@Override
    public OAuth20ResponseModeTypes resolveResponseModeType(final WebContext context) {
        val supportedResponseModes = jwtBuilder.getCasProperties().getAuthn().getOidc().getDiscovery().getResponseModesSupported();
        val responseType = resolveRequestParameter(context, OAuth20Constants.RESPONSE_MODE)
            .map(String::valueOf)
            .filter(typeName -> supportedResponseModes.stream().anyMatch(supported -> supported.equalsIgnoreCase(typeName)))
            .orElse(StringUtils.EMPTY);
        val type = Arrays.stream(OAuth20ResponseModeTypes.values())
            .filter(t -> t.getType().equalsIgnoreCase(responseType))
            .findFirst()
            .orElse(OAuth20ResponseModeTypes.NONE);
        LOGGER.debug("OAuth response type is [{}]", type);
        return type;
    }
This is {@link DefaultOAuth20RequestParameterResolver}.

@author Misagh Moayyed
@since 6.6.0
support/cas-server-support-oauth-core-api/src/main/java/org/apereo/cas/support/oauth/web/DefaultOAuth20RequestParameterResolver.java