| /* | |
| * Copyright (c) 2000, 2024, Oracle and/or its affiliates. All rights reserved. | |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. | |
| * | |
| * This code is free software; you can redistribute it and/or modify it | |
| * under the terms of the GNU General Public License version 2 only, as | |
| * published by the Free Software Foundation. Oracle designates this | |
| * particular file as subject to the "Classpath" exception as provided | |
| * by Oracle in the LICENSE file that accompanied this code. | |
| * | |
| * This code is distributed in the hope that it will be useful, but WITHOUT | |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | |
| * version 2 for more details (a copy is included in the LICENSE file that | |
| * accompanied this code). | |
| * | |
| * You should have received a copy of the GNU General Public License version | |
| * 2 along with this work; if not, write to the Free Software Foundation, | |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. | |
| * | |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA | |
| * or visit www.oracle.com if you need additional information or have any | |
| * questions. | |
| */ | |
| package java.util.prefs; | |
| import java.util.*; | |
| import java.io.*; | |
| /** | |
| * This class provides a skeletal implementation of the {@link Preferences} | |
| * class, greatly easing the task of implementing it. | |
| * | |
| * <p><strong>This class is for {@code Preferences} implementers only. | |
| * Normal users of the {@code Preferences} facility should have no need to | |
| * consult this documentation. The {@link Preferences} documentation | |
| * should suffice.</strong> | |
| * | |
| * <p>Implementors must override the nine abstract service-provider interface | |
| * (SPI) methods: {@link #getSpi(String)}, {@link #putSpi(String,String)}, | |
| * {@link #removeSpi(String)}, {@link #childSpi(String)}, {@link | |
| * #removeNodeSpi()}, {@link #keysSpi()}, {@link #childrenNamesSpi()}, {@link | |
| * #syncSpi()} and {@link #flushSpi()}. All of the concrete methods specify | |
| * precisely how they are implemented atop these SPI methods. The implementor | |
| * may, at his discretion, override one or more of the concrete methods if the | |
| * default implementation is unsatisfactory for any reason, such as | |
| * performance. | |
| * | |
| * <p>The SPI methods fall into three groups concerning exception | |
| * behavior. The {@code getSpi} method should never throw exceptions, but it | |
| * doesn't really matter, as any exception thrown by this method will be | |
| * intercepted by {@link #get(String,String)}, which will return the specified | |
| * default value to the caller. The {@code removeNodeSpi, keysSpi, | |
| * childrenNamesSpi, syncSpi} and {@code flushSpi} methods are specified | |
| * to throw {@link BackingStoreException}, and the implementation is required | |
| * to throw this checked exception if it is unable to perform the operation. | |
| * The exception propagates outward, causing the corresponding API method | |
| * to fail. | |
| * | |
| * <p>The remaining SPI methods {@link #putSpi(String,String)}, {@link | |
| * #removeSpi(String)} and {@link #childSpi(String)} have more complicated | |
| * exception behavior. They are not specified to throw | |
| * {@code BackingStoreException}, as they can generally obey their contracts | |
| * even if the backing store is unavailable. This is true because they return | |
| * no information and their effects are not required to become permanent until | |
| * a subsequent call to {@link Preferences#flush()} or | |
| * {@link Preferences#sync()}. Generally speaking, these SPI methods should not | |
| * throw exceptions. In some implementations, there may be circumstances | |
| * under which these calls cannot even enqueue the requested operation for | |
| * later processing. Even under these circumstances it is generally better to | |
| * simply ignore the invocation and return, rather than throwing an | |
| * exception. Under these circumstances, however, subsequently invoking | |
| * {@code flush()} or {@code sync} would not imply that all previous | |
| * operations had successfully been made permanent. | |
| * | |
| * <p>There is one circumstance under which {@code putSpi, removeSpi and | |
| * childSpi} <i>should</i> throw an exception: if the caller lacks | |
| * sufficient privileges on the underlying operating system to perform the | |
| * requested operation. This will, for instance, occur on most systems | |
| * if a non-privileged user attempts to modify system preferences. | |
| * (The required privileges will vary from implementation to | |
| * implementation. On some implementations, they are the right to modify the | |
| * contents of some directory in the file system; on others they are the right | |
| * to modify contents of some key in a registry.) Under any of these | |
| * circumstances, it would generally be undesirable to let the program | |
| * continue executing as if these operations would become permanent at a later | |
| * time. While implementations are not required to throw an exception under | |
| * these circumstances, they are encouraged to do so. A {@link | |
| * SecurityException} would be appropriate. | |
| * | |
| * <p>Most of the SPI methods require the implementation to read or write | |
| * information at a preferences node. The implementor should beware of the | |
| * fact that another VM may have concurrently deleted this node from the | |
| * backing store. It is the implementation's responsibility to recreate the | |
| * node if it has been deleted. | |
| * | |
| * <p>Implementation note: In Sun's default {@code Preferences} | |
| * implementations, the user's identity is inherited from the underlying | |
| * operating system and does not change for the lifetime of the virtual | |
