1 /* 2 * Copyright (C) 2014 The Android Open Source Project 3 * Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved. 4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 5 * 6 * This code is free software; you can redistribute it and/or modify it 7 * under the terms of the GNU General Public License version 2 only, as 8 * published by the Free Software Foundation. Oracle designates this 9 * particular file as subject to the "Classpath" exception as provided 10 * by Oracle in the LICENSE file that accompanied this code. 11 * 12 * This code is distributed in the hope that it will be useful, but WITHOUT 13 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 14 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 15 * version 2 for more details (a copy is included in the LICENSE file that 16 * accompanied this code). 17 * 18 * You should have received a copy of the GNU General Public License version 19 * 2 along with this work; if not, write to the Free Software Foundation, 20 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 21 * 22 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 23 * or visit www.oracle.com if you need additional information or have any 24 * questions. 25 */ 26 27 package java.util.prefs; 28 29 import java.util.*; 30 import java.io.*; 31 import java.security.AccessController; 32 import java.security.PrivilegedAction; 33 // These imports needed only as a workaround for a JavaDoc bug 34 import java.lang.Integer; 35 import java.lang.Long; 36 import java.lang.Float; 37 import java.lang.Double; 38 39 /** 40 * This class provides a skeletal implementation of the {@link Preferences} 41 * class, greatly easing the task of implementing it. 42 * 43 * <p><strong>This class is for <tt>Preferences</tt> implementers only. 44 * Normal users of the <tt>Preferences</tt> facility should have no need to 45 * consult this documentation. The {@link Preferences} documentation 46 * should suffice.</strong> 47 * 48 * <p>Implementors must override the nine abstract service-provider interface 49 * (SPI) methods: {@link #getSpi(String)}, {@link #putSpi(String,String)}, 50 * {@link #removeSpi(String)}, {@link #childSpi(String)}, {@link 51 * #removeNodeSpi()}, {@link #keysSpi()}, {@link #childrenNamesSpi()}, {@link 52 * #syncSpi()} and {@link #flushSpi()}. All of the concrete methods specify 53 * precisely how they are implemented atop these SPI methods. The implementor 54 * may, at his discretion, override one or more of the concrete methods if the 55 * default implementation is unsatisfactory for any reason, such as 56 * performance. 57 * 58 * <p>The SPI methods fall into three groups concerning exception 59 * behavior. The <tt>getSpi</tt> method should never throw exceptions, but it 60 * doesn't really matter, as any exception thrown by this method will be 61 * intercepted by {@link #get(String,String)}, which will return the specified 62 * default value to the caller. The <tt>removeNodeSpi, keysSpi, 63 * childrenNamesSpi, syncSpi</tt> and <tt>flushSpi</tt> methods are specified 64 * to throw {@link BackingStoreException}, and the implementation is required 65 * to throw this checked exception if it is unable to perform the operation. 66 * The exception propagates outward, causing the corresponding API method 67 * to fail. 68 * 69 * <p>The remaining SPI methods {@link #putSpi(String,String)}, {@link 70 * #removeSpi(String)} and {@link #childSpi(String)} have more complicated 71 * exception behavior. They are not specified to throw 72 * <tt>BackingStoreException</tt>, as they can generally obey their contracts 73 * even if the backing store is unavailable. This is true because they return 74 * no information and their effects are not required to become permanent until 75 * a subsequent call to {@link Preferences#flush()} or 76 * {@link Preferences#sync()}. Generally speaking, these SPI methods should not 77 * throw exceptions. In some implementations, there may be circumstances 78 * under which these calls cannot even enqueue the requested operation for 79 * later processing. Even under these circumstances it is generally better to 80 * simply ignore the invocation and return, rather than throwing an 81 * exception. Under these circumstances, however, all subsequent invocations 82 * of <tt>flush()</tt> and <tt>sync</tt> should return <tt>false</tt>, as 83 * returning <tt>true</tt> would imply that all previous operations had 84 * successfully been made permanent. 85 * 86 * <p>There is one circumstance under which <tt>putSpi, removeSpi and 87 * childSpi</tt> <i>should</i> throw an exception: if the caller lacks 88 * sufficient privileges on the underlying operating system to perform the 89 * requested operation. This will, for instance, occur on most systems 90 * if a non-privileged user attempts to modify system preferences. 91 * (The required privileges will vary from implementation to 92 * implementation. On some implementations, they are the right to modify the 93 * contents of some directory in the file system; on others they are the right 94 * to modify contents of some key in a registry.) Under any of these 95 * circumstances, it would generally be undesirable to let the program 96 * continue executing as if these operations would become permanent at a later 97 * time. While implementations are not required to throw an exception under 98 * these circumstances, they are encouraged to do so. A {@link 99 * SecurityException} would be appropriate. 100 * 101 * <p>Most of the SPI methods require the implementation to read or write 102 * information at a preferences node. The implementor should beware of the 103 * fact that another VM may have concurrently deleted this node from the 104 * backing store. It is the implementation's responsibility to recreate the 105 * node if it has been deleted. 106 * 107 * <p>Implementation note: In Sun's default <tt>Preferences</tt> 108 * implementations, the user's identity is inherited from the underlying 109 * operating system and does not change for the lifetime of the virtual 110 * machine. It is recognized that server-side <tt>Preferences</tt> 111 * implementations may have the user identity change from request to request, 112 * implicitly passed to <tt>Preferences</tt> methods via the use of a 113 * static {@link ThreadLocal} instance. Authors of such implementations are 114 * <i>strongly</i> encouraged to determine the user at the time preferences 115 * are accessed (for example by the {@link #get(String,String)} or {@link 116 * #put(String,String)} method) rather than permanently associating a user 117 * with each <tt>Preferences</tt> instance. The latter behavior conflicts 118 * with normal <tt>Preferences</tt> usage and would lead to great confusion. 119 * 120 * @author Josh Bloch 121 * @see Preferences 122 * @since 1.4 123 */ 124 public abstract class AbstractPreferences extends Preferences { 125 /** 126 * Our name relative to parent. 127 */ 128 private final String name; 129 130 /** 131 * Our absolute path name. 132 */ 133 private final String absolutePath; 134 135 /** 136 * Our parent node. 137 */ 138 final AbstractPreferences parent; 139 140 /** 141 * Our root node. 142 */ 143 private final AbstractPreferences root; // Relative to this node 144 145 /** 146 * This field should be <tt>true</tt> if this node did not exist in the 147 * backing store prior to the creation of this object. The field 148 * is initialized to false, but may be set to true by a subclass 149 * constructor (and should not be modified thereafter). This field 150 * indicates whether a node change event should be fired when 151 * creation is complete. 152 */ 153 protected boolean newNode = false; 154 155 /** 156 * All known unremoved children of this node. (This "cache" is consulted 157 * prior to calling childSpi() or getChild(). 158 */ 159 private Map<String, AbstractPreferences> kidCache = new HashMap<>(); 160 161 /** 162 * This field is used to keep track of whether or not this node has 163 * been removed. Once it's set to true, it will never be reset to false. 164 */ 165 private boolean removed = false; 166 167 /** 168 * Registered preference change listeners. 169 */ 170 // Android-changed: Copy-on-read List of listeners, not copy-on-write array. 171 // It's not clear if this change provides overall benefit; it might be 172 // reverted in future. Discussion: http://b/111195881 173 // private PreferenceChangeListener[] prefListeners = 174 // new PreferenceChangeListener[0]; 175 private final ArrayList<PreferenceChangeListener> prefListeners = new ArrayList<>(); 176 177 /** 178 * Registered node change listeners. 179 */ 180 // Android-changed: Copy-on-read List of listeners, not copy-on-write array. 