@Override
        protected String determineEventId(final RequestContext context) {
            var eventId = super.determineEventId(context);
            if (StringUtils.isBlank(eventId)) {
                val request = WebUtils.getHttpServletRequestFromExternalWebflowContext(context);
                eventId = (String) request.getAttribute("_eventId");
            }
            return eventId;
        }
This is {@link CasMvcViewFactoryCreator}.

@author Misagh Moayyed
@since 7.0.0
core/cas-server-core-webflow-api/src/main/java/org/apereo/cas/web/flow/resolver/CasMvcViewFactoryCreator.java