org.apache.shiro.event

Interface EventBus

All Known Implementing Classes:

DefaultEventBus

public interface EventBus

An event bus can publish events to event subscribers as well as provide a mechanism for registering and unregistering event subscribers.

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.

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 viewed/copied/imported (even though Guava code is Apache 2.0 licensed and could have been used).

Since:

1.3

Method Summary

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

Method Detail

publish

void publish(Object event)

Publishes the specified event to an event subsystem that will deliver events to relevant Subscribers.

Parameters:

event - The event object to distribute to relevant subscribers.

register

void register(Object subscriber)

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).

Parameters:

subscriber - the object whose event handler methods should be registered to receive events.

unregister

void unregister(Object subscriber)

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.

Parameters:

subscriber - the previously