<dependency>
  <groupId>io.jsonwebtoken</groupId>
  <artifactId>jjwt-api</artifactId>
  <version>0.11.5</version>
</dependency>
<dependency>
  <groupId>io.jsonwebtoken</groupId>
  <artifactId>jjwt-impl</artifactId>
  <version>0.11.5</version>
  <scope>runtime</scope>
</dependency>
<dependency>
  <groupId>io.jsonwebtoken</groupId>
  <artifactId>jjwt-jackson</artifactId>
  <version>0.11.5</version> <!-- for JSON serialization -->
  <scope>runtime</scope>
</dependency>

// RSA 2048（推薦生產(chǎn)至少 2048）
KeyPairGenerator kpg = KeyPairGenerator.getInstance("RSA");
kpg.initialize(2048);
KeyPair rsaKeyPair = kpg.generateKeyPair();

// Ed25519（更輕更快）
KeyPairGenerator ed = KeyPairGenerator.getInstance("Ed25519");
KeyPair edKeyPair = ed.generateKeyPair();

import io.jsonwebtoken.Jwts;
import io.jsonwebtoken.security.Keys;
import java.time.Instant;
import java.util.Date;
import java.util.Map;

// 使用 RSA 私鑰簽名（RS256）
String token = Jwts.builder()
    .setHeaderParam("kid", "key-2025-08")     // 便于輪換
    .setIssuer("https://auth.example.com")
    .setSubject("user-123")
    .setAudience("api.example.com")
    .setIssuedAt(new Date())
    .setExpiration(Date.from(Instant.now().plusSeconds(900))) // 15 分鐘
    .addClaims(Map.of(
        "roles", new String[]{"ADMIN","USER"},
        "tenantId", "t-1001"
    ))
    .signWith(rsaKeyPair.getPrivate())        // 默認(rèn)按密鑰類型選擇 RS256/ES256/EdDSA
    .compact();

import io.jsonwebtoken.*;

Jws<Claims> jws = Jwts.parserBuilder()
    .requireIssuer("https://auth.example.com")
    .requireAudience("api.example.com")
    .setAllowedClockSkewSeconds(60) // 允許 60s 時(shí)鐘偏差
    .setSigningKey(rsaKeyPair.getPublic())    // 或使用 JWKS 拉取的公鑰
    .build()
    .parseClaimsJws(token);

Claims claims = jws.getBody();
String userId = claims.getSubject();
String[] roles = claims.get("roles", String[].class);

<dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-security</artifactId>
</dependency>
<dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-oauth2-resource-server</artifactId>
</dependency>

server:
  port: 8080

spring:
  security:
    oauth2:
      resourceserver:
        jwt:
          jwk-set-uri: https://auth.example.com/.well-known/jwks.json
          issuer-uri: https://auth.example.com   # 建議同時(shí)配置，做 iss 校驗(yàn)

@Bean
SecurityFilterChain security(HttpSecurity http) throws Exception {
    http
      .csrf(csrf -> csrf.disable()) // 如果前端走 Bearer 頭，可關(guān)；若走 Cookie，需要保留并配置 CSRF
      .authorizeHttpRequests(reg -> reg
          .requestMatchers("/public/**").permitAll()
          .requestMatchers("/admin/**").hasRole("ADMIN")
          .anyRequest().authenticated()
      )
      .oauth2ResourceServer(oauth2 -> oauth2
          .jwt(jwt -> jwt.jwtAuthenticationConverter(jwtAuthConverter()))
      );
    return http.build();
}

// 可選：把自定義 claims 映射為權(quán)限
Converter<Jwt, ? extends AbstractAuthenticationToken> jwtAuthConverter() {
    return jwt -> {
        Collection<GrantedAuthority> authorities = new ArrayList<>();
        List<String> roles = jwt.getClaimAsStringList("roles");
        if (roles != null) {
            roles.forEach(r -> authorities.add(new SimpleGrantedAuthority("ROLE_" + r)));
        }
        return new JwtAuthenticationToken(jwt, authorities, jwt.getSubject());
    };
}

