Coverage Report - org.apache.commons.lang3.event.EventListenerSupport
 
Classes in this File Line Coverage Branch Coverage Complexity
EventListenerSupport
100%
45/45
100%
2/2
1,2
EventListenerSupport$ProxyInvocationHandler
100%
5/5
100%
2/2
1,2
 
 1  
 /*
 2  
  * Licensed to the Apache Software Foundation (ASF) under one or more
 3  
  * contributor license agreements.  See the NOTICE file distributed with
 4  
  * this work for additional information regarding copyright ownership.
 5  
  * The ASF licenses this file to You under the Apache License, Version 2.0
 6  
  * (the "License"); you may not use this file except in compliance with
 7  
  * the License.  You may obtain a copy of the License at
 8  
  *
 9  
  *      http://www.apache.org/licenses/LICENSE-2.0
 10  
  *
 11  
  * Unless required by applicable law or agreed to in writing, software
 12  
  * distributed under the License is distributed on an "AS IS" BASIS,
 13  
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 14  
  * See the License for the specific language governing permissions and
 15  
  * limitations under the License.
 16  
  */
 17  
 
 18  
 package org.apache.commons.lang3.event;
 19  
 
 20  
 import java.io.ByteArrayOutputStream;
 21  
 import java.io.IOException;
 22  
 import java.io.ObjectInputStream;
 23  
 import java.io.ObjectOutputStream;
 24  
 import java.io.Serializable;
 25  
 import java.lang.reflect.Array;
 26  
 import java.lang.reflect.InvocationHandler;
 27  
 import java.lang.reflect.Method;
 28  
 import java.lang.reflect.Proxy;
 29  
 import java.util.ArrayList;
 30  
 import java.util.List;
 31  
 import java.util.concurrent.CopyOnWriteArrayList;
 32  
 
 33  
 import org.apache.commons.lang3.Validate;
 34  
 
 35  
 /**
 36  
  * <p>An EventListenerSupport object can be used to manage a list of event
 37  
  * listeners of a particular type. The class provides
 38  
  * {@link #addListener(Object)} and {@link #removeListener(Object)} methods
 39  
  * for registering listeners, as well as a {@link #fire()} method for firing
 40  
  * events to the listeners.
 41  
  * </p>
 42  
  *
 43  
  * <p>
 44  
  * To use this class, suppose you want to support ActionEvents.  You would do:
 45  
  * </p>
 46  
  * <pre><code>
 47  
  * public class MyActionEventSource
 48  
  * {
 49  
  *   private EventListenerSupport&lt;ActionListener&gt; actionListeners =
 50  
  *       EventListenerSupport.create(ActionListener.class);
 51  
  *
 52  
  *   public void someMethodThatFiresAction()
 53  
  *   {
 54  
  *     ActionEvent e = new ActionEvent(this, ActionEvent.ACTION_PERFORMED, "somethingCool");
 55  
  *     actionListeners.fire().actionPerformed(e);
 56  
  *   }
 57  
  * }
 58  
  * </code></pre>
 59  
  *
 60  
  * <p>
 61  
  * Serializing an {@link EventListenerSupport} instance will result in any
 62  
  * non-{@link Serializable} listeners being silently dropped.
 63  
  * </p>
 64  
  *
 65  
  * @param <L> the type of event listener that is supported by this proxy.
 66  
  *
 67  
  * @since 3.0
 68  
  * @version $Id: EventListenerSupport.java 1583482 2014-03-31 22:54:57Z niallp $
 69  
  */
 70  9
 public class EventListenerSupport<L> implements Serializable {
 71  
 
 72  
     /** Serialization version */
 73  
     private static final long serialVersionUID = 3593265990380473632L;
 74  
 
 75  
     /**
 76  
      * The list used to hold the registered listeners. This list is
 77  
      * intentionally a thread-safe copy-on-write-array so that traversals over
 78  
      * the list of listeners will be atomic.
 79  
      */
 80  15
     private List<L> listeners = new CopyOnWriteArrayList<L>();
 81  
 
 82  
     /**
 83  
      * The proxy representing the collection of listeners. Calls to this proxy
 84  
      * object will sent to all registered listeners.
 85  
      */
 86  
     private transient L proxy;
 87  
 
 88  
     /**
 89  
      * Empty typed array for #getListeners().
 90  
      */
 91  
     private transient L[] prototypeArray;
 92  
 
