Use Thymeleaf to access session scoped proxy bean - spring

Question

I defined my session scoped proxy bean as below:
#Configuration
public class SessionScopeBeans {
#Bean
#SessionScope
public User user() {
return new User();
}
}
and then inject it into controller:
#Controller
public class MyController {
User user;
...
I tried all solutions I found:
// fail in Bean way but I don't know why
<span th:text="${#user.getName()}"></span>
// definitely fail because it doesn't relate to sessionAttribute
<span th:text="${session.user.name}"></span>
<span th:text="${#session.user.name}"></span>
I don't want to use sessionAttribute because I don't want to change controller method signiture. What can I do?
In question How to access spring session bean scope in thymeleaf , question owner said that he can access via bean way but I failed. Is it because of the way I define and inject my bean?
EDIT
I removed #Resource(name = "user") because I found that is not necessary for injecting User to my controller.
The error is:
2020-06-22 15:43:31.092 ERROR 17124 --- [nio-8083-exec-2] o.a.c.c.C.[.[.[/].[dispatcherServlet] : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is org.thymeleaf.exceptions.TemplateInputException: An error happened during template parsing (template: "class path resource [templates/home.html]")] with root cause
java.lang.IllegalStateException: Cannot create a session after the response has been committed
I found some discussion about this error but they all related to spring-security or spring-session. I didn't use these two modules!!
EDIT 2
After some code changes with no brain, suddenly I found <span th:text="${#user}"></span> can print out my class instance as string!! No matter how I inject my User bean: #Resource, #Autowired, or even no wiring annotation!! But, <span th:text="${#user.getName()}"></span> print nothing when I am sure it has value in it. A little step forward but block again...=(
EDIT 3
Finally, I found the stupid thing I did! Below is my controller and I assign user object to another one returned from DAO. So I have 2 user objects, one is controlled by Spring, wired into controller as a session scope bean which is all blank and another is created by DAO as a local variable in controller which contains information. Thymeleaf get the wired one...
#Autowired
private User user;
#PostMapping("/signin")
public String signin(#RequestParam String account, #RequestParam String password, Model model) {
user = dao.getUser(account);
return "redirect:/home";
}
#GetMapping("/home")
public String home(Model model) {
System.out.println(user.getTel());
return "home";
}