181 // private NodeChangeListener[] nodeListeners = new NodeChangeListener[0]; 182 private final ArrayList<NodeChangeListener> nodeListeners = new ArrayList<>(); 183 184 /** 185 * An object whose monitor is used to lock this node. This object 186 * is used in preference to the node itself to reduce the likelihood of 187 * intentional or unintentional denial of service due to a locked node. 188 * To avoid deadlock, a node is <i>never</i> locked by a thread that 189 * holds a lock on a descendant of that node. 190 */ 191 protected final Object lock = new Object(); 192 193 /** 194 * Creates a preference node with the specified parent and the specified 195 * name relative to its parent. 196 * 197 * @param parent the parent of this preference node, or null if this 198 * is the root. 199 * @param name the name of this preference node, relative to its parent, 200 * or <tt>""</tt> if this is the root. 201 * @throws IllegalArgumentException if <tt>name</tt> contains a slash 202 * (<tt>'/'</tt>), or <tt>parent</tt> is <tt>null</tt> and 203 * name isn't <tt>""</tt>. 204 */ AbstractPreferences(AbstractPreferences parent, String name)205 protected AbstractPreferences(AbstractPreferences parent, String name) { 206 if (parent==null) { 207 if (!name.equals("")) 208 throw new IllegalArgumentException("Root name '"+name+ 209 "' must be \"\""); 210 this.absolutePath = "/"; 211 root = this; 212 } else { 213 if (name.indexOf('/') != -1) 214 throw new IllegalArgumentException("Name '" + name + 215 "' contains '/'"); 216 if (name.equals("")) 217 throw new IllegalArgumentException("Illegal name: empty string"); 218 219 root = parent.root; 220 absolutePath = (parent==root ? "/" + name 221 : parent.absolutePath() + "/" + name); 222 } 223 this.name = name; 224 this.parent = parent; 225 } 226 227 /** 228 * Implements the <tt>put</tt> method as per the specification in 229 * {@link Preferences#put(String,String)}. 230 * 231 * <p>This implementation checks that the key and value are legal, 232 * obtains this preference node's lock, checks that the node 233 * has not been removed, invokes {@link #putSpi(String,String)}, and if 234 * there are any preference change listeners, enqueues a notification 235 * event for processing by the event dispatch thread. 236 * 237 * @param key key with which the specified value is to be associated. 238 * @param value value to be associated with the specified key. 239 * @throws NullPointerException if key or value is <tt>null</tt>. 240 * @throws IllegalArgumentException if <tt>key.length()</tt> exceeds 241 * <tt>MAX_KEY_LENGTH</tt> or if <tt>value.length</tt> exceeds 242 * <tt>MAX_VALUE_LENGTH</tt>. 243 * @throws IllegalStateException if this node (or an ancestor) has been 244 * removed with the {@link #removeNode()} method. 245 */ put(String key, String value)246 public void put(String key, String value) { 247 if (key==null || value==null) 248 throw new NullPointerException(); 249 if (key.length() > MAX_KEY_LENGTH) 250 throw new IllegalArgumentException("Key too long: "+key); 251 if (value.length() > MAX_VALUE_LENGTH) 252 throw new IllegalArgumentException("Value too long: "+value); 253 254 synchronized(lock) { 255 if (removed) 256 throw new IllegalStateException("Node has been removed."); 257 258 putSpi(key, value); 259 enqueuePreferenceChangeEvent(key, value); 260 } 261 } 262 263 /** 264 * Implements the <tt>get</tt> method as per the specification in 265 * {@link Preferences#get(String,String)}. 266 * 267 * <p>This implementation first checks to see if <tt>key</tt> is 268 * <tt>null</tt> throwing a <tt>NullPointerException</tt> if this is 269 * the case. Then it obtains this preference node's lock, 270 * checks that the node has not been removed, invokes {@link 271 * #getSpi(String)}, and returns the result, unless the <tt>getSpi</tt> 272 * invocation returns <tt>null</tt> or throws an exception, in which case 273 * this invocation returns <tt>def</tt>. 274 * 275 * @param key key whose associated value is to be returned. 276 * @param def the value to be returned in the event that this 277 * preference node has no value associated with <tt>key</tt>. 278 * @return the value associated with <tt>key</tt>, or <tt>def</tt> 279 * if no value is associated with <tt>key</tt>. 280 * @throws IllegalStateException if this node (or an ancestor) has been 281 * removed with the {@link #removeNode()} method. 282 * @throws NullPointerException if key is <tt>null</tt>. (A 283 * <tt>null</tt> default <i>is</i> permitted.) 284 */ get(String key, String def)285 public String get(String key, String def) { 286 if (key==null) 287 throw new NullPointerException("Null key"); 288 synchronized(lock) { 289 if (removed) 290 throw new IllegalStateException("Node has been removed."); 291 292 String result = null; 293 try { 294 result = getSpi(key); 295 } catch (Exception e) { 296 // Ignoring exception causes default to be returned 297 } 298 return (result==null ? def : result); 299 } 300 } 301 302 /** 303 * Implements the <tt>remove(String)</tt> method as per the specification 304 * in {@link Preferences#remove(String)}. 305 * 306 * <p>This implementation obtains this preference node's lock, 307 * checks that the node has not been removed, invokes 308 * {@link #removeSpi(String)} and if there are any preference 309 * change listeners, enqueues a notification event for processing by the 310 * event dispatch thread. 311 * 312 * @param key key whose mapping is to be removed from the preference node. 313 * @throws IllegalStateException if this node (or an ancestor) has been 314 * removed with the {@link #removeNode()} method. 315 * @throws NullPointerException {@inheritDoc}. 316 */ remove(String key)317 public void remove(String key) { 318 Objects.requireNonNull(key, "Specified key cannot be null"); 319 synchronized(lock) { 320 if (removed) 321 throw new IllegalStateException("Node has been removed."); 322 323 removeSpi(key); 324 enqueuePreferenceChangeEvent(key, null); 325 } 326 } 327 328 /** 329 * Implements the <tt>clear</tt> method as per the specification in 330 * {@link Preferences#clear()}. 331 * 332 * <p>This implementation obtains this preference node's lock, 333 * invokes {@link #keys()} to obtain an array of keys, and 334 * iterates over the array invoking {@link #remove(String)} on each key. 335 * 336 * @throws BackingStoreException if this operation cannot be completed 337 * due to a failure in the backing store, or inability to 338 * communicate with it. 339 * @throws IllegalStateException if this node (or an ancestor) has been 340 * removed with the {@link #removeNode()} method. 341 */ clear()342 public void clear() throws BackingStoreException { 343 synchronized(lock) { 344 String[] keys = keys(); 345 for (int i=0; i<keys.length; i++) 346 remove(keys[i]); 347 } 348 } 349 350 /** 351 * Implements the <tt>putInt</tt> method as per the specification in 352 * {@link Preferences#putInt(String,int)}. 353 * 354 * <p>This implementation translates <tt>value</tt> to a string with 355 * {@link Integer#toString(int)} and invokes {@link #put(String,String)} 356 * on the result. 357 * 358 * @param key key with which the string form of value is to be associated. 359 * @param value value whose string form is to be associated with key. 360 * @throws NullPointerException if key is <tt>null</tt>. 361 * @throws IllegalArgumentException if <tt>key.length()</tt> exceeds 362 * <tt>MAX_KEY_LENGTH</tt>. 363 * @throws IllegalStateException if this node (or an ancestor) has been 364 * removed with the {@link #removeNode()} method. 365 */ putInt(String key, int value)366 public void putInt(String key, int value) { 367 put(key, Integer.toString(value)); 368 } 369 370 /** 371 * Implements the <tt>getInt</tt> method as per the specification in 372 * {@link Preferences#getInt(String,int)}. 373 * 374 * <p>This implementation invokes {@link #get(String,String) <tt>get(key, 375 * null)</tt>}. If the return value is non-null, the implementation 376 * attempts to translate it to an <tt>int</tt> with 377 * {@link Integer#parseInt(String)}. If the attempt succeeds, the return 378 * value is returned by this method. Otherwise, <tt>def</tt> is returned. 379 * 380 * @param key key whose associated value is to be returned as an int. 381 * @param def the value to be returned in the event that this 382 * preference node has no value associated with <tt>key</tt> 383 * or the associated value cannot be interpreted as an int. 384 * @return the int value represented by the string associated with 385 * <tt>key</tt> in this preference node, or <tt>def</tt> if the 386 * associated value does not exist or cannot be interpreted as 387 * an int. 388 * @throws IllegalStateException if this node (or an ancestor) has been 389 * removed with the {@link #removeNode()} method. 390 * @throws NullPointerException if <tt>key</tt> is <tt>null</tt>. 