1 /*
   2  * Copyright (c) 1998, 2013, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package java.beans.beancontext;
  27 
  28 import java.beans.PropertyChangeEvent;
  29 import java.beans.PropertyChangeListener;
  30 import java.beans.PropertyChangeSupport;
  31 
  32 import java.beans.VetoableChangeListener;
  33 import java.beans.VetoableChangeSupport;
  34 
  35 import java.beans.PropertyVetoException;
  36 
  37 import java.io.IOException;
  38 import java.io.ObjectInputStream;
  39 import java.io.ObjectOutputStream;
  40 import java.io.Serializable;
  41 
  42 /**
  43  * <p>
  44  * This is a general support class to provide support for implementing the
  45  * BeanContextChild protocol.
  46  *
  47  * This class may either be directly subclassed, or encapsulated and delegated
  48  * to in order to implement this interface for a given component.
  49  * </p>
  50  *
  51  * @author      Laurence P. G. Cable
  52  * @since       1.2
  53  *
  54  * @see java.beans.beancontext.BeanContext
  55  * @see java.beans.beancontext.BeanContextServices
  56  * @see java.beans.beancontext.BeanContextChild
  57  */
  58 
  59 public class BeanContextChildSupport implements BeanContextChild, BeanContextServicesListener, Serializable {
  60 
  61     static final long serialVersionUID = 6328947014421475877L;
  62 
  63     /**
  64      * construct a BeanContextChildSupport where this class has been
  65      * subclassed in order to implement the JavaBean component itself.
  66      */
  67 
  68     public BeanContextChildSupport() {
  69         super();
  70 
  71         beanContextChildPeer = this;
  72 
  73         pcSupport = new PropertyChangeSupport(beanContextChildPeer);
  74         vcSupport = new VetoableChangeSupport(beanContextChildPeer);
  75     }
  76 
  77     /**
  78      * construct a BeanContextChildSupport where the JavaBean component
  79      * itself implements BeanContextChild, and encapsulates this, delegating
  80      * that interface to this implementation
  81      * @param bcc the underlying bean context child
  82      */
  83 
  84     public BeanContextChildSupport(BeanContextChild bcc) {
  85         super();
  86 
  87         beanContextChildPeer = (bcc != null) ? bcc : this;
  88 
  89         pcSupport = new PropertyChangeSupport(beanContextChildPeer);
  90         vcSupport = new VetoableChangeSupport(beanContextChildPeer);
  91     }
  92 
  93     /**
  94      * Sets the {@code BeanContext} for
  95      * this {@code BeanContextChildSupport}.
  96      * @param bc the new value to be assigned to the {@code BeanContext}
  97      * property
  98      * @throws PropertyVetoException if the change is rejected
  99      */
 100     public synchronized void setBeanContext(BeanContext bc) throws PropertyVetoException {
 101         if (bc == beanContext) return;
 102 
 103         BeanContext oldValue = beanContext;
 104         BeanContext newValue = bc;
 105 
 106         if (!rejectedSetBCOnce) {
 107             if (rejectedSetBCOnce = !validatePendingSetBeanContext(bc)) {
 108                 throw new PropertyVetoException(
 109                     "setBeanContext() change rejected:",
 110                     new PropertyChangeEvent(beanContextChildPeer, "beanContext", oldValue, newValue)
 111                 );
 112             }
 113 
 114             try {
 115                 fireVetoableChange("beanContext",
 116                                    oldValue,
 117                                    newValue
 118                 );
 119             } catch (PropertyVetoException pve) {
 120                 rejectedSetBCOnce = true;
 121 
 122                 throw pve; // re-throw
 123             }
 124         }
 125 
 126         if (beanContext != null) releaseBeanContextResources();
 127 
 128         beanContext       = newValue;
 129         rejectedSetBCOnce = false;
 130 
 131         firePropertyChange("beanContext",
 132                            oldValue,
 133                            newValue
 134         );
 135 
 136         if (beanContext != null) initializeBeanContextResources();
 137     }
 138 
 139     /**
 140      * Gets the nesting {@code BeanContext}
 141      * for this {@code BeanContextChildSupport}.
 142      * @return the nesting {@code BeanContext} for
 143      * this {@code BeanContextChildSupport}.
