final String value = getSearchEngineHttpSslCertificateAuthorities();
        if (value != null) {
            return value;
        }
        return get("elasticsearch.http.ssl.certificate_authorities");
    }

    String getSearchEngineUsername();

    default String getFesenUsername() {
        final String value = getSearchEngineUsername();
        if (value != null) {

    String search_engine_HTTP_URL = "search_engine.http.url";

    /** The key of the configuration. e.g.  */
    String search_engine_HTTP_SSL_certificate_authorities = "search_engine.http.ssl.certificate_authorities";

    /** The key of the configuration. e.g.  */
    String search_engine_USERNAME = "search_engine.username";

    /** The key of the configuration. e.g.  */

# For IPv6 environments, use brackets around the IPv6 address (e.g., http://[::1]:9201)
search_engine.http.url=http://localhost:9201
# Path to SSL certificate authorities for secure HTTP connections.
search_engine.http.ssl.certificate_authorities=
# Username for authenticating to the search engine.
search_engine.username=
# Password for authenticating to the search engine.
search_engine.password=
# Interval (ms) for heartbeat checks to the search engine.

        }
        final String authorities = fessConfig.getFesenHttpSslCertificateAuthorities();
        if (StringUtil.isNotBlank(authorities)) {
            builder.put("http.ssl.certificate_authorities", authorities);
        }
        return new HttpClient(builder.build(), null);
    }

    /**
     * Checks if an index exists in the search engine.
     *