protected String fetchRelayState(final HttpServletRequest request) {
        val relayState = StringUtils.defaultIfBlank((String) request.getAttribute(SamlProtocolConstants.PARAMETER_SAML_RELAY_STATE),
            request.getParameter(SamlProtocolConstants.PARAMETER_SAML_RELAY_STATE));
        LOGGER.debug("Relay state is [{}]", relayState);
        return relayState;
    }
This is {@link SamlIdPSingleLogoutRedirectionStrategy}.

@author Misagh Moayyed
@since 6.3.0
support/cas-server-support-saml-idp-web/src/main/java/org/apereo/cas/support/saml/web/idp/profile/slo/SamlIdPSingleLogoutRedirectionStrategy.java