Akka/Scala example source code file (EventBusJavaAPI.scala)

This example Akka source code file (EventBusJavaAPI.scala) is included in my "Source Code Warehouse" project. The intent of this project is to help you more easily find Akka and Scala source code examples by using tags.

All credit for the original source code belongs to akka.io; I'm just trying to make examples easier to find. (For my Scala work, see my Scala examples and tutorials.)

Akka tags/keywords

actor, actorref, akka, boolean, c, e, event, eventbus, int, japi, s, subscriber, unit, util

The EventBusJavaAPI.scala Akka example source code

/**
 * Copyright (C) 2009-2014 Typesafe Inc. <http://www.typesafe.com>
 */
package akka.event.japi

import akka.util.Subclassification
import akka.actor.{ ActorSystem, ActorRef }

/**
 * Java API: See documentation for [[akka.event.EventBus]]
 * E is the Event type
 * S is the Subscriber type
 * C is the Classifier type
 */
trait EventBus[E, S, C] {

  /**
   * Attempts to register the subscriber to the specified Classifier
   * @return true if successful and false if not (because it was already subscribed to that Classifier, or otherwise)
   */
  def subscribe(subscriber: S, to: C): Boolean

  /**
   * Attempts to deregister the subscriber from the specified Classifier
   * @return true if successful and false if not (because it wasn't subscribed to that Classifier, or otherwise)
   */
  def unsubscribe(subscriber: S, from: C): Boolean

  /**
   * Attempts to deregister the subscriber from all Classifiers it may be subscribed to
   */
  def unsubscribe(subscriber: S): Unit

  /**
   * Publishes the specified Event to this bus
   */
  def publish(event: E): Unit
}

/**
 * Java API: See documentation for [[akka.event.LookupClassification]]
 * E is the Event type
 * S is the Subscriber type
 * C is the Classifier type
 */
abstract class LookupEventBus[E, S, C] extends EventBus[E, S, C] {
  private val bus = new akka.event.EventBus with akka.event.LookupClassification {
    type Event = E
    type Subscriber = S
    type Classifier = C

    override protected def mapSize: Int = LookupEventBus.this.mapSize

    override protected def compareSubscribers(a: S, b: S): Int =
      LookupEventBus.this.compareSubscribers(a, b)

    override protected def classify(event: E): C =
      LookupEventBus.this.classify(event)

    override protected def publish(event: E, subscriber: S): Unit =
      LookupEventBus.this.publish(event, subscriber)
  }

  /**
   * This is a size hint for the number of Classifiers you expect to have (use powers of 2)
   */
  protected def mapSize(): Int

  /**
   * Provides a total ordering of Subscribers (think java.util.Comparator.compare)
   */
  protected def compareSubscribers(a: S, b: S): Int

  /**
   * Returns the Classifier associated with the given Event
   */
  protected def classify(event: E): C

  /**
   * Publishes the given Event to the given Subscriber
   */
  protected def publish(event: E, subscriber: S): Unit

  override def subscribe(subscriber: S, to: C): Boolean = bus.subscribe(subscriber, to)
  override def unsubscribe(subscriber: S, from: C): Boolean = bus.unsubscribe(subscriber, from)
  override def unsubscribe(subscriber: S): Unit = bus.unsubscribe(subscriber)
  override def publish(event: E): Unit = bus.publish(event)

}

/**
 * Java API: See documentation for [[akka.event.SubchannelClassification]]
 * E is the Event type
 * S is the Subscriber type
 * C is the Classifier type
 */
abstract class SubchannelEventBus[E, S, C] extends EventBus[E, S, C] {
  private val bus = new akka.event.EventBus with akka.event.SubchannelClassification {
    type Event = E
    type Subscriber = S
    type Classifier = C

    override protected def subclassification: Subclassification[Classifier] =
      SubchannelEventBus.this.subclassification

    override protected def classify(event: Event): Classifier =
      SubchannelEventBus.this.classify(event)

    override protected def publish(event: Event, subscriber: Subscriber): Unit =
      SubchannelEventBus.this.publish(event, subscriber)
  }