 93  
     /**
 94  
      * Creates an EventListenerSupport object which supports the specified
 95  
      * listener type.
 96  
      *
 97  
      * @param <T> the type of the listener interface
 98  
      * @param listenerInterface the type of listener interface that will receive
 99  
      *        events posted using this class.
 100  
      *
 101  
      * @return an EventListenerSupport object which supports the specified
 102  
      *         listener type.
 103  
      *
 104  
      * @throws NullPointerException if <code>listenerInterface</code> is
 105  
      *         <code>null</code>.
 106  
      * @throws IllegalArgumentException if <code>listenerInterface</code> is
 107  
      *         not an interface.
 108  
      */
 109  
     public static <T> EventListenerSupport<T> create(final Class<T> listenerInterface) {
 110  14
         return new EventListenerSupport<T>(listenerInterface);
 111  
     }
 112  
 
 113  
     /**
 114  
      * Creates an EventListenerSupport object which supports the provided
 115  
      * listener interface.
 116  
      *
 117  
      * @param listenerInterface the type of listener interface that will receive
 118  
      *        events posted using this class.
 119  
      *
 120  
      * @throws NullPointerException if <code>listenerInterface</code> is
 121  
      *         <code>null</code>.
 122  
      * @throws IllegalArgumentException if <code>listenerInterface</code> is
 123  
      *         not an interface.
 124  
      */
 125  
     public EventListenerSupport(final Class<L> listenerInterface) {
 126  15
         this(listenerInterface, Thread.currentThread().getContextClassLoader());
 127  13
     }
 128  
 
 129  
     /**
 130  
      * Creates an EventListenerSupport object which supports the provided
 131  
      * listener interface using the specified class loader to create the JDK
 132  
      * dynamic proxy.
 133  
      *
 134  
      * @param listenerInterface the listener interface.
 135  
      * @param classLoader       the class loader.
 136  
      *
 137  
      * @throws NullPointerException if <code>listenerInterface</code> or
 138  
      *         <code>classLoader</code> is <code>null</code>.
 139  
      * @throws IllegalArgumentException if <code>listenerInterface</code> is
 140  
      *         not an interface.
 141  
      */
 142  
     public EventListenerSupport(final Class<L> listenerInterface, final ClassLoader classLoader) {
 143  15
         this();
 144  15
         Validate.notNull(listenerInterface, "Listener interface cannot be null.");
 145  14
         Validate.notNull(classLoader, "ClassLoader cannot be null.");
 146  14
         Validate.isTrue(listenerInterface.isInterface(), "Class {0} is not an interface",
 147  
                 listenerInterface.getName());
 148  13
         initializeTransientFields(listenerInterface, classLoader);
 149  13
     }
 150  
 
 151  
     /**
 152  
      * Create a new EventListenerSupport instance.
 153  
      * Serialization-friendly constructor.
 154  
      */
 155  15
     private EventListenerSupport() {
 156  15
     }
 157  
 
 158  
     /**
 159  
      * Returns a proxy object which can be used to call listener methods on all
 160  
      * of the registered event listeners. All calls made to this proxy will be
 161  
      * forwarded to all registered listeners.
 162  
      *
 163  
      * @return a proxy object which can be used to call listener methods on all
 164  
      * of the registered event listeners
 165  
      */
 166  
     public L fire() {
 167  10
         return proxy;
 168  
     }
 169  
 
 170  
 //**********************************************************************************************************************
 171  
 // Other Methods
 172  
 //**********************************************************************************************************************
 173  
 
 174  
     /**
 175  
      * Registers an event listener.
 176  
      *
 177  
      * @param listener the event listener (may not be <code>null</code>).
 178  
      *
 179  
      * @throws NullPointerException if <code>listener</code> is
 180  
      *         <code>null</code>.
 181  
      */
 182  
     public void addListener(final L listener) {
 183  22
         Validate.notNull(listener, "Listener object cannot be null.");
 184  21
         listeners.add(listener);
 185  21
     }
 186  
 
 187  
     /**
 188  
      * Returns the number of registered listeners.
 189  
      *
 190  
      * @return the number of registered listeners.
 191  
      */
 192  
     int getListenerCount() {
 193  2
         return listeners.size();
 194  
     }
 195  
 
 196  
     /**
 197  
      * Unregisters an event listener.
 198  
      *
 199  
      * @param listener the event listener (may not be <code>null</code>).
 200  
      *
 201  
      * @throws NullPointerException if <code>listener</code> is
 202  
      *         <code>null</code>.
 203  
      */
 204  
     public void removeListener(final L listener) {
 205  14
         Validate.notNull(listener, "Listener object cannot be null.");
 206  13
         listeners.remove(listener);
 207  13
     }
 208  
 
 209  
     /**
 210  
      * Get an array containing the currently registered listeners.
 211  
      * Modification to this array's elements will have no effect on the
 212  
      * {@link EventListenerSupport} instance.
 213  
      * @return L[]
 214  
      */
 215  
     public L[] getListeners() {
 216  8
         return listeners.toArray(prototypeArray);
 217  
     }
 218  
 
