fix #43: Prevent ClassCastExceptions after plugin gets reloaded in a …

…cluster

This plugin caches instances of classes that are defined in the code of the plugin. This causes ClassCastExceptions, when the plugin gets unloaded (removing the class definitions) and updated/reloaded (replacing the class definitions). The cached values at that time will refer to classes that no longer exist, causing the exceptions.

https://igniterealtime.atlassian.net/browse/OF-2239 introduces a new type of Cache to work around this problem, the org.jivesoftware.util.cache.SerializingCache which is available since Openfire 4.7.0. This implementation does not cache the instance directly, but caches a serialized version instead. This way, there no longer is a reference to the class, which means that any (compatible) future class definition can be used to instantiate the cache entry again.

changelog.html

@@ -44,6 +44,7 @@ <h1>HTTP File Upload Plugin Changelog</h1>
 <p><b>1.4.1</b> -- (tbd)</p>
 <ul>
     <li>Updated Ukrainian (uk_UA) translation, by Vladislav Savchuk (Bruhmozavr)</li>
+    <li><a href="https://github.com/igniterealtime/openfire-httpFileUpload-plugin/issues/43">Issue #43:</a> ClassCastExceptions after reloading plugin in a cluster.</li>
 </ul>
 
 <p><b>1.4.0</b> -- (January 19, 2024)</p>

src/java/org/igniterealtime/openfire/plugins/httpfileupload/OpenfireSlotProvider.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017-2022 Ignite Realtime Foundation. All rights reserved.
+ * Copyright (c) 2017-2024 Ignite Realtime Foundation. All rights reserved.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -19,8 +19,8 @@
 import nl.goodbytes.xmpp.xep0363.Slot;
 import nl.goodbytes.xmpp.xep0363.SlotProvider;
 import org.jivesoftware.util.JiveGlobals;
-import org.jivesoftware.util.cache.Cache;
 import org.jivesoftware.util.cache.CacheFactory;
+import org.jivesoftware.util.cache.SerializingCache;
 
 import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
@@ -29,10 +29,10 @@
 
 public class OpenfireSlotProvider implements SlotProvider
 {
-    private final Cache<SecureUniqueId, Slot> slotsCache;
+    private final SerializingCache<SecureUniqueId, Slot> slotsCache;
 
     public OpenfireSlotProvider() {
-        slotsCache = CacheFactory.createCache("HTTP File Upload Slots");
+        slotsCache = CacheFactory.createSerializingCache("HTTP File Upload Slots", SecureUniqueId.class, Slot.class);
 
         // Unless there is specific configuration for this cache, default the max lifetime of entries in this cache to something that's fairly short.
         if (null == JiveGlobals.getProperty("cache." + slotsCache.getName().replaceAll(" ", "") + ".maxLifetime")) {