Unable to trigger replication from custom workflow step

[Vishal_Kagde]

Hey everyone,
I am working on an AEM 6.5.17 and trying to trigger content replication to the publish instance from a custom workflow step. I have injected the Replicator service in my workflow process implementation, but when the step is executed, I am getting a NullPointerException when calling replicator.replicate(...).

Here is a simple code:

public class CustomReplicationStep implements WorkflowProcess {
@reference
private Replicator replicator;

@Override
public void execute(WorkItem workItem, WorkflowSession workflowSession, MetaDataMap args) {
String payloadPath = workItem.getWorkflowData().getPayload().toString();
try {
Session session = workflowSession.adaptTo(Session.class);
replicator.replicate(session, ReplicationActionType.ACTIVATE, payloadPath);
} catch (Exception e) {
log.error("Replication failed", e);
}
}
}

I registered this workflow properly in OSGI, and it appears in the workflow model, but the error suggests the replicator is null. I even tried switching to @inject, but it didn’t help.

Has anyone faced this before? Do I need to handle service injection differently inside workflow steps?

Thanks in advance!

[SantoshSai · Accepted solution]

Hi @Vishal_Kagde,

The problem is that OSGi service injection (like @Reference) does not work if you're instantiating your class manually or it's not registered properly as an OSGi component.

Try the following approach to see if it resolves the issue:

1. Make sure your class is declared as an OSGi component with proper annotations:

   @Component(service = WorkflowProcess.class, 
              property = {"process.label=Custom Replication Step"})
   public class CustomReplicationStep implements WorkflowProcess {
       
       @Reference
       private Replicator replicator;
   
       @Override
       public void execute(WorkItem workItem, WorkflowSession workflowSession, MetaDataMap args) throws WorkflowException {
           try {
               String path = workItem.getWorkflowData().getPayload().toString();
               Session session = workflowSession.adaptTo(Session.class);
               replicator.replicate(session, ReplicationActionType.ACTIVATE, path);
           } catch (Exception e) {
               throw new WorkflowException("Replication failed", e);
           }
       }
   }
   

2. Ensure the bundle is active, and check OSGi console at /system/console/components to confirm your workflow step is registered and active.

3. One last thing worth to check: The session used for replication must have the necessary permissions. Ensure that the service user associated with the workflow has replication rights.

Official Adobe Documentation:

• Replicator API:
  The Replicator interface is part of AEM's API for content replication. You can find its documentation here:
  Replicator Interface - AEM SDK API

• Implementing Custom Workflow Process Steps:
  For guidance on creating custom workflow steps, refer to Adobe's tutorial:
  Implementing Custom Process Step | Adobe Experience Manager

Hope that helps!

[kapil_rajoria]

Hi @Vishal_Kagde ,
For @reference to work, I hope your class is annotated as an OSGI component by using the @component annotation.

@Component(service = WorkflowProcess.class,
           property = {"process.label=Custom Replication Step"})
public class CustomReplicationStep implements WorkflowProcess {

 
After this, If this doesn't work, check if your bundle (http://localhost:4502/system/console/bundles) is active or not and share the snapshot here, if there's any issue.

[AmitVishwakarma]

Hi @Vishal_Kagde ,

Please follow below steps:

Step 1: Use Correct OSGi Annotations and Service Injection

package com.yourcompany.core.workflow;

import com.adobe.granite.workflow.WorkflowException;
import com.adobe.granite.workflow.exec.WorkItem;
import com.adobe.granite.workflow.exec.WorkflowProcess;
import com.adobe.granite.workflow.metadata.MetaDataMap;
import com.day.cq.replication.ReplicationActionType;
import com.day.cq.replication.Replicator;
import org.apache.sling.api.resource.ResourceResolver;
import org.apache.sling.api.resource.ResourceResolverFactory;
import org.osgi.service.component.annotations.Component;
import org.osgi.service.component.annotations.Reference;
import javax.jcr.Session;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.util.HashMap;
import java.util.Map;

@Component(service = WorkflowProcess.class,
           property = {"process.label=Custom Page Replication Step"})
public class CustomReplicationStep implements WorkflowProcess {

    private static final Logger log = LoggerFactory.getLogger(CustomReplicationStep.class);

    @Reference
    private Replicator replicator;

    @Reference
    private ResourceResolverFactory resolverFactory;

    private static final String SERVICE_USER = "workflow-service-user";

    @Override
    public void execute(WorkItem workItem, com.adobe.granite.workflow.exec.WorkflowSession workflowSession, MetaDataMap args) throws WorkflowException {
        String payloadPath = workItem.getWorkflowData().getPayload().toString();
        log.info("Replicating path: {}", payloadPath);

        Map<String, Object> authMap = new HashMap<>();
        authMap.put(ResourceResolverFactory.SUBSERVICE, SERVICE_USER);

        try (ResourceResolver resolver = resolverFactory.getServiceResourceResolver(authMap)) {
            Session session = resolver.adaptTo(Session.class);
            replicator.replicate(session, ReplicationActionType.ACTIVATE, payloadPath);
            log.info("Replication succeeded for path: {}", payloadPath);
        } catch (Exception e) {
            log.error("Replication failed", e);
            throw new WorkflowException("Replication failed for: " + payloadPath, e);
        }
    }
}

Step 2: Create a Service User Mapping

Go to /system/console/configMgr

Search: Apache Sling Service User Mapper Service Amendment

Add entry:

com.yourcompany.core.workflow:workflow-service-user=replication-service

Step 3: Create Service User and Assign Permissions

Go to Useradmin (/useradmin)

Create system user: replication-service

Assign /content and replication rights:

  - jcr:read

  - replicate

  - replicate:Activate

Look in error.log for:

Replicating path: /content/yourpage
Replication succeeded for path: /content/yourpage

Regards,
Amit

[rahulp76079001]

It seems your session is not having replication permission for the particular resource you are trying to replicate.