client-credentials 방식 accessToken null 이슈

Cannot invoke "org.springframework.security.oauth2.client.OAuth2AuthorizedClient.getAccessToken()" because "oAuth2AuthorizedClient" is null] with root cause

keycloak 버전은 : 21.1.2

@GetMapping("/oauth2Login")
public String oauth2Login(Model model, HttpServletRequest request, HttpServletResponse response) {
    Authentication authentication = SecurityContextHolder.getContext().getAuthentication();

    OAuth2AuthorizeRequest oAuth2AuthorizeRequest = OAuth2AuthorizeRequest
            .withClientRegistrationId("keycloak")
            .principal(authentication)
            .attribute(HttpServletRequest.class.getName(), request)
            .attribute(HttpServletResponse.class.getName(), response)
            .build();

    OAuth2AuthorizationSuccessHandler successHandler = (authorizedClient, principal, attributes) -> {
        oAuth2AuthorizedClientRepository
            .saveAuthorizedClient(authorizedClient, principal,
                    (HttpServletRequest) attributes.get(HttpServletRequest.class.getName()),
                    (HttpServletResponse) attributes.get(HttpServletResponse.class.getName()));

        System.out.println("authorizedClient : " + authorizedClient);
        System.out.println("principal : " + principal);
        System.out.println("attributes : " + attributes);
    };

    auth2AuthorizedClientManager.setAuthorizationSuccessHandler(successHandler);

    OAuth2AuthorizedClient oAuth2AuthorizedClient = auth2AuthorizedClientManager.authorize(oAuth2AuthorizeRequest);

    model.addAttribute("oAuth2AuthorizedClient", oAuth2AuthorizedClient.getAccessToken().getTokenValue());

    return "home";
}

keycloak:
  clientId: oauath2-client-app
  clientSecret: HPWAsKr9dEy9DPU1babedRmpstowiXOs
  clientName: oauath2-client-app
  authorizationGrantType: client-credentials
  clientAuthenticationMethod: client_secret_basic
  provider: keycloak

<form sec:authorize="isAnonymous()" action="#">
    <p><input type="button" onclick="authorizationCode()" value="AuthorizationCode Grant"/></p>
    <p><div sec:authorize="isAnonymous()"><a th:href="@{/oauth2Login(username='user',password='1234')}">Password flow</a></div></p>
    <div sec:authorize="isAnonymous()"><a th:href="@{/oauth2Login}">Client Credentials Flow Login</a></div>
</form>

@Configuration
public class AppConfig {

    @Bean
    public DefaultOAuth2AuthorizedClientManager auth2AuthorizedClientManager(ClientRegistrationRepository clientRegistrationRepository,
                                                                      OAuth2AuthorizedClientRepository oAuth2AuthorizedClientRepository) {

        OAuth2AuthorizedClientProvider oAuth2AuthorizedClientProvider = OAuth2AuthorizedClientProviderBuilder.builder()
                .authorizationCode()
                .password()
                .clientCredentials()
                .refreshToken()
                .build();

        DefaultOAuth2AuthorizedClientManager defaultOAuth2AuthorizedClientManager = new DefaultOAuth2AuthorizedClientManager(clientRegistrationRepository, oAuth2AuthorizedClientRepository);

        defaultOAuth2AuthorizedClientManager.setAuthorizedClientProvider(oAuth2AuthorizedClientProvider);
        defaultOAuth2AuthorizedClientManager.setContextAttributesMapper(contextAttributeManager());

        return defaultOAuth2AuthorizedClientManager;
    }

    private Function<OAuth2AuthorizeRequest, Map<String, Object>> contextAttributeManager() {
        return oAuth2AuthorizeRequest -> {
            Map<String, Object> contextAttributes = new HashMap<>();
            HttpServletRequest httpServletRequest = oAuth2AuthorizeRequest.getAttribute(HttpServletRequest.class.getName());
            String userName = httpServletRequest.getParameter(OAuth2ParameterNames.USERNAME);
            String userPassword = httpServletRequest.getParameter(OAuth2ParameterNames.PASSWORD);

            if(StringUtils.hasText(userName) && StringUtils.hasText(userPassword)) {
                contextAttributes.put(OAuth2AuthorizationContext.USERNAME_ATTRIBUTE_NAME, userName);
                contextAttributes.put(OAuth2AuthorizationContext.PASSWORD_ATTRIBUTE_NAME, userPassword);
            }

            return contextAttributes;
        };
    }
}

이렇게 됩니다. 현재 상황으로 문제가 되어 있는 부분이 없는 것 같습니다.

어디부터 다시 확인해야 될지 조언 부탁드립니다.