| * machine. It is recognized that server-side {@code Preferences} | |
| * implementations may have the user identity change from request to request, | |
| * implicitly passed to {@code Preferences} methods via the use of a | |
| * static {@link ThreadLocal} instance. Authors of such implementations are | |
| * <i>strongly</i> encouraged to determine the user at the time preferences | |
| * are accessed (for example by the {@link #get(String,String)} or {@link | |
| * #put(String,String)} method) rather than permanently associating a user | |
| * with each {@code Preferences} instance. The latter behavior conflicts | |
| * with normal {@code Preferences} usage and would lead to great confusion. | |
| * | |
| * @author Josh Bloch | |
| * @see Preferences | |
| * @since 1.4 | |
| */ | |
| public abstract class AbstractPreferences extends Preferences { | |
| /** | |
| * The code point U+0000, assigned to the null control character, is the | |
| * only character encoded in Unicode and ISO/IEC 10646 that is always | |
| * invalid in any XML 1.0 and 1.1 document. | |
| */ | |
| static final int CODE_POINT_U0000 = '\u0000'; | |
| /** | |
| * Our name relative to parent. | |
| */ | |
| private final String name; | |
| /** | |
| * Our absolute path name. | |
| */ | |
| private final String absolutePath; | |
| /** | |
| * Our parent node. | |
| */ | |
| final AbstractPreferences parent; | |
| /** | |
| * Our root node. | |
| */ | |
| private final AbstractPreferences root; // Relative to this node | |
| /** | |
| * This field should be {@code true} if this node did not exist in the | |
| * backing store prior to the creation of this object. The field | |
| * is initialized to false, but may be set to true by a subclass | |
| * constructor (and should not be modified thereafter). This field | |
| * indicates whether a node change event should be fired when | |
| * creation is complete. | |
| */ | |
| protected boolean newNode = false; | |
| /** | |
| * All known unremoved children of this node. (This "cache" is consulted | |
| * prior to calling childSpi() or getChild(). | |
| */ | |
| private Map<String, AbstractPreferences> kidCache = new HashMap<>(); | |
| /** | |
| * This field is used to keep track of whether or not this node has | |
| * been removed. Once it's set to true, it will never be reset to false. | |
| */ | |
| private boolean removed = false; | |
| /** | |
| * Registered preference change listeners. | |
| */ | |
| private PreferenceChangeListener[] prefListeners = | |
| new PreferenceChangeListener[0]; | |
| /** | |
| * Registered node change listeners. | |
| */ | |
| private NodeChangeListener[] nodeListeners = new NodeChangeListener[0]; | |
| /** | |
| * An object whose monitor is used to lock this node. This object | |
| * is used in preference to the node itself to reduce the likelihood of | |
| * intentional or unintentional denial of service due to a locked node. | |
| * To avoid deadlock, a node is <i>never</i> locked by a thread that | |
| * holds a lock on a descendant of that node. | |
| */ | |
| protected final Object lock = new Object(); | |
| /** | |
| * Creates a preference node with the specified parent and the specified | |
| * name relative to its parent. | |
| * | |
| * @param parent the parent of this preference node, or null if this | |
| * is the root. | |
| * @param name the name of this preference node, relative to its parent, | |
| * or {@code ""} if this is the root. | |
| * @throws IllegalArgumentException if {@code name} contains a slash | |
| * ({@code '/'}), or {@code parent} is {@code null} and | |
| * name isn't {@code ""}. | |
| */ | |
| protected AbstractPreferences(AbstractPreferences parent, String name) { | |
| if (parent==null) { | |
| if (!name.isEmpty()) | |
| throw new IllegalArgumentException("Root name '"+name+ | |
| "' must be \"\""); | |
| this.absolutePath = "/"; | |
| root = this; | |
| } else { | |
| if (name.indexOf('/') != -1) | |
| throw new IllegalArgumentException("Name '" + name + | |
| "' contains '/'"); | |
| if (name.isEmpty()) | |
| throw new IllegalArgumentException("Illegal name: empty string"); | |
| root = parent.root; | |
| absolutePath = (parent==root ? "/" + name | |
| : parent.absolutePath() + "/" + name); | |
| } | |
| this.name = name; | |
| this.parent = parent; | |
| } | |
| /** | |
| * Implements the {@code put} method as per the specification in | |
| * {@link Preferences#put(String,String)}. | |
| * | |
| * <p>This implementation checks that the key and value are legal, | |
| * obtains this preference node's lock, checks that the node | |
| * has not been removed, invokes {@link #putSpi(String,String)}, and if | |
| * there are any preference change listeners, enqueues a notification | |
| * event for processing by the event dispatch thread. | |
| * | |
| * @param key key with which the specified value is to be associated. | |
| * @param value value to be associated with the specified key. | |
| * @throws NullPointerException if key or value is {@code null}. | |
| * @throws IllegalArgumentException if {@code key.length()} exceeds | |
| * {@code MAX_KEY_LENGTH} or if {@code value.length} exceeds | |
| * {@code MAX_VALUE_LENGTH}. | |
| * @throws IllegalArgumentException if either key or value contain | |
| * the null control character, code point U+0000. | |
| * @throws IllegalStateException if this node (or an ancestor) has been | |
| * removed with the {@link #removeNode()} method. | |
| */ | |
| public void put(String key, String value) { | |
| if (key==null || value==null) | |
| throw new NullPointerException(); | |
| if (key.length() > MAX_KEY_LENGTH) | |
| throw new IllegalArgumentException("Key too long: "+key); | |
| if (value.length() > MAX_VALUE_LENGTH) | |
| throw new IllegalArgumentException("Value too long: "+value); | |
| if (key.indexOf(CODE_POINT_U0000) != -1) | |
| throw new IllegalArgumentException("Key contains code point U+0000"); | |
