import org.opendaylight.yangtools.yang.binding.Notification;
/**
- * Interface implemented by objects interested in some sort of Notification. This
- * class acts as a base interface for specific listeners which usually are a type
+ * Interface for a generic listener that is interested in receiving YANG modeled notifications.
+ * This interface acts as a base interface for specific listeners which usually are a type
* capture of this interface.
*
- * @param <T> Notification type
+ * @param <T> the interested notification type
*/
public interface NotificationListener<T extends Notification> extends EventListener {
/**
- * Invoked to deliver the notification. Note that this method may be invoked
- * from a shared thread pool, so implementations SHOULD NOT perform CPU-intensive
- * operations and they definitely MUST NOT invoke any potentially blocking
- * operations.
+ * Invoked to deliver a notification.
+ * <p>
+ * Note that this method may be invoked from a shared thread pool, so implementations SHOULD NOT
+ * perform CPU-intensive operations and MUST NOT invoke any potentially blocking operations.
*
- * @param notification Notification being delivered.
+ * @param notification the notification.
*/
void onNotification(T notification);
}
import org.opendaylight.yangtools.concepts.ListenerRegistration;
import org.opendaylight.yangtools.yang.binding.Notification;
+/**
+ * Interface for a notification service that provides publish/subscribe capabilities for YANG
+ * modeled notifications. This interface is a combination of the {@link NotificationService} and
+ * {@link NotificationPublishService} interfaces.
+ */
public interface NotificationProviderService extends NotificationService, NotificationPublishService<Notification> {
+
/**
- * Publishes a notification.
- *
- * @param Notification
- * notification to publish.
- *
+ * {@inheritDoc}
*/
@Override
- void publish(Notification notification);
+ public void publish(Notification notification);
/**
- * Publishes a notification, listener calls are done in provided executor.
- *
+ * {@inheritDoc}
*/
@Override
- void publish(Notification notification, ExecutorService service);
+ void publish(Notification notification, ExecutorService executor);
+ /**
+ * Registers a listener to be notified about notification subscriptions. This
+ * enables a component to know when there is a notification listener subscribed
+ * for a particular notification type.
+ * <p>
+ * On registration of this listener, the
+ * {@link NotificationInterestListener#onNotificationSubscribtion(Class)} method
+ * will be invoked for every notification type that currently has a notification listener
+ * subscribed.
+ *
+ * @param interestListener the listener that will be notified when subscriptions
+ * for new notification types occur.
+ * @return a {@link ListenerRegistration} instance that should be used to unregister the listener
+ * by invoking the {@link ListenerRegistration#close()} method when no longer needed.
+ */
ListenerRegistration<NotificationInterestListener> registerInterestListener(
NotificationInterestListener interestListener);
+ /**
+ * Interface for a listener interested in being notified about notification subscriptions.
+ */
public interface NotificationInterestListener extends EventListener {
+ /**
+ * Callback that is invoked when a notification listener subscribes for a
+ * particular notification type.
+ * <p>
+ * This method is only called for the first subscription that occurs for a
+ * particular notification type. Subsequent subscriptions for the same
+ * notification type do not trigger invocation of this method.
+ * <p>
+ * <b>Note:</b>This callback is delivered from thread not owned by this listener,
+ * all processing should be as fast as possible and implementations should
+ * not do any blocking calls or block this thread.
+ *
+ * @param notificationType the notification type for the subscription that occurred.
+ */
void onNotificationSubscribtion(Class<? extends Notification> notificationType);
}
}
import org.opendaylight.yangtools.concepts.ListenerRegistration;
import org.opendaylight.yangtools.yang.binding.Notification;
+/**
+ * Notification broker which allows clients to subscribe for and publish YANG-modeled notifications.
+ *
+ *<p>
+ * Two styles of listeners are supported:
+ * <ul>
+ * <li>Generic listener</li>
+ * <li>Dispatch listener - listener, which implements <code>{ModelName}Listener</code> interface,
+ * which has dispatch methods for each defined notification. Methods are invoked based on notification type (class).
+ * </li>
+ *
+ * <h3>Generic Listener</h3>
+ * <p>
+ * A generic listener implements the {@link NotificationListener} interface which has one callback method
+ * <code>onNotification</code> that is invoked for any notification type the listener is subscribed to.
+ * <p>
+ * A generic listener is subscribed using the {@link #registerNotificationListener(Class, NotificationListener)}
+ * method by which you specify the type of notification to receive. A generic listener may be registered for
+ * multiple notification types via multiple subscriptions.
+ * <p>
+ * Generic listeners allow for a more flexible approach, allowing you to subscribe for just
+ * one type of notification from a YANG model. You could also have a general subscription
+ * for all notification in the system via
+ * <pre>
+ * service.registerNotificationListener(Notification.class, listener);
+ * </pre>
+ *
+ * <h3>Dispatch Listener</h3>
+ * <p>
+ * A dispatch listener implements a YANG-generated module interface <code>{ModuleName}Listener</code>
+ * which handles all the notifications defined in the YANG model. Each notification type translates to
+ * a specific method of the form <code>on{NotificationType}</code> on the generated interface.
