CustomOAuth2UserService.java

package com.example.oauth2.security;

import com.example.oauth2.entity.User;
import com.example.oauth2.repository.UserRepository;
import lombok.RequiredArgsConstructor;
import lombok.extern.slf4j.Slf4j;
import org.springframework.security.oauth2.client.userinfo.DefaultOAuth2UserService;
import org.springframework.security.oauth2.client.userinfo.OAuth2UserRequest;
import org.springframework.security.oauth2.core.OAuth2AuthenticationException;
import org.springframework.security.oauth2.core.user.OAuth2User;
import org.springframework.stereotype.Service;

import java.util.Map;

@Slf4j
@Service
@RequiredArgsConstructor
public class CustomOAuth2UserService extends DefaultOAuth2UserService {
    
    private final UserRepository userRepository;
    
    @Override
    public OAuth2User loadUser(OAuth2UserRequest userRequest) throws OAuth2AuthenticationException {
        OAuth2User oAuth2User = super.loadUser(userRequest);
        
        try {
            return processOAuth2User(userRequest, oAuth2User);
        } catch (Exception ex) {
            log.error("OAuth2 인증 처리 중 오류 발생", ex);
            throw new OAuth2AuthenticationException(ex.getMessage());
        }
    }
    
    private OAuth2User processOAuth2User(OAuth2UserRequest userRequest, OAuth2User oAuth2User) {
        String registrationId = userRequest.getClientRegistration().getRegistrationId();
        OAuth2UserInfo userInfo = OAuth2UserInfoFactory.getOAuth2UserInfo(registrationId, oAuth2User.getAttributes());
        
        if (userInfo.getEmail() == null || userInfo.getEmail().isEmpty()) {
            throw new OAuth2AuthenticationException("OAuth2 제공자로부터 이메일을 찾을 수 없습니다.");
        }
        
        User user = userRepository.findByEmail(userInfo.getEmail())
                .map(existingUser -> updateExistingUser(existingUser, userInfo))
                .orElse(registerNewUser(userRequest, userInfo));
        
        return CustomOAuth2User.create(user, oAuth2User.getAttributes());
    }
    
    private User registerNewUser(OAuth2UserRequest userRequest, OAuth2UserInfo userInfo) {
        User user = User.builder()
                .name(userInfo.getName())
                .email(userInfo.getEmail())
                .picture(userInfo.getImageUrl())
                .provider(User.SocialProvider.valueOf(
                    userRequest.getClientRegistration().getRegistrationId().toUpperCase()))
                .providerId(userInfo.getId())
                .role(User.Role.USER)
                .build();
        
        return userRepository.save(user);
    }
    
    private User updateExistingUser(User existingUser, OAuth2UserInfo userInfo) {
        User updatedUser = existingUser.update(userInfo.getName(), userInfo.getImageUrl());
        return userRepository.save(updatedUser);
    }
}

// OAuth2UserInfo 인터페이스
interface OAuth2UserInfo {
    String getId();
    String getName();
    String getEmail();
    String getImageUrl();
}

// Google OAuth2UserInfo 구현
class GoogleOAuth2UserInfo implements OAuth2UserInfo {
    private final Map<String, Object> attributes;
    
    public GoogleOAuth2UserInfo(Map<String, Object> attributes) {
        this.attributes = attributes;
    }
    
    @Override
    public String getId() {
        return (String) attributes.get("sub");
    }
    
    @Override
    public String getName() {
        return (String) attributes.get("name");
    }
    
    @Override
    public String getEmail() {
        return (String) attributes.get("email");
    }
    
    @Override
    public String getImageUrl() {
        return (String) attributes.get("picture");
    }
}

// Kakao OAuth2UserInfo 구현
class KakaoOAuth2UserInfo implements OAuth2UserInfo {
    private final Map<String, Object> attributes;
    private final Map<String, Object> kakaoAccount;
    private final Map<String, Object> profile;
    
    public KakaoOAuth2UserInfo(Map<String, Object> attributes) {
        this.attributes = attributes;
        this.kakaoAccount = (Map<String, Object>) attributes.get("kakao_account");
        this.profile = (Map<String, Object>) kakaoAccount.get("profile");
    }
    
    @Override
    public String getId() {
        return String.valueOf(attributes.get("id"));
    }
    
    @Override
    public String getName() {
        return (String) profile.get("nickname");
    }
    
    @Override
    public String getEmail() {
        return (String) kakaoAccount.get("email");
    }
    
    @Override
    public String getImageUrl() {
        return (String) profile.get("profile_image_url");
    }
}

// Naver OAuth2UserInfo 구현
class NaverOAuth2UserInfo implements OAuth2UserInfo {
    private final Map<String, Object> attributes;
    
    public NaverOAuth2UserInfo(Map<String, Object> attributes) {
        this.attributes = (Map<String, Object>) attributes.get("response");
    }
    
    @Override
    public String getId() {
        return (String) attributes.get("id");
    }
    
    @Override
    public String getName() {
        return (String) attributes.get("name");
    }
    
    @Override
    public String getEmail() {
        return (String) attributes.get("email");
    }
    
    @Override
    public String getImageUrl() {
        return (String) attributes.get("profile_image");
    }
}

// Factory 클래스
class OAuth2UserInfoFactory {
    public static OAuth2UserInfo getOAuth2UserInfo(String registrationId, Map<String, Object> attributes) {
        return switch (registrationId.toLowerCase()) {
            case "google" -> new GoogleOAuth2UserInfo(attributes);
            case "kakao" -> new KakaoOAuth2UserInfo(attributes);
            case "naver" -> new NaverOAuth2UserInfo(attributes);
            default -> throw new OAuth2AuthenticationException("지원하지 않는 OAuth2 제공자입니다: " + registrationId);
        };
    }
}