| if (value.indexOf(CODE_POINT_U0000) != -1) | |
| throw new IllegalArgumentException("Value contains code point U+0000"); | |
| synchronized(lock) { | |
| if (removed) | |
| throw new IllegalStateException("Node has been removed."); | |
| putSpi(key, value); | |
| enqueuePreferenceChangeEvent(key, value); | |
| } | |
| } | |
| /** | |
| * Implements the {@code get} method as per the specification in | |
| * {@link Preferences#get(String,String)}. | |
| * | |
| * <p>This implementation first checks to see if {@code key} is | |
| * {@code null} throwing a {@code NullPointerException} if this is | |
| * the case. Then it obtains this preference node's lock, | |
| * checks that the node has not been removed, invokes {@link | |
| * #getSpi(String)}, and returns the result, unless the {@code getSpi} | |
| * invocation returns {@code null} or throws an exception, in which case | |
| * this invocation returns {@code def}. | |
| * | |
| * @param key key whose associated value is to be returned. | |
| * @param def the value to be returned in the event that this | |
| * preference node has no value associated with {@code key}. | |
| * @return the value associated with {@code key}, or {@code def} | |
| * if no value is associated with {@code key}. | |
| * @throws IllegalStateException if this node (or an ancestor) has been | |
| * removed with the {@link #removeNode()} method. | |
| * @throws NullPointerException if key is {@code null}. (A | |
| * {@code null} default <i>is</i> permitted.) | |
| * @throws IllegalArgumentException if key contains the null control | |
| * character, code point U+0000. | |
| */ | |
| public String get(String key, String def) { | |
| if (key==null) | |
| throw new NullPointerException("Null key"); | |
| if (key.indexOf(CODE_POINT_U0000) != -1) | |
| throw new IllegalArgumentException("Key contains code point U+0000"); | |
| synchronized(lock) { | |
| if (removed) | |
| throw new IllegalStateException("Node has been removed."); | |
| String result = null; | |
| try { | |
| result = getSpi(key); | |
| } catch (Exception e) { | |
| // Ignoring exception causes default to be returned | |
| } | |
| return (result==null ? def : result); | |
| } | |
| } | |
| /** | |
| * Implements the {@code remove(String)} method as per the specification | |
| * in {@link Preferences#remove(String)}. | |
| * | |
| * <p>This implementation obtains this preference node's lock, | |
| * checks that the node has not been removed, invokes | |
| * {@link #removeSpi(String)} and if there are any preference | |
| * change listeners, enqueues a notification event for processing by the | |
| * event dispatch thread. | |
| * | |
| * @param key key whose mapping is to be removed from the preference node. | |
| * @throws IllegalStateException if this node (or an ancestor) has been | |
| * removed with the {@link #removeNode()} method. | |
| * @throws IllegalArgumentException if key contains the null control | |
| * character, code point U+0000. | |
| * @throws NullPointerException {@inheritDoc} | |
| */ | |
| public void remove(String key) { | |
| Objects.requireNonNull(key, "Specified key cannot be null"); | |
| if (key.indexOf(CODE_POINT_U0000) != -1) | |
| throw new IllegalArgumentException("Key contains code point U+0000"); | |
| synchronized(lock) { | |
| if (removed) | |
| throw new IllegalStateException("Node has been removed."); | |
| removeSpi(key); | |
| enqueuePreferenceChangeEvent(key, null); | |
| } | |
| } | |
| /** | |
| * Implements the {@code clear} method as per the specification in | |
| * {@link Preferences#clear()}. | |
| * | |
| * <p>This implementation obtains this preference node's lock, | |
| * invokes {@link #keys()} to obtain an array of keys, and | |
| * iterates over the array invoking {@link #remove(String)} on each key. | |
| * | |
| * @throws BackingStoreException if this operation cannot be completed | |
| * due to a failure in the backing store, or inability to | |
| * communicate with it. | |
| * @throws IllegalStateException if this node (or an ancestor) has been | |
| * removed with the {@link #removeNode()} method. | |
| */ | |
| public void clear() throws BackingStoreException { | |
| synchronized(lock) { | |
| for (String key : keys()) | |
| remove(key); | |
| } | |
| } | |
| /** | |
| * Implements the {@code putInt} method as per the specification in | |
| * {@link Preferences#putInt(String,int)}. | |
| * | |
| * <p>This implementation translates {@code value} to a string with | |
| * {@link Integer#toString(int)} and invokes {@link #put(String,String)} | |
| * on the result. | |
| * | |
| * @param key key with which the string form of value is to be associated. | |
| * @param value value whose string form is to be associated with key. | |
| * @throws NullPointerException if key is {@code null}. | |
| * @throws IllegalArgumentException if {@code key.length()} exceeds | |
| * {@code MAX_KEY_LENGTH}. | |
| * @throws IllegalArgumentException if key contains | |
| * the null control character, code point U+0000. | |
| * @throws IllegalStateException if this node (or an ancestor) has been | |
| * removed with the {@link #removeNode()} method. | |
| */ | |
| public void putInt(String key, int value) { | |
| put(key, Integer.toString(value)); | |
| } | |
| /** | |
| * Implements the {@code getInt} method as per the specification in | |
| * {@link Preferences#getInt(String,int)}. | |
| * | |
| * <p>This implementation invokes {@link #get(String,String) get(key, | |
| * null)}. If the return value is non-null, the implementation | |
| * attempts to translate it to an {@code int} with | |
| * {@link Integer#parseInt(String)}. If the attempt succeeds, the return | |
| * value is returned by this method. Otherwise, {@code def} is returned. | |
| * | |
| * @param key key whose associated value is to be returned as an int. | |