391 */ getInt(String key, int def)392 public int getInt(String key, int def) { 393 int result = def; 394 try { 395 String value = get(key, null); 396 if (value != null) 397 result = Integer.parseInt(value); 398 } catch (NumberFormatException e) { 399 // Ignoring exception causes specified default to be returned 400 } 401 402 return result; 403 } 404 405 /** 406 * Implements the <tt>putLong</tt> method as per the specification in 407 * {@link Preferences#putLong(String,long)}. 408 * 409 * <p>This implementation translates <tt>value</tt> to a string with 410 * {@link Long#toString(long)} and invokes {@link #put(String,String)} 411 * on the result. 412 * 413 * @param key key with which the string form of value is to be associated. 414 * @param value value whose string form is to be associated with key. 415 * @throws NullPointerException if key is <tt>null</tt>. 416 * @throws IllegalArgumentException if <tt>key.length()</tt> exceeds 417 * <tt>MAX_KEY_LENGTH</tt>. 418 * @throws IllegalStateException if this node (or an ancestor) has been 419 * removed with the {@link #removeNode()} method. 420 */ putLong(String key, long value)421 public void putLong(String key, long value) { 422 put(key, Long.toString(value)); 423 } 424 425 /** 426 * Implements the <tt>getLong</tt> method as per the specification in 427 * {@link Preferences#getLong(String,long)}. 428 * 429 * <p>This implementation invokes {@link #get(String,String) <tt>get(key, 430 * null)</tt>}. If the return value is non-null, the implementation 431 * attempts to translate it to a <tt>long</tt> with 432 * {@link Long#parseLong(String)}. If the attempt succeeds, the return 433 * value is returned by this method. Otherwise, <tt>def</tt> is returned. 434 * 435 * @param key key whose associated value is to be returned as a long. 436 * @param def the value to be returned in the event that this 437 * preference node has no value associated with <tt>key</tt> 438 * or the associated value cannot be interpreted as a long. 439 * @return the long value represented by the string associated with 440 * <tt>key</tt> in this preference node, or <tt>def</tt> if the 441 * associated value does not exist or cannot be interpreted as 442 * a long. 443 * @throws IllegalStateException if this node (or an ancestor) has been 444 * removed with the {@link #removeNode()} method. 445 * @throws NullPointerException if <tt>key</tt> is <tt>null</tt>. 446 */ getLong(String key, long def)447 public long getLong(String key, long def) { 448 long result = def; 449 try { 450 String value = get(key, null); 451 if (value != null) 452 result = Long.parseLong(value); 453 } catch (NumberFormatException e) { 454 // Ignoring exception causes specified default to be returned 455 } 456 457 return result; 458 } 459 460 /** 461 * Implements the <tt>putBoolean</tt> method as per the specification in 462 * {@link Preferences#putBoolean(String,boolean)}. 463 * 464 * <p>This implementation translates <tt>value</tt> to a string with 465 * {@link String#valueOf(boolean)} and invokes {@link #put(String,String)} 466 * on the result. 467 * 468 * @param key key with which the string form of value is to be associated. 469 * @param value value whose string form is to be associated with key. 470 * @throws NullPointerException if key is <tt>null</tt>. 471 * @throws IllegalArgumentException if <tt>key.length()</tt> exceeds 472 * <tt>MAX_KEY_LENGTH</tt>. 473 * @throws IllegalStateException if this node (or an ancestor) has been 474 * removed with the {@link #removeNode()} method. 475 */ putBoolean(String key, boolean value)476 public void putBoolean(String key, boolean value) { 477 put(key, String.valueOf(value)); 478 } 479 480 /** 481 * Implements the <tt>getBoolean</tt> method as per the specification in 482 * {@link Preferences#getBoolean(String,boolean)}. 483 * 484 * <p>This implementation invokes {@link #get(String,String) <tt>get(key, 485 * null)</tt>}. If the return value is non-null, it is compared with 486 * <tt>"true"</tt> using {@link String#equalsIgnoreCase(String)}. If the 487 * comparison returns <tt>true</tt>, this invocation returns 488 * <tt>true</tt>. Otherwise, the original return value is compared with 489 * <tt>"false"</tt>, again using {@link String#equalsIgnoreCase(String)}. 490 * If the comparison returns <tt>true</tt>, this invocation returns 491 * <tt>false</tt>. Otherwise, this invocation returns <tt>def</tt>. 492 * 493 * @param key key whose associated value is to be returned as a boolean. 494 * @param def the value to be returned in the event that this 495 * preference node has no value associated with <tt>key</tt> 496 * or the associated value cannot be interpreted as a boolean. 497 * @return the boolean value represented by the string associated with 498 * <tt>key</tt> in this preference node, or <tt>def</tt> if the 499 * associated value does not exist or cannot be interpreted as 500 * a boolean. 501 * @throws IllegalStateException if this node (or an ancestor) has been 502 * removed with the {@link #removeNode()} method. 503 * @throws NullPointerException if <tt>key</tt> is <tt>null</tt>. 504 */ getBoolean(String key, boolean def)505 public boolean getBoolean(String key, boolean def) { 506 boolean result = def; 507 String value = get(key, null); 508 if (value != null) { 509 if (value.equalsIgnoreCase("true")) 510 result = true; 511 else if (value.equalsIgnoreCase("false")) 512 result = false; 513 } 514 515 return result; 516 } 517 518 /** 519 * Implements the <tt>putFloat</tt> method as per the specification in 520 * {@link Preferences#putFloat(String,float)}. 521 * 522 * <p>This implementation translates <tt>value</tt> to a string with 523 * {@link Float#toString(float)} and invokes {@link #put(String,String)} 524 * on the result. 525 * 526 * @param key key with which the string form of value is to be associated. 527 * @param value value whose string form is to be associated with key. 528 * @throws NullPointerException if key is <tt>null</tt>. 529 * @throws IllegalArgumentException if <tt>key.length()</tt> exceeds 530 * <tt>MAX_KEY_LENGTH</tt>. 531 * @throws IllegalStateException if this node (or an ancestor) has been 532 * removed with the {@link #removeNode()} method. 533 */ putFloat(String key, float value)534 public void putFloat(String key, float value) { 535 put(key, Float.toString(value)); 536 } 537 538 /** 539 * Implements the <tt>getFloat</tt> method as per the specification in 540 * {@link Preferences#getFloat(String,float)}. 541 * 542 * <p>This implementation invokes {@link #get(String,String) <tt>get(key, 543 * null)</tt>}. If the return value is non-null, the implementation 544 * attempts to translate it to an <tt>float</tt> with 545 * {@link Float#parseFloat(String)}. If the attempt succeeds, the return 546 * value is returned by this method. Otherwise, <tt>def</tt> is returned. 547 * 548 * @param key key whose associated value is to be returned as a float. 549 * @param def the value to be returned in the event that this 550 * preference node has no value associated with <tt>key</tt> 551 * or the associated value cannot be interpreted as a float. 552 * @return the float value represented by the string associated with 553 * <tt>key</tt> in this preference node, or <tt>def</tt> if the 554 * associated value does not exist or cannot be interpreted as 555 * a float. 556 * @throws IllegalStateException if this node (or an ancestor) has been 557 * removed with the {@link #removeNode()} method. 558 * @throws NullPointerException if <tt>key</tt> is <tt>null</tt>. 559 */ getFloat(String key, float def)560 public float getFloat(String key, float def) { 561 float result = def; 562 try { 563 String value = get(key, null); 564 if (value != null) 565 result = Float.parseFloat(value); 566 } catch (NumberFormatException e) { 567 // Ignoring exception causes specified default to be returned 568 } 569 570 return result; 571 } 572 573 /** 574 * Implements the <tt>putDouble</tt> method as per the specification in 575 * {@link Preferences#putDouble(String,double)}. 576 * 577 * <p>This implementation translates <tt>value</tt> to a string with 578 * {@link Double#toString(double)} and invokes {@link #put(String,String)} 579 * on the result. 580 * 581 * @param key key with which the string form of value is to be associated. 582 * @param value value whose string form is to be associated with key. 583 * @throws NullPointerException if key is <tt>null</tt>. 584 * @throws IllegalArgumentException if <tt>key.length()</tt> exceeds 585 * <tt>MAX_KEY_LENGTH</tt>. 586 * @throws IllegalStateException if this node (or an ancestor) has been 587 * removed with the {@link #removeNode()} method. 