Spring Security: Implementing Authentication & Authorization

Introduction

Security is a critical component in modern web applications, and Spring Security is the de facto framework for handling authentication and authorization in Spring Boot applications. Whether you are developing a REST API, microservices, or monolithic applications, Spring Security provides robust security configurations and features to protect your application.

This guide covers how to implement authentication and authorization using Spring Security, covering JWT, OAuth2, role-based access control (RBAC), and method-level security.

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1. Understanding Spring Security

Spring Security is a powerful and customizable authentication and access control framework for Spring-based applications.

Key Features of Spring Security:

• Authentication & Authorization
• CSRF Protection
• Session Management
• OAuth2 & JWT Integration
• Method-Level Security
• Password Encoding & Hashing

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2. Setting Up Spring Security in a Spring Boot Application

Step 1: Add Spring Security Dependency

Add the following dependency in pom.xml:

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-security</artifactId>
</dependency>

Spring Boot auto-configures a default security layer, requiring users to authenticate before accessing any endpoint.

Step 2: Configure Security in Spring Boot

Spring Security requires a SecurityFilterChain bean configuration in Spring Boot 3+.

@Configuration
@EnableWebSecurity
public class SecurityConfig {

    @Bean
    public SecurityFilterChain securityFilterChain(HttpSecurity http) throws Exception {
        http
            .csrf(AbstractHttpConfigurer::disable)
            .authorizeHttpRequests(auth -> auth
                .requestMatchers("/public/**").permitAll()
                .anyRequest().authenticated())
            .formLogin(Customizer.withDefaults());

        return http.build();
    }
}

This configuration:

• Disables CSRF (use with caution in REST APIs).
• Allows unauthenticated access to /public/**.
• Requires authentication for all other requests.
• Enables a default login form.

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3. Implementing User Authentication

Authentication is the process of verifying who a user is.

Step 1: Create a User Entity & Repository

@Entity
public class User {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String username;
    private String password;
    private String role;

    // Getters and Setters
}

@Repository
public interface UserRepository extends JpaRepository<User, Long> {
    Optional<User> findByUsername(String username);
}

Step 2: Implement UserDetailsService

@Service
public class CustomUserDetailsService implements UserDetailsService {

    @Autowired
    private UserRepository userRepository;

    @Override
    public UserDetails loadUserByUsername(String username) throws UsernameNotFoundException {
        User user = userRepository.findByUsername(username)
                .orElseThrow(() -> new UsernameNotFoundException("User not found"));

        return new User(user.getUsername(), user.getPassword(),
                List.of(new SimpleGrantedAuthority(user.getRole())));
    }
}

Step 3: Password Encoding

Spring Security recommends using BCryptPasswordEncoder for storing passwords securely.

@Bean
public PasswordEncoder passwordEncoder() {
    return new BCryptPasswordEncoder();
}

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4. Implementing JWT Authentication

JSON Web Tokens (JWT) are widely used for stateless authentication in Spring Security.

Step 1: Add JWT Dependencies

<dependency>
    <groupId>io.jsonwebtoken</groupId>
    <artifactId>jjwt</artifactId>
    <version>0.11.5</version>
</dependency>

Step 2: Generate and Validate JWT

@Component
public class JwtUtil {

    private final String SECRET_KEY = "mySecretKey";

    public String generateToken(String username) {
        return Jwts.builder()
                .setSubject(username)
                .setIssuedAt(new Date())
                .setExpiration(new Date(System.currentTimeMillis() + 1000 * 60 * 60))
                .signWith(SignatureAlgorithm.HS256, SECRET_KEY)
                .compact();
    }

    public String extractUsername(String token) {
        return Jwts.parser().setSigningKey(SECRET_KEY).parseClaimsJws(token).getBody().getSubject();
    }
}

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5. Implementing Role-Based Authorization (RBAC)

Authorization controls what users can do in the application.

@Configuration
@EnableMethodSecurity
public class MethodSecurityConfig {
}

Use @PreAuthorize to restrict access to specific roles:

@PreAuthorize("hasRole('ADMIN')")
@GetMapping("/admin")
public String adminEndpoint() {
    return "Admin Access Granted";
}

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6. Best Practices for Secure Spring Applications

1. Use strong password encoding – Always hash passwords before storing them.
2. Enable HTTPS – Encrypt communication between clients and the server.
3. Implement token expiration & refresh tokens – Prevent long-lived JWT tokens.
4. Use environment variables for secrets – Avoid hardcoding secrets.
5. Enable security logging – Monitor authentication attempts and failures.

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Conclusion

Spring Security provides a comprehensive security framework for securing applications using authentication and authorization mechanisms. By implementing JWT, OAuth2, role-based access control, and method-level security, developers can ensure a secure environment for their applications.

Would you like to see a step-by-step tutorial on implementing OAuth2 with Spring Security? Let us know in the comments!

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