| * @param def the value to be returned in the event that this | |
| * preference node has no value associated with {@code key} | |
| * or the associated value cannot be interpreted as an int. | |
| * @return the int value represented by the string associated with | |
| * {@code key} in this preference node, or {@code def} if the | |
| * associated value does not exist or cannot be interpreted as | |
| * an int. | |
| * @throws IllegalStateException if this node (or an ancestor) has been | |
| * removed with the {@link #removeNode()} method. | |
| * @throws NullPointerException if {@code key} is {@code null}. | |
| * @throws IllegalArgumentException if key contains the null control | |
| * character, code point U+0000. | |
| */ | |
| public int getInt(String key, int def) { | |
| int result = def; | |
| try { | |
| String value = get(key, null); | |
| if (value != null) | |
| result = Integer.parseInt(value); | |
| } catch (NumberFormatException e) { | |
| // Ignoring exception causes specified default to be returned | |
| } | |
| return result; | |
| } | |
| /** | |
| * Implements the {@code putLong} method as per the specification in | |
| * {@link Preferences#putLong(String,long)}. | |
| * | |
| * <p>This implementation translates {@code value} to a string with | |
| * {@link Long#toString(long)} and invokes {@link #put(String,String)} | |
| * on the result. | |
| * | |
| * @param key key with which the string form of value is to be associated. | |
| * @param value value whose string form is to be associated with key. | |
| * @throws NullPointerException if key is {@code null}. | |
| * @throws IllegalArgumentException if {@code key.length()} exceeds | |
| * {@code MAX_KEY_LENGTH}. | |
| * @throws IllegalArgumentException if key contains | |
| * the null control character, code point U+0000. | |
| * @throws IllegalStateException if this node (or an ancestor) has been | |
| * removed with the {@link #removeNode()} method. | |
| */ | |
| public void putLong(String key, long value) { | |
| put(key, Long.toString(value)); | |
| } | |
| /** | |
| * Implements the {@code getLong} method as per the specification in | |
| * {@link Preferences#getLong(String,long)}. | |
| * | |
| * <p>This implementation invokes {@link #get(String,String) get(key, | |
| * null)}. If the return value is non-null, the implementation | |
| * attempts to translate it to a {@code long} with | |
| * {@link Long#parseLong(String)}. If the attempt succeeds, the return | |
| * value is returned by this method. Otherwise, {@code def} is returned. | |
| * | |
| * @param key key whose associated value is to be returned as a long. | |
| * @param def the value to be returned in the event that this | |
| * preference node has no value associated with {@code key} | |
| * or the associated value cannot be interpreted as a long. | |
| * @return the long value represented by the string associated with | |
| * {@code key} in this preference node, or {@code def} if the | |
| * associated value does not exist or cannot be interpreted as | |
| * a long. | |
| * @throws IllegalStateException if this node (or an ancestor) has been | |
| * removed with the {@link #removeNode()} method. | |
| * @throws NullPointerException if {@code key} is {@code null}. | |
| * @throws IllegalArgumentException if key contains the null control | |
| * character, code point U+0000. | |
| */ | |
| public long getLong(String key, long def) { | |
| long result = def; | |
| try { | |
| String value = get(key, null); | |
| if (value != null) | |
| result = Long.parseLong(value); | |
| } catch (NumberFormatException e) { | |
| // Ignoring exception causes specified default to be returned | |
| } | |
| return result; | |
| } | |
| /** | |
| * Implements the {@code putBoolean} method as per the specification in | |
| * {@link Preferences#putBoolean(String,boolean)}. | |
| * | |
| * <p>This implementation translates {@code value} to a string with | |
| * {@link String#valueOf(boolean)} and invokes {@link #put(String,String)} | |
| * on the result. | |
| * | |
| * @param key key with which the string form of value is to be associated. | |
| * @param value value whose string form is to be associated with key. | |
| * @throws NullPointerException if key is {@code null}. | |
| * @throws IllegalArgumentException if {@code key.length()} exceeds | |
| * {@code MAX_KEY_LENGTH}. | |
| * @throws IllegalArgumentException if key contains | |
| * the null control character, code point U+0000. | |
| * @throws IllegalStateException if this node (or an ancestor) has been | |
| * removed with the {@link #removeNode()} method. | |
| */ | |
| public void putBoolean(String key, boolean value) { | |
| put(key, String.valueOf(value)); | |
| } | |
| /** | |
| * Implements the {@code getBoolean} method as per the specification in | |
| * {@link Preferences#getBoolean(String,boolean)}. | |
| * | |
| * <p>This implementation invokes {@link #get(String,String) get(key, | |
| * null)}. If the return value is non-null, it is compared with | |
| * {@code "true"} using {@link String#equalsIgnoreCase(String)}. If the | |
| * comparison returns {@code true}, this invocation returns | |
| * {@code true}. Otherwise, the original return value is compared with | |
| * {@code "false"}, again using {@link String#equalsIgnoreCase(String)}. | |
| * If the comparison returns {@code true}, this invocation returns | |
| * {@code false}. Otherwise, this invocation returns {@code def}. | |
| * | |
| * @param key key whose associated value is to be returned as a boolean. | |
| * @param def the value to be returned in the event that this | |
| * preference node has no value associated with {@code key} | |
| * or the associated value cannot be interpreted as a boolean. | |
| * @return the boolean value represented by the string associated with | |
| * {@code key} in this preference node, or {@code def} if the | |
