Package org.onehippo.cms7.services.eventbus

Interface HippoEventBus

public interface HippoEventBus

Generic Hippo event bus. Specific implementations can dispatch events based on metadata of the listener and event objects. (see e.g. the guava implementation)

Listeners must be registered through the HippoEventListenerRegistry which the HippoEventBus service will (must) query, or track itself, for the available listeners to dispatch events to (Whiteboard pattern).

Methods in the listener class hierarchy annotated with the Subscribe annotation will be invoked when events of a suitable type are dispatched. (see the Subscribe documentation for details). Example:

Example listener implementation using the Subscribe annotation:

     MyObject() {
         ... initialization

         // register as a listener using the HippoEventListenerRegistry:
         HippoEventListenerRegistry.get().register(this);

         // implement a HippoEvent receiver method and annotate it with 'Subscribe'
         // Note that the method with the annotation MUST be public
         @Subscribe
         public void processHippoEvent(HippoEvent<?> event) {
             System.out.println(event);
         }
     }

     // get the eventBus
     HippoEventBus eventBus = HippoServiceRegistry.getService(HippoEventBus.class);
     // post an event which subsequently will be printed by the @Subscribe annotated method defined above
     eventBus.post(new HippoEvent("foo").message("bar"));
     

When you are only interested in HippoEvents, you also can implement the HippoEventListener instead. Then you also don't need to annotate the onEvent method. For example:

     HippoEventListenerRegistry.get().register(new HippoEventListener() {
         // implement the onEvent method
         // Note that the method MUST be public
         public void onEvent(HippoEvent<?> event) {
             System.out.println(event);
         }
     });

Method Summary

Modifier and Type	Method	Description
void	post(Object event)	Publish an event to registered listeners.

Method Details

post

void post(Object event)

Publish an event to registered listeners. Their Subscribe annotated methods (with suitable parameter types), or implementations their HippoEventListener.onEvent(HippoEvent) method will be invoked.

Parameters:

event - event to be published