Spring-authorization-server SLO issue with OIDC

Question

I have a customize IDP server which implemented with Spring-authorization-server(1.1.2) and spring-security(6.1.1). With that I implemented the SSO with between the clients.

I met wit an issue that when doing RP-Initiated SLO.

Client: Client will redirect a request to IDP server when user clicking logout button.

@GetMapping("/custom-logout/{idToken}")
    public String customLogout(HttpServletRequest request, @PathVariable(value = "idToken") String idToken) {
        // Get the user's ID token (replace with actual retrieval logic)

        // Create the logout URL with the id_token_hint parameter
        String logoutUrl = "http://auth-server:8000/connect/logout?id_token_hint=" + idToken
                + "&post_logout_redirect_uri=http://127.0.0.1:8080/logged-out";

        // Redirect the user to the authorization server's logout endpoint
        return "redirect:" + logoutUrl;
    }

IDP Server The idp server can get the request and try to convert the request via OidcLogoutAuthenticationConverter. However, there's an issue that SecurityContextHolder.getContext().getAuthentication(); return null. Also, the HttpSession session = request.getSession(false); is null too.

@Override
    public Authentication convert(HttpServletRequest request) {
        MultiValueMap<String, String> parameters = getParameters(request);

        // id_token_hint (REQUIRED)     // RECOMMENDED as per spec
        String idTokenHint = request.getParameter("id_token_hint");
        if (!StringUtils.hasText(idTokenHint) ||
                request.getParameterValues("id_token_hint").length != 1) {
            throwError(OAuth2ErrorCodes.INVALID_REQUEST, "id_token_hint");
        }

        Authentication principal = SecurityContextHolder.getContext().getAuthentication();
        if (principal == null) {
            principal = ANONYMOUS_AUTHENTICATION;
        }

        String sessionId = null;
        HttpSession session = request.getSession(false);
        if (session != null) {
            sessionId = session.getId();
        }

Any ideas about the issue or what I did wrong? Thanks in advance!

I tried to hit the end_session_endpoint with both GET and POST. But didn't work.