@RestController
public class DemoController {

  @GetMapping("/me")
  public Map<String, Object> me(@AuthenticationPrincipal Jwt jwt) {
    return Map.of(
      "sub", jwt.getSubject(),
      "roles", jwt.getClaimAsStringList("roles"),
      "tenantId", jwt.getClaim("tenantId")
    );
  }

  @GetMapping("/admin/hello")
  public String admin() { return "hello, admin"; }
}

// 假設(shè)你用 Spring Security 自己做用戶名/密碼認(rèn)證
@PostMapping("/auth/login")
public Map<String, String> login(@RequestBody LoginReq req) {
    // 1. 校驗(yàn)用戶名密碼（略）
    // 2. 頒發(fā) Token
    Instant now = Instant.now();
    String access = Jwts.builder()
        .setHeaderParam("kid", "key-2025-08")
        .setIssuer("https://auth.example.com")
        .setSubject("user-" + req.username())
        .setAudience("api.example.com")
        .setIssuedAt(Date.from(now))
        .setExpiration(Date.from(now.plusSeconds(900)))
        .claim("roles", List.of("USER"))
        .signWith(rsaPrivateKey) // 你的私鑰
        .compact();

    String refreshId = UUID.randomUUID().toString(); // 存入數(shù)據(jù)庫，標(biāo)記有效
    String refresh = Jwts.builder()
        .setIssuer("https://auth.example.com")
        .setSubject("user-" + req.username())
        .setId(refreshId)
        .setIssuedAt(Date.from(now))
        .setExpiration(Date.from(now.plusSeconds(30 * 24 * 3600))) // 30 天
        .signWith(rsaPrivateKey)
        .compact();

    // refresh 建議放 HttpOnly Cookie 返回
    return Map.of("access_token", access, "token_type", "Bearer");
}

@PostMapping("/auth/refresh")
public Map<String, String> refresh(@CookieValue("refresh_token") String refreshToken) {
    // 1. 驗(yàn)證 refreshToken 簽名與過期
    Jws<Claims> jws = Jwts.parserBuilder()
        .setSigningKey(rsaPublicKey)
        .build()
        .parseClaimsJws(refreshToken);

    String jti = jws.getBody().getId();
    // 2. 校驗(yàn) jti 是否未吊銷，且未被使用（輪換）
    // 3. 頒發(fā)新 access（并輪換 refresh：生成新 refresh，舊的置為 revoked）

    String newAccess = ...;
    // Set-Cookie: refresh_token=<new>; HttpOnly; Secure; SameSite=Strict
    return Map.of("access_token", newAccess, "token_type", "Bearer");
}

@Component
public class JwtAuthFilter extends OncePerRequestFilter {

  private final PublicKey publicKey;

  public JwtAuthFilter(PublicKey publicKey) { this.publicKey = publicKey; }

  @Override
  protected void doFilterInternal(HttpServletRequest req, HttpServletResponse res, FilterChain chain)
      throws ServletException, IOException {

    String auth = req.getHeader("Authorization");
    if (auth != null && auth.startsWith("Bearer ")) {
      String token = auth.substring(7);
      try {
        Jws<Claims> jws = Jwts.parserBuilder()
            .requireIssuer("https://auth.example.com")
            .requireAudience("api.example.com")
            .setAllowedClockSkewSeconds(60)
            .setSigningKey(publicKey)
            .build()
            .parseClaimsJws(token);

        Claims c = jws.getBody();
        List<GrantedAuthority> auths = new ArrayList<>();
        List<String> roles = c.get("roles", List.class);
        if (roles != null) roles.forEach(r -> auths.add(new SimpleGrantedAuthority("ROLE_" + r)));

        UsernamePasswordAuthenticationToken authentication =
            new UsernamePasswordAuthenticationToken(c.getSubject(), null, auths);

        SecurityContextHolder.getContext().setAuthentication(authentication);
      } catch (JwtException e) {
        res.setStatus(HttpServletResponse.SC_UNAUTHORIZED);
        return;
      }
    }
    chain.doFilter(req, res);
  }
}