JwtUtil.java

package com.aleprimo.Booking_System_App.security;

import io.jsonwebtoken.Claims;
import io.jsonwebtoken.Jwts;
import io.jsonwebtoken.SignatureAlgorithm;
import io.jsonwebtoken.security.Keys;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;

import java.security.Key;
import java.util.Base64;
import java.util.Date;
import java.util.function.Function;

@Component
public class JwtUtil {


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

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

    private Key getSigningKey() {
        byte[] keyBytes = Base64.getDecoder().decode(secret);
        return Keys.hmacShaKeyFor(keyBytes);
    }


    public String generateToken(String email) {
        return Jwts.builder()
                .setSubject(email)
                .setIssuedAt(new Date())
                .setExpiration(new Date(System.currentTimeMillis() + jwtExpirationMs))
                .signWith(getSigningKey(), SignatureAlgorithm.HS512)
                .compact();
    }


    public String extractUsername(String token) {
        return extractClaim(token, Claims::getSubject);
    }


    public boolean validateToken(String token, String userEmail) {
        final String username = extractUsername(token);
        return (username.equals(userEmail) && !isTokenExpired(token));
    }


    private boolean isTokenExpired(String token) {
        return extractExpiration(token).before(new Date());
    }

    private Date extractExpiration(String token) {
        return extractClaim(token, Claims::getExpiration);
    }

    private <T> T extractClaim(String token, Function<Claims, T> claimsResolver) {
        final Claims claims = extractAllClaims(token);
        return claimsResolver.apply(claims);
    }

    Claims extractAllClaims(String token) {
        return Jwts.parserBuilder()
                .setSigningKey(getSigningKey())
                .build()
                .parseClaimsJws(token)
                .getBody();
    }
}