Defining System Events for Deletions

Enabling Staging and Export/Import
Step 6 of 7

The Staging framework tracks entity modifications in a few different ways. Actions like adding a guestbook or editing an entry are tracked automatically by the framework with the configuration of staged models and their data handlers. Entity deletions are handled slightly differently using system events.

For the Guestbook app, you must define system events for entity deletions so they’re appropriately tracked by the Staging framework. If Staging can’t track your entity deletions, they can’t be managed on the staged Site, which means you can only delete entities from the live Site.

You must define your system events in your local services.

1. Open the guestbook-service module’s com.liferay.docs.guestbook.service.impl.GuestbookLocalServiceImpl class and add the following deleteGuestbook methods. These override the default Service Builder generated methods the application has been using:

   @Indexable(type = IndexableType.DELETE)
   @Override
   public Guestbook deleteGuestbook(long guestbookId)
       throws PortalException {
   
       Guestbook guestbook =
           guestbookPersistence.findByPrimaryKey(guestbookId);
   
       return guestbookLocalService.deleteGuestbook(guestbook);
   }
   
   @Indexable(type = IndexableType.DELETE)
   @Override
   @SystemEvent(type = SystemEventConstants.TYPE_DELETE)
   public Guestbook deleteGuestbook(Guestbook guestbook) {
   
       return guestbookPersistence.remove(guestbook);
   }
   

   These methods override the GuestbookLocalServiceBaseImpl’s deleteGuestbook methods. The major addition is the @SystemEvent annotation added to the deleteGuestbook(Guestbook) method. This notifies the Staging framework that a deletion system event occurs when the method is called.

   The deleteGuestbook(long) method is rerouted to call the SystemEvent tracked method, so all deletions are accounted for.

2. Ensure that the remaining deleteGuestbook method triggers the system event. Within the deleteGuestbook(long, ServiceContext) method, change

   guestbook = deleteGuestbook(guestbook);
   

   to this

   guestbook = guestbookLocalService.deleteGuestbook(guestbook);
   

   Now all guestbook deletions are tracked via SystemEvent.

3. Add the import packages for the new SystemEvent annotation ([CTRL]+[SHIFT]+O) and then save the file.

4. You must apply the deletion system event to both entities. Open the com.liferay.docs.guestbook.service.impl.EntryLocalServiceImpl class and add similar delete methods:

   @Indexable(type = IndexableType.DELETE)
   @Override
   public Entry deleteEntry(long entryId)
       throws PortalException {
   
       Entry entry = entryPersistence.findByPrimaryKey(entryId);
   
       return entryLocalService.deleteEntry(entry);
   }
   
   @Indexable(type = IndexableType.DELETE)
   @Override
   @SystemEvent(type = SystemEventConstants.TYPE_DELETE)
   public Entry deleteEntry(Entry entry) {
   
       return entryPersistence.remove(entry);
   }
   

   This is the same logic as before, except the delete system event is now applied for the entry.

5. Make sure the remaining deleteEntry method triggers the system event. Within the deleteEntry(long, ServiceContext) method, change

   entry = deleteEntry(entryId);
   

   to this

   entry = entryLocalService.deleteEntry(entry);
   

   Now all entry deletions are tracked via SystemEvent.

6. Add the import packages for the new SystemEvent annotation ([CTRL]+[SHIFT]+O) and then save the file.

7. Run Service Builder by navigating to the Gradle Tasks pane on the right side of Developer Studio and selecting your project’s build → buildService task.

Your Guestbook app’s deletions are now properly tracked by the Staging framework.