HelloWorld.java

//DEPS com.cajunsystems:cajun:0.1.4
//JAVA 21+
//PREVIEW

import com.cajunsystems.*;
import com.cajunsystems.handler.Handler;

public class HelloWorld {
    
    // Define your message types with explicit replyTo
    public record HelloMessage(String name, Pid replyTo) {}
    public record GreetingResponse(String greeting) {}
    
    // Greeter actor that processes requests
    public static class GreeterHandler implements Handler<HelloMessage> {
        @Override
        public void receive(HelloMessage message, ActorContext context) {
            context.getLogger().info("Received greeting request for: {}", message.name());
            
            // Process and reply
            String greeting = "Hello, " + message.name() + "!";
            context.tell(message.replyTo(), new GreetingResponse(greeting));
        }
    }
    
    // Receiver actor that handles responses
    public static class ReceiverHandler implements Handler<GreetingResponse> {
        @Override
        public void receive(GreetingResponse message, ActorContext context) {
            System.out.println("Received: " + message.greeting());
        }
    }
    
    public static void main(String[] args) throws Exception {
        // 1. Create the ActorSystem
        ActorSystem system = new ActorSystem();
        
        // 2. Spawn actors
        Pid greeter = system.actorOf(GreeterHandler.class)
            .withId("greeter")
            .spawn();
        
        Pid receiver = system.actorOf(ReceiverHandler.class)
            .withId("receiver")
            .spawn();
        
        // 3. Send a message with explicit replyTo
        greeter.tell(new HelloMessage("World", receiver));
        
        // Wait a bit for async processing
        Thread.sleep(100);
        
        // 4. Shutdown the system when done
        system.shutdown();
    }
}