| * associated value does not exist or cannot be interpreted as | |
| * a boolean. | |
| * @throws IllegalStateException if this node (or an ancestor) has been | |
| * removed with the {@link #removeNode()} method. | |
| * @throws NullPointerException if {@code key} is {@code null}. | |
| * @throws IllegalArgumentException if key contains the null control | |
| * character, code point U+0000. | |
| */ | |
| public boolean getBoolean(String key, boolean def) { | |
| boolean result = def; | |
| String value = get(key, null); | |
| if (value != null) { | |
| if (value.equalsIgnoreCase("true")) | |
| result = true; | |
| else if (value.equalsIgnoreCase("false")) | |
| result = false; | |
| } | |
| return result; | |
| } | |
| /** | |
| * Implements the {@code putFloat} method as per the specification in | |
| * {@link Preferences#putFloat(String,float)}. | |
| * | |
| * <p>This implementation translates {@code value} to a string with | |
| * {@link Float#toString(float)} and invokes {@link #put(String,String)} | |
| * on the result. | |
| * | |
| * @param key key with which the string form of value is to be associated. | |
| * @param value value whose string form is to be associated with key. | |
| * @throws NullPointerException if key is {@code null}. | |
| * @throws IllegalArgumentException if {@code key.length()} exceeds | |
| * {@code MAX_KEY_LENGTH}. | |
| * @throws IllegalArgumentException if key contains | |
| * the null control character, code point U+0000. | |
| * @throws IllegalStateException if this node (or an ancestor) has been | |
| * removed with the {@link #removeNode()} method. | |
| */ | |
| public void putFloat(String key, float value) { | |
| put(key, Float.toString(value)); | |
| } | |
| /** | |
| * Implements the {@code getFloat} method as per the specification in | |
| * {@link Preferences#getFloat(String,float)}. | |
| * | |
| * <p>This implementation invokes {@link #get(String,String) get(key, | |
| * null)}. If the return value is non-null, the implementation | |
| * attempts to translate it to an {@code float} with | |
| * {@link Float#parseFloat(String)}. If the attempt succeeds, the return | |
| * value is returned by this method. Otherwise, {@code def} is returned. | |
| * | |
| * @param key key whose associated value is to be returned as a float. | |
| * @param def the value to be returned in the event that this | |
| * preference node has no value associated with {@code key} | |
| * or the associated value cannot be interpreted as a float. | |
| * @return the float value represented by the string associated with | |
| * {@code key} in this preference node, or {@code def} if the | |
| * associated value does not exist or cannot be interpreted as | |
| * a float. | |
| * @throws IllegalStateException if this node (or an ancestor) has been | |
| * removed with the {@link #removeNode()} method. | |
| * @throws NullPointerException if {@code key} is {@code null}. | |
| * @throws IllegalArgumentException if key contains the null control | |
| * character, code point U+0000. | |
| */ | |
| public float getFloat(String key, float def) { | |
| float result = def; | |
| try { | |
| String value = get(key, null); | |
| if (value != null) | |
| result = Float.parseFloat(value); | |
| } catch (NumberFormatException e) { | |
| // Ignoring exception causes specified default to be returned | |
| } | |
| return result; | |
| } | |
| /** | |
| * Implements the {@code putDouble} method as per the specification in | |
| * {@link Preferences#putDouble(String,double)}. | |
| * | |
| * <p>This implementation translates {@code value} to a string with | |
| * {@link Double#toString(double)} and invokes {@link #put(String,String)} | |
| * on the result. | |
| * | |
| * @param key key with which the string form of value is to be associated. | |
| * @param value value whose string form is to be associated with key. | |
| * @throws NullPointerException if key is {@code null}. | |
| * @throws IllegalArgumentException if {@code key.length()} exceeds | |
| * {@code MAX_KEY_LENGTH}. | |
| * @throws IllegalArgumentException if key contains | |
| * the null control character, code point U+0000. | |
| * @throws IllegalStateException if this node (or an ancestor) has been | |
| * removed with the {@link #removeNode()} method. | |
| */ | |
| public void putDouble(String key, double value) { | |
| put(key, Double.toString(value)); | |
| } | |
| /** | |
| * Implements the {@code getDouble} method as per the specification in | |
| * {@link Preferences#getDouble(String,double)}. | |
| * | |
| * <p>This implementation invokes {@link #get(String,String) get(key, | |
| * null)}. If the return value is non-null, the implementation | |
| * attempts to translate it to an {@code double} with | |
| * {@link Double#parseDouble(String)}. If the attempt succeeds, the return | |
| * value is returned by this method. Otherwise, {@code def} is returned. | |
| * | |
| * @param key key whose associated value is to be returned as a double. | |
| * @param def the value to be returned in the event that this | |
| * preference node has no value associated with {@code key} | |
| * or the associated value cannot be interpreted as a double. | |
| * @return the double value represented by the string associated with | |
| * {@code key} in this preference node, or {@code def} if the | |
| * associated value does not exist or cannot be interpreted as | |
| * a double. | |
| * @throws IllegalStateException if this node (or an ancestor) has been | |
| * removed with the {@link #removeNode()} method. | |
| * @throws NullPointerException if {@code key} is {@code null}. | |
| * @throws IllegalArgumentException if key contains the null control | |
| * character, code point U+0000. | |
| */ | |
| public double getDouble(String key, double def) { | |
| double result = def; | |
| try { | |
| String value = get(key, null); | |