588 */ putDouble(String key, double value)589 public void putDouble(String key, double value) { 590 put(key, Double.toString(value)); 591 } 592 593 /** 594 * Implements the <tt>getDouble</tt> method as per the specification in 595 * {@link Preferences#getDouble(String,double)}. 596 * 597 * <p>This implementation invokes {@link #get(String,String) <tt>get(key, 598 * null)</tt>}. If the return value is non-null, the implementation 599 * attempts to translate it to an <tt>double</tt> with 600 * {@link Double#parseDouble(String)}. If the attempt succeeds, the return 601 * value is returned by this method. Otherwise, <tt>def</tt> is returned. 602 * 603 * @param key key whose associated value is to be returned as a double. 604 * @param def the value to be returned in the event that this 605 * preference node has no value associated with <tt>key</tt> 606 * or the associated value cannot be interpreted as a double. 607 * @return the double value represented by the string associated with 608 * <tt>key</tt> in this preference node, or <tt>def</tt> if the 609 * associated value does not exist or cannot be interpreted as 610 * a double. 611 * @throws IllegalStateException if this node (or an ancestor) has been 612 * removed with the {@link #removeNode()} method. 613 * @throws NullPointerException if <tt>key</tt> is <tt>null</tt>. 614 */ getDouble(String key, double def)615 public double getDouble(String key, double def) { 616 double result = def; 617 try { 618 String value = get(key, null); 619 if (value != null) 620 result = Double.parseDouble(value); 621 } catch (NumberFormatException e) { 622 // Ignoring exception causes specified default to be returned 623 } 624 625 return result; 626 } 627 628 /** 629 * Implements the <tt>putByteArray</tt> method as per the specification in 630 * {@link Preferences#putByteArray(String,byte[])}. 631 * 632 * @param key key with which the string form of value is to be associated. 633 * @param value value whose string form is to be associated with key. 634 * @throws NullPointerException if key or value is <tt>null</tt>. 635 * @throws IllegalArgumentException if key.length() exceeds MAX_KEY_LENGTH 636 * or if value.length exceeds MAX_VALUE_LENGTH*3/4. 637 * @throws IllegalStateException if this node (or an ancestor) has been 638 * removed with the {@link #removeNode()} method. 639 */ putByteArray(String key, byte[] value)640 public void putByteArray(String key, byte[] value) { 641 put(key, Base64.byteArrayToBase64(value)); 642 } 643 644 /** 645 * Implements the <tt>getByteArray</tt> method as per the specification in 646 * {@link Preferences#getByteArray(String,byte[])}. 647 * 648 * @param key key whose associated value is to be returned as a byte array. 649 * @param def the value to be returned in the event that this 650 * preference node has no value associated with <tt>key</tt> 651 * or the associated value cannot be interpreted as a byte array. 652 * @return the byte array value represented by the string associated with 653 * <tt>key</tt> in this preference node, or <tt>def</tt> if the 654 * associated value does not exist or cannot be interpreted as 655 * a byte array. 656 * @throws IllegalStateException if this node (or an ancestor) has been 657 * removed with the {@link #removeNode()} method. 658 * @throws NullPointerException if <tt>key</tt> is <tt>null</tt>. (A 659 * <tt>null</tt> value for <tt>def</tt> <i>is</i> permitted.) 660 */ getByteArray(String key, byte[] def)661 public byte[] getByteArray(String key, byte[] def) { 662 byte[] result = def; 663 String value = get(key, null); 664 try { 665 if (value != null) 666 result = Base64.base64ToByteArray(value); 667 } 668 catch (RuntimeException e) { 669 // Ignoring exception causes specified default to be returned 670 } 671 672 return result; 673 } 674 675 /** 676 * Implements the <tt>keys</tt> method as per the specification in 677 * {@link Preferences#keys()}. 678 * 679 * <p>This implementation obtains this preference node's lock, checks that 680 * the node has not been removed and invokes {@link #keysSpi()}. 681 * 682 * @return an array of the keys that have an associated value in this 683 * preference node. 684 * @throws BackingStoreException if this operation cannot be completed 685 * due to a failure in the backing store, or inability to 686 * communicate with it. 687 * @throws IllegalStateException if this node (or an ancestor) has been 688 * removed with the {@link #removeNode()} method. 689 */ keys()690 public String[] keys() throws BackingStoreException { 691 synchronized(lock) { 692 if (removed) 693 throw new IllegalStateException("Node has been removed."); 694 695 return keysSpi(); 696 } 697 } 698 699 /** 700 * Implements the <tt>children</tt> method as per the specification in 701 * {@link Preferences#childrenNames()}. 702 * 703 * <p>This implementation obtains this preference node's lock, checks that 704 * the node has not been removed, constructs a <tt>TreeSet</tt> initialized 705 * to the names of children already cached (the children in this node's 706 * "child-cache"), invokes {@link #childrenNamesSpi()}, and adds all of the 707 * returned child-names into the set. The elements of the tree set are 708 * dumped into a <tt>String</tt> array using the <tt>toArray</tt> method, 709 * and this array is returned. 710 * 711 * @return the names of the children of this preference node. 712 * @throws BackingStoreException if this operation cannot be completed 713 * due to a failure in the backing store, or inability to 714 * communicate with it. 715 * @throws IllegalStateException if this node (or an ancestor) has been 716 * removed with the {@link #removeNode()} method. 717 * @see #cachedChildren() 718 */ childrenNames()719 public String[] childrenNames() throws BackingStoreException { 720 synchronized(lock) { 721 if (removed) 722 throw new IllegalStateException("Node has been removed."); 723 724 Set<String> s = new TreeSet<>(kidCache.keySet()); 725 for (String kid : childrenNamesSpi()) 726 s.add(kid); 727 return s.toArray(EMPTY_STRING_ARRAY); 728 } 729 } 730 731 private static final String[] EMPTY_STRING_ARRAY = new String[0]; 732 733 /** 734 * Returns all known unremoved children of this node. 735 * 736 * @return all known unremoved children of this node. 737 */ cachedChildren()738 protected final AbstractPreferences[] cachedChildren() { 739 return kidCache.values().toArray(EMPTY_ABSTRACT_PREFS_ARRAY); 740 } 741 742 private static final AbstractPreferences[] EMPTY_ABSTRACT_PREFS_ARRAY 743 = new AbstractPreferences[0]; 744 745 /** 746 * Implements the <tt>parent</tt> method as per the specification in 747 * {@link Preferences#parent()}. 748 * 749 * <p>This implementation obtains this preference node's lock, checks that 750 * the node has not been removed and returns the parent value that was 751 * passed to this node's constructor. 752 * 753 * @return the parent of this preference node. 754 * @throws IllegalStateException if this node (or an ancestor) has been 755 * removed with the {@link #removeNode()} method. 756 */ parent()757 public Preferences parent() { 758 synchronized(lock) { 759 if (removed) 760 throw new IllegalStateException("Node has been removed."); 761 762 return parent; 763 } 764 } 765 766 /** 767 * Implements the <tt>node</tt> method as per the specification in 768 * {@link Preferences#node(String)}. 769 * 770 * <p>This implementation obtains this preference node's lock and checks 771 * that the node has not been removed. If <tt>path</tt> is <tt>""</tt>, 772 * this node is returned; if <tt>path</tt> is <tt>"/"</tt>, this node's 773 * root is returned. If the first character in <tt>path</tt> is 774 * not <tt>'/'</tt>, the implementation breaks <tt>path</tt> into 775 * tokens and recursively traverses the path from this node to the 776 * named node, "consuming" a name and a slash from <tt>path</tt> at 777 * each step of the traversal. At each step, the current node is locked 778 * and the node's child-cache is checked for the named node. If it is 779 * not found, the name is checked to make sure its length does not 780 * exceed <tt>MAX_NAME_LENGTH</tt>. Then the {@link #childSpi(String)} 781 * method is invoked, and the result stored in this node's child-cache. 782 * If the newly created <tt>Preferences</tt> object's {@link #newNode} 783 * field is <tt>true</tt> and there are any node change listeners, 784 * a notification event is enqueued for processing by the event dispatch 785 * thread. 786 * 787 * <p>When there are no more tokens, the last value found in the 788 * child-cache or returned by <tt>childSpi</tt> is returned by this 789 * method. If during the traversal, two <tt>"/"</tt> tokens occur 790 * consecutively, or the final token is <tt>"/"</tt> (rather than a name), 791 * an appropriate <tt>IllegalArgumentException</tt> is thrown. 