(코드는 계속해서 수정 중,,,,틀린 부분 있을 가능성 다분,,,기록용,,,)

build.gradle

dependencies {
	implementation 'org.springframework.boot:spring-boot-starter-security'
	implementation 'org.springframework.boot:spring-boot-starter-oauth2-client'
}

application.yml

  security:
    oauth2:
      client:
        registration:
          google:
            client-id: "보안 주의!"
            client-secret: "보안 주의!"
            scope: profile, email
  redirect-uri: http://localhost:8080/login/oauth2/code/google
  provider:
    google:
      authorization-uri: https://accounts.google.com/o/oauth2/auth
      token-uri: https://oauth2.googleapis.com/token
      user-info-uri: https://www.googleapis.com/oauth2/v2/userinfo

yml 파일은 꼭 .gitignore로 관리해서 개인의 키나 비밀번호가 유출되지 않도록 하는 것이 좋다!!! 특히 AWS 관련 정보,,, 진짜 찾아보면 과금 폭탄 맞는 사람이 여럿 보인다.
client-id, secret를 받기 위해서는 여기로 가보시라....!

LoginDTO

package com.example.demo.dto;

import lombok.Getter;
import lombok.Setter;

@Getter
@Setter
public class LoginDTO {
    String id;
    String email;
    String nickname;
}

LoginService

package com.example.demo.service;

import org.springframework.security.core.authority.SimpleGrantedAuthority;
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.DefaultOAuth2User;
import org.springframework.security.oauth2.core.user.OAuth2User;
import org.springframework.stereotype.Service;

import java.util.Collections;
import java.util.Map;

@Service
public class LoginService extends DefaultOAuth2UserService {

    private static final String ALLOWED_DOMAIN = "@dgu.ac.kr";

    @Override
    public OAuth2User loadUser(OAuth2UserRequest userRequest) throws OAuth2AuthenticationException {
        OAuth2User oAuth2User = super.loadUser(userRequest);

        // 사용자 정보를 추가로 처리
        Map<String, Object> attributes = oAuth2User.getAttributes();
        String email = (String) attributes.get("email");

        // 이메일 도메인 검증
        if (!email.endsWith(ALLOWED_DOMAIN)) {
            throw new OAuth2AuthenticationException("허용되지 않는 이메일 도메인입니다.");
        }

        // 사용자 정보를 포함한 커스터마이징된 OAuth2User 객체 생성
        return new DefaultOAuth2User(
                Collections.singleton(new SimpleGrantedAuthority("ROLE_USER")),
                attributes,
                "email"
        );
    }
}

LoginController

package com.example.demo.controller;

import com.example.demo.dto.LoginDTO;
import org.springframework.security.core.annotation.AuthenticationPrincipal;
import org.springframework.security.oauth2.core.user.OAuth2User;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.GetMapping;

@Controller
public class LoginController {

    @GetMapping("/login")
    public String login() {
        return "loginPage"; // Ensure this matches the name of your loginPage.html file
    }

    @GetMapping("/home")
    public String home(Model model, @AuthenticationPrincipal OAuth2User principal) {
        if (principal != null) {
            String id = principal.getAttribute("sub");
            String email = principal.getAttribute("email");
            String nickname = principal.getAttribute("name");

            LoginDTO loginDTO = new LoginDTO();
            loginDTO.setId(id);
            loginDTO.setEmail(email);
            loginDTO.setNickname(nickname);

            model.addAttribute("user", loginDTO);
        } else {
            model.addAttribute("user", null);
        }
        return "home";
    }
}

OAuth2ClientConfig

package com.example.demo;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.security.oauth2.client.*;
import org.springframework.security.oauth2.client.registration.ClientRegistration;
import org.springframework.security.oauth2.client.registration.ClientRegistrationRepository;
import org.springframework.security.oauth2.client.registration.InMemoryClientRegistrationRepository;
import org.springframework.security.oauth2.client.web.AuthenticatedPrincipalOAuth2AuthorizedClientRepository;
import org.springframework.security.oauth2.client.web.DefaultOAuth2AuthorizedClientManager;
import org.springframework.security.oauth2.client.web.OAuth2AuthorizedClientRepository;
import org.springframework.security.oauth2.core.AuthorizationGrantType;