 144      */
 145     public synchronized BeanContext getBeanContext() { return beanContext; }
 146 
 147     /**
 148      * Add a PropertyChangeListener for a specific property.
 149      * The same listener object may be added more than once.  For each
 150      * property,  the listener will be invoked the number of times it was added
 151      * for that property.
 152      * If {@code name} or {@code pcl} is null, no exception is thrown
 153      * and no action is taken.
 154      *
 155      * @param name The name of the property to listen on
 156      * @param pcl The {@code PropertyChangeListener} to be added
 157      */
 158     public void addPropertyChangeListener(String name, PropertyChangeListener pcl) {
 159         pcSupport.addPropertyChangeListener(name, pcl);
 160     }
 161 
 162     /**
 163      * Remove a PropertyChangeListener for a specific property.
 164      * If {@code pcl} was added more than once to the same event
 165      * source for the specified property, it will be notified one less time
 166      * after being removed.
 167      * If {@code name} is null, no exception is thrown
 168      * and no action is taken.
 169      * If {@code pcl} is null, or was never added for the specified
 170      * property, no exception is thrown and no action is taken.
 171      *
 172      * @param name The name of the property that was listened on
 173      * @param pcl The PropertyChangeListener to be removed
 174      */
 175     public void removePropertyChangeListener(String name, PropertyChangeListener pcl) {
 176         pcSupport.removePropertyChangeListener(name, pcl);
 177     }
 178 
 179     /**
 180      * Add a VetoableChangeListener for a specific property.
 181      * The same listener object may be added more than once.  For each
 182      * property,  the listener will be invoked the number of times it was added
 183      * for that property.
 184      * If {@code name} or {@code vcl} is null, no exception is thrown
 185      * and no action is taken.
 186      *
 187      * @param name The name of the property to listen on
 188      * @param vcl The {@code VetoableChangeListener} to be added
 189      */
 190     public void addVetoableChangeListener(String name, VetoableChangeListener vcl) {
 191         vcSupport.addVetoableChangeListener(name, vcl);
 192     }
 193 
 194     /**
 195      * Removes a {@code VetoableChangeListener}.
 196      * If {@code pcl} was added more than once to the same event
 197      * source for the specified property, it will be notified one less time
 198      * after being removed.
 199      * If {@code name} is null, no exception is thrown
 200      * and no action is taken.
 201      * If {@code vcl} is null, or was never added for the specified
 202      * property, no exception is thrown and no action is taken.
 203      *
 204      * @param name The name of the property that was listened on
 205      * @param vcl The {@code VetoableChangeListener} to be removed
 206      */
 207     public void removeVetoableChangeListener(String name, VetoableChangeListener vcl) {
 208         vcSupport.removeVetoableChangeListener(name, vcl);
 209     }
 210 
 211     /**
 212      * A service provided by the nesting BeanContext has been revoked.
 213      *
 214      * Subclasses may override this method in order to implement their own
 215      * behaviors.
 216      * @param bcsre The {@code BeanContextServiceRevokedEvent} fired as a
 217      * result of a service being revoked
 218      */
 219     public void serviceRevoked(BeanContextServiceRevokedEvent bcsre) { }
 220 
 221     /**
 222      * A new service is available from the nesting BeanContext.
 223      *
 224      * Subclasses may override this method in order to implement their own
 225      * behaviors
 226      * @param bcsae The BeanContextServiceAvailableEvent fired as a
 227      * result of a service becoming available
 228      *
 229      */
 230     public void serviceAvailable(BeanContextServiceAvailableEvent bcsae) { }
 231 
 232     /**
 233      * Gets the {@code BeanContextChild} associated with this
 234      * {@code BeanContextChildSupport}.
 235      *
 236      * @return the {@code BeanContextChild} peer of this class
 237      */
 238     public BeanContextChild getBeanContextChildPeer() { return beanContextChildPeer; }
 239 
 240     /**
 241      * Reports whether or not this class is a delegate of another.
 242      *
 243      * @return true if this class is a delegate of another
 244      */
 245     public boolean isDelegated() { return !this.equals(beanContextChildPeer); }
 246 
 247     /**
 248      * Report a bound property update to any registered listeners. No event is
 249      * fired if old and new are equal and non-null.