792 * 793 * <p> If the first character of <tt>path</tt> is <tt>'/'</tt> 794 * (indicating an absolute path name) this preference node's 795 * lock is dropped prior to breaking <tt>path</tt> into tokens, and 796 * this method recursively traverses the path starting from the root 797 * (rather than starting from this node). The traversal is otherwise 798 * identical to the one described for relative path names. Dropping 799 * the lock on this node prior to commencing the traversal at the root 800 * node is essential to avoid the possibility of deadlock, as per the 801 * {@link #lock locking invariant}. 802 * 803 * @param path the path name of the preference node to return. 804 * @return the specified preference node. 805 * @throws IllegalArgumentException if the path name is invalid (i.e., 806 * it contains multiple consecutive slash characters, or ends 807 * with a slash character and is more than one character long). 808 * @throws IllegalStateException if this node (or an ancestor) has been 809 * removed with the {@link #removeNode()} method. 810 */ node(String path)811 public Preferences node(String path) { 812 synchronized(lock) { 813 if (removed) 814 throw new IllegalStateException("Node has been removed."); 815 if (path.equals("")) 816 return this; 817 if (path.equals("/")) 818 return root; 819 if (path.charAt(0) != '/') 820 return node(new StringTokenizer(path, "/", true)); 821 } 822 823 // Absolute path. Note that we've dropped our lock to avoid deadlock 824 return root.node(new StringTokenizer(path.substring(1), "/", true)); 825 } 826 827 /** 828 * tokenizer contains <name> {'/' <name>}* 829 */ node(StringTokenizer path)830 private Preferences node(StringTokenizer path) { 831 String token = path.nextToken(); 832 if (token.equals("/")) // Check for consecutive slashes 833 throw new IllegalArgumentException("Consecutive slashes in path"); 834 synchronized(lock) { 835 AbstractPreferences child = kidCache.get(token); 836 if (child == null) { 837 if (token.length() > MAX_NAME_LENGTH) 838 throw new IllegalArgumentException( 839 "Node name " + token + " too long"); 840 child = childSpi(token); 841 if (child.newNode) 842 enqueueNodeAddedEvent(child); 843 kidCache.put(token, child); 844 } 845 if (!path.hasMoreTokens()) 846 return child; 847 path.nextToken(); // Consume slash 848 if (!path.hasMoreTokens()) 849 throw new IllegalArgumentException("Path ends with slash"); 850 return child.node(path); 851 } 852 } 853 854 /** 855 * Implements the <tt>nodeExists</tt> method as per the specification in 856 * {@link Preferences#nodeExists(String)}. 857 * 858 * <p>This implementation is very similar to {@link #node(String)}, 859 * except that {@link #getChild(String)} is used instead of {@link 860 * #childSpi(String)}. 861 * 862 * @param path the path name of the node whose existence is to be checked. 863 * @return true if the specified node exists. 864 * @throws BackingStoreException if this operation cannot be completed 865 * due to a failure in the backing store, or inability to 866 * communicate with it. 867 * @throws IllegalArgumentException if the path name is invalid (i.e., 868 * it contains multiple consecutive slash characters, or ends 869 * with a slash character and is more than one character long). 870 * @throws IllegalStateException if this node (or an ancestor) has been 871 * removed with the {@link #removeNode()} method and 872 * <tt>pathname</tt> is not the empty string (<tt>""</tt>). 873 */ nodeExists(String path)874 public boolean nodeExists(String path) 875 throws BackingStoreException 876 { 877 synchronized(lock) { 878 if (path.equals("")) 879 return !removed; 880 if (removed) 881 throw new IllegalStateException("Node has been removed."); 882 if (path.equals("/")) 883 return true; 884 if (path.charAt(0) != '/') 885 return nodeExists(new StringTokenizer(path, "/", true)); 886 } 887 888 // Absolute path. Note that we've dropped our lock to avoid deadlock 889 return root.nodeExists(new StringTokenizer(path.substring(1), "/", 890 true)); 891 } 892 893 /** 894 * tokenizer contains <name> {'/' <name>}* 895 */ nodeExists(StringTokenizer path)896 private boolean nodeExists(StringTokenizer path) 897 throws BackingStoreException 898 { 899 String token = path.nextToken(); 900 if (token.equals("/")) // Check for consecutive slashes 901 throw new IllegalArgumentException("Consecutive slashes in path"); 902 synchronized(lock) { 903 AbstractPreferences child = kidCache.get(token); 904 if (child == null) 905 child = getChild(token); 906 if (child==null) 907 return false; 908 if (!path.hasMoreTokens()) 909 return true; 910 path.nextToken(); // Consume slash 911 if (!path.hasMoreTokens()) 912 throw new IllegalArgumentException("Path ends with slash"); 913 return child.nodeExists(path); 914 } 915 } 916 917 /** 918 919 * Implements the <tt>removeNode()</tt> method as per the specification in 920 * {@link Preferences#removeNode()}. 921 * 922 * <p>This implementation checks to see that this node is the root; if so, 923 * it throws an appropriate exception. Then, it locks this node's parent, 924 * and calls a recursive helper method that traverses the subtree rooted at 925 * this node. The recursive method locks the node on which it was called, 926 * checks that it has not already been removed, and then ensures that all 927 * of its children are cached: The {@link #childrenNamesSpi()} method is 928 * invoked and each returned child name is checked for containment in the 929 * child-cache. If a child is not already cached, the {@link 930 * #childSpi(String)} method is invoked to create a <tt>Preferences</tt> 931 * instance for it, and this instance is put into the child-cache. Then 932 * the helper method calls itself recursively on each node contained in its 933 * child-cache. Next, it invokes {@link #removeNodeSpi()}, marks itself 934 * as removed, and removes itself from its parent's child-cache. Finally, 935 * if there are any node change listeners, it enqueues a notification 936 * event for processing by the event dispatch thread. 937 * 938 * <p>Note that the helper method is always invoked with all ancestors up 939 * to the "closest non-removed ancestor" locked. 940 * 941 * @throws IllegalStateException if this node (or an ancestor) has already 942 * been removed with the {@link #removeNode()} method. 943 * @throws UnsupportedOperationException if this method is invoked on 944 * the root node. 945 * @throws BackingStoreException if this operation cannot be completed 946 * due to a failure in the backing store, or inability to 947 * communicate with it. 948 */ removeNode()949 public void removeNode() throws BackingStoreException { 950 if (this==root) 951 throw new UnsupportedOperationException("Can't remove the root!"); 952 synchronized(parent.lock) { 953 removeNode2(); 954 parent.kidCache.remove(name); 955 } 956 } 957 958 /* 959 * Called with locks on all nodes on path from parent of "removal root" 960 * to this (including the former but excluding the latter). 961 */ removeNode2()962 private void removeNode2() throws BackingStoreException { 963 synchronized(lock) { 964 if (removed) 965 throw new IllegalStateException("Node already removed."); 966 967 // Ensure that all children are cached 968 String[] kidNames = childrenNamesSpi(); 969 for (int i=0; i<kidNames.length; i++) 970 if (!kidCache.containsKey(kidNames[i])) 971 kidCache.put(kidNames[i], childSpi(kidNames[i])); 972 973 // Recursively remove all cached children 974 for (Iterator<AbstractPreferences> i = kidCache.values().iterator(); 975 i.hasNext();) { 976 try { 977 i.next().removeNode2(); 978 i.remove(); 979 } catch (BackingStoreException x) { } 980 } 981 982 // Now we have no descendants - it's time to die! 983 removeNodeSpi(); 984 removed = true; 985 parent.enqueueNodeRemovedEvent(this); 986 } 987 } 988 989 /** 990 * Implements the <tt>name</tt> method as per the specification in 991 * {@link Preferences#name()}. 992 * 993 * <p>This implementation merely returns the name that was 994 * passed to this node's constructor. 995 * 996 * @return this preference node's name, relative to its parent. 997 */ name()998 public String name() { 999 return name; 1000 } 1001 1002 /** 1003 * Implements the <tt>absolutePath</tt> method as per the specification in 1004 * {@link Preferences#absolutePath()}. 1005 * 1006 * <p>This implementation merely returns the absolute path name that 1007 * was computed at the time that this node was constructed (based on 1008 * the name that was passed to this node's constructor, and the names 1009 * that were passed to this node's ancestors' constructors). 1010 * 1011 * @return this preference node's absolute path name. 1012 */ absolutePath()1013 public String absolutePath() { 1014 return absolutePath; 1015 } 1016 1017 /** 1018 * Implements the <tt>isUserNode</tt> method as per the specification in 1019 * {@link Preferences#isUserNode()}. 