Akka

Actors have:

  • A mailbox (the queue where messages end up).
  • A behavior (the state of the actor, internal variables etc.).
  • Messages (pieces of data representing a signal, similar to method calls and their parameters).
  • An execution environment (the machinery that takes actors that have messages to react to and invokes their message handling code).
  • An address.

sbt:

libraryDependencies ++= Seq(
  "com.typesafe.akka" %% "akka-actor" % "2.5.6",
  "com.typesafe.akka" %% "akka-testkit" % "2.5.6" % Test
)

Basic Example

//#full-example
package com.lightbend.akka.sample

import akka.actor.{ Actor, ActorLogging, ActorRef, ActorSystem, Props }
import scala.io.StdIn

//#greeter-companion
//#greeter-messages
object Greeter {
  //#greeter-messages
  def props(message: String, printerActor: ActorRef): Props = Props(new Greeter(message, printerActor))
  //#greeter-messages
  final case class WhoToGreet(who: String)
  case object Greet
}
//#greeter-messages
//#greeter-companion

//#greeter-actor
class Greeter(message: String, printerActor: ActorRef) extends Actor {
  import Greeter._
  import Printer._

  var greeting = ""

  def receive = {
    case WhoToGreet(who) =>
      greeting = s"$message, $who"
    case Greet           =>
      //#greeter-send-message
      printerActor ! Greeting(greeting)
      //#greeter-send-message
  }
}
//#greeter-actor

//#printer-companion
//#printer-messages
object Printer {
  //#printer-messages
  def props: Props = Props[Printer]
  //#printer-messages
  final case class Greeting(greeting: String)
}
//#printer-messages
//#printer-companion

//#printer-actor
class Printer extends Actor with ActorLogging {
  import Printer._

  def receive = {
    case Greeting(greeting) =>
      log.info(s"Greeting received (from ${sender()}): $greeting")
  }
}
//#printer-actor

//#main-class
object AkkaQuickstart extends App {
  import Greeter._

  // Create the 'helloAkka' actor system
  val system: ActorSystem = ActorSystem("helloAkka")

  try {
    //#create-actors
    // Create the printer actor
    val printer: ActorRef = system.actorOf(Printer.props, "printerActor")

    // Create the 'greeter' actors
    val howdyGreeter: ActorRef =
      system.actorOf(Greeter.props("Howdy", printer), "howdyGreeter")
    val helloGreeter: ActorRef =
      system.actorOf(Greeter.props("Hello", printer), "helloGreeter")
    val goodDayGreeter: ActorRef =
      system.actorOf(Greeter.props("Good day", printer), "goodDayGreeter")
    //#create-actors

    //#main-send-messages
    howdyGreeter ! WhoToGreet("Akka")
    howdyGreeter ! Greet

    howdyGreeter ! WhoToGreet("Lightbend")
    howdyGreeter ! Greet

    helloGreeter ! WhoToGreet("Scala")
    helloGreeter ! Greet

    goodDayGreeter ! WhoToGreet("Play")
    goodDayGreeter ! Greet
    //#main-send-messages

    println(">>> Press ENTER to exit <<<")
    StdIn.readLine()
  } finally {
    system.terminate()
  }
}
//#main-class
//#full-example