Fixed exception in caching mechanism, if no user was logged in.

src/Services/UserCacheKeyGenerator.php

@@ -0,0 +1,73 @@
+<?php
+/**
+ *
+ * part-db version 0.1
+ * Copyright (C) 2005 Christoph Lechner
+ * http://www.cl-projects.de/
+ *
+ * part-db version 0.2+
+ * Copyright (C) 2009 K. Jacobs and others (see authors.php)
+ * http://code.google.com/p/part-db/
+ *
+ * Part-DB Version 0.4+
+ * Copyright (C) 2016 - 2019 Jan Böhmer
+ * https://github.com/jbtronics
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA
+ *
+ */
+
+namespace App\Services;
+
+
+use App\Entity\UserSystem\User;
+use Symfony\Component\Security\Core\Security;
+
+/**
+ * Purpose of this service is to generate a key unique for a user, to use in Cache keys and tags.
+ * @package App\Services
+ */
+class UserCacheKeyGenerator
+{
+    protected $security;
+
+    public function __construct(Security $security)
+    {
+        $this->security = $security;
+    }
+
+    /**
+     * Generates a key for the given user.
+     * @param User|null $user The user for which the key should be generated. When set to null, the currently logged in
+     * user is used.
+     * @return string
+     */
+    public function generateKey(User $user = null) : string
+    {
+        //If no user was specified, use the currently used one.
+        if ($user === null) {
+            $user = $this->security->getUser();
+        }
+
+        //If the user is null, then treat it as anonymous user.
+        //When the anonymous user is passed as user then use this path too.
+        if ($user === null || $user->getID() === User::ID_ANONYMOUS) {
+            return 'user$_' . User::ID_ANONYMOUS;
+        }
+
+        //In the most cases we can just use the username (its unique)
+        return "user_" . $user->getUsername();
+    }
+}