| 1 | /* java.beans.beancontext.BeanContextChildSupport |
| 2 | Copyright (C) 1999 Free Software Foundation, Inc. |
| 3 | |
| 4 | This file is part of GNU Classpath. |
| 5 | |
| 6 | GNU Classpath is free software; you can redistribute it and/or modify |
| 7 | it under the terms of the GNU General Public License as published by |
| 8 | the Free Software Foundation; either version 2, or (at your option) |
| 9 | any later version. |
| 10 | |
| 11 | GNU Classpath is distributed in the hope that it will be useful, but |
| 12 | WITHOUT ANY WARRANTY; without even the implied warranty of |
| 13 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| 14 | General Public License for more details. |
| 15 | |
| 16 | You should have received a copy of the GNU General Public License |
| 17 | along with GNU Classpath; see the file COPYING. If not, write to the |
| 18 | Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA |
| 19 | 02110-1301 USA. |
| 20 | |
| 21 | Linking this library statically or dynamically with other modules is |
| 22 | making a combined work based on this library. Thus, the terms and |
| 23 | conditions of the GNU General Public License cover the whole |
| 24 | combination. |
| 25 | |
| 26 | As a special exception, the copyright holders of this library give you |
| 27 | permission to link this library with independent modules to produce an |
| 28 | executable, regardless of the license terms of these independent |
| 29 | modules, and to copy and distribute the resulting executable under |
| 30 | terms of your choice, provided that you also meet, for each linked |
| 31 | independent module, the terms and conditions of the license of that |
| 32 | module. An independent module is a module which is not derived from |
| 33 | or based on this library. If you modify this library, you may extend |
| 34 | this exception to your version of the library, but you are not |
| 35 | obligated to do so. If you do not wish to do so, delete this |
| 36 | exception statement from your version. */ |
| 37 | |
| 38 | |
| 39 | package java.beans.beancontext; |
| 40 | |
| 41 | import java.beans.PropertyChangeEvent; |
| 42 | import java.beans.PropertyChangeListener; |
| 43 | import java.beans.PropertyChangeSupport; |
| 44 | import java.beans.PropertyVetoException; |
| 45 | import java.beans.VetoableChangeListener; |
| 46 | import java.beans.VetoableChangeSupport; |
| 47 | import java.io.Serializable; |
| 48 | |
| 49 | /** |
| 50 | * Support for creating a <code>BeanContextChild</code>. |
| 51 | * This class contains the most common implementations of the methods in |
| 52 | * the <code>BeanContextChild</code> |
| 53 | * |
| 54 | * @specnote This class is not very well specified. I had to "fill in the |
| 55 | * blanks" in most places with what I thought was reasonable |
| 56 | * behavior. If there are problems, let me know. |
| 57 | * |
| 58 | * @author John Keiser |
| 59 | * @since 1.2 |
| 60 | * @see java.beans.beancontext.BeanContextChild |
| 61 | */ |
| 62 | public class BeanContextChildSupport |
| 63 | implements BeanContextChild, BeanContextServicesListener, Serializable |
| 64 | { |
| 65 | static final long serialVersionUID = 6328947014421475877L; |
| 66 | |
| 67 | /** |
| 68 | * The peer on which to perform <code>set</code> actions. |
| 69 | * This is here so that this class can be used as a peer. |
| 70 | * <P> |
| 71 | * |
| 72 | * When extending this class, this variable will be set to |
| 73 | * <code>this</code>. |
| 74 | */ |
| 75 | public BeanContextChild beanContextChildPeer; |
| 76 | |
| 77 | /** |
| 78 | * The parent <code>BeanContext</code>. |
| 79 | */ |
| 80 | protected transient BeanContext beanContext; |
| 81 | |
| 82 | /** |
| 83 | * If <code>setBeanContext()</code> was vetoed once before, this |
