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) {

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

    public boolean existsIndex(final String indexName) {