 219  
     /**
 220  
      * Serialize.
 221  
      * @param objectOutputStream the output stream
 222  
      * @throws IOException if an IO error occurs
 223  
      */
 224  
     private void writeObject(final ObjectOutputStream objectOutputStream) throws IOException {
 225  1
         final ArrayList<L> serializableListeners = new ArrayList<L>();
 226  
 
 227  
         // don't just rely on instanceof Serializable:
 228  1
         ObjectOutputStream testObjectOutputStream = new ObjectOutputStream(new ByteArrayOutputStream());
 229  1
         for (final L listener : listeners) {
 230  
             try {
 231  2
                 testObjectOutputStream.writeObject(listener);
 232  1
                 serializableListeners.add(listener);
 233  1
             } catch (final IOException exception) {
 234  
                 //recreate test stream in case of indeterminate state
 235  1
                 testObjectOutputStream = new ObjectOutputStream(new ByteArrayOutputStream());
 236  1
             }
 237  2
         }
 238  
         /*
 239  
          * we can reconstitute everything we need from an array of our listeners,
 240  
          * which has the additional advantage of typically requiring less storage than a list:
 241  
          */
 242  1
         objectOutputStream.writeObject(serializableListeners.toArray(prototypeArray));
 243  1
     }
 244  
 
 245  
     /**
 246  
      * Deserialize.
 247  
      * @param objectInputStream the input stream
 248  
      * @throws IOException if an IO error occurs
 249  
      * @throws ClassNotFoundException if the class cannot be resolved
 250  
      */
 251  
     private void readObject(final ObjectInputStream objectInputStream) throws IOException, ClassNotFoundException {
 252  
         @SuppressWarnings("unchecked") // Will throw CCE here if not correct
 253  
         final
 254  1
         L[] srcListeners = (L[]) objectInputStream.readObject();
 255  
 
 256  1
         this.listeners = new CopyOnWriteArrayList<L>(srcListeners);
 257  
 
 258  
         @SuppressWarnings("unchecked") // Will throw CCE here if not correct
 259  
         final
 260  1
         Class<L> listenerInterface = (Class<L>) srcListeners.getClass().getComponentType();
 261  
 
 262  1
         initializeTransientFields(listenerInterface, Thread.currentThread().getContextClassLoader());
 263  1
     }
 264  
 
 265  
     /**
 266  
      * Initialize transient fields.
 267  
      * @param listenerInterface the class of the listener interface
 268  
      * @param classLoader the class loader to be used
 269  
      */
 270  
     private void initializeTransientFields(final Class<L> listenerInterface, final ClassLoader classLoader) {
 271  
         @SuppressWarnings("unchecked") // Will throw CCE here if not correct
 272  
         final
 273  14
         L[] array = (L[]) Array.newInstance(listenerInterface, 0);
 274  14
         this.prototypeArray = array;
 275  14
         createProxy(listenerInterface, classLoader);
 276  14
     }
 277  
 
 278  
     /**
 279  
      * Create the proxy object.
 280  
      * @param listenerInterface the class of the listener interface
 281  
      * @param classLoader the class loader to be used
 282  
      */
 283  
     private void createProxy(final Class<L> listenerInterface, final ClassLoader classLoader) {
 284  14
         proxy = listenerInterface.cast(Proxy.newProxyInstance(classLoader,
 285  
                 new Class[] { listenerInterface }, createInvocationHandler()));
 286  14
     }
 287  
 
 288  
     /**
 289  
      * Create the {@link InvocationHandler} responsible for broadcasting calls
 290  
      * to the managed listeners.  Subclasses can override to provide custom behavior.
 291  
      * @return ProxyInvocationHandler
 292  
      */
 293  
     protected InvocationHandler createInvocationHandler() {
 294  13
         return new ProxyInvocationHandler();
 295  
     }
 296  
 
 297  
     /**
 298  
      * An invocation handler used to dispatch the event(s) to all the listeners.
 299  
      */
 300  14
     protected class ProxyInvocationHandler implements InvocationHandler {
 301  
 
 302  
         /**
 303  
          * Propagates the method call to all registered listeners in place of
 304  
          * the proxy listener object.
 305  
          *
 306  
          * @param unusedProxy the proxy object representing a listener on which the
 307  
          *        invocation was called; not used
 308  
          * @param method the listener method that will be called on all of the
 309  
          *        listeners.
 310  
          * @param args event arguments to propagate to the listeners.
 311  
          * @return the result of the method call
 312  
          * @throws Throwable if an error occurs
 313  
          */
 314  
         @Override
 315  
         public Object invoke(final Object unusedProxy, final Method method, final Object[] args) throws Throwable {
 316  9
             for (final L listener : listeners) {
 317  19
                 method.invoke(listener, args);
 318  19
             }
 319  9
             return null;
 320  
         }
 321  
     }
 322  
 }