| 84 | * is set to <code>true</code> so that the next time, vetoes will |
| 85 | * be ignored. |
| 86 | */ |
| 87 | protected transient boolean rejectedSetBCOnce; |
| 88 | |
| 89 | /** |
| 90 | * Listeners are registered here and events are fired through here. |
| 91 | */ |
| 92 | protected PropertyChangeSupport pcSupport; |
| 93 | |
| 94 | /** |
| 95 | * Listeners are registered here and events are fired through here. |
| 96 | */ |
| 97 | protected VetoableChangeSupport vcSupport; |
| 98 | |
| 99 | /** |
| 100 | * Create a new <code>BeanContextChildSupport</code> with itself as the peer. |
| 101 | * This is meant to be used when you subclass |
| 102 | * <code>BeanContextChildSupport</code> to create your child. |
| 103 | */ |
| 104 | public BeanContextChildSupport() |
| 105 | { |
| 106 | this (null); |
| 107 | } |
| 108 | |
| 109 | /** |
| 110 | * Create a new <code>BeanContextChildSupport</code> with the specified peer. |
| 111 | * @param peer the peer to use, or <code>null</code> to specify |
| 112 | * <code>this</code>. |
| 113 | */ |
| 114 | public BeanContextChildSupport (BeanContextChild peer) |
| 115 | { |
| 116 | if (peer == null) |
| 117 | { |
| 118 | peer = this; |
| 119 | } |
| 120 | |
| 121 | beanContextChildPeer = peer; |
| 122 | pcSupport = new PropertyChangeSupport (peer); |
| 123 | vcSupport = new VetoableChangeSupport (peer); |
| 124 | } |
| 125 | |
| 126 | /** |
| 127 | * Set the parent <code>BeanContext</code>. |
| 128 | * <P> |
| 129 | * |
| 130 | * When this Object is being added to a new BeanContext or moved |
| 131 | * from an old one, a non-null value will be passed in. |
| 132 | * <P> |
| 133 | * |
| 134 | * When this Object is being removed from the current |
| 135 | * <code>BeanContext</code>, <code>setBeanContext()</code> will |
| 136 | * receive the parameter <code>null</code>. |
| 137 | * <P> |
| 138 | * |
| 139 | * Order of events: |
| 140 | * <OL> |
| 141 | * <LI> |
| 142 | * If the new <code>BeanContext</code> is the same as the old |
| 143 | * one, nothing happens. |
| 144 | * </LI> |
| 145 | * <LI> |
| 146 | * If the change has not been rejected or vetoed before, call |
| 147 | * <code>validatePendingSetBeanContext()</code>. If this call |
| 148 | * returns <code>false</code>, the change is rejected and a |
| 149 | * <code>PropertyVetoException</code> is thrown. |
| 150 | * </LI> |
| 151 | * <LI> |
| 152 | * If the change has not been rejected or vetoed before, |
| 153 | * <code>VetoableChangeEvent</code>s are fired with the name |
| 154 | * <code>"beanContext"</code>, using the |
| 155 | * <code>fireVetoableChange()</code> method. If a veto |
| 156 | * occurs, reversion events are fired using the same method, |
| 157 | * the change is rejected, and the veto is rethrown. |
| 158 | * </LI> |
| 159 | * <LI> |
| 160 | * <code>releaseBeanContextResources()</code> is called. |
| 161 | * </LI> |
| 162 | * <LI> |
| 163 | * The change is made. |
| 164 | * </LI> |
| 165 | * <LI> |
| 166 | * <code>PropertyChangeEvent</code>s are fired using the |
| 167 | * <code>firePropertyChange()</code> method. |
| 168 | * </LI> |
| 169 | * <LI> |
| 170 | * <code>initializeBeanContextResources()</code> is called. |
| 171 | * </LI> |
| 172 | * </OL> |
| 173 | * <P> |
| 174 | * |
| 175 | * @param newBeanContext the new parent for the |
| 176 | * <code>BeanContextChild</code>, or <code>null</code> to |
| 177 | * signify removal from a tree. |
| 178 | * @exception PropertyVetoException if the |
| 179 | * <code>BeanContextChild</code> implementor does not |
| 180 | * wish to have its parent changed. |
| 181 | */ |
| 182 | public void setBeanContext(BeanContext newBeanContext) |
| 183 | throws PropertyVetoException |
| 184 | { |
| 185 | synchronized (beanContextChildPeer) |
| 186 | { |
| 187 | if (newBeanContext == beanContext) |
