spring-security-jwt

# Spring Security — JWT

Spring Boot 4.x ships **Spring Security 7**: the lambda DSL is the *only* style — `and()`,
`authorizeRequests()`, `antMatchers()`, and `WebSecurityConfigurerAdapter` no longer exist, and
`AntPathRequestMatcher`/`MvcRequestMatcher` are replaced by `PathPatternRequestMatcher`
(`requestMatchers("/path/**")` uses it under the hood).

## Dependencies

```xml
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-security</artifactId>
</dependency>
<dependency>
    <groupId>io.jsonwebtoken</groupId>
    <artifactId>jjwt-api</artifactId>
    <version>0.12.6</version>
</dependency>
<dependency>
    <groupId>io.jsonwebtoken</groupId>
    <artifactId>jjwt-impl</artifactId>
    <version>0.12.6</version>
    <scope>runtime</scope>
</dependency>
<dependency>
    <groupId>io.jsonwebtoken</groupId>
    <artifactId>jjwt-jackson</artifactId>
    <version>0.12.6</version>
    <scope>runtime</scope>
</dependency>
```

## Security Configuration

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

    private final JwtAuthenticationFilter jwtAuthFilter;
    private final UserDetailsService userDetailsService;

    @Bean
    public SecurityFilterChain filterChain(HttpSecurity http) throws Exception {
        return http
            .csrf(AbstractHttpConfigurer::disable)
            .sessionManagement(s -> s.sessionCreationPolicy(STATELESS))
            .authorizeHttpRequests(auth -> auth
                .requestMatchers("/api/v1/auth/**").permitAll()
                .requestMatchers("/actuator/health").permitAll()
                .requestMatchers("/api/v1/admin/**").hasRole("ADMIN")
                .anyRequest().authenticated()
            )
            .addFilterBefore(jwtAuthFilter, UsernamePasswordAuthenticationFilter.class)
            .build();
    }

    @Bean
    public AuthenticationProvider authenticationProvider() {
        var provider = new DaoAuthenticationProvider(userDetailsService); // Security 7: constructor, not setter
        provider.setPasswordEncoder(passwordEncoder());
        return provider;
    }

    @Bean
    public AuthenticationManager authenticationManager(AuthenticationConfiguration config) throws Exception {
        return config.getAuthenticationManager();
    }

    @Bean
    public PasswordEncoder passwordEncoder() {
        return new BCryptPasswordEncoder(12);
    }
}
```

## JWT Service

```java
@Service
public class JwtService {

    @Value("${app.jwt.secret}")
    private String secretKey;

    @Value("${app.jwt.access-token-expiry:900000}") // 15 min default
    private long accessTokenExpiry;

    @Value("${app.jwt.refresh-token-expiry:604800000}") // 7 days default
    private long refreshTokenExpiry;

    public String generateAccessToken(UserDetails user) {
        return generateToken(Map.of("type", "access"), user, accessTokenExpiry);
    }

    public String generateRefreshToken(UserDetails user) {
        return generateToken(Map.of("type", "refresh"), user, refreshTokenExpiry);
    }

    private String generateToken(Map<String, Object> claims, UserDetails user, long expiry) {
        return Jwts.builder()
            .claims(claims)
            .subject(user.getUsername())
            .issuedAt(new Date())
            .expiration(new Date(System.currentTimeMillis() + expiry))
            .signWith(getSigningKey())
            .compact();
    }

    public boolean isAccessTokenValid(String token, UserDetails user) {
        Claims claims = extractClaims(token);
        return "access".equals(claims.get("type", String.class))
            && user.getUsername().equals(claims.getSubject())
            && !claims.getExpiration().before(new Date());
    }

    public String extractUsername(String token) {
        return extractClaims(token).getSubject();
    }

    private Claims extractClaims(String token) {
        return Jwts.parser().verifyWith(getSigningKey()).build()
            .parseSignedClaims(token).getPayload();
    }

    private SecretKey getSigningKey() {
        return Keys.hmacShaKeyFor(Decoders.BASE64.decode(secretKey));
    }
}
```

## JWT Filter

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

        String token = authHeader.substring(7);
        try {
            String username = jwtService.extractUsername(token);

            if (username != null && SecurityContextHolder.getContext().getAuthentication() == null) {
                UserDetails user = userDetailsService.loadUserByUsername(username);
                if (jwtService.isAccessTokenValid(token, user)) {
                    var auth = new UsernamePasswordAuthenticationToken(user, null, user.getAuthorities());
                    auth.setDetails(new WebAuthenticationDetailsSource().buildDetails(request));
                    SecurityContextHolder.getContext().setAuthentication(auth);
                }
            }
        } catch (ExpiredJwtException | MalformedJwtException | SignatureException e) {
            // Parsing throws on expired/tampered tokens. Without this catch the exception
            // escapes the filter chain as a 500. Leave the context empty — the entry
            // point below turns it into a clean 401.
            SecurityContextHolder.clearContext();
        }
        chain.doFilter(request, response);
    }
}
```

## JSON