spring-security Skill | Agent Skills

When to use this skill

Use this skill whenever the user wants to:

Configure authentication and authorization in Spring Boot applications
Set up SecurityFilterChain, UserDetailsService, and PasswordEncoder
Implement JWT-based stateless authentication
Integrate OAuth2 client or resource server
Use method-level security with @PreAuthorize and @Secured
Configure CORS, CSRF, session management, and security headers

How to use this skill

Workflow

Add the Spring Security starter dependency
Configure SecurityFilterChain to define URL-based access rules
Implement authentication: in-memory, JDBC, LDAP, or custom UserDetailsService
Add authorization: role-based or expression-based access control

1. Basic Security Configuration

@Configuration
@EnableWebSecurity
public class SecurityConfig {

    @Bean
    public SecurityFilterChain filterChain(HttpSecurity http) throws Exception {
        http
            .authorizeHttpRequests(auth -> auth
                .requestMatchers("/api/public/**").permitAll()
                .requestMatchers("/api/admin/**").hasRole("ADMIN")
                .anyRequest().authenticated()
            )
            .httpBasic(Customizer.withDefaults());
        return http.build();
    }

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

2. Custom UserDetailsService

@Service
public class CustomUserDetailsService implements UserDetailsService {
    private final UserRepository userRepository;

    public CustomUserDetailsService(UserRepository userRepository) {
        this.userRepository = userRepository;
    }

    @Override
    public UserDetails loadUserByUsername(String username) {
        User user = userRepository.findByUsername(username)
            .orElseThrow(() -> new UsernameNotFoundException("User not found: " + username));
        return new org.springframework.security.core.userdetails.User(
            user.getUsername(), user.getPassword(), user.getAuthorities()
        );
    }
}

3. JWT Authentication Filter

@Component
public class JwtAuthFilter extends OncePerRequestFilter {
    private final JwtService jwtService;
    private final UserDetailsService userDetailsService;

    @Override
    protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain chain)
            throws ServletException, IOException {
        String token = extractToken(request);
        if (token != null && jwtService.isValid(token)) {
            String username = jwtService.extractUsername(token);
            UserDetails userDetails = userDetailsService.loadUserByUsername(username);
            var authToken = new UsernamePasswordAuthenticationToken(userDetails, null, userDetails.getAuthorities());
            SecurityContextHolder.getContext().setAuthentication(authToken);
        }
        chain.doFilter(request, response);
    }
}

4. Method-Level Security

@EnableMethodSecurity
@Configuration
public class MethodSecurityConfig {}

@Service
public class AdminService {
    @PreAuthorize("hasRole('ADMIN')")
    public void deleteUser(Long id) { /* ... */ }

    @PreAuthorize("#userId == authentication.principal.id")
    public UserProfile getProfile(Long userId) { /* ... */ }
}

Best Practices

Always encode passwords with BCrypt or Argon2; never store plaintext passwords
Use HTTPS in production; configure security headers (HSTS, X-Content-Type-Options)
Apply the principle of least privilege; design roles and permissions carefully
Protect sensitive endpoints; use CSRF protection for browser-based applications
Configure CORS explicitly for API servers

Resources

Official reference: https://docs.spring.io/spring-security/reference/
Spring Security samples: https://github.com/spring-projects/spring-security-samples

Keywords

spring security, authentication, authorization, JWT, OAuth2, SecurityFilterChain, UserDetailsService, BCrypt, CORS, CSRF, method security, PreAuthorize, roles, permissions

Agent Skills: spring-security

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