| 188 | return; |
| 189 | |
| 190 | if (!rejectedSetBCOnce) |
| 191 | { |
| 192 | if (!validatePendingSetBeanContext (newBeanContext)) |
| 193 | { |
| 194 | rejectedSetBCOnce = true; |
| 195 | throw new PropertyVetoException ("validatePendingSetBeanContext() rejected change", |
| 196 | new PropertyChangeEvent(beanContextChildPeer, "beanContext", beanContext, newBeanContext)); |
| 197 | } |
| 198 | |
| 199 | try |
| 200 | { |
| 201 | fireVetoableChange ("beanContext", beanContext, newBeanContext); |
| 202 | } |
| 203 | catch (PropertyVetoException e) |
| 204 | { |
| 205 | rejectedSetBCOnce = true; |
| 206 | throw e; |
| 207 | } |
| 208 | } |
| 209 | |
| 210 | releaseBeanContextResources (); |
| 211 | |
| 212 | beanContext = newBeanContext; |
| 213 | rejectedSetBCOnce = false; |
| 214 | |
| 215 | firePropertyChange ("beanContext", beanContext, newBeanContext); |
| 216 | |
| 217 | initializeBeanContextResources (); |
| 218 | } |
| 219 | } |
| 220 | |
| 221 | /** |
| 222 | * Get the parent <code>BeanContext</code>. |
| 223 | * @return the parent <code>BeanContext</code>. |
| 224 | */ |
| 225 | public BeanContext getBeanContext() |
| 226 | { |
| 227 | return beanContext; |
| 228 | } |
| 229 | |
| 230 | /** |
| 231 | * Get the peer (or <code>this</code> if there is no peer). |
| 232 | * @return the peer, or <code>this</code> if there is no peer. |
| 233 | */ |
| 234 | public BeanContextChild getBeanContextChildPeer() { |
| 235 | return beanContextChildPeer; |
| 236 | } |
| 237 | |
| 238 | /** |
| 239 | * Determine whether there is a peer. |
| 240 | * This is true iff <code>getBeanContextChildPeer() == this</code>. |
| 241 | * @return whether there is a peer. |
| 242 | */ |
| 243 | public boolean isDelegated() { |
| 244 | return beanContextChildPeer == this; |
| 245 | } |
| 246 | |
| 247 | /** |
| 248 | * Add a listener that will be notified when a specific property changes. |
| 249 | * @param propertyName the name of the property to listen on. |
| 250 | * @param listener the listener to listen on the property. |
| 251 | */ |
| 252 | public void addPropertyChangeListener(String propertyName, PropertyChangeListener listener) { |
| 253 | pcSupport.addPropertyChangeListener(propertyName, listener); |
| 254 | } |
| 255 | |
| 256 | /** |
| 257 | * Remove a listener to a certain property. |
| 258 | * |
| 259 | * @param propertyName the name of the property being listened on. |
| 260 | * @param listener the listener listening on the property. |
| 261 | */ |
| 262 | public void removePropertyChangeListener(String propertyName, PropertyChangeListener listener) { |
| 263 | pcSupport.removePropertyChangeListener(propertyName, listener); |
| 264 | } |
| 265 | |
| 266 | /** |
| 267 | * Add a listener that will be notified when a specific property |
| 268 | * change is requested (a PropertyVetoException may be thrown) as |
| 269 | * well as after the change is successfully made. |
| 270 | * |
| 271 | * @param propertyName the name of the property to listen on. |
| 272 | * @param listener the listener to listen on the property. |
| 273 | */ |
| 274 | public void addVetoableChangeListener(String propertyName, VetoableChangeListener listener) { |
| 275 | vcSupport.addVetoableChangeListener(propertyName, listener); |
| 276 | } |
| 277 | |
| 278 | /** |
| 279 | * Remove a listener to a certain property. |
| 280 | * |
| 281 | * @param propertyName the name of the property being listened on |
| 282 | * @param listener the listener listening on the property. |
| 283 | */ |
| 284 | public void removeVetoableChangeListener(String propertyName, VetoableChangeListener listener) { |
| 285 | vcSupport.removeVetoableChangeListener(propertyName, listener); |
| 286 | } |
| 287 | |
| 288 | /** |
| 289 | * Fire a property change. |
