com.netflix.eventbus.spi

Interface EventCreator

public interface EventCreator

A contract for delayed creation of event(s) objects for conditional event publishing.

The responsibility of storing enough context to create the event(s) later lies on the implementations. As one would imagine, this creator will mostly be stateful and hence be instantiated afresh for every call.

The event(s) will be created iff there exists a listener that will process these event(s). However, due to the concurrent nature of the event bus, this may not always be the case, as the listeners may come and go between the existence check and actual invocation.

Multiple events

A single event creator can create multiple events at the same time. This is required to batch multiple event types together in one conditional publish to aid optimization of multiple publish calls. The event bus takes care of managing the mapping between the event type and listeners that showed interest when EventBus.publishIffNotDead(EventCreator, Class[]) was called for this creator.

Method Summary

Methods

Modifier and Type	Method and Description
java.util.List<?>	createEvent(java.util.Set<java.lang.Class<?>> liveEventTypes) A callback when the event bus determines that there is atleast one listener for any of the passed event types to the corresponding EventBus.publishIffNotDead(EventCreator, Class[]) call.

Method Detail

createEvent

java.util.List<?> createEvent(java.util.Set<java.lang.Class<?>> liveEventTypes)

A callback when the event bus determines that there is atleast one listener for any of the passed event types to the corresponding EventBus.publishIffNotDead(EventCreator, Class[]) call.
The event bus makes sure to establish a mapping between the event types and the live listeners before calling this method and publishes the created events only to the associated live listeners (determined before this callback)

Parameters:

liveEventTypes - A subset of event types passed to the corresponding EventBus.publishIffNotDead(EventCreator, Class[]) call which have atleast one listener to receive the event. Events created only for these event types will be published by the event bus.

Returns:

Newly created events corresponding to the live event types. null if no events are created.