Package org.apache.commons.configuration2.event

## Interface EventListener<T extends Event>

- Type Parameters:
    `T` - the type of events this listener can process
  All Known Implementing Classes:
    `CombinedConfiguration`, `DynamicCombinedConfiguration`, `PropertiesConfigurationLayout`

      public interface EventListener<T extends Event>

  Definition of a generic event listener interface.

  This event listener interface is used throughout the Commons Configuration library for reacting on all kinds of supported events. The interface is pretty minimalistic, defining only a single `onEvent()` method. This simplifies the implementation of custom event listeners and also supports the new language features introduced with Java 8 (`EventListener` is a functional interface and thus can be represented by a Lambda expression).

  Since:
    2.0

- - ### Method Summary

    All Methods Instance Methods Abstract Methods
    Modifier and Type | Method | Description
    --- | --- | ---
    `void` | `onEvent​(T event)` | Notifies this event listener about the arrival of a new event.

- - ### Method Detail

    - #### onEvent

          void onEvent​(T event)

      Notifies this event listener about the arrival of a new event. Typically, event listeners are registered at an event source providing an `EventType`. This event type acts as a filter; all events matched by the filter are passed to the listener. The type parameters defined by the `EventType` class and this interface guarantee that the events delivered to the handler are compatible with the concrete method signature of `onEvent()`.
      Parameters:
        `event` - the event