| if (value != null) | |
| result = Double.parseDouble(value); | |
| } catch (NumberFormatException e) { | |
| // Ignoring exception causes specified default to be returned | |
| } | |
| return result; | |
| } | |
| /** | |
| * Implements the {@code putByteArray} method as per the specification in | |
| * {@link Preferences#putByteArray(String,byte[])}. | |
| * | |
| * @param key key with which the string form of value is to be associated. | |
| * @param value value whose string form is to be associated with key. | |
| * @throws NullPointerException if key or value is {@code null}. | |
| * @throws IllegalArgumentException if key.length() exceeds MAX_KEY_LENGTH | |
| * or if value.length exceeds MAX_VALUE_LENGTH*3/4. | |
| * @throws IllegalArgumentException if key contains | |
| * the null control character, code point U+0000. | |
| * @throws IllegalStateException if this node (or an ancestor) has been | |
| * removed with the {@link #removeNode()} method. | |
| */ | |
| public void putByteArray(String key, byte[] value) { | |
| put(key, Base64.byteArrayToBase64(value)); | |
| } | |
| /** | |
| * Implements the {@code getByteArray} method as per the specification in | |
| * {@link Preferences#getByteArray(String,byte[])}. | |
| * | |
| * @param key key whose associated value is to be returned as a byte array. | |
| * @param def the value to be returned in the event that this | |
| * preference node has no value associated with {@code key} | |
| * or the associated value cannot be interpreted as a byte array. | |
| * @return the byte array value represented by the string associated with | |
| * {@code key} in this preference node, or {@code def} if the | |
| * associated value does not exist or cannot be interpreted as | |
| * a byte array. | |
| * @throws IllegalStateException if this node (or an ancestor) has been | |
| * removed with the {@link #removeNode()} method. | |
| * @throws NullPointerException if {@code key} is {@code null}. (A | |
| * {@code null} value for {@code def} <i>is</i> permitted.) | |
| * @throws IllegalArgumentException if key contains the null control | |
| * character, code point U+0000. | |
| */ | |
| public byte[] getByteArray(String key, byte[] def) { | |
| byte[] result = def; | |
| String value = get(key, null); | |
| try { | |
| if (value != null) | |
| result = Base64.base64ToByteArray(value); | |
| } | |
| catch (RuntimeException e) { | |
| // Ignoring exception causes specified default to be returned | |
| } | |
| return result; | |
| } | |
| /** | |
| * Implements the {@code keys} method as per the specification in | |
| * {@link Preferences#keys()}. | |
| * | |
| * <p>This implementation obtains this preference node's lock, checks that | |
| * the node has not been removed and invokes {@link #keysSpi()}. | |
| * | |
| * @return an array of the keys that have an associated value in this | |
| * preference node. | |
| * @throws BackingStoreException if this operation cannot be completed | |
| * due to a failure in the backing store, or inability to | |
| * communicate with it. | |
| * @throws IllegalStateException if this node (or an ancestor) has been | |
| * removed with the {@link #removeNode()} method. | |
| */ | |
| public String[] keys() throws BackingStoreException { | |
| synchronized(lock) { | |
| if (removed) | |
| throw new IllegalStateException("Node has been removed."); | |
| return keysSpi(); | |
| } | |
| } | |
| /** | |
| * Implements the {@code children} method as per the specification in | |
| * {@link Preferences#childrenNames()}. | |
| * | |
| * <p>This implementation obtains this preference node's lock, checks that | |
| * the node has not been removed, constructs a {@code TreeSet} initialized | |
| * to the names of children already cached (the children in this node's | |
| * "child-cache"), invokes {@link #childrenNamesSpi()}, and adds all of the | |
| * returned child-names into the set. The elements of the tree set are | |
| * dumped into a {@code String} array using the {@code toArray} method, | |
| * and this array is returned. | |
| * | |
| * @return the names of the children of this preference node. | |
| * @throws BackingStoreException if this operation cannot be completed | |
| * due to a failure in the backing store, or inability to | |
| * communicate with it. | |
| * @throws IllegalStateException if this node (or an ancestor) has been | |
| * removed with the {@link #removeNode()} method. | |
| * @see #cachedChildren() | |
| */ | |
| public String[] childrenNames() throws BackingStoreException { | |
| synchronized(lock) { | |
| if (removed) | |
| throw new IllegalStateException("Node has been removed."); | |
| Set<String> s = new TreeSet<>(kidCache.keySet()); | |
| for (String kid : childrenNamesSpi()) | |
| s.add(kid); | |
| return s.toArray(EMPTY_STRING_ARRAY); | |
| } | |
| } | |
| private static final String[] EMPTY_STRING_ARRAY = new String[0]; | |
| /** | |
| * Returns all known unremoved children of this node. | |
| * | |
| * @return all known unremoved children of this node. | |
| */ | |
| protected final AbstractPreferences[] cachedChildren() { | |
| return kidCache.values().toArray(EMPTY_ABSTRACT_PREFS_ARRAY); | |
| } | |
| private static final AbstractPreferences[] EMPTY_ABSTRACT_PREFS_ARRAY | |
| = new AbstractPreferences[0]; | |
| /** | |
| * Implements the {@code parent} method as per the specification in | |
| * {@link Preferences#parent()}. | |
| * | |
| * <p>This implementation obtains this preference node's lock, checks that | |
| * the node has not been removed and returns the parent value that was | |
| * passed to this node's constructor. | |
| * | |
| * @return the parent of this preference node. | |
| * @throws IllegalStateException if this node (or an ancestor) has been | |
| * removed with the {@link #removeNode()} method. | |
| */ | |
| public Preferences parent() { | |
