Class EventListenerSupport<L>

java.lang.Object
org.apache.commons.lang3.event.EventListenerSupport<L>
Type Parameters:
L - The type of event listener that is supported by this proxy.
All Implemented Interfaces:
Serializable
public class EventListenerSupport<L> extends Object implements Serializable
Manages a list of event listeners of a given generic type. This class provides addListener(Object) and removeListener(Object) methods for managing listeners, as well as a fire() method for firing events to the listeners.

For example, to support ActionEvents: 

public class MyActionEventSource {

    private EventListenerSupport<ActionListener> actionListeners = EventListenerSupport.create(ActionListener.class);

    public void someMethodThatFiresAction() {
        ActionEvent e = new ActionEvent(this, ActionEvent.ACTION_PERFORMED, "something");
        actionListeners.fire().actionPerformed(e);
    }
}

Events are fired

Serializing an EventListenerSupport instance will result in any non-Serializable listeners being silently dropped.

Since:
3.0
See Also:

  • Constructor Details

    • EventListenerSupport

      public EventListenerSupport(Class<L> listenerInterface)
      Constructs an EventListenerSupport object which supports the provided listener interface.
      Parameters:
      listenerInterface - The type of listener interface that will receive events posted using this class.
      Throws:
      NullPointerException - Thrown if listenerInterface is null.
      IllegalArgumentException - Thrown if listenerInterface is not an interface.

    • EventListenerSupport

      public EventListenerSupport(Class<L> listenerInterface, ClassLoader classLoader)
      Constructs an EventListenerSupport object which supports the provided listener interface using the specified class loader to create the JDK dynamic proxy.
      Parameters:
      listenerInterface - The listener interface.
      classLoader - The class loader.
      Throws:
      NullPointerException - Thrown if listenerInterface or classLoader is null.
      IllegalArgumentException - Thrown if listenerInterface is not an interface.

  • Method Details

    • create

      public static <T> EventListenerSupport<T> create(Class<T> listenerInterface)
      Creates an EventListenerSupport object which supports the specified listener type.
      Type Parameters:
      T - The type of the listener interface
      Parameters:
      listenerInterface - The type of listener interface that will receive events posted using this class.
      Returns:
      An EventListenerSupport object which supports the specified listener type.
      Throws:
      NullPointerException - Thrown if listenerInterface is null.
      IllegalArgumentException - Thrown if listenerInterface is not an interface.

    • addListener

      public void addListener(L listener)
      Adds an event listener.

      Listeners are called in the order added.

      Parameters:
      listener - The event listener (may not be null).
      Throws:
      NullPointerException - Thrown if listener is null.

    • addListener

      public void addListener(L listener, boolean allowDuplicate)
      Adds an event listener. Will not add a pre-existing listener object to the list if allowDuplicate is false.

      Listeners are called in the order added.

      Parameters:
      listener - The event listener (may not be null).
      allowDuplicate - The flag for determining if duplicate listener objects are allowed to be registered.
      Throws:
      NullPointerException - Thrown if listener is null.
      Since:
      3.5

    • createInvocationHandler

      protected InvocationHandler createInvocationHandler()
      Creates the InvocationHandler responsible for calling to the managed listeners. Subclasses can override to provide custom behavior.
      Returns:
      ProxyInvocationHandler

    • fire

      public L fire()
      Returns a proxy object which can be used to call listener methods on all of the registered event listeners. All calls made to this proxy will be forwarded to all registered listeners.
      Returns:
      A proxy object which can be used to call listener methods on all of the registered event listeners

    • getListeners

      public L[] getListeners()
      Gets an array containing the currently registered listeners. Modification to this array's elements will have no effect on the EventListenerSupport instance.
      Returns:
      L[]

    • removeListener

      public void removeListener(L listener)
      Removes an event listener.
      Parameters:
      listener - The event listener (may not be null).
      Throws:
      NullPointerException - Thrown if listener is null.