package sample.persistence;
//#persistent-actor-example
import akka.actor.ActorRef;
import akka.actor.ActorSystem;
import akka.actor.Props;
import akka.japi.Procedure;
import akka.persistence.SnapshotOffer;
import akka.persistence.UntypedPersistentActor;
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<String>());
}
public ExampleState(ArrayList<String> events) {
this.events = events;
}
public ExampleState copy() {
return new ExampleState(new ArrayList<String>(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 UntypedPersistentActor {
@Override
public String persistenceId() { return "sample-id-1"; }
private ExampleState state = new ExampleState();
public int getNumEvents() {
return state.size();
}
@Override
public void onReceiveRecover(Object msg) {
if (msg instanceof Evt) {
state.update((Evt) msg);
} else if (msg instanceof SnapshotOffer) {
state = (ExampleState)((SnapshotOffer)msg).snapshot();
} else {
unhandled(msg);
}
}
@Override
public void onReceiveCommand(Object msg) {
if (msg instanceof Cmd) {
final String data = ((Cmd)msg).getData();
final Evt evt1 = new Evt(data + "-" + getNumEvents());
final Evt evt2 = new Evt(data + "-" + (getNumEvents() + 1));
persist(asList(evt1, evt2), new Procedure<Evt>() {
public void apply(Evt evt) throws Exception {
state.update(evt);
if (evt.equals(evt2)) {
getContext().system().eventStream().publish(evt);
}
}
});
} else if (msg.equals("snap")) {
// IMPORTANT: create a copy of snapshot
// because ExampleState is mutable !!!
saveSnapshot(state.copy());
} else if (msg.equals("print")) {
System.out.println(state);
} else {
unhandled(msg);
}
}
}
//#persistent-actor-example
public class PersistentActorExample {
public static void main(String... args) throws Exception {
final ActorSystem system = ActorSystem.create("example");
final ActorRef persistentActor =
system.actorOf(Props.create(ExamplePersistentActor.class), "persistentActor-4-java");
persistentActor.tell(new Cmd("foo"), null);
persistentActor.tell(new Cmd("baz"), null);
persistentActor.tell(new Cmd("bar"), null);
persistentActor.tell("snap", null);
persistentActor.tell(new Cmd("buzz"), null);
persistentActor.tell("print", null);
Thread.sleep(1000);
system.terminate();
}
}