| synchronized(lock) { | |
| if (removed) | |
| throw new IllegalStateException("Node has been removed."); | |
| return parent; | |
| } | |
| } | |
| /** | |
| * Implements the {@code node} method as per the specification in | |
| * {@link Preferences#node(String)}. | |
| * | |
| * <p>This implementation obtains this preference node's lock and checks | |
| * that the node has not been removed. If {@code path} is {@code ""}, | |
| * this node is returned; if {@code path} is {@code "/"}, this node's | |
| * root is returned. If the first character in {@code path} is | |
| * not {@code '/'}, the implementation breaks {@code path} into | |
| * tokens and recursively traverses the path from this node to the | |
| * named node, "consuming" a name and a slash from {@code path} at | |
| * each step of the traversal. At each step, the current node is locked | |
| * and the node's child-cache is checked for the named node. If it is | |
| * not found, the name is checked to make sure its length does not | |
| * exceed {@code MAX_NAME_LENGTH}. Then the {@link #childSpi(String)} | |
| * method is invoked, and the result stored in this node's child-cache. | |
| * If the newly created {@code Preferences} object's {@link #newNode} | |
| * field is {@code true} and there are any node change listeners, | |
| * a notification event is enqueued for processing by the event dispatch | |
| * thread. | |
| * | |
| * <p>When there are no more tokens, the last value found in the | |
| * child-cache or returned by {@code childSpi} is returned by this | |
| * method. If during the traversal, two {@code "/"} tokens occur | |
| * consecutively, or the final token is {@code "/"} (rather than a name), | |
| * an appropriate {@code IllegalArgumentException} is thrown. | |
| * | |
| * <p> If the first character of {@code path} is {@code '/'} | |
| * (indicating an absolute path name) this preference node's | |
| * lock is dropped prior to breaking {@code path} into tokens, and | |
| * this method recursively traverses the path starting from the root | |
| * (rather than starting from this node). The traversal is otherwise | |
| * identical to the one described for relative path names. Dropping | |
| * the lock on this node prior to commencing the traversal at the root | |
| * node is essential to avoid the possibility of deadlock, as per the | |
| * {@link #lock locking invariant}. | |
| * | |
| * @param path the path name of the preference node to return. | |
| * @return the specified preference node. | |
| * @throws IllegalArgumentException if the path name is invalid (i.e., | |
| * it contains multiple consecutive slash characters, or ends | |
| * with a slash character and is more than one character long). | |
| * @throws IllegalStateException if this node (or an ancestor) has been | |
| * removed with the {@link #removeNode()} method. | |
| */ | |
| public Preferences node(String path) { | |
| synchronized(lock) { | |
| if (removed) | |
| throw new IllegalStateException("Node has been removed."); | |
| if (path.isEmpty()) | |
| return this; | |
| if (path.equals("/")) | |
| return root; | |
| if (path.charAt(0) != '/') | |
| return node(new StringTokenizer(path, "/", true)); | |
| } | |
| // Absolute path. Note that we've dropped our lock to avoid deadlock | |
| return root.node(new StringTokenizer(path.substring(1), "/", true)); | |
| } | |
| /** | |
| * tokenizer contains <name> {'/' <name>}* | |
| */ | |
| private Preferences node(StringTokenizer path) { | |
| String token = path.nextToken(); | |
| if (token.equals("/")) // Check for consecutive slashes | |
| throw new IllegalArgumentException("Consecutive slashes in path"); | |
| synchronized(lock) { | |
| AbstractPreferences child = kidCache.get(token); | |
| if (child == null) { | |
| if (token.length() > MAX_NAME_LENGTH) | |
| throw new IllegalArgumentException( | |
| "Node name " + token + " too long"); | |
| child = childSpi(token); | |
| if (child.newNode) | |
| enqueueNodeAddedEvent(child); | |
| kidCache.put(token, child); | |
| } | |
| if (!path.hasMoreTokens()) | |
| return child; | |
| path.nextToken(); // Consume slash | |
| if (!path.hasMoreTokens()) | |
| throw new IllegalArgumentException("Path ends with slash"); | |
| return child.node(path); | |
| } | |
| } | |
| /** | |
| * Implements the {@code nodeExists} method as per the specification in | |
| * {@link Preferences#nodeExists(String)}. | |
| * | |
| * <p>This implementation is very similar to {@link #node(String)}, | |
| * except that {@link #getChild(String)} is used instead of {@link | |
| * #childSpi(String)}. | |
| * | |
| * @param path the path name of the node whose existence is to be checked. | |
| * @return true if the specified node exists. | |
| * @throws BackingStoreException if this operation cannot be completed | |
| * due to a failure in the backing store, or inability to | |
| * communicate with it. | |
| * @throws IllegalArgumentException if the path name is invalid (i.e., | |
| * it contains multiple consecutive slash characters, or ends | |
| * with a slash character and is more than one character long). | |
| * @throws IllegalStateException if this node (or an ancestor) has been | |
| * removed with the {@link #removeNode()} method and | |
| * {@code pathname} is not the empty string ({@code ""}). | |
| */ | |
| public boolean nodeExists(String path) | |
| throws BackingStoreException | |
| { | |
| synchronized(lock) { | |
| if (path.isEmpty()) | |
| return !removed; | |
| if (removed) | |
| throw new IllegalStateException("Node has been removed."); | |
| if (path.equals("/")) | |
| return true; | |
| if (path.charAt(0) != '/') | |
| return nodeExists(new StringTokenizer(path, "/", true)); | |
| } | |
| // Absolute path. Note that we've dropped our lock to avoid deadlock | |
| return root.nodeExists(new StringTokenizer(path.substring(1), "/", | |
| true)); | |
| } | |
| /** | |
