Dynamic Path for ResourceChangeListener

As a authoring environment grows, the paths that a ResourceChangeListener should listen to, might change. They could either:

• become more granular
• become more generic
• apply for only specific AEM instances

A developer can use OSGi configurations to adapt to such changes. This would assure that no code changes are required to deal with the path updates.

Step 1: Create a service that activates only when a configuration node is available in AEM Instance.

@Component(label = "Service Label", immediate = true, metatype = true, policy = ConfigurationPolicy.REQUIRE)
@Service
@Properties(value = { @Property(name = ResourceChangeListener.CHANGES, value = { "CHANGED", "ADDED",
"REMOVED" }, propertyPrivate = true) })
public class SampleServiceImpl implements SampleService, ResourceChangeListener {
....

Step 2: Declare a property  for ‘resource.paths’:

public class SampleServiceImpl implements SampleService, ResourceChangeListener {

// Paths to watch for cache update
@Property(label = "Paths to watch for cache update", value = { PageConstants.DUTY_STATION_FOLDER_PATH,
AssetConstants.FLAG_IMAGE_FOLDER_PATH })
private static final String PATHS_TO_WATCH = ResourceChangeListener.PATHS;
....

Step 3: Create an OSGi configuration for the service with property ‘resource.paths’

Step 4: Deploy your code. Verify that the Listener listens to the updated paths configured via:

• OSGi Configuration node created in Step 3
• Path updates via OSGi Web Console

Here is the sample code using DS annotations

	package blog.techrevel.listeners;
	import java.util.List;
	import org.apache.sling.api.resource.observation.ResourceChange;
	import org.apache.sling.api.resource.observation.ResourceChangeListener;
	import org.osgi.service.component.annotations.Component;
	import org.osgi.service.metatype.annotations.Designate;
	import org.osgi.service.metatype.annotations.ObjectClassDefinition;
	import org.osgi.service.metatype.annotations.AttributeDefinition;
	import org.slf4j.Logger;
	import org.slf4j.LoggerFactory;
	@Component(service = ResourceChangeListener.class, property = { ResourceChangeListener.PATHS + "=" + "/content",
	ResourceChangeListener.CHANGES + "=" + "ADDED", ResourceChangeListener.CHANGES + "=" + "REMOVED",
	ResourceChangeListener.CHANGES + "=" + "CHANGED"
	})
	@Designate(ocd = DynamicPathListener.Config.class)
	public class DynamicPathListener implements ResourceChangeListener {
	public static final Logger LOGGER = LoggerFactory.getLogger(DynamicPathListener.class);
	@ObjectClassDefinition(name = "Dynamic Path Listener Config")
	public @interface Config {
	@AttributeDefinition(name = "Path")
	String resource_paths() default "/content";
	}
	@Override
	public void onChange(List<ResourceChange> changeList) {
	for (ResourceChange change : changeList) {
	LOGGER.info(change.getPath());
	LOGGER.info(change.getType().name());
	}
	}
	}

view raw DynamicPathListener.java hosted with ❤ by GitHub