Coverage Report - org.apache.commons.lang3.event.EventListenerSupport
 
Classes in this File Line Coverage Branch Coverage Complexity
EventListenerSupport
98%
49/50
83%
5/6
1,312
EventListenerSupport$ProxyInvocationHandler
100%
5/5
100%
2/2
1,312
 
 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  
  */
 69  9
 public class EventListenerSupport<L> implements Serializable {
 70  
 
 71  
     /** Serialization version */
 72  
     private static final long serialVersionUID = 3593265990380473632L;
 73  
 
 74  
     /**
 75  
      * The list used to hold the registered listeners. This list is
 76  
      * intentionally a thread-safe copy-on-write-array so that traversals over
 77  
      * the list of listeners will be atomic.
 78  
      */
 79  16
     private List<L> listeners = new CopyOnWriteArrayList<L>();
 80  
 
 81  
     /**
 82  
      * The proxy representing the collection of listeners. Calls to this proxy
 83  
      * object will sent to all registered listeners.
 84  
      */
 85  
     private transient L proxy;
 86  
 
 87  
     /**
 88  
      * Empty typed array for #getListeners().
 89  
      */
 90  
     private transient L[] prototypeArray;
 91  
 
 92  
     /**
 93  
      * Creates an EventListenerSupport object which supports the specified
 94  
      * listener type.
 95  
      *
 96  
      * @param <T> the type of the listener interface
 97  
      * @param listenerInterface the type of listener interface that will receive
 98  
      *        events posted using this class.
 99  
      *
 100  
      * @return an EventListenerSupport object which supports the specified
 101  
      *         listener type.
 102  
      *
 103  
      * @throws NullPointerException if <code>listenerInterface</code> is
 104  
      *         <code>null</code>.
 105  
      * @throws IllegalArgumentException if <code>listenerInterface</code> is
 106  
      *         not an interface.
 107  
      */
 108  
     public static <T> EventListenerSupport<T> create(final Class<T> listenerInterface) {
 109  15
         return new EventListenerSupport<T>(listenerInterface);
 110  
     }
 111  
 
 112  
     /**
 113  
      * Creates an EventListenerSupport object which supports the provided
 114  
      * listener interface.
 115  
      *
 116  
      * @param listenerInterface the type of listener interface that will receive
 117  
      *        events posted using this class.
 118  
      *
 119  
      * @throws NullPointerException if <code>listenerInterface</code> is
 120  
      *         <code>null</code>.
 121  
      * @throws IllegalArgumentException if <code>listenerInterface</code> is
 122  
      *         not an interface.
 123  
      */
 124  
     public EventListenerSupport(final Class<L> listenerInterface) {
 125  16
         this(listenerInterface, Thread.currentThread().getContextClassLoader());
 126  14
     }
 127  
 
 128  
     /**
 129  
      * Creates an EventListenerSupport object which supports the provided
 130  
      * listener interface using the specified class loader to create the JDK
 131  
      * dynamic proxy.
 132  
      *
 133  
      * @param listenerInterface the listener interface.
 134  
      * @param classLoader       the class loader.
 135  
      *
 136  
      * @throws NullPointerException if <code>listenerInterface</code> or
 137  
      *         <code>classLoader</code> is <code>null</code>.
 138  
      * @throws IllegalArgumentException if <code>listenerInterface</code> is
 139  
      *         not an interface.
 140  
      */
 141  
     public EventListenerSupport(final Class<L> listenerInterface, final ClassLoader classLoader) {
 142  16
         this();
 143  16
         Validate.notNull(listenerInterface, "Listener interface cannot be null.");
 144  15
         Validate.notNull(classLoader, "ClassLoader cannot be null.");
 145  15
         Validate.isTrue(listenerInterface.isInterface(), "Class {0} is not an interface",
 146  
                 listenerInterface.getName());
 147  14
         initializeTransientFields(listenerInterface, classLoader);
 148  14
     }
 149  
 