+ * The generated interface also extends the
+ * {@link org.opendaylight.yangtools.yang.binding.NotificationListener} interface and implementations
+ * are registered using {@link #registerNotificationListener(org.opendaylight.yangtools.yang.binding.NotificationListener)}
+ * method.
+ *
+ * <h5>Dispatch Listener Example</h5>
+ * <p>
+ * Lets assume we have following YANG model:
+ *
+ * <pre>
+ * module example {
+ * ...
+ *
+ * notification start {
+ * ...
+ * }
+ *
+ * notification stop {
+ * ...
+ * }
+ * }
+ * </pre>
+ *
+ * The generated interface will be:
+ * <pre>
+ * public interface ExampleListener extends NotificationListener {
+ * void onStart(Start notification);
+ * void onStop(Stop notification);
+ * }
+ * </pre>
+ * The following defines an implementation of the generated interface:
+ * <pre>
+ * public class MyExampleListener implements ExampleListener {
+ * public void onStart(Start notification) {
+ * // do something
+ * }
+ *
+ * public void onStop(Stop notification) {
+ * // do something
+ * }
+ * }
+ * </pre>
+ * The implementation is registered as follows:
+ * <pre>
+ * MyExampleListener listener = new MyExampleListener();
+ * ListenerRegistration<NotificationListener> reg = service.registerNotificationListener( listener );
+ * </pre>
+ * The <code>onStart</code> method will be invoked when someone publishes a <code>Start</code> notification and
+ * the <code>onStop</code> method will be invoked when someone publishes a <code>Stop</code> notification.
+ */
public interface NotificationService extends BindingAwareService {
/**
- * Register a generic listener for specified notification type only.
+ * Registers a generic listener implementation for a specified notification type.
*
- * @param notificationType
- * @param listener
- * @return Registration for listener. To unregister listener invoke {@link ListenerRegistration#close()} method.
+ * @param notificationType the YANG-generated interface of the notification type.
+ * @param listener the listener implementation that will receive notifications.
+ * @return a {@link ListenerRegistration} instance that should be used to unregister the listener
+ * by invoking the {@link ListenerRegistration#close()} method when no longer needed.
*/
<T extends Notification> ListenerRegistration<NotificationListener<T>> registerNotificationListener(
Class<T> notificationType, NotificationListener<T> listener);
/**
- * Register a listener which implements generated notification interfaces derived from
+ * Registers a listener which implements a YANG-generated notification interface derived from
* {@link org.opendaylight.yangtools.yang.binding.NotificationListener}.
- * Listener is registered for all notifications present in implemented interfaces.
+ * The listener is registered for all notifications present in the implemented interface.
*
- * @param listener
- * @return Registration for listener. To unregister listener invoke {@link ListenerRegistration#close()} method.
+ * @param listener the listener implementation that will receive notifications.
+ * @return a {@link ListenerRegistration} instance that should be used to unregister the listener
+ * by invoking the {@link ListenerRegistration#close()} method when no longer needed.
*/
ListenerRegistration<org.opendaylight.yangtools.yang.binding.NotificationListener> registerNotificationListener(
org.opendaylight.yangtools.yang.binding.NotificationListener listener);
import java.util.concurrent.ExecutorService;
+/**
+ * Interface for publishing YANG-modeled notifications.
+ * <p>
+ * Users of this interface can publish any YANG-modeled notification which will
+ * be delivered to all subscribed listeners.
+ * <p>
+ * Prefered way of publishing of notifications is done by invoking {@link #publish(Object)}.
+ *
+ * <p>You may consider using {@link #publish(Object, ExecutorService)} if and only if
+ * your use-case requires customized execution policy or run-to-completion
+ * inside process.
+ *
+ * <p>
+ * The metadata required to deliver a notification to the correct listeners is
+ * extracted from the published notification.
+ *
+ *
+ * FIXME: Consider clarification of execution/delivery policy, how it will be
+ * affected by Actor model and cluster-wide notifications.
+ *
+ * @param <N>
+ * the type of notifications
+ */
public interface NotificationPublishService<N> {
+ /**
+ * Publishes a notification and notifies subscribed listeners. All listener
+ * notifications are done via a default executor.
+ * <p>
+ * <b>Note:</b> This call will block when the default executor is saturated
+ * and the notification queue for this executor is full.
+ *
+ * @param notification
+ * the notification to publish.
+ */
void publish(N notification);
- void publish(N notification,ExecutorService executor);
+ /**
+ * Publishes a notification and notifies subscribed listeners. All listener
+ * notifications are done via the provided executor.
+ * <p>
+ * <b>Note:</b> Use only if ineccessary. Consider using
+ * {@link #publish(Object)} for most use-cases.
+ *
+ * <p>
+ * By using this method you could customize execution policy of listeners present
+ * inside process (e.g. using single-threaded executor or even same-thread executor
+ * delivery.
+ *
+ * <p>
+ * This executor is used only for inside-process notification deliveries.
+ *
+ * @param notification
+ * the notification to publish.
+ * @param executor
+ * the executor that will be used to deliver notifications to
+ * subscribed listeners.
+ */
+ void publish(N notification, ExecutorService executor);
}