Spring Security - Quick Reference

When to Use This Skill

• Configure JWT authentication
• Role-based access control
• Method-level security

Deep Knowledge: Use mcp__documentation__fetch_docs with technology: spring-security for comprehensive documentation.

Essential Patterns

Security Config

@Configuration
@EnableWebSecurity
@EnableMethodSecurity
@RequiredArgsConstructor
public class SecurityConfig {

    private final JwtAuthenticationFilter jwtAuthFilter;

    @Bean
    public SecurityFilterChain securityFilterChain(HttpSecurity http) throws Exception {
        return http
            .csrf(AbstractHttpConfigurer::disable)
            .cors(Customizer.withDefaults())
            .sessionManagement(s -> s.sessionCreationPolicy(SessionCreationPolicy.STATELESS))
            .authorizeHttpRequests(auth -> auth
                .requestMatchers("/api/v1/auth/**").permitAll()
                .requestMatchers("/swagger-ui/**", "/v3/api-docs/**").permitAll()
                .requestMatchers("/api/v1/admin/**").hasRole("ADMIN")
                .anyRequest().authenticated())
            .addFilterBefore(jwtAuthFilter, UsernamePasswordAuthenticationFilter.class)
            .build();
    }

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

JWT Filter

@Component
@RequiredArgsConstructor
public class JwtAuthenticationFilter extends OncePerRequestFilter {

    private final JwtService jwtService;
    private final UserDetailsService userDetailsService;

    @Override
    protected void doFilterInternal(HttpServletRequest request,
            HttpServletResponse response, FilterChain chain) throws Exception {

        String authHeader = request.getHeader("Authorization");
        if (authHeader == null || !authHeader.startsWith("Bearer ")) {
            chain.doFilter(request, response);
            return;
        }

        String jwt = authHeader.substring(7);
        String email = jwtService.extractUsername(jwt);

        if (email != null && SecurityContextHolder.getContext().getAuthentication() == null) {
            UserDetails user = userDetailsService.loadUserByUsername(email);
            if (jwtService.isTokenValid(jwt, user)) {
                var auth = new UsernamePasswordAuthenticationToken(user, null, user.getAuthorities());
                SecurityContextHolder.getContext().setAuthentication(auth);
            }
        }
        chain.doFilter(request, response);
    }
}

Method Security

@PreAuthorize("hasRole('ADMIN')")
@DeleteMapping("/{id}")
public void delete(@PathVariable Long id) { ... }

@PreAuthorize("#id == authentication.principal.id or hasRole('ADMIN')")
@GetMapping("/{id}/profile")
public UserProfile getProfile(@PathVariable Long id) { ... }

UserDetails

public class UserPrincipal implements UserDetails {
    @Override
    public Collection<? extends GrantedAuthority> getAuthorities() {
        return List.of(new SimpleGrantedAuthority("ROLE_" + role.name()));
    }
}

Common Annotations

Annotation	Usage
@PreAuthorize	Check before method execution
hasRole('X')	Requires role
hasAnyRole	Any of the roles

Anti-Patterns to Avoid

• Do not disable CSRF without stateless
• Do not forget CORS for frontend
• Do not hardcode JWT secret

Production Readiness

JWT Service

@Service
@RequiredArgsConstructor
public class JwtService {

    @Value("${security.jwt.secret-key}")
    private String secretKey;

    @Value("${security.jwt.expiration}")
    private long jwtExpiration;

    @Value("${security.jwt.refresh-expiration}")
    private long refreshExpiration;

    public String generateToken(UserDetails userDetails) {
        return buildToken(userDetails, jwtExpiration);
    }

    public String generateRefreshToken(UserDetails userDetails) {
        return buildToken(userDetails, refreshExpiration);
    }

    private String buildToken(UserDetails userDetails, long expiration) {
        return Jwts.builder()
            .setSubject(userDetails.getUsername())
            .claim("roles", userDetails.getAuthorities().stream()
                .map(GrantedAuthority::getAuthority)
                .toList())
            .setIssuedAt(new Date())
            .setExpiration(new Date(System.currentTimeMillis() + expiration))
            .signWith(getSigningKey(), SignatureAlgorithm.HS256)
            .compact();
    }

    public boolean isTokenValid(String token, UserDetails userDetails) {
        try {
            final String username = extractUsername(token);
            return username.equals(userDetails.getUsername()) && !isTokenExpired(token);
        } catch (ExpiredJwtException | MalformedJwtException e) {
            return false;
        }
    }

    private SecretKey getSigningKey() {
        byte[] keyBytes = Decoders.BASE64.decode(secretKey);
        return Keys.hmacShaKeyFor(keyBytes);
    }
}

