@Override
    public Map<String, Set<String>> resolveRequestParameters(final Collection<String> attributes,
                                                             final WebContext context) {
        return attributes
            .stream()
            .map(name -> {
                val values = resolveRequestParameter(context, name)
                    .map(EncodingUtils::urlDecode)
                    .map(value -> Arrays.stream(value.split(" ")).collect(Collectors.toSet()))
                    .orElseGet(Set::of);
                return Pair.of(name, values);
            })
            .collect(Collectors.toMap(Pair::getKey, Pair::getValue));
    }
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