* When enabled, frequently searched terms are tracked and displayed.
     */
    @Size(max = 10)
    public String popularWord;

    /**
     * Character encoding to use for CSV file exports.
     * This setting affects the encoding of downloaded CSV files.
     */
    @Required
    @Size(max = 20)
    public String csvFileEncoding;

    /**

            logger.warn("Failed to export documents.", e);
            resultBuf.append(e.getMessage()).append("\n");
        }

        return resultBuf.toString();
    }

    /**
     * Exports a single document as a file.
     *
     * @param source the document source map
     * @param exportPath the base export directory path
     * @param excludeFields the set of field names to exclude from output