Package com.google.web.bindery.event.shared

Class EventBus

java.lang.Object
com.google.web.bindery.event.shared.EventBus
Direct Known Subclasses:
CountingEventBus, EventBus, RecordingEventBus, ResettableEventBus, SimpleEventBus
public abstract class EventBus extends Object
Dispatches Events to interested parties. Eases decoupling by allowing objects to interact without having direct dependencies upon one another, and without requiring event sources to deal with maintaining handler lists. There will typically be one EventBus per application, broadcasting events that may be of general interest.
See Also:

  • Constructor Details

    • EventBus

      public EventBus()

  • Method Details

    • dispatchEvent

      protected static <H> void dispatchEvent(Event<H> event, H handler)
      Invokes event.dispatch with handler.

      Protected to allow EventBus implementations in different packages to dispatch events even though the event.dispatch method is protected.

    • setSourceOfEvent

      protected static void setSourceOfEvent(Event<?> event, Object source)
      Sets source as the source of event.

      Protected to allow EventBus implementations in different packages to set an event source even though the event.setSource method is protected.

    • addHandler

      public abstract <H> HandlerRegistration addHandler(Event.Type<H> type, H handler)
      Adds an unfiltered handler to receive events of this type from all sources.

      It is rare to call this method directly. More typically an Event subclass will provide a static register method, or a widget will accept handlers directly.

      Type Parameters:
      H - The type of handler
      Parameters:
      type - the event type associated with this handler
      handler - the handler
      Returns:
      the handler registration, can be stored in order to remove the handler later

    • addHandlerToSource

      public abstract <H> HandlerRegistration addHandlerToSource(Event.Type<H> type, Object source, H handler)
      Adds a handler to receive events of this type from the given source.

      It is rare to call this method directly. More typically a Event subclass will provide a static register method, or a widget will accept handlers directly.

      Type Parameters:
      H - The type of handler
      Parameters:
      type - the event type associated with this handler
      source - the source associated with this handler
      handler - the handler
      Returns:
      the handler registration, can be stored in order to remove the handler later

    • fireEvent

      public abstract void fireEvent(Event<?> event)
      Fires the event from no source. Only unfiltered handlers will receive it.

      Any exceptions thrown by handlers will be bundled into a UmbrellaException and then re-thrown after all handlers have completed. An exception thrown by a handler will not prevent other handlers from executing.

      Parameters:
      event - the event to fire
      Throws:
      UmbrellaException - wrapping exceptions thrown by handlers

    • fireEventFromSource

      public abstract void fireEventFromSource(Event<?> event, Object source)
      Fires the given event to the handlers listening to the event's type.

      Any exceptions thrown by handlers will be bundled into a UmbrellaException and then re-thrown after all handlers have completed. An exception thrown by a handler will not prevent other handlers from executing.

      Parameters:
      event - the event to fire
      Throws:
      UmbrellaException - wrapping exceptions thrown by handlers