CustomUserDetailsService.java

package contactapp.security;

import org.springframework.security.core.userdetails.UserDetails;
import org.springframework.security.core.userdetails.UserDetailsService;
import org.springframework.security.core.userdetails.UsernameNotFoundException;
import org.springframework.stereotype.Service;

/**
 * Custom UserDetailsService implementation that loads users from the database.
 * Used by Spring Security for authentication.
 */
@Service
public class CustomUserDetailsService implements UserDetailsService {

    private final UserRepository userRepository;

    public CustomUserDetailsService(final UserRepository userRepository) {
        this.userRepository = userRepository;
    }

    @Override
    public UserDetails loadUserByUsername(final String username) throws UsernameNotFoundException {
        return userRepository.findByUsername(username)
                .orElseThrow(() -> new UsernameNotFoundException("User not found: " + username));
    }
}