Class DefaultEventBus

java.lang.Object
org.apache.shiro.event.support.DefaultEventBus
All Implemented Interfaces:
EventBus
public class DefaultEventBus extends Object implements EventBus
A default event bus implementation that synchronously publishes events to registered listeners. Listeners can be registered or unregistered for events as necessary.

An event bus enables a publish/subscribe paradigm within Shiro - components can publish or consume events they find relevant without needing to be tightly coupled to other components. This affords great flexibility within Shiro by promoting loose coupling and high cohesion between components and a much safer pluggable architecture that is more resilient to change over time.

Sending Events

If a component wishes to publish events to other components: 
     MyEvent myEvent = createMyEvent();
     eventBus.publish(myEvent);
The event bus will determine the type of event and then dispatch the event to components that wish to receive events of that type.

Receiving Events

A component can receive events of interest by doing the following.
  1. For each type of event you wish to consume, create a public method that accepts a single event argument. The method argument type indicates the type of event to receive.
  2. Annotate each of these public methods with the Subscribe annotation.
  3. Register the component with the event bus: 
             eventBus.register(myComponent);
After registering the component, when when an event of a respective type is published, the component's Subscribe-annotated method(s) will be invoked as expected.

This design (and its constituent helper components) was largely influenced by Guava's EventBus concept, although no code was shared/imported (even though Guava is Apache 2.0 licensed and could have been used).

This implementation is thread-safe and may be used concurrently.

Since:
1.3

  • Constructor Details

  • Method Details

    • getEventListenerResolver

      public EventListenerResolver getEventListenerResolver()

    • setEventListenerResolver

      public void setEventListenerResolver(EventListenerResolver eventListenerResolver)

    • publish

      public void publish(Object event)
      Description copied from interface: EventBus
      Publishes the specified event to an event subsystem that will deliver events to relevant Subscribers.
      Specified by:
      publish in interface EventBus
      Parameters:
      event - The event object to distribute to relevant subscribers.

    • register

      public void register(Object instance)
      Description copied from interface: EventBus
      Registers all event handler methods on the specified instance to receive relevant events. The handler methods are determined by the EventBus implementation, typically by using an EventListenerResolver (e.g. AnnotationEventListenerResolver).
      Specified by:
      register in interface EventBus
      Parameters:
      instance - the object whose event handler methods should be registered to receive events.

    • unregister

      public void unregister(Object instance)
      Description copied from interface: EventBus
      Unregisters all previously-registered event handler methods on the specified instance. If the specified object was not previously registered, calling this method has no effect.
      Specified by:
      unregister in interface EventBus
      Parameters:
      instance - the previously