Package org.apache.commons.lang3.event

Class EventListenerSupport<L>

  • Type Parameters:
    L - the type of event listener that is supported by this proxy.
    All Implemented Interfaces:
    java.io.Serializable
    public class EventListenerSupport<L>
extends java.lang.Object
implements java.io.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:
    Serialized Form

    • Constructor Summary

      Constructors 
      Constructor Description
      EventListenerSupport​(java.lang.Class<L> listenerInterface)
      Constructs an EventListenerSupport object which supports the provided listener interface.
      EventListenerSupport​(java.lang.Class<L> listenerInterface, java.lang.ClassLoader classLoader)
      Constructs an EventListenerSupport object which supports the provided listener interface using the specified class loader to create the JDK dynamic proxy.

    • Method Summary

      All Methods Static Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      void addListener​(L listener)
      Adds an event listener.
      void addListener​(L listener, boolean allowDuplicate)
      Adds an event listener.
      static <T> EventListenerSupport<T> create​(java.lang.Class<T> listenerInterface)
      Creates an EventListenerSupport object which supports the specified listener type.
      protected java.lang.reflect.InvocationHandler createInvocationHandler()
      Creates the InvocationHandler responsible for calling to the managed listeners.
      L fire()
      Returns a proxy object which can be used to call listener methods on all of the registered event listeners.
      L[] getListeners()
      Gets an array containing the currently registered listeners.
      void removeListener​(L listener)
      Removes an event listener.

      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

    • Constructor Detail

      • EventListenerSupport

        public EventListenerSupport​(java.lang.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:
        java.lang.NullPointerException - if listenerInterface is null.
        java.lang.IllegalArgumentException - if listenerInterface is not an interface.

      • EventListenerSupport

        public EventListenerSupport​(java.lang.Class<L> listenerInterface,
                            java.lang.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:
        java.lang.NullPointerException - if listenerInterface or classLoader is null.
        java.lang.IllegalArgumentException - if listenerInterface is not an interface.

    • Method Detail

      • create

        public static <T> EventListenerSupport<T> create​(java.lang.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:
        java.lang.NullPointerException - if listenerInterface is null.
        java.lang.IllegalArgumentException - 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:
        java.lang.NullPointerException - 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:
        java.lang.NullPointerException - if listener is null.
        Since:
        3.5

      • createInvocationHandler

        protected java.lang.reflect.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:
        java.lang.NullPointerException - if listener is null.