Events

Geyser has an Event Manager that allows one to listen to or trigger an event easily. Events can be easily defined either by defining a method to be an event handler or by providing a lambda. Each event handler will be executed in turn based upon their priority.

Triggering an Event

An event derives from GeyserEvent and can implement Cancellable if it should support being cancelled, and EventSession if it should support a GeyserSession.

Example

public class MyCustomEvent extends GeyserEvent implements Cancellable {
}

The event can be triggered through the triggerEvent method of the EventManager.

Example

EventManager.getInstance().triggerEvent(new MyCustomEvent());

This returns an EventResult which can be used to chain additional commands based upon the result. They include onNotCancelled(), onCancelled() and orElse() to more easily execute based upon the result. All methods can be chained together.

Example

EventManager.getInstance().triggerEvent(new MyCustomEvent())
    .onNotCancelled(result -> {
        // Code executed if events were not cancelled
    })
    .orElse((result) -> {
        // Code executed if the above condition was not satisfied
    });

Example

EventResult<MyCustomEvent> result = EventManager.getInstance().triggerEvent(new MyCustomEvent());
if (!result.isCancelled()) {
    // do something
}

Listening to an Event

There are two ways to listen for an event. One can either create an event handler method or one can create an anonymous lamda to be executed when the event is triggered.

Class Event Handler

An event handler method is a method that is annotated with @GeyserEventHandler. The class it belongs to must also be registered with the event manager.

Example

public class MyClass {

    @Event
    public void onMyEvent(MyCustomEvent event) {
        GeyserConnector.getInstance().getLogger().info("Hello World");
    }
}

...

EventManager().getInstance().registerEvents(new MyClass());

Important

Extensions should use the registerEvents method inherited from GeyserExtension.

MyCustomEvent is the event defined previously.

Anonymous Lambda

An event can be hooked through the on method of the EventManager provided with an anonymous function. This allows code to be placed logically close to where it is related in the code instead of having to set up a separate class and method listeners. You will need to remember to unregister an event handler when needed.

Example

EventHandler<MyCustomEvent> handler = EventManager.getInstance().on(MyCustomEvent.class, event -> {
    System.err.println("Hello World");
})
    .build();

Important

Extensions should use the on method inherited from GeyserExtension.

You'll note the build() on the end. on() returns a Builder that can add optional parameters. This must be finalized with a build() that generates the EventHandler and registers it with the EventManager.

The following additional parameters are available:

• priority(int) - Set the event priority. Default EventHandler.Priority.NORMAL
• ignoreCancelled(boolean) - If true the handler will not execute if cancelled. Default true.

Example

EventHandler<MyCustomEvent> handler = EventManager.getInstance().on(MyCustomEvent.class, event -> {
    System.err.println("Hello World");
})
    .priority(30)
    .ignoreCancelled(false)
    .build();

Events

Please refer to the API Docs for more information. Geyser events are defined under org.geysermc.connector.event.events.

Geyser has the following predefined Events.

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