@Configuration
@EnableWebSecurity
@RequiredArgsConstructor
public class SecurityConfig {
    private final CustomUserDetailsService customUserDetailsService; // 일반 로그인 처리를 위한 CustomUserDetailsService
    private final CustomOAuth2UserService customOAuth2UserService; // OAuth2 로그인을 처리할 CustomOAuth2UserService
}

 
  @Bean
  public SecurityFilterChain filterChain(HttpSecurity http) throws Exception {
      http
          
          .oauth2Login(oauth2Login ->
              oauth2Login
                  .loginPage("/login") // 사용자 정의 로그인 페이지 설정
                  .userInfoEndpoint(userInfoEndpoint -> 
                      userInfoEndpoint.userService(customOAuth2UserService())
                  )
                  .successHandler((request, response, authentication) -> {
                      // OAuth 로그인 성공 후 토큰을 확인하고 사용할 수 있는 곳
                      OAuth2AuthenticationToken authToken = (OAuth2AuthenticationToken) authentication;
                      OAuth2User oAuth2User = authToken.getPrincipal();
                      String accessToken = authToken.getAuthorizedClientRegistrationId();
                      System.out.println("Access Token: " + accessToken);
                      response.sendRedirect("/");
                  })
          );
      return http.build();
  }
 
  @Bean
  public CustomOAuth2UserService customOAuth2UserService() {
      return new CustomOAuth2UserService();
  }

@Service
public class CustomOAuth2UserService extends DefaultOAuth2UserService {
    
    @Autowired
    private MemberJpaRepository memberRepository;
 
    @Override
    public OAuth2User loadUser(OAuth2UserRequest userRequest) throws OAuth2AuthenticationException {
        OAuth2User oAuth2User = super.loadUser(userRequest);
 
        String email = oAuth2User.getAttribute("email");
        String name = oAuth2User.getAttribute("name");
 
        // 상황에 맞는 로직. DB에서 사용자 확인 또는 저장
        
    }
}
 

public Map<String, Object> getUserInfo(String accessToken) {
    RestTemplate restTemplate = new RestTemplate();
    String url = "https://www.googleapis.com/oauth2/v3/userinfo";
 
    HttpHeaders headers = new HttpHeaders();
    headers.setBearerAuth(accessToken); // Access token을 이용한 인증
 
    HttpEntity<String> request = new HttpEntity<>(headers);
    ResponseEntity<Map> response = restTemplate.exchange(url, HttpMethod.GET, request, Map.class);
 
    return response.getBody();
}