- Added extractSubject() and getClaimValue() methods

- Updated token generator to use User object instead of username

src/main/java/de/w665/sharepulse/service/AuthenticationService.java

@@ -46,19 +46,20 @@ public class AuthenticationService {
         }
         Optional<User> user = userRepository.retrieveUserByUsername(username);
         if (user.isPresent() && passwordEncoder.matches(password, user.get().getPassword())) {
-            return generateToken(username);
+            return generateToken(user.get());
         }
         return null;
     }
 
-    private String generateToken(String username) {
+    private String generateToken(User username) {
         long nowMillis = System.currentTimeMillis();
         Date now = new Date(nowMillis);
         Date expiryDate = new Date(nowMillis + expirationTime);
 
         return Jwts.builder()
-                .subject(username)
+                .subject(username.getUsername())
                 .issuedAt(now)
+                .claim("role", username.getRole())
                 .expiration(expiryDate)
                 .signWith(secretKey)
                 .compact();
@@ -73,4 +74,28 @@ public class AuthenticationService {
             return false;
         }
     }
+
+    public String extractSubject(String token) {
+        return Jwts.parser().verifyWith(secretKey).build().parseSignedClaims(token).getPayload().getSubject();
+    }
+
+    /**
+     * Retrieves a typed claim from the JWT.
+     * @param token the JWT from which to extract the claim
+     * @param claimName the name of the claim to retrieve
+     * @param claimType the Class object of the type T of the claim
+     * @param <T> the expected type of the claim value
+     * @return the value of the specified claim as type T, or null if not found or in case of an error
+     * Usage example: getClaimValue(token, "role", String.class)
+     */
+    public <T> T getClaimValue(String token, String claimName, Class<T> claimType) {
+        try {
+            Jwt<?, ?> jwt = Jwts.parser().verifyWith(secretKey).build().parseSignedClaims(token);
+            Claims claims = (Claims) jwt.getPayload();
+            return claims.get(claimName, claimType);
+        } catch (Exception e) {
+            log.error("Error parsing claims from token: ", e);
+            return null;
+        }
+    }
 }