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

This example Akka source code file (PersistentActorExample.java) 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, akka, arraylist, boxedunit, cmd, evt, examplestate, japi, override, partialfunction, persistence, receivebuilder, runtime, serializable, string

The PersistentActorExample.java Akka example source code

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

package sample.persistence;

//#persistent-actor-example

import akka.actor.ActorRef;
import akka.actor.ActorSystem;
import akka.actor.Props;
import akka.japi.pf.ReceiveBuilder;
import akka.persistence.AbstractPersistentActor;
import akka.persistence.SnapshotOffer;
import scala.PartialFunction;
import scala.runtime.BoxedUnit;

import java.io.Serializable;
import java.util.ArrayList;

import static java.util.Arrays.asList;

class Cmd implements Serializable {
    private final String data;

    public Cmd(String data) {
        this.data = data;
    }

    public String getData() {
        return data;
    }
}

class Evt implements Serializable {
    private final String data;

    public Evt(String data) {
        this.data = data;
    }

    public String getData() {
        return data;
    }
}

class ExampleState implements Serializable {
    private final ArrayList<String> events;

    public ExampleState() {
        this(new ArrayList<>());
    }

    public ExampleState(ArrayList<String> events) {
        this.events = events;
    }

    public ExampleState copy() {
        return new ExampleState(new ArrayList<>(events));
    }

    public void update(Evt evt) {
        events.add(evt.getData());
    }

    public int size() {
        return events.size();
    }

    @Override
    public String toString() {
        return events.toString();
    }
}

class ExamplePersistentActor extends AbstractPersistentActor {

    private ExampleState state = new ExampleState();

    public int getNumEvents() {
        return state.size();
    }

    @Override
    public String persistenceId() { return "sample-id-1"; }

    @Override
    public PartialFunction<Object, BoxedUnit> receiveRecover() {
        return ReceiveBuilder.
            match(Evt.class, state::update).
            match(SnapshotOffer.class, ss -> state = (ExampleState) ss.snapshot()).build();
    }

    @Override
    public PartialFunction<Object, BoxedUnit> receiveCommand() {
        return ReceiveBuilder.
            match(Cmd.class, c -> {
                final String data = c.getData();
                final Evt evt1 = new Evt(data + "-" + getNumEvents());
                final Evt evt2 = new Evt(data + "-" + (getNumEvents() + 1));
                persist(asList(evt1, evt2), (Evt evt) -> {
                    state.update(evt);
                    if (evt.equals(evt2)) {
                        context().system().eventStream().publish(evt);
                    }
                });
            }).
            match(String.class, s -> s.equals("snap"), s -> saveSnapshot(state.copy())).
            match(String.class, s -> s.equals("print"), s -> System.out.println(state)).
            build();
    }

}
//#persistent-actor-example

public class PersistentActorExample {
    public static void main(String... args) throws Exception {
        final ActorSystem system = ActorSystem.create("example");
        final ActorRef processor = system.actorOf(Props.create(ExamplePersistentActor.class), "processor-4-java8");
        processor.tell(new Cmd("foo"), null);
        processor.tell(new Cmd("baz"), null);
        processor.tell(new Cmd("bar"), null);
        processor.tell("snap", null);
        processor.tell(new Cmd("buzz"), null);
        processor.tell("print", null);

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