How to Manage Events in SlingPage edited by Jean-Christophe KAUTZMANNChanges (2)
Full ContentApache Sling provides some mechanisms and support for managing events. This page describes ... Sling makes a distinction between 2 types of events:
The event mechanism is leveraging the OSGi Event Admin Specification (OSGi Compendium 113).
You can learn more in the Eventing, Jobs and Scheduling section (http://sling.apache.org/site/eventing-and-jobs.html). To get started with the Sling eventing API, you will implement here a service that listens to files posted to /tmp/dropbox and moves them to the appropriate locations depending on the mime-type:
To do that, you will implement 2 services. The first one, called OsgiDropBoxService:
Listening to OSGI EventsTo listen to the specific osgi event resource added:
To get a list of possible events available in Sling (resource added, removed or changed), refer to the org.apache.sling.api.SlingConstants class in the Javadocs. Sending Job EventsTo send a job event:
The first part of the code looks as follows: /** * The <code>OsgiDropBoxService</code> is listening content added to /tmp/dropbox by using OSGI events * * @scr.component immediate="true" * @scr.service interface="org.osgi.service.event.EventHandler" * @scr.property name="event.topics" valueRef="org.apache.sling.api.SlingConstants.TOPIC_RESOURCE_ADDED" */ public class OsgiDropBoxService implements JobProcessor, EventHandler {
public boolean process(Event event) { String propPath = (String) event.getProperty(SlingConstants.PROPERTY_PATH); String propResType = (String) event.getProperty(SlingConstants.PROPERTY_RESOURCE_TYPE); // an event is sent if a file is added to /tmp/dropbox if (propPath.startsWith("/tmp/dropbox") && propResType.equals("nt:file")) { final Dictionary<String, Object> props = new Hashtable<String, Object>(); props.put(EventUtil.PROPERTY_JOB_TOPIC, JOB_TOPIC); props.put("resourcePath", propPath); Event dropboxJobEvent = new Event(EventUtil.TOPIC_JOB, props); eventAdmin.sendEvent(dropboxJobEvent); log.info("the dropbox job has been sent: {}", propPath); } return true; } The whole service looks now as follows: Now that you have a service that sends job events whenever a file is uploaded to /tmp/dropbox, you will create the service DropBoxEventHandler that listens to those job events and moves the files to a location corresponding to their mime-types. Listening to Job EventsTo listen to the job events that have been defined before:
To move the files:
The first part of the code looks as follows: /** * @scr.component immediate="true" * @scr.service interface="org.osgi.service.event.EventHandler" * @scr.property name="event.topics" valueRef="com.jck.sling.eventing.osgi.OsgiDropBoxService.JOB_TOPIC" */ public class DropBoxEventHandler implements JobProcessor, EventHandler { Several class fields are defined:
/** Default log. */ protected final Logger log = LoggerFactory.getLogger(this.getClass()); private Session adminSession; /** @scr.reference */ private SlingRepository repository; /** * @scr.reference */ private JcrResourceResolverFactory resolverFactory; private final static String IMAGES_PATH = "/dropbox/images/"; private final static String MUSIC_PATH = "/dropbox/music/"; private final static String MOVIES_PATH = "/dropbox/movies/"; private final static String OTHER_PATH = "/dropbox/other/"; Handling Job EventsThe org.osgi.service.event.EventHandler#handleEvent(Event event) method needs to be implemented: public void handleEvent(Event event) { if (EventUtil.isLocal(event)) { EventUtil.processJob(event, this); } } The org.apache.sling.event.JobProcessor#process(Event event) method needs to be implemented.
public boolean process(Event event) { try { String resourcePath = (String) event.getProperty("resourcePath"); String resourceName = resourcePath.substring(resourcePath.lastIndexOf("/") + 1); adminSession = repository.loginAdministrative(null); ResourceResolver resourceResolver = resolverFactory.getResourceResolver(adminSession); Resource res = resourceResolver.getResource(resourcePath); if (ResourceUtil.isA(res, "nt:file")) { String mimeType = res.getResourceMetadata().getContentType(); String destDir; if (mimeType.equals("image/png")) { destDir = IMAGES_PATH; } else if (mimeType.equals("audio/mpeg")) { destDir = MUSIC_PATH; } else if (mimeType.equals("video/x-msvideo")) { destDir = MOVIES_PATH; } else { destDir = OTHER_PATH; } adminSession.move(resourcePath, destDir + resourceName); adminSession.save(); log.info("The file {} has been moved to {}", resourceName, destDir); } return true; } catch (RepositoryException e) { log.error("RepositoryException: " + e); return false; } finally { if (adminSession != null && adminSession.isLive()) { adminSession.logout(); adminSession = null; } } } The complete code for the service looks as follows:
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