CORS Configuration

@Configuration
public class CorsConfig {

    @Bean
    public CorsFilter corsFilter() {
        UrlBasedCorsConfigurationSource source = new UrlBasedCorsConfigurationSource();
        CorsConfiguration config = new CorsConfiguration();

        config.setAllowCredentials(true);
        config.setAllowedOrigins(List.of(
            "https://yourdomain.com",
            "https://app.yourdomain.com"
        ));
        config.setAllowedMethods(List.of("GET", "POST", "PUT", "DELETE", "OPTIONS"));
        config.setAllowedHeaders(List.of("*"));
        config.setExposedHeaders(List.of("Authorization"));
        config.setMaxAge(3600L);

        source.registerCorsConfiguration("/**", config);
        return new CorsFilter(source);
    }
}

Rate Limiting

@Component
public class RateLimitingFilter extends OncePerRequestFilter {

    private final Cache<String, AtomicInteger> requestCounts = Caffeine.newBuilder()
        .expireAfterWrite(1, TimeUnit.MINUTES)
        .build();

    @Override
    protected void doFilterInternal(HttpServletRequest request,
            HttpServletResponse response, FilterChain chain) throws Exception {

        String clientIP = getClientIP(request);
        AtomicInteger count = requestCounts.get(clientIP, k -> new AtomicInteger(0));

        if (count.incrementAndGet() > 100) {
            response.setStatus(HttpStatus.TOO_MANY_REQUESTS.value());
            response.getWriter().write("{\"error\": \"Rate limit exceeded\"}");
            return;
        }

        chain.doFilter(request, response);
    }

    private String getClientIP(HttpServletRequest request) {
        String xForwardedFor = request.getHeader("X-Forwarded-For");
        if (xForwardedFor != null && !xForwardedFor.isEmpty()) {
            return xForwardedFor.split(",")[0].trim();
        }
        return request.getRemoteAddr();
    }
}

Security Headers

@Bean
public SecurityFilterChain securityFilterChain(HttpSecurity http) throws Exception {
    return http
        // ... existing config
        .headers(headers -> headers
            .contentSecurityPolicy(csp -> csp
                .policyDirectives("default-src 'self'; frame-ancestors 'none'"))
            .frameOptions(frame -> frame.deny())
            .xssProtection(xss -> xss.block(true))
            .contentTypeOptions(Customizer.withDefaults())
            .referrerPolicy(referrer -> referrer
                .policy(ReferrerPolicyHeaderWriter.ReferrerPolicy.STRICT_ORIGIN_WHEN_CROSS_ORIGIN)))
        .build();
}

Security Testing

@WebMvcTest(UserController.class)
@Import(SecurityConfig.class)
class UserControllerSecurityTest {

    @Autowired
    private MockMvc mockMvc;

    @MockBean
    private UserService userService;

    @Test
    void unauthenticated_shouldReturn401() throws Exception {
        mockMvc.perform(get("/api/v1/users"))
            .andExpect(status().isUnauthorized());
    }

    @Test
    @WithMockUser(roles = "ADMIN")
    void adminEndpoint_withAdminRole_shouldSucceed() throws Exception {
        mockMvc.perform(delete("/api/v1/admin/users/1"))
            .andExpect(status().isOk());
    }

    @Test
    @WithMockUser(roles = "USER")
    void adminEndpoint_withUserRole_shouldReturn403() throws Exception {
        mockMvc.perform(delete("/api/v1/admin/users/1"))
            .andExpect(status().isForbidden());
    }
}

Monitoring Metrics

Metric	Target
Failed auth attempts	Monitor spikes
Token validation time	< 5ms
Rate limit hits	< 1%
Security exceptions	0 unhandled

Checklist

• JWT secret from environment variable
• Token expiration configured
• Refresh token mechanism
• CORS whitelist (no wildcards in prod)
• Rate limiting enabled
• Security headers configured
• Method-level security (@PreAuthorize)
• Password encoding (BCrypt)
• HTTPS enforced
• Security integration tests

When NOT to Use This Skill

• Spring Boot application setup → Use spring-boot skill
• OAuth2 server implementation → Use OAuth2-specific skill
• General cryptography → Use security-expert skill
• Database access → Use spring-data-jpa skill
• REST API patterns → Use spring-web skill

Anti-Patterns

Anti-Pattern	Why It's Bad	Correct Approach
Hardcoded JWT secret	Security risk	Use environment variables
Disable CSRF without stateless	Vulnerable to attacks	Only disable with JWT (stateless)
Permit all in production	No security	Configure proper authorization
Store passwords in plain text	Critical security flaw	Use BCryptPasswordEncoder
No token expiration	Tokens never invalidate	Set proper expiration time
Allow all CORS origins	CSRF vulnerability	Whitelist specific origins

Quick Troubleshooting

Problem	Likely Cause	Solution
401 Unauthorized	Token missing/invalid	Check Authorization header format
403 Forbidden	Insufficient permissions	Check user roles and @PreAuthorize
CORS errors	Origin not allowed	Add origin to CORS configuration
Filter not executing	Wrong filter order	Check addFilterBefore placement
JWT parsing fails	Wrong secret key	Verify JWT_SECRET matches
Authentication null	Filter not applied	Ensure SecurityContextHolder is set

Further Reading

For advanced configurations: mcp__documentation__fetch_docs

• Technology: spring-security, Topic: basics
• Spring Security Docs