment: Whether to append data to documents.
     * @return The determination, true or false. (if not found, exception but basically no way)
     */
    boolean isCrawlerDocumentAppendData();

    /**
     * Get the value for the key 'crawler.document.append.filename'. <br>
     * The value is, e.g. false <br>
     * comment: Whether to append filename to documents.