GitHub user pjfanning added a comment to the discussion: Reducing boilerplate
with annotations
I'm not sure if anyone is going to take this on but if they want, it will be
reviewed. For me, people who want to use Pekko and Java for new actors, they
should consider using Java Records for the message definitions, new style Java
switch statements for matching the messages and typed actors instead of classic
actors.
Example generated by AI.
```
// Requires Java 21+ and Apache Pekko (org.apache.pekko:pekko-actor-typed_2.13)
//
// This shows the least-boilerplate way to write a Pekko Typed actor in Java
today:
// - sealed interface + records for the protocol (no getters, no
equals/hashCode/toString to write)
// - Behaviors.setup + Behaviors.receiveMessage instead of extending
AbstractBehavior
// (skips the ReceiveBuilder entirely)
// - a switch expression over the sealed interface, which the compiler checks
for
// exhaustiveness — add a new Command subtype and forget to handle it, and
this won't compile
// - record patterns to destructure messages inline instead of calling
accessor methods
package example;
import org.apache.pekko.actor.typed.ActorRef;
import org.apache.pekko.actor.typed.ActorSystem;
import org.apache.pekko.actor.typed.Behavior;
import org.apache.pekko.actor.typed.javadsl.Behaviors;
public class CounterActor {
// --- Protocol ---
// sealed = the compiler knows every possible message type, so the switch
below
// needs no `default` branch and breaks at compile time if you add a case
and
// forget to handle it.
sealed interface Command {}
record Increment(int by) implements Command {}
record GetCount(ActorRef<Count> replyTo) implements Command {}
record Reset() implements Command {}
record Count(int value) {}
// --- Behavior ---
// No class to extend, no constructor, no builder. State is just a method
parameter,
// and "changing state" means calling counting(...) again with a new value.
public static Behavior<Command> create() {
return counting(0);
}
private static Behavior<Command> counting(int total) {
return Behaviors.receiveMessage(command -> switch (command) {
case Increment(var by) -> counting(total + by);
case GetCount(var replyTo) -> {
replyTo.tell(new Count(total));
yield Behaviors.same();
}
case Reset() -> counting(0);
});
}
// --- Demo ---
public static void main(String[] args) throws InterruptedException {
ActorSystem<Command> system = ActorSystem.create(CounterActor.create(),
"counter-system");
system.tell(new Increment(5));
system.tell(new Increment(10));
// In real code you'd use the ask pattern to get Count back
asynchronously;
// this is just enough to show messages flowing.
Thread.sleep(200);
system.terminate();
}
}
```
GitHub link:
https://github.com/apache/pekko/discussions/3350#discussioncomment-17635995
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