在一层中设置登录UserDetails，并在任意java MVC的DAO层中访问它。

// CustomUserDetailsService.java
@Service
public class CustomUserDetailsService implements UserDetailsService {

    @Autowired
    private UserDao userDao;

    @Override
    public UserDetails loadUserByUsername(String username) throws UsernameNotFoundException {
        User user = userDao.findByUsername(username);
        if (user == null) {
            throw new UsernameNotFoundException("User not found");
        }
        return new org.springframework.security.core.userdetails.User(user.getUsername(), user.getPassword(), getAuthorities(user));
    }

    private Collection<? extends GrantedAuthority> getAuthorities(User user) {
        List<GrantedAuthority> authorities = new ArrayList<>();
        // Add user roles to authorities
        for (Role role : user.getRoles()) {
            authorities.add(new SimpleGrantedAuthority(role.getName()));
        }
        return authorities;
    }
}

// UserDao.java
@Repository
public class UserDao {

    // DAO methods to access user data from the database
    // ...

    public User findByUsername(String username) {
        // Implement the logic to find a user by username
        // ...
    }
}

// Example usage in a DAO method
@Repository
public class ExampleDao {

    @Autowired
    private CustomUserDetailsService userDetailsService;

    public void exampleMethod() {
        // Get the current logged-in user's details
        Authentication authentication = SecurityContextHolder.getContext().getAuthentication();
        String username = authentication.getName();
        UserDetails userDetails = userDetailsService.loadUserByUsername(username);

        // Access the user's details
        String userRole = userDetails.getAuthorities().iterator().next().getAuthority();
        // ...
    }
}