 150  
     /**
 151  
      * Create a new EventListenerSupport instance.
 152  
      * Serialization-friendly constructor.
 153  
      */
 154  16
     private EventListenerSupport() {
 155  16
     }
 156  
 
 157  
     /**
 158  
      * Returns a proxy object which can be used to call listener methods on all
 159  
      * of the registered event listeners. All calls made to this proxy will be
 160  
      * forwarded to all registered listeners.
 161  
      *
 162  
      * @return a proxy object which can be used to call listener methods on all
 163  
      * of the registered event listeners
 164  
      */
 165  
     public L fire() {
 166  10
         return proxy;
 167  
     }
 168  
 
 169  
 //**********************************************************************************************************************
 170  
 // Other Methods
 171  
 //**********************************************************************************************************************
 172  
 
 173  
     /**
 174  
      * Registers an event listener.
 175  
      *
 176  
      * @param listener the event listener (may not be <code>null</code>).
 177  
      *
 178  
      * @throws NullPointerException if <code>listener</code> is
 179  
      *         <code>null</code>.
 180  
      */
 181  
     public void addListener(final L listener) {
 182  23
         addListener(listener, true);
 183  22
     }
 184  
 
 185  
     /**
 186  
      * Registers an event listener.  Will not add a pre-existing listener
 187  
      * object to the list if <code>allowDuplicate</code> is false.
 188  
      *
 189  
      * @param listener the event listener (may not be <code>null</code>).
 190  
      * @param allowDuplicate the flag for determining if duplicate listener
 191  
      * objects are allowed to be registered.
 192  
      *
 193  
      * @throws NullPointerException if <code>listener</code> is
 194  
      * <code>null</code>.
 195  
      */
 196  
     public void addListener(final L listener, boolean allowDuplicate) {
 197  24
         Validate.notNull(listener, "Listener object cannot be null.");
 198  23
         if (allowDuplicate) {
 199  22
             listeners.add(listener);
 200  1
         } else if (!listeners.contains(listener)) {
 201  0
             listeners.add(listener);
 202  
         }
 203  23
     }
 204  
 
 205  
     /**
 206  
      * Returns the number of registered listeners.
 207  
      *
 208  
      * @return the number of registered listeners.
 209  
      */
 210  
     int getListenerCount() {
 211  2
         return listeners.size();
 212  
     }
 213  
 
 214  
     /**
 215  
      * Unregisters an event listener.
 216  
      *
 217  
      * @param listener the event listener (may not be <code>null</code>).
 218  
      *
 219  
      * @throws NullPointerException if <code>listener</code> is
 220  
      *         <code>null</code>.
 221  
      */
 222  
     public void removeListener(final L listener) {
 223  15
         Validate.notNull(listener, "Listener object cannot be null.");
 224  14
         listeners.remove(listener);
 225  14
     }
 226  
 
 227  
     /**
 228  
      * Get an array containing the currently registered listeners.
 229  
      * Modification to this array's elements will have no effect on the
 230  
      * {@link EventListenerSupport} instance.
 231  
      * @return L[]
 232  
      */
 233  
     public L[] getListeners() {
 234  13
         return listeners.toArray(prototypeArray);
 235  
     }
 236  
 
 237  
     /**
 238  
      * Serialize.
 239  
      * @param objectOutputStream the output stream
 240  
      * @throws IOException if an IO error occurs
 241  
      */
 242  
     private void writeObject(final ObjectOutputStream objectOutputStream) throws IOException {
 243  1
         final ArrayList<L> serializableListeners = new ArrayList<L>();
 244  
 
 245  
         // don't just rely on instanceof Serializable:
 246  1
         ObjectOutputStream testObjectOutputStream = new ObjectOutputStream(new ByteArrayOutputStream());
 247  1
         for (final L listener : listeners) {
 248  
             try {
 249  2
                 testObjectOutputStream.writeObject(listener);
 250  1
                 serializableListeners.add(listener);
 251  1
             } catch (final IOException exception) {
 252  
                 //recreate test stream in case of indeterminate state
 253  1
                 testObjectOutputStream = new ObjectOutputStream(new ByteArrayOutputStream());
 254  1
             }
 255  2
         }
 256  
         /*
 257  
          * we can reconstitute everything we need from an array of our listeners,
 258  
          * which has the additional advantage of typically requiring less storage than a list:
 259  
          */
 260  1
         objectOutputStream.writeObject(serializableListeners.toArray(prototypeArray));
 261  1
     }
 262  
 
