How to use Firestore on a Spring Boot application

Question

I'm developing an application with Spring Boot that will be released on Cloud Run. Cloud Run containers are stateless, so to save user experience session information I thought of using Firestore. I will save an instance of the UserService class on the document and the document id is the user id.

public class UserService {
      private Loginform loginForm;
      private SearchForm searchForm;
      private ModifyForm modifyForm;

     //setter and getter method
}

I had thought that in every Controller class (e.g. Home, Search Page, Edit Page etc) to use this technique to return me the information in the user's document:

Authentication authentication = SecurityContextHolder.getContext().getAuthentication();
String clientId = authentication.getName();
        
UserService  userData = getUserService(clientId);

but Authentication is still linked to the session so I would still encounter the container problem. How can I solve it?

Furthermore, in each controller class I have implemented the getUserService(String ClientId) method, perhaps the best solution is to create a Utility Class with the static getUserService method that I can call from each controller class?

public class Utility {

   @Autowired
   private Firestore firestore;

   public UserService getUserService(String clientId) {
       DocumentReference docRef = firestore.collection("users").document(clientId);
       
       ApiFuture<DocumentSnapshot> future = docRef.get();
       
       DocumentSnapshot document = future.get();
       UserService user = document.toObject(UserService.class);
       
       return user;
   }
}