Implement token blacklist for JWT logout support

- TokenBlacklistService tracks invalidated tokens using Caffeine cache.
- AuthController adds tokens to blacklist on logout.
- JwtAuthenticationFilter blocks blacklisted tokens during authentication.

src/main/java/com/skycrate/backend/skycrateBackend/controller/AuthController.java

@@ -4,6 +4,9 @@ import com.skycrate.backend.skycrateBackend.dto.LoginRequest;
 import com.skycrate.backend.skycrateBackend.security.JwtService;
 import com.skycrate.backend.skycrateBackend.entity.User;
 import com.skycrate.backend.skycrateBackend.repository.UserRepository;
+import com.skycrate.backend.skycrateBackend.security.TokenBlacklistService;
+import jakarta.servlet.http.HttpServletRequest;
+import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.http.ResponseEntity;
 import org.springframework.security.authentication.AuthenticationManager;
 import org.springframework.security.authentication.UsernamePasswordAuthenticationToken;
@@ -48,9 +51,19 @@ public class AuthController {
         return ResponseEntity.ok().body(token);
     }
 
+    @Autowired
+    private TokenBlacklistService tokenBlacklistService;
+
     @PostMapping("/logout")
-    public ResponseEntity<?> logout() {
-        // Client-side token deletion (or implement blacklist)
-        return ResponseEntity.ok("Logged out (client should delete token)");
+    public ResponseEntity<?> logout(HttpServletRequest request) {
+        String authHeader = request.getHeader("Authorization");
+        if (authHeader == null || !authHeader.startsWith("Bearer ")) {
+            return ResponseEntity.badRequest().body("Missing or invalid Authorization header");
+        }
+
+        String token = authHeader.substring(7);
+        tokenBlacklistService.blacklistToken(token);
+
+        return ResponseEntity.ok("Logged out successfully");
     }
 }

src/main/java/com/skycrate/backend/skycrateBackend/security/JwtAuthenticationFilter.java

@@ -20,10 +20,14 @@ public class JwtAuthenticationFilter extends OncePerRequestFilter {
 
     private final JwtService jwtService;
     private final UserRepository userRepository;
+    private final TokenBlacklistService tokenBlacklistService;
 
-    public JwtAuthenticationFilter(JwtService jwtService, UserRepository userRepository) {
+    public JwtAuthenticationFilter(JwtService jwtService,
+                                   UserRepository userRepository,
+                                   TokenBlacklistService tokenBlacklistService) {
         this.jwtService = jwtService;
         this.userRepository = userRepository;
+        this.tokenBlacklistService = tokenBlacklistService;
     }
 
     @Override
@@ -42,6 +46,14 @@ public class JwtAuthenticationFilter extends OncePerRequestFilter {
         }
 
         jwt = authHeader.substring(7);
+
+        // Check if token is blacklisted
+        if (tokenBlacklistService.isTokenBlacklisted(jwt)) {
+            response.setStatus(HttpServletResponse.SC_UNAUTHORIZED);
+            response.getWriter().write("Token has been blacklisted");
+            return;
+        }
+
         try {
             userEmail = jwtService.extractUsername(jwt);
         } catch (Exception e) {

src/main/java/com/skycrate/backend/skycrateBackend/security/TokenBlacklistService.java

@@ -0,0 +1,27 @@
+package com.skycrate.backend.skycrateBackend.security;
+
+import com.github.benmanes.caffeine.cache.Cache;
+import com.github.benmanes.caffeine.cache.Caffeine;
+import org.springframework.stereotype.Service;
+
+import java.util.concurrent.TimeUnit;
+
+@Service
+public class TokenBlacklistService {
+
+    private final Cache<String, Boolean> blacklistCache;
+
+    public TokenBlacklistService() {
+        this.blacklistCache = Caffeine.newBuilder()
+                .expireAfterWrite(1, TimeUnit.HOURS)
+                .build();
+    }
+
+    public void blacklistToken(String token) {
+        blacklistCache.put(token, true);
+    }
+
+    public boolean isTokenBlacklisted(String token) {
+        return blacklistCache.getIfPresent(token) != null;
+    }
+}