 263  
     /**
 264  
      * Deserialize.
 265  
      * @param objectInputStream the input stream
 266  
      * @throws IOException if an IO error occurs
 267  
      * @throws ClassNotFoundException if the class cannot be resolved
 268  
      */
 269  
     private void readObject(final ObjectInputStream objectInputStream) throws IOException, ClassNotFoundException {
 270  
         @SuppressWarnings("unchecked") // Will throw CCE here if not correct
 271  
         final
 272  1
         L[] srcListeners = (L[]) objectInputStream.readObject();
 273  
 
 274  1
         this.listeners = new CopyOnWriteArrayList<L>(srcListeners);
 275  
 
 276  
         @SuppressWarnings("unchecked") // Will throw CCE here if not correct
 277  
         final
 278  1
         Class<L> listenerInterface = (Class<L>) srcListeners.getClass().getComponentType();
 279  
 
 280  1
         initializeTransientFields(listenerInterface, Thread.currentThread().getContextClassLoader());
 281  1
     }
 282  
 
 283  
     /**
 284  
      * Initialize transient fields.
 285  
      * @param listenerInterface the class of the listener interface
 286  
      * @param classLoader the class loader to be used
 287  
      */
 288  
     private void initializeTransientFields(final Class<L> listenerInterface, final ClassLoader classLoader) {
 289  
         @SuppressWarnings("unchecked") // Will throw CCE here if not correct
 290  
         final
 291  15
         L[] array = (L[]) Array.newInstance(listenerInterface, 0);
 292  15
         this.prototypeArray = array;
 293  15
         createProxy(listenerInterface, classLoader);
 294  15
     }
 295  
 
 296  
     /**
 297  
      * Create the proxy object.
 298  
      * @param listenerInterface the class of the listener interface
 299  
      * @param classLoader the class loader to be used
 300  
      */
 301  
     private void createProxy(final Class<L> listenerInterface, final ClassLoader classLoader) {
 302  15
         proxy = listenerInterface.cast(Proxy.newProxyInstance(classLoader,
 303  
                 new Class[] { listenerInterface }, createInvocationHandler()));
 304  15
     }
 305  
 
 306  
     /**
 307  
      * Create the {@link InvocationHandler} responsible for broadcasting calls
 308  
      * to the managed listeners.  Subclasses can override to provide custom behavior.
 309  
      * @return ProxyInvocationHandler
 310  
      */
 311  
     protected InvocationHandler createInvocationHandler() {
 312  14
         return new ProxyInvocationHandler();
 313  
     }
 314  
 
 315  
     /**
 316  
      * An invocation handler used to dispatch the event(s) to all the listeners.
 317  
      */
 318  15
     protected class ProxyInvocationHandler implements InvocationHandler {
 319  
 
 320  
         /**
 321  
          * Propagates the method call to all registered listeners in place of
 322  
          * the proxy listener object.
 323  
          *
 324  
          * @param unusedProxy the proxy object representing a listener on which the
 325  
          *        invocation was called; not used
 326  
          * @param method the listener method that will be called on all of the
 327  
          *        listeners.
 328  
          * @param args event arguments to propagate to the listeners.
 329  
          * @return the result of the method call
 330  
          * @throws Throwable if an error occurs
 331  
          */
 332  
         @Override
 333  
         public Object invoke(final Object unusedProxy, final Method method, final Object[] args) throws Throwable {
 334  9
             for (final L listener : listeners) {
 335  19
                 method.invoke(listener, args);
 336  19
             }
 337  9
             return null;
 338  
         }
 339  
     }
 340  
 }