provide read access to the registered listener instances

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/lang/trunk@986954 13f79535-47bb-0310-9956-ffa450edef68

src/main/java/org/apache/commons/lang3/event/EventListenerSupport.java

@@ -17,6 +17,7 @@
 
 package org.apache.commons.lang3.event;
 
+import java.lang.reflect.Array;
 import java.lang.reflect.InvocationHandler;
 import java.lang.reflect.Method;
 import java.lang.reflect.Proxy;
@@ -68,6 +69,11 @@ public class EventListenerSupport<L>
      */
     private final L proxy;
 
+    /**
+     * Empty typed array for #getListeners().
+     */
+    private final L[] prototypeArray;
+
     /**
      * Creates an EventListenerSupport object which supports the specified 
      * listener type.
@@ -128,6 +134,9 @@ public class EventListenerSupport<L>
         proxy = listenerInterface.cast(Proxy.newProxyInstance(classLoader, 
                 new Class[]{listenerInterface},
                 new ProxyInvocationHandler()));
+        @SuppressWarnings("unchecked")
+        final L[] prototypeArray = (L[]) Array.newInstance(listenerInterface, 0);
+        this.prototypeArray = prototypeArray;
     }
 
     /**
@@ -185,6 +194,16 @@ public class EventListenerSupport<L>
         listeners.remove(listener);
     }
 
+    /**
+     * Get an array containing the currently registered listeners.
+     * Modification to this array's elements will have no effect on the
+     * {@link EventListenerSupport} instance.
+     * @return L[]
+     */
+    public L[] getListeners() {
+        return listeners.toArray(prototypeArray);
+    }
+
     /**
      * An invocation handler used to dispatch the event(s) to all the listeners.
      */

src/test/java/org/apache/commons/lang3/event/EventListenerSupportTest.java

@@ -24,6 +24,8 @@ import java.awt.event.ActionListener;
 import java.util.ArrayList;
 import java.util.List;
 
+import org.easymock.EasyMock;
+
 /**
  * @since 3.0
  * @version $Id$
@@ -111,6 +113,28 @@ public class EventListenerSupportTest extends TestCase
         assertEquals(listenerSupport.getListenerCount(), 0);
     }
 
+    public void testGetListeners() {
+        final EventListenerSupport<ActionListener> listenerSupport = EventListenerSupport.create(ActionListener.class);
+
+        ActionListener[] listeners = listenerSupport.getListeners();
+        assertEquals(0, listeners.length);
+        ActionListener[] empty = listeners;
+        //for fun, show that the same empty instance is used 
+        assertSame(empty, listenerSupport.getListeners());
+
+        ActionListener listener1 = EasyMock.createNiceMock(ActionListener.class);
+        listenerSupport.addListener(listener1);
+        assertEquals(1, listenerSupport.getListeners().length);
+        assertEquals(ActionListener.class, listenerSupport.getListeners().getClass().getComponentType());
+        ActionListener listener2 = EasyMock.createNiceMock(ActionListener.class);
+        listenerSupport.addListener(listener2);
+        assertEquals(2, listenerSupport.getListeners().length);
+        listenerSupport.removeListener(listener1);
+        assertEquals(1, listenerSupport.getListeners().length);
+        listenerSupport.removeListener(listener2);
+        assertSame(empty, listenerSupport.getListeners());
+    }
+
     private void addDeregisterListener(final EventListenerSupport<ActionListener> listenerSupport)
     {
         listenerSupport.addListener(new ActionListener()