How to Catch and Process Workflow Events

Problem

You search for an example how to catch and process workflow events.

Resolution

A Class to catch and handle Workflow Events must implement the Interfaces EventHandler and JobProcessor.

This Class must be a OSGI Service and implement the method process(Event event). In this method the provided object event (Event) can be used to access all event related data.

As soon as this Service is available in the system (for example when you include it in a bundle and install it) the worklow events will be catched and handled with this Class...

Example

Note: The following example is just very simple and not to be used in production as it is.
You have to include the example Class into one of your bundles and mark the package com.day.cq.examples.wf external to make the service available in the system...

package com.day.cq.examples.wf; 
 
import javax.jcr.RepositoryException; 
import javax.jcr.Session; 
 
import org.slf4j.Logger; 
import org.slf4j.LoggerFactory; 
 
import com.day.cq.workflow.WorkflowService; 
import com.day.cq.workflow.WorkflowSession; 
import com.day.cq.workflow.WorkflowException; 
import com.day.cq.workflow.exec.Workflow; 
import com.day.cq.workflow.exec.WorkflowData; 
import com.day.cq.workflow.event.WorkflowEvent; 
 
import org.osgi.service.event.Event; 
import org.osgi.service.event.EventHandler; 
import org.apache.sling.event.EventUtil; 
import org.apache.sling.event.JobProcessor; 
import org.apache.sling.jcr.api.SlingRepository; 
 
/** 
 * <code>WorkFlowTest</code>... 
 * 
 * @scr.component metatype="false" 
 * @scr.service interface="org.osgi.service.event.EventHandler" 
 * @scr.property name="event.topics" refValues.a="com.day.cq.workflow.event.WorkflowEvent.EVENT_TOPIC" 
 */ 
 
public class WorkflowEventCatcher implements EventHandler, JobProcessor { 
 
    protected final Logger log = LoggerFactory.getLogger(WorkflowEventCatcher.class); 
 
    /** 
     * @scr.reference policy="static" 
     */ 
    private WorkflowService workflowService; 
 
    /** 
     * @scr.reference policy="static" 
     */ 
    protected SlingRepository repository; 
 
 
    public void handleEvent(Event event) { 
        EventUtil.processJob(event, this); 
    } 
 
    /** 
     * @return boolean 
     * @see org.apache.sling.event.JobProcessor#process(org.osgi.service.event.Event) 
     */ 
    public boolean process(Event event) { 
        log.info("Received event of topic: " + event.getTopic()); 
 
        if (EventUtil.isLocal(event)) { 
            WorkflowSession wfSession = null; 
            try { 
                wfSession = getWorkflowSession(); 
                String topic = event.getTopic(); 
                if (topic.equals(WorkflowEvent.EVENT_TOPIC)) { 
                    Object eventType = event.getProperty(WorkflowEvent.EVENT_TYPE); 
                    if (eventType.equals(WorkflowEvent.WORKFLOW_STARTED_EVENT)) { 
                        log.info("Workflow has started"); 
                        String instanceId = (String) event.getProperty(WorkflowEvent.WORKFLOW_INSTANCE_ID); 
                        try { 
                            Workflow instance = wfSession.getWorkflow(instanceId); 
                            WorkflowData data = instance.getWorkflowData(); 
                            // additional code comes here 
                            // ... 
                        } catch (WorkflowException we) { 
                            log.warn("Unable to load workflow instance", we); 
                        } 
                    } else if (eventType.equals(WorkflowEvent.WORKFLOW_COMPLETED_EVENT)) { 
                        log.info("Workflow has ended"); 
                    } else if (eventType.equals(WorkflowEvent.NODE_TRANSITION_EVENT)) { 
                        log.info("Workflow in transition"); 
                    } 
                } 
            } 
            catch (Exception e) { 
                log.error(e.getMessage()); 
            } 
            finally { 
                if (wfSession != null) { 
                    wfSession.getSession().logout(); 
                } 
            } 
        } 
        return true; 
    } 
 
    /** 
     * helper to get WorkflowSession 
     * 
     * @return WorkflowSession 
     */ 
    private WorkflowSession getWorkflowSession() { 
        try { 
            Session adminSession = repository.loginAdministrative(null); 
            return workflowService.getWorkflowSession(adminSession); 
        } catch (RepositoryException re) { 
            log.error(re.getMessage()); 
        } 
        return null; 
    } 
} 

Applies to

CQ5.2+