How to correctly implement the UserDetailsService without having an username?

Question

I am creating an oauth service in spring-boot and want to use user information from a MariaDB for authentication. When implementing UserDetailsService I have to override the function loadUserByUsername. The problem is that my user model does not have a field username, instead of this I want to load the users using their mail address. So my question: How do I correctly implement the UserDetailsService without having an username?

Answer 1

Then the mail address is the user name.

It is just a text value that uniquely identify the user with the domain. It can be a:

• login name (domain: application)
• email address (domain: global)
• SSN (domain: US resident)
• student id (domain: school)
• employees id (domain: company)
• gamer id (domain: game site)
• or whatever you want it to be

as long as it is unique, so that loadUserByUsername can find exactly one record.

Answer 2

Option 1 can be you have to pass the emailId in username and field and use the emailId to validate in your Custom UserDetailsService

Option 2 you need to have some mapping using which you can derive the emailId from the username field.

@Component
public class AppUserDetailsService implements UserDetailsService{


    @Override
    public UserDetails loadUserByUsername(String s) throws UsernameNotFoundException {
        User user = userRepository.findByEmailId(s.toLowerCase());
        if(user == null) {
            throw new UsernameNotFoundException(String.format("The username %s doesn't exist", s));
        }

        List<GrantedAuthority> authorities = new ArrayList<>();
        authorities.add(new SimpleGrantedAuthority("STANDARD_USER"));

        UserDetails userDetails = new org.springframework.security.core.userdetails.User(user.getEmailId(), user.getPassword(), authorities);

        return userDetails;
    }
}