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LyonMartin
Level 3
March 18, 2025
Solved

Implementing EventHandler leads to inconsistent behaviour

  • March 18, 2025
  • 3 replies
  • 546 views

Hi, I would like to ask if anyone encountered similar issues regarding to EventsHandler, particularly Page Event Topic. We've added this on top of the EventHandler that we created:

@Component(service = EventHandler.class, immediate = true, configurationPolicy = ConfigurationPolicy.OPTIONAL, property = {
       "event.topics=" + PageEvent.EVENT_TOPIC })

and added 

@Override
public void handleEvent(Event event) {}


The issue here is that, the override handleEvent didn't seem to run even if we trigger a page modification or page creation event. What else we could check for this? Thanks!

Best answer by arunpatidar

Hi @lyonmartin 

can you try with below topics for page(jcr:content) type

EventConstants.EVENT_TOPIC + "=org/apache/sling/api/resource/Resource/ADDED",
EventConstants.EVENT_TOPIC + "=org/apache/sling/api/resource/Resource/CHANGED",

 

https://github.com/arunpatidar02/aem63app-repo/blob/master/java/TestEventHandler.java 

3 replies

arunpatidar
Community Advisor
arunpatidarCommunity AdvisorAccepted solution
Community Advisor
March 18, 2025

Hi @lyonmartin 

can you try with below topics for page(jcr:content) type

EventConstants.EVENT_TOPIC + "=org/apache/sling/api/resource/Resource/ADDED",
EventConstants.EVENT_TOPIC + "=org/apache/sling/api/resource/Resource/CHANGED",

 

https://github.com/arunpatidar02/aem63app-repo/blob/master/java/TestEventHandler.java 

Arun Patidar
    konstantyn_diachenko
    Community Advisor
    konstantyn_diachenkoCommunity Advisor
    Community Advisor
    March 18, 2025

    Hi @lyonmartin ,

     

    I would suggest to consider using org.apache.sling.api.resource.observation.ResourceChangeListener.

     

    Example: https://experienceleaguecommunities.adobe.com/t5/adobe-experience-manager/resourcechangelistener/td-p/670848

     

    Best regards,

    Kostiantyn Diachenko.

    Kostiantyn Diachenko, Community Advisor, Certified Senior AEM Developer, creator of free AEM VLT Tool, maintainer of AEM Tools plugin.
      AmitVishwakarma
      Community Advisor
      AmitVishwakarmaCommunity Advisor
      Community Advisor
      March 18, 2025

      Hi @lyonmartin ,

      This is a common issue when working with AEM EventHandlers and listening to Page Events via PageEvent.EVENT_TOPIC. Here’s a breakdown of why your handleEvent() may not be triggered and how to fix it.


      Root Causes & Solutions

      1. PageEvent.EVENT_TOPIC Might Not Be Triggered as Expected

      You're listening to:

      "event.topics=" + PageEvent.EVENT_TOPIC

      which resolves to:

      com/day/cq/wcm/core/page

      However, AEM doesn’t always trigger this topic for all page modifications/creations. It’s often used for specific programmatic page events, not low-level JCR events.

      What You Can Check or Do:

      A. Ensure Event Admin is Working

      Confirm in /system/console/bundles that Apache Sling Event and EventAdmin bundles are active.
      Check logs (error.log) for any activation issues with your handler.

       

      B. Add Logging in handleEvent() for Confirmation

      Add logs to see if it’s triggered at all:

      @Override public void handleEvent(Event event) { System.out.println("Event received: " + event.getTopic()); }

      C. Alternative Approach: Use Sling Resource Events

      Try listening to Sling resource-level events which are more reliable for content changes.

      @Component(service = EventHandler.class, immediate = true, property = { EventConstants.EVENT_TOPIC + "=org/apache/sling/api/resource/Resource/ADDED", EventConstants.EVENT_TOPIC + "=org/apache/sling/api/resource/Resource/CHANGED" }) public class ResourceEventHandler implements EventHandler { @Override public void handleEvent(Event event) { System.out.println("Resource Event: " + event.getTopic()); } }

      D. Preferred Solution: Use ResourceChangeListener

      Adobe recommends this modern approach:

      @Component(service = ResourceChangeListener.class, immediate = true, property = { ResourceChangeListener.PATHS + "=/content", ResourceChangeListener.CHANGES + "=ADDED", ResourceChangeListener.CHANGES + "=CHANGED", ResourceChangeListener.CHANGES + "=REMOVED" }) public class PageChangeListener implements ResourceChangeListener { @Override public void onChange(List<ResourceChange> changes) { for (ResourceChange change : changes) { System.out.println("Change detected: " + change.getPath()); } } }

       
      Regards,
      Amit Vishwakarma

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