JwtService.java

package com.codecool.bytebattlers.config;

import io.jsonwebtoken.Claims;
import io.jsonwebtoken.Jwts;
import io.jsonwebtoken.io.Decoders;
import io.jsonwebtoken.security.Keys;
import org.springframework.security.core.userdetails.UserDetails;
import org.springframework.stereotype.Service;

import javax.crypto.SecretKey;
import java.util.Date;
import java.util.HashMap;
import java.util.Map;
import java.util.UUID;
import java.util.function.Function;

@Service
public class JwtService {
    private static final String SECRET_KEY = System.getenv("SECRET_KEY");

    private static final long ONE_DAY_EXPIRATION_DATE_IN_MILLISECONDS = 86400000;

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

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

    public String generateToken(UserDetails userDetails, UUID pubID, String name) {
        return generateToken(new HashMap<>(), userDetails, pubID, name);
    }


    public String generateToken(
            Map<String, Object> extraClaims,
            UserDetails userDetails, UUID pubID, String name
    ) {

        extraClaims.put("role", userDetails.getAuthorities());
        extraClaims.put("name",pubID);
        extraClaims.put("user_name", name);
        return Jwts.builder()
                .claims()
                .add(extraClaims)                .subject(userDetails.getUsername())
                .issuedAt(new Date(System.currentTimeMillis()))
                .expiration(new Date(System.currentTimeMillis() + ONE_DAY_EXPIRATION_DATE_IN_MILLISECONDS))
                .and()
                .signWith(getSignInKey())
                .compact();
    }

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

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

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

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

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