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

This example Akka source code file (PersistentActorExample.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, app, cmd, evt, examplestate, int, nil, persistence, persistentactorexample, receive, string

The PersistentActorExample.scala Akka example source code

package sample.persistence

//#persistent-actor-example
import akka.actor._
import akka.persistence._

case class Cmd(data: String)
case class Evt(data: String)

case class ExampleState(events: List[String] = Nil) {
  def updated(evt: Evt): ExampleState = copy(evt.data :: events)
  def size: Int = events.length
  override def toString: String = events.reverse.toString
}

class ExamplePersistentActor extends PersistentActor {
  override def persistenceId = "sample-id-1"

  var state = ExampleState()

  def updateState(event: Evt): Unit =
    state = state.updated(event)

  def numEvents =
    state.size

  val receiveRecover: Receive = {
    case evt: Evt                                 => updateState(evt)
    case SnapshotOffer(_, snapshot: ExampleState) => state = snapshot
  }

  val receiveCommand: Receive = {
    case Cmd(data) =>
      persist(Evt(s"${data}-${numEvents}"))(updateState)
      persist(Evt(s"${data}-${numEvents + 1}")) { event =>
        updateState(event)
        context.system.eventStream.publish(event)
      }
    case "snap"  => saveSnapshot(state)
    case "print" => println(state)
  }

}
//#persistent-actor-example

object PersistentActorExample extends App {

  val system = ActorSystem("example")
  val persistentActor = system.actorOf(Props[ExamplePersistentActor], "persistentActor-4-scala")

  persistentActor ! Cmd("foo")
  persistentActor ! Cmd("baz")
  persistentActor ! Cmd("bar")
  persistentActor ! "snap"
  persistentActor ! Cmd("buzz")
  persistentActor ! "print"

  Thread.sleep(1000)
  system.shutdown()
}