package sample.persistence;
import akka.actor.ActorRef;
import akka.actor.ActorSystem;
import akka.actor.Props;
import akka.japi.Procedure;
import akka.persistence.SaveSnapshotFailure;
import akka.persistence.SaveSnapshotSuccess;
import akka.persistence.SnapshotOffer;
import akka.persistence.UntypedPersistentActor;
import java.io.Serializable;
import java.util.ArrayList;
public class SnapshotExample {
public static class ExampleState implements Serializable {
private final ArrayList<String> received;
public ExampleState() {
this(new ArrayList<String>());
}
public ExampleState(ArrayList<String> received) {
this.received = received;
}
public ExampleState copy() {
return new ExampleState(new ArrayList<String>(received));
}
public void update(String s) {
received.add(s);
}
@Override
public String toString() {
return received.toString();
}
}
public static class ExamplePersistentActor extends UntypedPersistentActor {
@Override
public String persistenceId() { return "sample-id-3"; }
private ExampleState state = new ExampleState();
@Override
public void onReceiveCommand(Object message) {
if (message.equals("print")) {
System.out.println("current state = " + state);
} else if (message.equals("snap")) {
// IMPORTANT: create a copy of snapshot
// because ExampleState is mutable !!!
saveSnapshot(state.copy());
} else if (message instanceof SaveSnapshotSuccess) {
// ...
} else if (message instanceof SaveSnapshotFailure) {
// ...
} else if (message instanceof String) {
String s = (String) message;
persist(s, new Procedure<String>() {
public void apply(String evt) throws Exception {
state.update(evt);
}
});
} else {
unhandled(message);
}
}
@Override
public void onReceiveRecover(Object message) {
if (message instanceof SnapshotOffer) {
ExampleState s = (ExampleState)((SnapshotOffer)message).snapshot();
System.out.println("offered state = " + s);
state = s;
} else if (message instanceof String) {
state.update((String) message);
} else {
unhandled(message);
}
}
}
public static void main(String... args) throws Exception {
final ActorSystem system = ActorSystem.create("example");
final ActorRef persistentActor = system.actorOf(Props.create(ExamplePersistentActor.class), "persistentActor-3-java");
persistentActor.tell("a", null);
persistentActor.tell("b", null);
persistentActor.tell("snap", null);
persistentActor.tell("c", null);
persistentActor.tell("d", null);
persistentActor.tell("print", null);
Thread.sleep(1000);
system.terminate();
}
}