org.apache.shiro.event.support

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 Summary

Constructors

Constructor and Description
DefaultEventBus()

Method Summary

Modifier and Type	Method and Description
EventListenerResolver	getEventListenerResolver()
void	publish(Object event) Publishes the specified event to an event subsystem that will deliver events to relevant Subscribers.
void	register(Object instance) Registers all event handler methods on the specified instance to receive relevant events.
void	setEventListenerResolver(EventListenerResolver eventListenerResolver)
void	unregister(Object instance) Unregisters all previously-registered event handler methods on the specified instance.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

DefaultEventBus

public DefaultEventBus()

Method Detail

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