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

This example Akka source code file (ExtensionDocSpec.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, actorsystem, akka, countextension, countextensionimpl, counting, extensiondocspec, extensionid, myactor, mycounteractor, scala, test, testing, testkit

The ExtensionDocSpec.scala Akka example source code

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

import java.util.concurrent.atomic.AtomicLong
import akka.actor.Actor
import akka.testkit.AkkaSpec

//#extension
import akka.actor.Extension

class CountExtensionImpl extends Extension {
  //Since this Extension is a shared instance
  // per ActorSystem we need to be threadsafe
  private val counter = new AtomicLong(0)

  //This is the operation this Extension provides
  def increment() = counter.incrementAndGet()
}
//#extension

//#extensionid
import akka.actor.ActorSystem
import akka.actor.ExtensionId
import akka.actor.ExtensionIdProvider
import akka.actor.ExtendedActorSystem

object CountExtension
  extends ExtensionId[CountExtensionImpl]
  with ExtensionIdProvider {
  //The lookup method is required by ExtensionIdProvider,
  // so we return ourselves here, this allows us
  // to configure our extension to be loaded when
  // the ActorSystem starts up
  override def lookup = CountExtension

  //This method will be called by Akka
  // to instantiate our Extension
  override def createExtension(system: ExtendedActorSystem) = new CountExtensionImpl

  /**
   * Java API: retrieve the Count extension for the given system.
   */
  override def get(system: ActorSystem): CountExtensionImpl = super.get(system)
}
//#extensionid

object ExtensionDocSpec {

  val config = """
    //#config
    akka {
      extensions = ["docs.extension.CountExtension"]
    }
    //#config
    """

  //#extension-usage-actor

  class MyActor extends Actor {
    def receive = {
      case someMessage =>
        CountExtension(context.system).increment()
    }
  }
  //#extension-usage-actor

  //#extension-usage-actor-trait

  trait Counting { self: Actor =>
    def increment() = CountExtension(context.system).increment()
  }
  class MyCounterActor extends Actor with Counting {
    def receive = {
      case someMessage => increment()
    }
  }
  //#extension-usage-actor-trait
}

class ExtensionDocSpec extends AkkaSpec(ExtensionDocSpec.config) {
  import ExtensionDocSpec._

  "demonstrate how to create an extension in Scala" in {
    //#extension-usage
    CountExtension(system).increment
    //#extension-usage
  }

  "demonstrate how to lookup a configured extension in Scala" in {
    //#extension-lookup
    system.extension(CountExtension)
    //#extension-lookup
  }

}