com.netflix.eventbus.spi.DynamicSubscriber Maven / Gradle / Ivy
package com.netflix.eventbus.spi;
/**
* Eventbus subscribers, by design, are statically tied to a particular type of object i.e. the class of the event it
* is interested in. This in most cases is beneficial and easy to use, however, in some cases (typically event agnostic,
* middlemen, which stores the event for later investigation), the event processing is much the same irrespective of the
* type of event it receives. In such a case, it will be an overhead (even if possible) to define a subscriber for
* each kind of event existing in the system.
* This special subscriber is a way to achieve dynamic interests (immutable after registration) in subscribers. Although,
* this subscriber can only listen to one type of event but the type is defined at runtime as opposed to compile time
* in a normal subscriber.
* Although, this subscriber does not mandate that the subscriber must have a subscribe method (one annotated with
* {@link Subscribe}) listening to event type {@link Object} but in most of the cases, such a subscribe method will
* prove to be more useful. {@link EventBus} allows specifying the subscribe method with argument {@link Object}
* only for these subscribers.
*
* Implementations must only have a single subscriber method or else the registration with eventbus will be rejected.
* This limitation is imposed as we do not want to make runtime decisions on which subscribe method an event must be
* directed to.
*
* @author Nitesh Kant
*/
public interface DynamicSubscriber {
/**
* Returns the event type i.e. the class of the event that this subscriber will be interested in.
* {@link EventBus} allows specifying the subscribe method with argument {@link Object} only for
* these subscribers.
* The implementers of this interface must make sure that the subscribe method accepts the event class returned by
* this method.
*
* @return The event type i.e. the class of the event that this subscriber will be interested in.
*/
Class getEventType();
}