1020 * 1021 * <p>This implementation compares this node's root node (which is stored 1022 * in a private field) with the value returned by 1023 * {@link Preferences#userRoot()}. If the two object references are 1024 * identical, this method returns true. 1025 * 1026 * @return <tt>true</tt> if this preference node is in the user 1027 * preference tree, <tt>false</tt> if it's in the system 1028 * preference tree. 1029 */ isUserNode()1030 public boolean isUserNode() { 1031 return AccessController.doPrivileged( 1032 new PrivilegedAction<Boolean>() { 1033 public Boolean run() { 1034 return root == Preferences.userRoot(); 1035 } 1036 }).booleanValue(); 1037 } 1038 1039 public void addPreferenceChangeListener(PreferenceChangeListener pcl) { 1040 if (pcl==null) 1041 throw new NullPointerException("Change listener is null."); 1042 synchronized(lock) { 1043 if (removed) 1044 throw new IllegalStateException("Node has been removed."); 1045 1046 // Android-changed: Copy-on-read List of listeners, not copy-on-write array. 1047 /* 1048 // Copy-on-write 1049 PreferenceChangeListener[] old = prefListeners; 1050 prefListeners = new PreferenceChangeListener[old.length + 1]; 1051 System.arraycopy(old, 0, prefListeners, 0, old.length); 1052 prefListeners[old.length] = pcl; 1053 */ 1054 prefListeners.add(pcl); 1055 } 1056 startEventDispatchThreadIfNecessary(); 1057 } 1058 1059 public void removePreferenceChangeListener(PreferenceChangeListener pcl) { 1060 synchronized(lock) { 1061 if (removed) 1062 throw new IllegalStateException("Node has been removed."); 1063 // Android-changed: Copy-on-read List of listeners, not copy-on-write array. 1064 // if ((prefListeners == null) || (prefListeners.length == 0)) 1065 if (!prefListeners.contains(pcl)) { 1066 throw new IllegalArgumentException("Listener not registered."); 1067 } 1068 1069 // Android-changed: Copy-on-read List of listeners, not copy-on-write array. 1070 /* 1071 // Copy-on-write 1072 PreferenceChangeListener[] newPl = 1073 new PreferenceChangeListener[prefListeners.length - 1]; 1074 int i = 0; 1075 while (i < newPl.length && prefListeners[i] != pcl) 1076 newPl[i] = prefListeners[i++]; 1077 1078 if (i == newPl.length && prefListeners[i] != pcl) 1079 throw new IllegalArgumentException("Listener not registered."); 1080 while (i < newPl.length) 1081 newPl[i] = prefListeners[++i]; 1082 prefListeners = newPl; 1083 */ 1084 prefListeners.remove(pcl); 1085 } 1086 } 1087 1088 public void addNodeChangeListener(NodeChangeListener ncl) { 1089 if (ncl==null) 1090 throw new NullPointerException("Change listener is null."); 1091 synchronized(lock) { 1092 if (removed) 1093 throw new IllegalStateException("Node has been removed."); 1094 1095 // Android-changed: Copy-on-read List of listeners, not copy-on-write array. 1096 /* 1097 // Copy-on-write 1098 if (nodeListeners == null) { 1099 nodeListeners = new NodeChangeListener[1]; 1100 nodeListeners[0] = ncl; 1101 } else { 1102 NodeChangeListener[] old = nodeListeners; 1103 nodeListeners = new NodeChangeListener[old.length + 1]; 1104 System.arraycopy(old, 0, nodeListeners, 0, old.length); 1105 nodeListeners[old.length] = ncl; 1106 } 1107 */ 1108 nodeListeners.add(ncl); 1109 } 1110 startEventDispatchThreadIfNecessary(); 1111 } 1112 1113 public void removeNodeChangeListener(NodeChangeListener ncl) { 1114 synchronized(lock) { 1115 if (removed) 1116 throw new IllegalStateException("Node has been removed."); 1117 // Android-changed: Copy-on-read List of listeners, not copy-on-write array. 1118 // if ((nodeListeners == null) || (nodeListeners.length == 0)) 1119 if (!nodeListeners.contains(ncl)) { 1120 throw new IllegalArgumentException("Listener not registered."); 1121 } 1122 1123 // Android-changed: Copy-on-read List of listeners, not copy-on-write array. 1124 /* 1125 // Copy-on-write 1126 int i = 0; 1127 while (i < nodeListeners.length && nodeListeners[i] != ncl) 1128 i++; 1129 if (i == nodeListeners.length) 1130 throw new IllegalArgumentException("Listener not registered."); 1131 NodeChangeListener[] newNl = 1132 new NodeChangeListener[nodeListeners.length - 1]; 1133 if (i != 0) 1134 System.arraycopy(nodeListeners, 0, newNl, 0, i); 1135 if (i != newNl.length) 1136 System.arraycopy(nodeListeners, i + 1, 1137 newNl, i, newNl.length - i); 1138 nodeListeners = newNl; 1139 */ 1140 nodeListeners.remove(ncl); 1141 } 1142 } 1143 1144 // "SPI" METHODS 1145 1146 /** 1147 * Put the given key-value association into this preference node. It is 1148 * guaranteed that <tt>key</tt> and <tt>value</tt> are non-null and of 1149 * legal length. Also, it is guaranteed that this node has not been 1150 * removed. (The implementor needn't check for any of these things.) 1151 * 1152 * <p>This method is invoked with the lock on this node held. 1153 * @param key the key 1154 * @param value the value 1155 */ 1156 protected abstract void putSpi(String key, String value); 1157 1158 /** 1159 * Return the value associated with the specified key at this preference 1160 * node, or <tt>null</tt> if there is no association for this key, or the 1161 * association cannot be determined at this time. It is guaranteed that 1162 * <tt>key</tt> is non-null. Also, it is guaranteed that this node has 1163 * not been removed. (The implementor needn't check for either of these 1164 * things.) 1165 * 1166 * <p> Generally speaking, this method should not throw an exception 1167 * under any circumstances. If, however, if it does throw an exception, 1168 * the exception will be intercepted and treated as a <tt>null</tt> 1169 * return value. 1170 * 1171 * <p>This method is invoked with the lock on this node held. 1172 * 1173 * @param key the key 1174 * @return the value associated with the specified key at this preference 1175 * node, or <tt>null</tt> if there is no association for this 1176 * key, or the association cannot be determined at this time. 1177 */ 1178 protected abstract String getSpi(String key); 1179 1180 /** 1181 * Remove the association (if any) for the specified key at this 1182 * preference node. It is guaranteed that <tt>key</tt> is non-null. 1183 * Also, it is guaranteed that this node has not been removed. 1184 * (The implementor needn't check for either of these things.) 1185 * 1186 * <p>This method is invoked with the lock on this node held. 1187 * @param key the key 1188 */ 1189 protected abstract void removeSpi(String key); 1190 1191 /** 1192 * Removes this preference node, invalidating it and any preferences that 1193 * it contains. The named child will have no descendants at the time this 1194 * invocation is made (i.e., the {@link Preferences#removeNode()} method 1195 * invokes this method repeatedly in a bottom-up fashion, removing each of 1196 * a node's descendants before removing the node itself). 1197 * 1198 * <p>This method is invoked with the lock held on this node and its 1199 * parent (and all ancestors that are being removed as a 1200 * result of a single invocation to {@link Preferences#removeNode()}). 1201 * 1202 * <p>The removal of a node needn't become persistent until the 1203 * <tt>flush</tt> method is invoked on this node (or an ancestor). 1204 * 1205 * <p>If this node throws a <tt>BackingStoreException</tt>, the exception 1206 * will propagate out beyond the enclosing {@link #removeNode()} 1207 * invocation. 1208 * 1209 * @throws BackingStoreException if this operation cannot be completed 1210 * due to a failure in the backing store, or inability to 1211 * communicate with it. 1212 */ 1213 protected abstract void removeNodeSpi() throws BackingStoreException; 1214 1215 /** 1216 * Returns all of the keys that have an associated value in this 1217 * preference node. (The returned array will be of size zero if 1218 * this node has no preferences.) It is guaranteed that this node has not 1219 * been removed. 1220 * 1221 * <p>This method is invoked with the lock on this node held. 1222 * 1223 * <p>If this node throws a <tt>BackingStoreException</tt>, the exception 1224 * will propagate out beyond the enclosing {@link #keys()} invocation. 1225 * 1226 * @return an array of the keys that have an associated value in this 1227 * preference node. 1228 * @throws BackingStoreException if this operation cannot be completed 1229 * due to a failure in the backing store, or inability to 1230 * communicate with it. 1231 */ 1232 protected abstract String[] keysSpi() throws BackingStoreException; 1233 1234 /** 1235 * Returns the names of the children of this preference node. (The 1236 * returned array will be of size zero if this node has no children.) 