UserDetailsServiceImpl.java

@Service
public class UserDetailsServiceImpl implements UserDetailsService {
    private DeveloperRepository developerRepository;

    public UserDetailsServiceImpl(DeveloperRepository developerRepository) {
        this.developerRepository = developerRepository;
    }

    @Override
    public UserDetails loadUserByUsername(String username) throws UsernameNotFoundException {
        Developer developer = developerRepository.findByUsername(username);
        if (developer == null) {
            throw new UsernameNotFoundException(username);
        }
        return new User(developer.getUsername(), developer.getPassword(), emptyList());
    }
}