@Configuration
public class OAuth2ClientConfig {

    @Value("${spring.security.oauth2.client.registration.google.client-id}")
    private String clientId;

    @Value("${spring.security.oauth2.client.registration.google.client-secret}")
    private String clientSecret;

    @Bean
    public ClientRegistrationRepository clientRegistrationRepository() {
        ClientRegistration registration = ClientRegistration.withRegistrationId("google")
                .clientId(clientId)
                .clientSecret(clientSecret)
                .scope("profile", "email")
                .authorizationUri("https://accounts.google.com/o/oauth2/auth")
                .tokenUri("https://oauth2.googleapis.com/token")
                .userInfoUri("https://www.googleapis.com/oauth2/v2/userinfo")
                .redirectUri("{baseUrl}/login/oauth2/code/{registrationId}")
                .authorizationGrantType(AuthorizationGrantType.AUTHORIZATION_CODE)
                .clientName("Google")
                .build();
        return new InMemoryClientRegistrationRepository(registration);
    }

    @Bean
    public OAuth2AuthorizedClientService authorizedClientService(ClientRegistrationRepository clientRegistrationRepository) {
        return new InMemoryOAuth2AuthorizedClientService(clientRegistrationRepository);
    }

    @Bean
    public OAuth2AuthorizedClientRepository authorizedClientRepository(OAuth2AuthorizedClientService authorizedClientService) {
        return new AuthenticatedPrincipalOAuth2AuthorizedClientRepository(authorizedClientService);
    }

    @Bean
    public OAuth2AuthorizedClientManager authorizedClientManager(
            ClientRegistrationRepository clientRegistrationRepository,
            OAuth2AuthorizedClientRepository authorizedClientRepository) {
        OAuth2AuthorizedClientProvider authorizedClientProvider = OAuth2AuthorizedClientProviderBuilder.builder()
                .authorizationCode()
                .refreshToken()
                .clientCredentials()
                .password()
                .build();

        DefaultOAuth2AuthorizedClientManager authorizedClientManager =
                new DefaultOAuth2AuthorizedClientManager(clientRegistrationRepository, authorizedClientRepository);
        authorizedClientManager.setAuthorizedClientProvider(authorizedClientProvider);

        return authorizedClientManager;
    }
}

SecurityConfig

package com.example.demo;

import com.example.demo.service.LoginService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Lazy;
import org.springframework.security.config.annotation.web.builders.HttpSecurity;
import org.springframework.security.config.annotation.web.configuration.EnableWebSecurity;
import org.springframework.security.config.annotation.web.configuration.WebSecurityConfigurerAdapter;
import org.springframework.security.oauth2.client.OAuth2AuthorizedClientManager;
import org.springframework.security.oauth2.client.OAuth2AuthorizedClientService;
import org.springframework.security.oauth2.client.registration.ClientRegistrationRepository;
import org.springframework.security.oauth2.client.userinfo.OAuth2UserRequest;
import org.springframework.security.oauth2.client.userinfo.OAuth2UserService;
import org.springframework.security.oauth2.client.web.DefaultOAuth2AuthorizedClientManager;
import org.springframework.security.oauth2.client.web.OAuth2AuthorizedClientRepository;
import org.springframework.security.oauth2.client.web.OAuth2LoginAuthenticationFilter;
import org.springframework.security.oauth2.core.user.OAuth2User;
import org.springframework.security.web.authentication.AuthenticationSuccessHandler;

@EnableWebSecurity
@Configuration
public class SecurityConfig extends WebSecurityConfigurerAdapter {

    @Autowired
    private LoginService loginService;

    @Override
    protected void configure(HttpSecurity http) throws Exception {
        http
                .authorizeRequests()
                .antMatchers("/", "/login", "/oauth2/**").permitAll()
                .anyRequest().authenticated()
                .and()
                .oauth2Login()
                .loginPage("/login")
                .defaultSuccessUrl("/home")
                .failureUrl("/login?error=true")
                .userInfoEndpoint()
                .userService(loginService);
    }
}

• SecurityConfig: Spring Security 설정을 관리하며, 애플리케이션의 보안 규칙과 인증/인가 절차를 정의
• OAuth2ClientConfig: OAuth2 클라이언트 설정을 관리하며, 구글 등의 외부 인증 제공자와의 상호작용을 위한 설정을 정의