private static String extractClientNameFromRelayStateUrl(final String relayState) {
        return FunctionUtils.doAndHandle(() -> {
            val uriBuilder = new URIBuilder(relayState);
            val relayStateParam = uriBuilder.getFirstQueryParam(Pac4jConstants.DEFAULT_CLIENT_NAME_PARAMETER);
            return relayStateParam != null ? relayStateParam.getValue() : null;
        });
    }
Extract client name from http request parameter.

@return the delegated client name extractor
support/cas-server-support-pac4j-api/src/main/java/org/apereo/cas/pac4j/client/DelegatedClientNameExtractor.java