 250      * @param name The programmatic name of the property that was changed
 251      * @param oldValue  The old value of the property
 252      * @param newValue  The new value of the property
 253      */
 254     public void firePropertyChange(String name, Object oldValue, Object newValue) {
 255         pcSupport.firePropertyChange(name, oldValue, newValue);
 256     }
 257 
 258     /**
 259      * Report a vetoable property update to any registered listeners.
 260      * If anyone vetos the change, then fire a new event
 261      * reverting everyone to the old value and then rethrow
 262      * the PropertyVetoException. <P>
 263      *
 264      * No event is fired if old and new are equal and non-null.
 265      *
 266      * @param name The programmatic name of the property that is about to
 267      * change
 268      *
 269      * @param oldValue The old value of the property
 270      * @param newValue - The new value of the property
 271      *
 272      * @throws PropertyVetoException if the recipient wishes the property
 273      * change to be rolled back.
 274      */
 275     public void fireVetoableChange(String name, Object oldValue, Object newValue) throws PropertyVetoException {
 276         vcSupport.fireVetoableChange(name, oldValue, newValue);
 277     }
 278 
 279     /**
 280      * Called from setBeanContext to validate (or otherwise) the
 281      * pending change in the nesting BeanContext property value.
 282      * Returning false will cause setBeanContext to throw
 283      * PropertyVetoException.
 284      * @param newValue the new value that has been requested for
 285      *  the BeanContext property
 286      * @return {@code true} if the change operation is to be vetoed
 287      */
 288     public boolean validatePendingSetBeanContext(BeanContext newValue) {
 289         return true;
 290     }
 291 
 292     /**
 293      * This method may be overridden by subclasses to provide their own
 294      * release behaviors. When invoked any resources held by this instance
 295      * obtained from its current BeanContext property should be released
 296      * since the object is no longer nested within that BeanContext.
 297      */
 298 
 299     protected  void releaseBeanContextResources() {
 300         // do nothing
 301     }
 302 
 303     /**
 304      * This method may be overridden by subclasses to provide their own
 305      * initialization behaviors. When invoked any resources required by the
 306      * BeanContextChild should be obtained from the current BeanContext.
 307      */
 308 
 309     protected void initializeBeanContextResources() {
 310         // do nothing
 311     }
 312 
 313     /**
 314      * Write the persistence state of the object.
 315      */
 316 
 317     private void writeObject(ObjectOutputStream oos) throws IOException {
 318 
 319         /*
 320          * don't serialize if we are delegated and the delegator is not also
 321          * serializable.
 322          */
 323 
 324         if (!equals(beanContextChildPeer) && !(beanContextChildPeer instanceof Serializable))
 325             throw new IOException("BeanContextChildSupport beanContextChildPeer not Serializable");
 326 
 327         else
 328             oos.defaultWriteObject();
 329 
 330     }
 331 
 332 
 333     /**
 334      * Restore a persistent object, must wait for subsequent setBeanContext()
 335      * to fully restore any resources obtained from the new nesting
 336      * BeanContext
 337      */
 338 
 339     private void readObject(ObjectInputStream ois) throws IOException, ClassNotFoundException {
 340         ois.defaultReadObject();
 341     }
 342 
 343     /*
 344      * fields
 345      */
 346 
 347     /**
 348      * The {@code BeanContext} in which
 349      * this {@code BeanContextChild} is nested.
 350      */
 351     public    BeanContextChild      beanContextChildPeer;
 352 
 353    /**
 354     * The {@code PropertyChangeSupport} associated with this
 355     * {@code BeanContextChildSupport}.
 356     */
 357     protected PropertyChangeSupport pcSupport;
 358 
 359    /**
 360     * The {@code VetoableChangeSupport} associated with this
 361     * {@code BeanContextChildSupport}.
 362     */
 363     protected VetoableChangeSupport vcSupport;
 364 
 365     /**
 366      * The bean context.
 367      */
 368     protected transient BeanContext           beanContext;
 369 
 370    /**
 371     * A flag indicating that there has been
 372     * at least one {@code PropertyChangeVetoException}
 373     * thrown for the attempted setBeanContext operation.
 374     */
 375     protected transient boolean               rejectedSetBCOnce;
 376 
 377 }