  /**
   * The logic to form sub-class hierarchy
   */
  def subclassification: Subclassification[C]

  /**
   * Returns the Classifier associated with the given Event
   */
  protected def classify(event: E): C

  /**
   * Publishes the given Event to the given Subscriber
   */
  protected def publish(event: E, subscriber: S): Unit

  override def subscribe(subscriber: S, to: C): Boolean = bus.subscribe(subscriber, to)
  override def unsubscribe(subscriber: S, from: C): Boolean = bus.unsubscribe(subscriber, from)
  override def unsubscribe(subscriber: S): Unit = bus.unsubscribe(subscriber)
  override def publish(event: E): Unit = bus.publish(event)

}

/**
 * Java API: See documentation for [[akka.event.ScanningClassification]]
 * E is the Event type
 * S is the Subscriber type
 * C is the Classifier type
 */
abstract class ScanningEventBus[E, S, C] extends EventBus[E, S, C] {
  private val bus = new akka.event.EventBus with akka.event.ScanningClassification {
    type Event = E
    type Subscriber = S
    type Classifier = C

    override protected def compareClassifiers(a: C, b: C): Int =
      ScanningEventBus.this.compareClassifiers(a, b)

    override protected def compareSubscribers(a: S, b: S): Int =
      ScanningEventBus.this.compareSubscribers(a, b)

    override protected def matches(classifier: C, event: E): Boolean =
      ScanningEventBus.this.matches(classifier, event)

    override protected def publish(event: E, subscriber: S): Unit =
      ScanningEventBus.this.publish(event, subscriber)
  }

  /**
   * Provides a total ordering of Classifiers (think java.util.Comparator.compare)
   */
  protected def compareClassifiers(a: C, b: C): Int

  /**
   * Provides a total ordering of Subscribers (think java.util.Comparator.compare)
   */
  protected def compareSubscribers(a: S, b: S): Int

  /**
   * Returns whether the specified Classifier matches the specified Event
   */
  protected def matches(classifier: C, event: E): Boolean

  /**
   * Publishes the specified Event to the specified Subscriber
   */
  protected def publish(event: E, subscriber: S): Unit

  override def subscribe(subscriber: S, to: C): Boolean = bus.subscribe(subscriber, to)
  override def unsubscribe(subscriber: S, from: C): Boolean = bus.unsubscribe(subscriber, from)
  override def unsubscribe(subscriber: S): Unit = bus.unsubscribe(subscriber)
  override def publish(event: E): Unit = bus.publish(event)
}

/**
 * Java API: See documentation for [[akka.event.ActorClassification]]
 * An EventBus where the Subscribers are ActorRefs and the Classifier is ActorRef
 * Means that ActorRefs "listen" to other ActorRefs
 * E is the Event type
 */
abstract class ActorEventBus[E](system: ActorSystem) extends EventBus[E, ActorRef, ActorRef] {
  private val bus = new akka.event.ActorEventBus with akka.event.ActorClassification with akka.event.ActorClassifier {
    type Event = E

    override val system = ActorEventBus.this.system

    override protected def mapSize: Int = ActorEventBus.this.mapSize

    override protected def classify(event: E): ActorRef =
      ActorEventBus.this.classify(event)
  }

  /**
   * This is a size hint for the number of Classifiers you expect to have (use powers of 2)
   */
  protected def mapSize(): Int

  /**
   * Returns the Classifier associated with the given Event
   */
  protected def classify(event: E): ActorRef

  override def subscribe(subscriber: ActorRef, to: ActorRef): Boolean = bus.subscribe(subscriber, to)
  override def unsubscribe(subscriber: ActorRef, from: ActorRef): Boolean = bus.unsubscribe(subscriber, from)
  override def unsubscribe(subscriber: ActorRef): Unit = bus.unsubscribe(subscriber)
  override def publish(event: E): Unit = bus.publish(event)
}