Java JWT Token Üretme Utility

import io.jsonwebtoken.*;
import io.jsonwebtoken.io.Decoders;
import io.jsonwebtoken.security.Keys;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.security.core.GrantedAuthority;
import org.springframework.security.core.userdetails.UserDetails;
import org.springframework.stereotype.Component;

import javax.crypto.SecretKey;
import java.util.*;
import java.util.function.Function;

@Component
public class JwtUtil {

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

    @Value("${jwt.access-token-expiration:900000}")  // 15 dakika
    private long accessTokenExpiration;

    @Value("${jwt.refresh-token-expiration:604800000}")  // 7 gün
    private long refreshTokenExpiration;

    // Access token üret
    public String generateAccessToken(UserDetails userDetails) {
        Map<String, Object> claims = new HashMap<>();
        claims.put("roles", userDetails.getAuthorities().stream()
            .map(GrantedAuthority::getAuthority)
            .toList());
        return buildToken(claims, userDetails.getUsername(), accessTokenExpiration);
    }

    // Refresh token üret
    public String generateRefreshToken(UserDetails userDetails) {
        return buildToken(new HashMap<>(), userDetails.getUsername(), refreshTokenExpiration);
    }

    // Token oluştur
    private String buildToken(Map<String, Object> claims, String subject, long expiration) {
        return Jwts.builder()
            .claims(claims)
            .subject(subject)
            .issuedAt(new Date())
            .expiration(new Date(System.currentTimeMillis() + expiration))
            .signWith(getSigningKey())
            .compact();
    }

    // Token'dan username çıkar
    public String extractUsername(String token) {
        return extractClaim(token, Claims::getSubject);
    }

    // Token geçerli mi?
    public boolean isTokenValid(String token, UserDetails userDetails) {
        final String username = extractUsername(token);
        return username.equals(userDetails.getUsername()) && !isTokenExpired(token);
    }

    // Token süresi dolmuş mu?
    private boolean isTokenExpired(String token) {
        return extractClaim(token, Claims::getExpiration).before(new Date());
    }

    // Belirli bir claim çıkar
    private <T> T extractClaim(String token, Function<Claims, T> resolver) {
        final Claims claims = Jwts.parser()
            .verifyWith(getSigningKey())
            .build()
            .parseSignedClaims(token)
            .getPayload();
        return resolver.apply(claims);
    }

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