Example of annotation driven events using EventBus (Google Guava library)

TestAnnotationDrivenEvent.java

import static org.mockito.Mockito.verify;

import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.mockito.Spy;
import org.mockito.runners.MockitoJUnitRunner;

import com.google.common.eventbus.EventBus;

@RunWith(MockitoJUnitRunner.class)
public class TestAnnotationDrivenEvent {

    private final EventBus eventBus = new EventBus();

    @Spy
    private final MessageRecievedEventConsumer listener = new MessageRecievedEventConsumer();

    @Before
    public void registerListener() {
        eventBus.register(listener);
    }

    @Test
    public void fireEvent() {
        Message msg = new Message("marlly", "Interface vs annotation driven events", "Post about differences between those event architectures");
        MessageRecievedEvent msgEvent = new MessageRecievedEvent(msg);
        eventBus.post(msgEvent);
        verify(listener).messageRecieved(msgEvent);
    }
}

Message.java

public class Message {

    private final String sender;

    private final String subject;

    private final String text;

    public Message(String sender, String subject, String text) {
        this.sender = sender;
        this.subject = subject;
        this.text = text;
    }

    public String getSender() {
        return sender;
    }

    public String getSubject() {
        return subject;
    }

    public String getText() {
        return text;
    }
}

MessageRecievedEvent.java

public class MessageRecievedEvent {

    private final Message msg;

    public MessageRecievedEvent(Message msg) {
        this.msg = msg;
    }

    public Message getMsg() {
        return msg;
    }
}

MessageRecievedEventConsumer.java

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.google.common.eventbus.Subscribe;

public class MessageRecievedEventConsumer {

    private static final Logger LOG = LoggerFactory.getLogger(MessageRecievedEventConsumer.class);

    @Subscribe
    public void messageRecieved(MessageRecievedEvent e) {
        LOG.info("messageRecieved(), msg: {}", e.getMsg());
    }
}