@Component
public class CustomAuthenticationProvider implements AuthenticationProvider {

    @Autowired
    private AuthServiceImpl authService;

    @Override
    public Authentication authenticate(Authentication authentication) throws AuthenticationException {
        String username = authentication.getName();
        String password = (String) authentication.getCredentials();

        AdminUser user = (AdminUser) authService.loadUserByUsername(username);

        if (user == null || !user.getUsername().equalsIgnoreCase(username)) {
            throw new BadCredentialsException("Username not found.");
        }

        BCryptPasswordEncoder passwordEncoder = new BCryptPasswordEncoder();

        if (!passwordEncoder.matches(password, user.getPassword())) {
            throw new BadCredentialsException("Wrong password.");
        }

        Collection<? extends GrantedAuthority> authorities = user.getAuthorities();

        return new UsernamePasswordAuthenticationToken(user, password, authorities);
    }

    @Override
    public boolean supports(Class<?> aClass) {
        return true;
    }
}