I have spring boot 3.3.0 application.
This code works, but when I go to any other endpoint, and the cookies are already set, then principall == null.

How make available Principal in second endpoint too? How make authorization persistent ?

    @RequestMapping(method = RequestMethod.GET)
public @ResponseBody String anonAuth(
        Principal principal,
        HttpServletRequest request,
        HttpServletResponse response
                                    ) throws Exception {
        AppUser user;
        if (principal != null) {
            user = userRepository.findByUsername(principal.getName()).orElseThrow();
        } else {
            user = new AppUser();
            user.setUsername(UUID.randomUUID().toString());
            user.setPassword(UUID.randomUUID().toString());
            AnonymousAuthenticationToken token = new AnonymousAuthenticationToken(
                    "anonymous", user.getUsername(), user.getAuthorities());
            SecurityContext context = SecurityContextHolder.getContext();
            context.setAuthentication(token);
        }
        userRepository.save(user);
    }

    Authentication currentAuth = SecurityContextHolder.getContext().getAuthentication();

    return "Hello, " + currentAuth.getName() +"! Your authorities are: " + currentAuth.getAuthorities()";
}

Return to me

Hello, 83d24a72-8e63-4f97-8dd1-eb47ac1b7d5f! Your authorities are: [entity.AppUser$$Lambda/0x000076007cb7e000@5a7f3805]

My test endpoint :

 @GetMapping("/test")
public String userInfoDtoTest(Principal principal) {
    if (Objects.isNull(principal)) {
        log.error("Principal is null");
    }
    Authentication currentAuth = SecurityContextHolder.getContext().getAuthentication();
    log.info("Hello, " + currentAuth.getName() +"! Your authorities are: " + currentAuth.getAuthorities());
    return currentAuth.getName();
}

Logs:

ERROR 200361 --- [nio-8494-exec-6] UserController   : Principal is null
INFO  200361 --- [nio-8494-exec-6] UserController   : Hello, anonymousUser! Your authorities are: [ROLE_ANONYMOUS]