Package org.apache.commons.lang3.event

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:

java.io.Serializable

public class EventListenerSupport<L>
extends java.lang.Object
implements java.io.Serializable

An EventListenerSupport object can be used to manage a list of event listeners of a particular type. The class provides addListener(Object) and removeListener(Object) methods for registering listeners, as well as a fire() method for firing events to the listeners.

To use this class, suppose you want to support ActionEvents. You would do:

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

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

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

Since:

3.0

See Also:

Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
protected class	EventListenerSupport.ProxyInvocationHandler	An invocation handler used to dispatch the event(s) to all the listeners.

Constructor Summary

Constructors

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

Method Summary

Modifier and Type	Method	Description
void	addListener(L listener)	Registers an event listener.
void	addListener(L listener, boolean allowDuplicate)	Registers 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()	Create the InvocationHandler responsible for broadcasting calls 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()	Get an array containing the currently registered listeners.
void	removeListener(L listener)	Unregisters 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)

Creates 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)

Creates 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.

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

addListener

public void addListener(L listener)

Registers an event listener.

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)

Registers an event listener. Will not add a pre-existing listener object to the list if allowDuplicate is false.

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

removeListener

public void removeListener(L listener)

Unregisters an event listener.

Parameters:

listener - the event listener (may not be null).

Throws:

java.lang.NullPointerException - if listener is null.

getListeners

public L[] getListeners()

Get an array containing the currently registered listeners. Modification to this array's elements will have no effect on the EventListenerSupport instance.

Returns:

L[]

createInvocationHandler

protected java.lang.reflect.InvocationHandler createInvocationHandler()

Create the InvocationHandler responsible for broadcasting calls to the managed listeners. Subclasses can override to provide custom behavior.

Returns:

ProxyInvocationHandler