In recent years, the security and user authentication methods of web applications have changed dramatically. In particular, OAuth2 has established itself as the standard for handling user authentication in many web services. This course will detail how to implement login and logout using OAuth2 with Spring Boot, as well as the token issuance process. Through this article, you will learn the basic principles of OAuth2 and gain the skills needed to build real applications.
1. What is OAuth2?
OAuth2 is a protocol for user authentication that allows users to grant access without providing their information to third-party services. This enables apps or services to access the user’s resources. The main components of OAuth2 are as follows:
- User (Resource Owner): The entity that protects and manages their information.
- Client: An application that seeks to access resources on behalf of the user.
- Resource Server: The server that provides protected resources.
- Authorization Server: The server that handles user authentication and issues access tokens to the client.
2. What is Spring Boot?
Spring Boot is a project based on Java’s Spring Framework that helps in quickly developing applications. Spring Boot offers the following advantages:
- Simplified configuration: Thanks to various defaults, you can get started quickly without complex configurations.
- Auto-configuration: You can easily add the necessary libraries for automatic configuration.
- Starter packages: These provide starter packages that combine multiple dependencies and configurations to speed up development.
3. Preparing to Build an OAuth2 Login System
3.1 Project Setup
To start a Spring Boot project, use Spring Initializr to create a basic project. Add the following dependencies:
- Spring Web
- Spring Security
- OAuth2 Client
- Spring Data JPA
- H2 Database (for development)
3.2 Project Structure
/src
└── main
├── java
│ └── com
│ └── example
│ └── oauth2demo
│ ├── controller
│ ├── model
│ ├── repository
│ ├── security
│ └── service
└── resources
├── application.properties
└── static
3.3 Configuring application.properties
To use OAuth2, configure as below. I will use Google OAuth2 as an example:
spring.security.oauth2.client.registration.google.client-id=YOUR_CLIENT_ID
spring.security.oauth2.client.registration.google.client-secret=YOUR_CLIENT_SECRET
spring.security.oauth2.client.registration.google.redirect-uri={baseUrl}/login/oauth2/code/{registrationId}
spring.security.oauth2.client.registration.google.scope=profile, email
spring.security.oauth2.client.provider.google.authorization-uri=https://accounts.google.com/o/oauth2/auth
spring.security.oauth2.client.provider.google.token-uri=https://oauth2.googleapis.com/token
spring.security.oauth2.client.provider.google.user-info-uri=https://www.googleapis.com/oauth2/v3/userinfo
4. Spring Security Configuration
Spring Security is used to manage authentication and authorization. Below is a basic security configuration example:
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
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;
@Configuration
@EnableWebSecurity
public class SecurityConfig extends WebSecurityConfigurerAdapter {
@Override
protected void configure(HttpSecurity http) throws Exception {
http
.authorizeRequests()
.anyRequest().authenticated()
.and()
.oauth2Login();
}
}
5. Retrieving User Information
Once the user has completed the login, the client application can obtain the authentication information. To fetch user’s information, implement the service below:
import org.springframework.security.core.Authentication;
import org.springframework.security.oauth2.core.user.OAuth2User;
import org.springframework.stereotype.Service;
@Service
public class UserService {
public String getCurrentUserName(Authentication authentication) {
OAuth2User oauth2User = (OAuth2User) authentication.getPrincipal();
return oauth2User.getAttribute("name");
}
}
6. Implementing Logout
Logout is also a common requirement. You can implement a simple logout feature using the configuration below:
http
.logout()
.logoutSuccessUrl("/login")
.invalidateHttpSession(true)
.clearAuthentication(true);
7. Running and Testing the Application
After completing all configurations, run the application and access http://localhost:8080 in your web browser. If configured correctly, the Google login screen will appear. You will also be able to view a screen that retrieves the user’s name after logging in.
8. Conclusion
In this course, we explored how to implement login and logout functions based on OAuth2 using Spring Boot. OAuth2 is a widely used authentication method in modern web applications, and we have seen how easily it can be configured using Spring Boot. We hope to build a more secure and convenient user authentication system by adding more advanced features in the future.
Additional Resources
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