Async

Long-running or fire-and-forget work should not block the HTTP thread. The EventBus publishes payloads to Subscriber implementations, and delivery runs on virtual threads, so you can write straightforward blocking code inside a subscriber without starving Undertow's worker pool.

Subscribers are discovered at startup through a classpath scan. Each subscriber type is tied to a queue name equal to the payload class's canonical name. There is no unregister method, so if you need multiple handlers for the same payload type, register additional subscribers by class instead.

Subscribers

Implement io.mangoo.async.Subscriber, and mangoo I/O registers every implementation it finds on startup. The queue name is the canonical name of the payload type, so a Subscriber<String> registers under java.lang.String.

package subscribers;

import io.mangoo.async.Subscriber;

public class AuditSubscriber implements Subscriber<String> {
    @Override
    public void receive(String payload) {
        // handle payload
    }
}

Subscribers are created through Guice, so you can inject dependencies.

Publishing

@Inject
private EventBus eventBus;

public void notify(String message) {
    eventBus.publish(message);
}

publish looks up subscribers for payload.getClass().getCanonicalName(), and again, there is no unregister. You can also call eventBus.register("java.lang.String", AuditSubscriber.class) yourself, though classpath scanning already does that for you for any Subscriber type.

Use a dedicated payload class if you need separate queues:

public record OrderPlaced(String id) {}

public class OrderSubscriber implements Subscriber<OrderPlaced> {
    @Override
    public void receive(OrderPlaced payload) { }
}

eventBus.publish(new OrderPlaced("42"));