1237 * This method need not return the names of any nodes already cached, 1238 * but may do so without harm. 1239 * 1240 * <p>This method is invoked with the lock on this node held. 1241 * 1242 * <p>If this node throws a <tt>BackingStoreException</tt>, the exception 1243 * will propagate out beyond the enclosing {@link #childrenNames()} 1244 * invocation. 1245 * 1246 * @return an array containing the names of the children of this 1247 * preference node. 1248 * @throws BackingStoreException if this operation cannot be completed 1249 * due to a failure in the backing store, or inability to 1250 * communicate with it. 1251 */ 1252 protected abstract String[] childrenNamesSpi() 1253 throws BackingStoreException; 1254 1255 /** 1256 * Returns the named child if it exists, or <tt>null</tt> if it does not. 1257 * It is guaranteed that <tt>nodeName</tt> is non-null, non-empty, 1258 * does not contain the slash character ('/'), and is no longer than 1259 * {@link #MAX_NAME_LENGTH} characters. Also, it is guaranteed 1260 * that this node has not been removed. (The implementor needn't check 1261 * for any of these things if he chooses to override this method.) 1262 * 1263 * <p>Finally, it is guaranteed that the named node has not been returned 1264 * by a previous invocation of this method or {@link #childSpi} after the 1265 * last time that it was removed. In other words, a cached value will 1266 * always be used in preference to invoking this method. (The implementor 1267 * needn't maintain his own cache of previously returned children if he 1268 * chooses to override this method.) 1269 * 1270 * <p>This implementation obtains this preference node's lock, invokes 1271 * {@link #childrenNames()} to get an array of the names of this node's 1272 * children, and iterates over the array comparing the name of each child 1273 * with the specified node name. If a child node has the correct name, 1274 * the {@link #childSpi(String)} method is invoked and the resulting 1275 * node is returned. If the iteration completes without finding the 1276 * specified name, <tt>null</tt> is returned. 1277 * 1278 * @param nodeName name of the child to be searched for. 1279 * @return the named child if it exists, or null if it does not. 1280 * @throws BackingStoreException if this operation cannot be completed 1281 * due to a failure in the backing store, or inability to 1282 * communicate with it. 1283 */ 1284 protected AbstractPreferences getChild(String nodeName) 1285 throws BackingStoreException { 1286 synchronized(lock) { 1287 // assert kidCache.get(nodeName)==null; 1288 String[] kidNames = childrenNames(); 1289 for (int i=0; i<kidNames.length; i++) 1290 if (kidNames[i].equals(nodeName)) 1291 return childSpi(kidNames[i]); 1292 } 1293 return null; 1294 } 1295 1296 /** 1297 * Returns the named child of this preference node, creating it if it does 1298 * not already exist. It is guaranteed that <tt>name</tt> is non-null, 1299 * non-empty, does not contain the slash character ('/'), and is no longer 1300 * than {@link #MAX_NAME_LENGTH} characters. Also, it is guaranteed that 1301 * this node has not been removed. (The implementor needn't check for any 1302 * of these things.) 1303 * 1304 * <p>Finally, it is guaranteed that the named node has not been returned 1305 * by a previous invocation of this method or {@link #getChild(String)} 1306 * after the last time that it was removed. In other words, a cached 1307 * value will always be used in preference to invoking this method. 1308 * Subclasses need not maintain their own cache of previously returned 1309 * children. 1310 * 1311 * <p>The implementer must ensure that the returned node has not been 1312 * removed. If a like-named child of this node was previously removed, the 1313 * implementer must return a newly constructed <tt>AbstractPreferences</tt> 1314 * node; once removed, an <tt>AbstractPreferences</tt> node 1315 * cannot be "resuscitated." 1316 * 1317 * <p>If this method causes a node to be created, this node is not 1318 * guaranteed to be persistent until the <tt>flush</tt> method is 1319 * invoked on this node or one of its ancestors (or descendants). 1320 * 1321 * <p>This method is invoked with the lock on this node held. 1322 * 1323 * @param name The name of the child node to return, relative to 1324 * this preference node. 1325 * @return The named child node. 1326 */ 1327 protected abstract AbstractPreferences childSpi(String name); 1328 1329 /** 1330 * Returns the absolute path name of this preferences node. 1331 */ 1332 public String toString() { 1333 return (this.isUserNode() ? "User" : "System") + 1334 " Preference Node: " + this.absolutePath(); 1335 } 1336 1337 /** 1338 * Implements the <tt>sync</tt> method as per the specification in 1339 * {@link Preferences#sync()}. 1340 * 1341 * <p>This implementation calls a recursive helper method that locks this 1342 * node, invokes syncSpi() on it, unlocks this node, and recursively 1343 * invokes this method on each "cached child." A cached child is a child 1344 * of this node that has been created in this VM and not subsequently 1345 * removed. In effect, this method does a depth first traversal of the 1346 * "cached subtree" rooted at this node, calling syncSpi() on each node in 1347 * the subTree while only that node is locked. Note that syncSpi() is 1348 * invoked top-down. 1349 * 1350 * @throws BackingStoreException if this operation cannot be completed 1351 * due to a failure in the backing store, or inability to 1352 * communicate with it. 1353 * @throws IllegalStateException if this node (or an ancestor) has been 1354 * removed with the {@link #removeNode()} method. 1355 * @see #flush() 1356 */ 1357 public void sync() throws BackingStoreException { 1358 sync2(); 1359 } 1360 1361 private void sync2() throws BackingStoreException { 1362 AbstractPreferences[] cachedKids; 1363 1364 synchronized(lock) { 1365 if (removed) 1366 throw new IllegalStateException("Node has been removed"); 1367 syncSpi(); 1368 cachedKids = cachedChildren(); 1369 } 1370 1371 for (int i=0; i<cachedKids.length; i++) 1372 cachedKids[i].sync2(); 1373 } 1374 1375 /** 1376 * This method is invoked with this node locked. The contract of this 1377 * method is to synchronize any cached preferences stored at this node 1378 * with any stored in the backing store. (It is perfectly possible that 1379 * this node does not exist on the backing store, either because it has 1380 * been deleted by another VM, or because it has not yet been created.) 1381 * Note that this method should <i>not</i> synchronize the preferences in 1382 * any subnodes of this node. If the backing store naturally syncs an 1383 * entire subtree at once, the implementer is encouraged to override 1384 * sync(), rather than merely overriding this method. 1385 * 1386 * <p>If this node throws a <tt>BackingStoreException</tt>, the exception 1387 * will propagate out beyond the enclosing {@link #sync()} invocation. 1388 * 1389 * @throws BackingStoreException if this operation cannot be completed 1390 * due to a failure in the backing store, or inability to 1391 * communicate with it. 1392 */ 1393 protected abstract void syncSpi() throws BackingStoreException; 1394 1395 /** 1396 * Implements the <tt>flush</tt> method as per the specification in 1397 * {@link Preferences#flush()}. 1398 * 1399 * <p>This implementation calls a recursive helper method that locks this 1400 * node, invokes flushSpi() on it, unlocks this node, and recursively 1401 * invokes this method on each "cached child." A cached child is a child 1402 * of this node that has been created in this VM and not subsequently 1403 * removed. In effect, this method does a depth first traversal of the 1404 * "cached subtree" rooted at this node, calling flushSpi() on each node in 1405 * the subTree while only that node is locked. Note that flushSpi() is 1406 * invoked top-down. 1407 * 1408 * <p> If this method is invoked on a node that has been removed with 1409 * the {@link #removeNode()} method, flushSpi() is invoked on this node, 1410 * but not on others. 1411 * 1412 * @throws BackingStoreException if this operation cannot be completed 1413 * due to a failure in the backing store, or inability to 1414 * communicate with it. 1415 * @see #flush() 1416 */ 1417 public void flush() throws BackingStoreException { 1418 flush2(); 1419 } 1420 1421 private void flush2() throws BackingStoreException { 1422 AbstractPreferences[] cachedKids; 1423 1424 synchronized(lock) { 1425 flushSpi(); 1426 if(removed) 1427 return; 1428 cachedKids = cachedChildren(); 1429 } 1430 1431 for (int i = 0; i < cachedKids.length; i++) 1432 cachedKids[i].flush2(); 1433 } 1434 1435 /** 1436 * This method is invoked with this node locked. The contract of this 1437 * method is to force any cached changes in the contents of this 1438 * preference node to the backing store, guaranteeing their persistence. 