SAK-52117 Forums avoid stale id link issue (sakaiproject#14216)

Co-authored-by: Sakai Developer <[email protected]>

Author: ottenhoff

msgcntr/messageforums-app/src/java/org/sakaiproject/tool/messageforums/DiscussionForumTool.java

@@ -1016,7 +1016,9 @@ public String processActionDisplayForum()
     forumClickCount++;
     if (getDecoratedForum() == null)
     {
-      log.error("Forum not found");
+      log.warn("Forum not found for id {}", getExternalParameterByKey(FORUM_ID));
+      // Clear cached state so main view rebuilds after import/replace
+      reset();
       return gotoMain();
     }
     return FORUM_DETAILS;
@@ -3798,6 +3800,12 @@ private Boolean resetTopicById(String externalTopicId)
 	        {
 	          Long.parseLong(topicId);
 	          topic = forumManager.getTopicById(Long.valueOf(topicId));
+	          if (topic == null) {
+	            // Topic was not found, likely due to an import/replace or deletion.
+	            log.warn("Topic with id '{}' not found", topicId);
+	            setErrorMessage(getResourceBundleString(TOPIC_WITH_ID) + topicId + getResourceBundleString(NOT_FOUND_WITH_QUOTE));
+	            return false;
+	          }
 	        }
 	        catch (NumberFormatException e)
 	        {
@@ -3841,9 +3849,11 @@ private String displayTopicById(String externalTopicId)
         Event event = eventTrackingService.newEvent(DiscussionForumService.EVENT_FORUMS_TOPIC_READ, getEventReference(selectedTopic.getTopic()), null, true, NotificationService.NOTI_OPTIONAL, statement);
         eventTrackingService.post(event);
 
-    	return ALL_MESSAGES;
+        return ALL_MESSAGES;
     } else {
-    	return gotoMain();
+        // Clear cached state so main view rebuilds after import/replace
+        reset();
+        return gotoMain();
     }
   }
 
@@ -3853,6 +3863,8 @@ private void reset()
     this.selectedForum = null;
     this.selectedTopic = null;
     this.selectedMessage = null;
+    this.selectedThreadHead = null;
+    this.selectedThread = new ArrayList();
 //    this.templateControlPermissions = null;
 //    this.templateMessagePermissions = null;
     this.permissions=null;

msgcntr/messageforums-component-impl/src/java/org/sakaiproject/component/app/messageforums/MessageForumsForumManagerImpl.java

@@ -614,7 +614,8 @@ public Topic getTopicById(final boolean open, final Long topicId) {
         HibernateCallback<Topic> hcb = session -> {
             Query q = session.getNamedQuery(QUERY_BY_TOPIC_ID);
             q.setParameter("id", topicId, LongType.INSTANCE);
-            return (Topic) q.getSingleResult();
+            // Use uniqueResult() so missing topics return null instead of throwing NoResultException.
+            return (Topic) q.uniqueResult();
         };
 
         Topic topic = (Topic) Hibernate.unproxy(getHibernateTemplate().execute(hcb));