| 290 | * |
| 291 | * @param propertyName the name of the property that changed |
| 292 | * @param oldVal the old value of the property |
| 293 | * @param newVal the new value of the property |
| 294 | */ |
| 295 | public void firePropertyChange(String propertyName, Object oldVal, Object newVal) { |
| 296 | pcSupport.firePropertyChange(propertyName, oldVal, newVal); |
| 297 | } |
| 298 | |
| 299 | /** |
| 300 | * Fire a vetoable property change. |
| 301 | * |
| 302 | * @param propertyName the name of the property that changed |
| 303 | * @param oldVal the old value of the property |
| 304 | * @param newVal the new value of the property |
| 305 | * @exception PropertyVetoException if the change is vetoed. |
| 306 | */ |
| 307 | public void fireVetoableChange(String propertyName, Object oldVal, Object newVal) |
| 308 | throws PropertyVetoException { |
| 309 | vcSupport.fireVetoableChange(propertyName, oldVal, newVal); |
| 310 | } |
| 311 | |
| 312 | /** |
| 313 | * Called by <code>BeanContextServices.revokeService()</code> to indicate that a service has been revoked. |
| 314 | * If you have a reference to such a service, it should be |
| 315 | * discarded and may no longer function properly. |
| 316 | * <code>getService()</code> will no longer work on the specified |
| 317 | * service class after this event has been fired. |
| 318 | * <P> |
| 319 | * |
| 320 | * <EM>This method is meant to be overriden.</EM> |
| 321 | * <code>BeanContextChildSupport</code>'s implementation does |
| 322 | * nothing. |
| 323 | * |
| 324 | * @param event the service revoked event. |
| 325 | * @see java.beans.beancontext.BeanContextServices#revokeService(java.lang.Class,java.beans.beancontext.BeanContextServiceProvider,boolean) |
| 326 | */ |
| 327 | public void serviceRevoked(BeanContextServiceRevokedEvent event) { |
| 328 | } |
| 329 | |
| 330 | /** |
| 331 | * Called by <code>BeanContextServices</code> whenever a service is made available. |
| 332 | * <P> |
| 333 | * |
| 334 | * <EM>This method is meant to be overriden.</EM> |
| 335 | * <code>BeanContextChildSupport</code>'s implementation does |
| 336 | * nothing. |
| 337 | * |
| 338 | * @param event the service revoked event, with useful information |
| 339 | * about the new service. |
| 340 | */ |
| 341 | public void serviceAvailable(BeanContextServiceAvailableEvent event) { |
| 342 | } |
| 343 | |
| 344 | /** |
| 345 | * Called by <code>setBeanContext()</code> to determine whether the set should be rejected. |
| 346 | * <P> |
| 347 | * |
| 348 | * <EM>This method is meant to be overriden.</EM> |
| 349 | * <code>BeanContextChildSupport</code>'s implementation simply |
| 350 | * returns <code>true</code>. |
| 351 | * |
| 352 | * @param newBeanContext the new parent. |
| 353 | * @return whether to allow the parent to be changed to the new |
| 354 | * value. |
| 355 | */ |
| 356 | public boolean validatePendingSetBeanContext(BeanContext newBeanContext) { |
| 357 | return true; |
| 358 | } |
| 359 | |
| 360 | /** |
| 361 | * Called by <code>setBeanContext()</code> to release resources of a what will soon no longer be the parent. |
| 362 | * <P> |
| 363 | * |
| 364 | * <EM>This method is meant to be overriden.</EM> |
| 365 | * <code>BeanContextChildSupport</code>'s implementation does |
| 366 | * nothing. |
| 367 | */ |
| 368 | protected void releaseBeanContextResources() { |
| 369 | } |
| 370 | |
| 371 | /** |
| 372 | * Called by <code>setBeanContext()</code> to grab resources when the parent has been set. |
| 373 | * <P> |
| 374 | * |
| 375 | * <EM>This method is meant to be overriden.</EM> |
| 376 | * <code>BeanContextChildSupport</code>'s implementation does |
| 377 | * nothing. |
| 378 | */ |
| 379 | protected void initializeBeanContextResources() { |
| 380 | } |
| 381 | } |