feat: 구글 소셜 로그인 서비스 로직 구현

Author: larama-C

src/main/java/com/back/web7_9_codecrete_be/domain/auth/service/AuthService.java

@@ -1,5 +1,6 @@
 package com.back.web7_9_codecrete_be.domain.auth.service;
 
+import com.back.web7_9_codecrete_be.domain.auth.dto.google.GoogleUserInfo;
 import com.back.web7_9_codecrete_be.domain.auth.dto.kakao.KakaoUserInfo;
 import com.back.web7_9_codecrete_be.domain.auth.dto.request.LoginRequest;
 import com.back.web7_9_codecrete_be.domain.auth.dto.request.SignupRequest;
@@ -8,6 +9,7 @@
 import com.back.web7_9_codecrete_be.domain.users.entity.SocialType;
 import com.back.web7_9_codecrete_be.domain.users.entity.User;
 import com.back.web7_9_codecrete_be.domain.users.repository.UserRepository;
+import com.back.web7_9_codecrete_be.domain.users.util.NicknameGenerator;
 import com.back.web7_9_codecrete_be.global.error.code.AuthErrorCode;
 import com.back.web7_9_codecrete_be.global.error.code.UserErrorCode;
 import com.back.web7_9_codecrete_be.global.error.exception.BusinessException;
@@ -28,6 +30,8 @@ public class AuthService {
     private final EmailService emailService;
     private final TokenService tokenService;
     private final KakaoOAuthService kakaoOAuthService;
+    private final GoogleOAuthService googleOAuthService;
+    private final NicknameGenerator nicknameGenerator;
 
     // 회원가입
     public void signUp(SignupRequest req) {
@@ -165,7 +169,7 @@ public LoginResponse kakaoLogin(String code) {
 
     private User registerKakaoUser(KakaoUserInfo info) {
 
-        String nickname = info.getNickname();
+        String nickname = nicknameGenerator.generate();
         if (userRepository.existsByNickname(nickname)) {
             nickname = nickname + "_" + System.currentTimeMillis();
         }
@@ -183,8 +187,55 @@ private User registerKakaoUser(KakaoUserInfo info) {
         return userRepository.save(user);
     }
 
+    @Transactional
     public LoginResponse googleLogin(String code) {
-        // TODO: 구글 인가 코드 → 사용자 정보 → 로그인 처리
-        throw new UnsupportedOperationException("구글 로그인 미구현");
+
+        // 1. 인가 코드 → 구글 Access Token
+        String googleAccessToken = googleOAuthService.getAccessToken(code);
+
+        // 2. Access Token → 사용자 정보
+        GoogleUserInfo googleUserInfo = googleOAuthService.getUserInfo(googleAccessToken);
+
+        if (googleUserInfo.getEmail() == null) {
+            throw new BusinessException(AuthErrorCode.SOCIAL_EMAIL_NOT_PROVIDED);
+        }
+
+        // 3. 소셜 ID 기준 사용자 조회
+        User user = userRepository
+                .findBySocialTypeAndSocialId(
+                        SocialType.GOOGLE,
+                        googleUserInfo.getSocialId()
+                )
+                .orElseGet(() -> registerGoogleUser(googleUserInfo));
+
+        // 4. 탈퇴 사용자 체크
+        if (user.getIsDeleted()) {
+            throw new BusinessException(UserErrorCode.USER_DELETED);
+        }
+
+        // 5. 토큰 발급
+        tokenService.issueTokens(user);
+
+        return new LoginResponse(user.getId(), user.getNickname());
+    }
+
+    private User registerGoogleUser(GoogleUserInfo info) {
+
+        String nickname = nicknameGenerator.generate();
+        if (userRepository.existsByNickname(nickname)) {
+            nickname = nickname + "_" + System.currentTimeMillis();
+        }
+
+        User user = User.builder()
+                .email(info.getEmail())
+                .nickname(nickname)
+                .password(null)
+                .birth(null)
+                .profileImage(info.getProfileImageUrl())
+                .socialType(SocialType.GOOGLE)
+                .socialId(info.getSocialId())
+                .build();
+
+        return userRepository.save(user);
     }
 }

src/main/java/com/back/web7_9_codecrete_be/domain/auth/service/GoogleOAuthService.java

@@ -0,0 +1,74 @@
+package com.back.web7_9_codecrete_be.domain.auth.service;
+
+import com.back.web7_9_codecrete_be.domain.auth.dto.google.GoogleTokenResponse;
+import com.back.web7_9_codecrete_be.domain.auth.dto.google.GoogleUserInfo;
+import com.back.web7_9_codecrete_be.domain.auth.dto.google.GoogleUserResponse;
+import lombok.RequiredArgsConstructor;
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.http.*;
+import org.springframework.stereotype.Service;
+import org.springframework.util.LinkedMultiValueMap;
+import org.springframework.util.MultiValueMap;
+import org.springframework.web.client.RestTemplate;
+
+@Service
+@RequiredArgsConstructor
+public class GoogleOAuthService {
+
+    @Value("${oauth.google.client-id}")
+    private String clientId;
+
+    @Value("${oauth.google.client-secret}")
+    private String clientSecret;
+
+    @Value("${oauth.google.redirect-uri}")
+    private String redirectUri;
+
+    private static final String TOKEN_URL = "https://oauth2.googleapis.com/token";
+    private static final String USER_INFO_URL = "https://www.googleapis.com/oauth2/v2/userinfo";
+
+    private final RestTemplate restTemplate = new RestTemplate();
+
+    // 인가 코드 → 액세스 토큰
+    public String getAccessToken(String code) {
+        HttpHeaders headers = new HttpHeaders();
+        headers.setContentType(MediaType.APPLICATION_FORM_URLENCODED);
+
+        MultiValueMap<String, String> params = new LinkedMultiValueMap<>();
+        params.add("grant_type", "authorization_code");
+        params.add("client_id", clientId);
+        params.add("client_secret", clientSecret);
+        params.add("redirect_uri", redirectUri);
+        params.add("code", code);
+
+        HttpEntity<MultiValueMap<String, String>> request =
+                new HttpEntity<>(params, headers);
+
+        ResponseEntity<GoogleTokenResponse> response =
+                restTemplate.postForEntity(
+                        TOKEN_URL,
+                        request,
+                        GoogleTokenResponse.class
+                );
+
+        return response.getBody().getAccessToken();
+    }
+
+    // 액세스 토큰 → 구글 사용자 정보
+    public GoogleUserInfo getUserInfo(String accessToken) {
+        HttpHeaders headers = new HttpHeaders();
+        headers.setBearerAuth(accessToken);
+
+        HttpEntity<Void> request = new HttpEntity<>(headers);
+
+        ResponseEntity<GoogleUserResponse> response =
+                restTemplate.exchange(
+                        USER_INFO_URL,
+                        HttpMethod.GET,
+                        request,
+                        GoogleUserResponse.class
+                );
+
+        return response.getBody().toUserInfo();
+    }
+}