1439 * (It is perfectly possible that this node does not exist on the backing 1440 * store, either because it has been deleted by another VM, or because it 1441 * has not yet been created.) Note that this method should <i>not</i> 1442 * flush the preferences in any subnodes of this node. If the backing 1443 * store naturally flushes an entire subtree at once, the implementer is 1444 * encouraged to override flush(), rather than merely overriding this 1445 * method. 1446 * 1447 * <p>If this node throws a <tt>BackingStoreException</tt>, the exception 1448 * will propagate out beyond the enclosing {@link #flush()} invocation. 1449 * 1450 * @throws BackingStoreException if this operation cannot be completed 1451 * due to a failure in the backing store, or inability to 1452 * communicate with it. 1453 */ 1454 protected abstract void flushSpi() throws BackingStoreException; 1455 1456 /** 1457 * Returns <tt>true</tt> iff this node (or an ancestor) has been 1458 * removed with the {@link #removeNode()} method. This method 1459 * locks this node prior to returning the contents of the private 1460 * field used to track this state. 1461 * 1462 * @return <tt>true</tt> iff this node (or an ancestor) has been 1463 * removed with the {@link #removeNode()} method. 1464 */ 1465 protected boolean isRemoved() { 1466 synchronized(lock) { 1467 return removed; 1468 } 1469 } 1470 1471 /** 1472 * Queue of pending notification events. When a preference or node 1473 * change event for which there are one or more listeners occurs, 1474 * it is placed on this queue and the queue is notified. A background 1475 * thread waits on this queue and delivers the events. This decouples 1476 * event delivery from preference activity, greatly simplifying 1477 * locking and reducing opportunity for deadlock. 1478 */ 1479 private static final List<EventObject> eventQueue = new LinkedList<>(); 1480 1481 /** 1482 * These two classes are used to distinguish NodeChangeEvents on 1483 * eventQueue so the event dispatch thread knows whether to call 1484 * childAdded or childRemoved. 1485 */ 1486 private class NodeAddedEvent extends NodeChangeEvent { 1487 private static final long serialVersionUID = -6743557530157328528L; 1488 NodeAddedEvent(Preferences parent, Preferences child) { 1489 super(parent, child); 1490 } 1491 } 1492 private class NodeRemovedEvent extends NodeChangeEvent { 1493 private static final long serialVersionUID = 8735497392918824837L; 1494 NodeRemovedEvent(Preferences parent, Preferences child) { 1495 super(parent, child); 1496 } 1497 } 1498 1499 /** 1500 * A single background thread ("the event notification thread") monitors 1501 * the event queue and delivers events that are placed on the queue. 1502 */ 1503 private static class EventDispatchThread extends Thread { 1504 public void run() { 1505 while(true) { 1506 // Wait on eventQueue till an event is present 1507 EventObject event = null; 1508 synchronized(eventQueue) { 1509 try { 1510 while (eventQueue.isEmpty()) 1511 eventQueue.wait(); 1512 event = eventQueue.remove(0); 1513 } catch (InterruptedException e) { 1514 // XXX Log "Event dispatch thread interrupted. Exiting" 1515 return; 1516 } 1517 } 1518 1519 // Now we have event & hold no locks; deliver evt to listeners 1520 AbstractPreferences src=(AbstractPreferences)event.getSource(); 1521 if (event instanceof PreferenceChangeEvent) { 1522 PreferenceChangeEvent pce = (PreferenceChangeEvent)event; 1523 PreferenceChangeListener[] listeners = src.prefListeners(); 1524 for (int i=0; i<listeners.length; i++) 1525 listeners[i].preferenceChange(pce); 1526 } else { 1527 NodeChangeEvent nce = (NodeChangeEvent)event; 1528 NodeChangeListener[] listeners = src.nodeListeners(); 1529 if (nce instanceof NodeAddedEvent) { 1530 for (int i=0; i<listeners.length; i++) 1531 listeners[i].childAdded(nce); 1532 } else { 1533 // assert nce instanceof NodeRemovedEvent; 1534 for (int i=0; i<listeners.length; i++) 1535 listeners[i].childRemoved(nce); 1536 } 1537 } 1538 } 1539 } 1540 } 1541 1542 private static Thread eventDispatchThread = null; 1543 1544 /** 1545 * This method starts the event dispatch thread the first time it 1546 * is called. The event dispatch thread will be started only 1547 * if someone registers a listener. 1548 */ 1549 private static synchronized void startEventDispatchThreadIfNecessary() { 1550 if (eventDispatchThread == null) { 1551 // XXX Log "Starting event dispatch thread" 1552 eventDispatchThread = new EventDispatchThread(); 1553 eventDispatchThread.setDaemon(true); 1554 eventDispatchThread.start(); 1555 } 1556 } 1557 1558 // BEGIN Android-changed: Copy-on-read List of listeners, not copy-on-write array. 1559 // Changed documentation. 1560 /* 1561 /** 1562 * Return this node's preference/node change listeners. Even though 1563 * we're using a copy-on-write lists, we use synchronized accessors to 1564 * ensure information transmission from the writing thread to the 1565 * reading thread. 1566 * 1567 */ 1568 /** 1569 * Return this node's preference/node change listeners. All accesses to prefListeners 1570 * and nodeListeners are guarded by |lock|. We return a copy of the list so that the 1571 * EventQueue thread will iterate over a fixed snapshot of the listeners at the time of 1572 * this call. 1573 */ 1574 // END Android-changed: Copy-on-read List of listeners, not copy-on-write array. 1575 PreferenceChangeListener[] prefListeners() { 1576 synchronized(lock) { 1577 // Android-changed: Copy-on-read List of listeners, not copy-on-write array. 1578 // return prefListeners; 1579 return prefListeners.toArray(new PreferenceChangeListener[prefListeners.size()]); 1580 } 1581 } 1582 NodeChangeListener[] nodeListeners() { 1583 synchronized(lock) { 1584 // Android-changed: Copy-on-read List of listeners, not copy-on-write array. 1585 // return nodeListeners; 1586 return nodeListeners.toArray(new NodeChangeListener[nodeListeners.size()]); 1587 } 1588 } 1589 1590 /** 1591 * Enqueue a preference change event for delivery to registered 1592 * preference change listeners unless there are no registered 1593 * listeners. Invoked with this.lock held. 1594 */ 1595 private void enqueuePreferenceChangeEvent(String key, String newValue) { 1596 // Android-changed: Copy-on-read List of listeners, not copy-on-write array. 1597 // if (prefListeners.length != 0) { 1598 if (!prefListeners.isEmpty()) { 1599 synchronized(eventQueue) { 1600 eventQueue.add(new PreferenceChangeEvent(this, key, newValue)); 1601 eventQueue.notify(); 1602 } 1603 } 1604 } 1605 1606 /** 1607 * Enqueue a "node added" event for delivery to registered node change 1608 * listeners unless there are no registered listeners. Invoked with 1609 * this.lock held. 1610 */ 1611 private void enqueueNodeAddedEvent(Preferences child) { 1612 // Android-changed: Copy-on-read List of listeners, not copy-on-write array. 1613 // if (nodeListeners.length != 0) { 1614 if (!nodeListeners.isEmpty()) { 1615 synchronized(eventQueue) { 1616 eventQueue.add(new NodeAddedEvent(this, child)); 1617 eventQueue.notify(); 1618 } 1619 } 1620 } 1621 1622 /** 1623 * Enqueue a "node removed" event for delivery to registered node change 1624 * listeners unless there are no registered listeners. Invoked with 1625 * this.lock held. 1626 */ 1627 private void enqueueNodeRemovedEvent(Preferences child) { 1628 // Android-changed: Copy-on-read List of listeners, not copy-on-write array. 1629 // if (nodeListeners.length != 0) { 1630 if (!nodeListeners.isEmpty()) { 1631 synchronized(eventQueue) { 1632 eventQueue.add(new NodeRemovedEvent(this, child)); 1633 eventQueue.notify(); 1634 } 1635 } 1636 } 1637 1638 /** 1639 * Implements the <tt>exportNode</tt> method as per the specification in 1640 * {@link Preferences#exportNode(OutputStream)}. 1641 * 1642 * @param os the output stream on which to emit the XML document. 1643 * @throws IOException if writing to the specified output stream 1644 * results in an <tt>IOException</tt>. 1645 * @throws BackingStoreException if preference data cannot be read from 1646 * backing store. 1647 */ 1648 public void exportNode(OutputStream os) 1649 throws IOException, BackingStoreException 1650 { 1651 XmlSupport.export(os, this, false); 1652 } 1653 1654 /** 1655 * Implements the <tt>exportSubtree</tt> method as per the specification in 1656 * {@link Preferences#exportSubtree(OutputStream)}. 1657 * 1658 * @param os the output stream on which to emit the XML document. 1659 * @throws IOException if writing to the specified output stream 1660 * results in an <tt>IOException</tt>. 1661 * @throws BackingStoreException if preference data cannot be read from 1662 * backing store. 1663 */ 1664 public void exportSubtree(OutputStream os) 1665 throws IOException, BackingStoreException 1666 { 1667 XmlSupport.export(os, this, true); 1668 } 1669 } 1670