/** Map of HTTP client properties */
    private final Map<String, Object> httpClientPropertyMap = new HashMap<>();

    /** List of request headers */
    private final List<Header> requestHeaderList = new ArrayList<>();

    /**
     * Constructs a new ApiExtractor.
     */
    public ApiExtractor() {
        // NOP
    }

    /**

    /** The HTTP client instance */
    protected volatile CloseableHttpClient httpClient;

    /** List of request headers to be sent with each request */
    private final List<Header> requestHeaderList = new ArrayList<>();

    /** Map of HTTP client properties */
    private final Map<String, Object> httpClientPropertyMap = new HashMap<>();

    /** Task for monitoring idle connections */

        // request header
        final List<RequestHeader> requestHeaderList = requestHeaderService.getRequestHeaderList(getId());
        final List<org.codelibs.fess.crawler.client.http.RequestHeader> rhList = new ArrayList<>();
        for (final RequestHeader requestHeader : requestHeaderList) {
            rhList.add(requestHeader.getCrawlerRequestHeader());
        }