Java library for event driven applications

Design your application with a more modular approach by using events to create hooks and manipulate data from within other components.

repositories {
    maven { url 'https://registry.provided.space' }
}

dependencies {
    implementation 'space.provided:event-system:VERSION'
}

<repositories>
    <repository>
        <id>provided</id>
        <name>provided.space</name>
        <url>https://registry.provided.space</url>
    </repository>
</repositories>

<dependencies>
    <dependency>
        <groupId>space.provided</groupId>
        <artifactId>event-system</artifactId>
        <version>VERSION</version>
    </dependency>
</dependencies>

The events that are going to be dispatched as well as the listeners, can be any object without the need inheritance.

In this case we want to listen to when a message is being sent. Only methods with exact class matches will be invoked.
If you need to control how early/late a method should be executed, you can take advantage of the sequence parameter on the Annotation. The higher the sequence, the later the method will be invoked.

public final class MessageSendEvent {
    
    private MessageSender sender;
    private String message;

    // constructor, getters and setters
}

public final class MessageSendListener {

    @Subscribe
    public void onMessageSend(MessageSendEvent event) {
        System.out.println(String.format("A message is being sent by %1$s.", event.getSender().getUUID()));
    }

    @Subscribe(sequence = 1)
    public void onMessageSend(MessageSendEvent event) {
        System.out.println("A message is being sent.");
    }
}

The event bus can be obtained with a new instance of EventBus. To start listening to events, you have to register a listener. When unregistering a listener, no more events will be dispatched.

To dispatch an event, simply call the post method on your EventBus instance and pass your event.

final EventBus events = new EventBus<>();

final MessageSendListener listener = new MessageSendListener();
events.subscribe(listener);
events.post(new MessageSendEvent(sender, message));

events.unsubscribe(listener);
events.post(new MessageSendEvent(sender, message));