protected void writeFessConfig(final ZipOutputStream zos, final String id) {
        if (fessConfig instanceof SimpleImpl) {
            final Properties prop = new Properties();
            ((SimpleImpl) fessConfig).keySet().stream().forEach(k -> prop.setProperty(k, fessConfig.get(k)));

            final ZipEntry entry = new ZipEntry(id + "/fess_config.properties");
            try {
                zos.putNextEntry(entry);