| * tokenizer contains <name> {'/' <name>}* | |
| */ | |
| private boolean nodeExists(StringTokenizer path) | |
| throws BackingStoreException | |
| { | |
| String token = path.nextToken(); | |
| if (token.equals("/")) // Check for consecutive slashes | |
| throw new IllegalArgumentException("Consecutive slashes in path"); | |
| synchronized(lock) { | |
| AbstractPreferences child = kidCache.get(token); | |
| if (child == null) | |
| child = getChild(token); | |
| if (child==null) | |
| return false; | |
| if (!path.hasMoreTokens()) | |
| return true; | |
| path.nextToken(); // Consume slash | |
| if (!path.hasMoreTokens()) | |
| throw new IllegalArgumentException("Path ends with slash"); | |
| return child.nodeExists(path); | |
| } | |
| } | |
| /** | |
| * Implements the {@code removeNode()} method as per the specification in | |
| * {@link Preferences#removeNode()}. | |
| * | |
| * <p>This implementation checks to see that this node is the root; if so, | |
| * it throws an appropriate exception. Then, it locks this node's parent, | |
| * and calls a recursive helper method that traverses the subtree rooted at | |
| * this node. The recursive method locks the node on which it was called, | |
| * checks that it has not already been removed, and then ensures that all | |
| * of its children are cached: The {@link #childrenNamesSpi()} method is | |
| * invoked and each returned child name is checked for containment in the | |
| * child-cache. If a child is not already cached, the {@link | |
| * #childSpi(String)} method is invoked to create a {@code Preferences} | |
| * instance for it, and this instance is put into the child-cache. Then | |
| * the helper method calls itself recursively on each node contained in its | |
| * child-cache. Next, it invokes {@link #removeNodeSpi()}, marks itself | |
| * as removed, and removes itself from its parent's child-cache. Finally, | |
| * if there are any node change listeners, it enqueues a notification | |
| * event for processing by the event dispatch thread. | |
| * | |
| * <p>Note that the helper method is always invoked with all ancestors up | |
| * to the "closest non-removed ancestor" locked. | |
| * | |
| * @throws IllegalStateException if this node (or an ancestor) has already | |
| * been removed with the {@link #removeNode()} method. | |
| * @throws UnsupportedOperationException if this method is invoked on | |
| * the root node. | |
| * @throws BackingStoreException if this operation cannot be completed | |
| * due to a failure in the backing store, or inability to | |
| * communicate with it. | |
| */ | |
| public void removeNode() throws BackingStoreException { | |
| if (this==root) | |
| throw new UnsupportedOperationException("Can't remove the root!"); | |
| synchronized(parent.lock) { | |
| removeNode2(); | |
| parent.kidCache.remove(name); | |
| } | |
| } | |
| /* | |
| * Called with locks on all nodes on path from parent of "removal root" | |
| * to this (including the former but excluding the latter). | |
| */ | |
| private void removeNode2() throws BackingStoreException { | |
| synchronized(lock) { | |
| if (removed) | |
| throw new IllegalStateException("Node already removed."); | |
| // Ensure that all children are cached | |
| String[] kidNames = childrenNamesSpi(); | |
| for (String kidName : kidNames) | |
| if (!kidCache.containsKey(kidName)) | |
| kidCache.put(kidName, childSpi(kidName)); | |
| // Recursively remove all cached children | |
| for (Iterator<AbstractPreferences> i = kidCache.values().iterator(); | |
| i.hasNext();) { | |
| try { | |
| i.next().removeNode2(); | |
| i.remove(); | |
| } catch (BackingStoreException x) { } | |
| } | |
| // Now we have no descendants - it's time to die! | |
| removeNodeSpi(); | |
| removed = true; | |
| parent.enqueueNodeRemovedEvent(this); | |
| } | |
| } | |
| /** | |
| * Implements the {@code name} method as per the specification in | |
| * {@link Preferences#name()}. | |
| * | |
| * <p>This implementation merely returns the name that was | |
| * passed to this node's constructor. | |
| * | |
| * @return this preference node's name, relative to its parent. | |
| */ | |
| public String name() { | |
| return name; | |
| } | |
| /** | |
| * Implements the {@code absolutePath} method as per the specification in | |
| * {@link Preferences#absolutePath()}. | |
| * | |
| * <p>This implementation merely returns the absolute path name that | |
| * was computed at the time that this node was constructed (based on | |
| * the name that was passed to this node's constructor, and the names | |
| * that were passed to this node's ancestors' constructors). | |
| * | |
| * @return this preference node's absolute path name. | |
| */ | |
| public String absolutePath() { | |
| return absolutePath; | |
| } | |
| /** | |
| * Implements the {@code isUserNode} method as per the specification in | |
| * {@link Preferences#isUserNode()}. | |
| * | |
| * <p>This implementation compares this node's root node (which is stored | |
| * in a private field) with the value returned by | |
| * {@link Preferences#userRoot()}. If the two object references are | |
| * identical, this method returns true. | |
| * | |
| * @return {@code true} if this preference node is in the user | |
| * preference tree, {@code false} if it's in the system | |
| * preference tree. | |
| */ | |
| public boolean isUserNode() { | |
| return root == Preferences.userRoot(); | |
| } | |
| public void addPreferenceChangeListener(PreferenceChangeListener pcl) { | |
| if (pcl==null) | |
| throw new NullPointerException("Change listener is null."); | |
| synchronized(lock) { | |
| if (removed) | |
| throw new IllegalStateException("Node has been removed."); | |
| // Copy-on-write | |
| PreferenceChangeListener[] old = prefListeners; | |
| prefListeners = new PreferenceChangeListener[old.length + 1]; | |
| System.arraycopy(old, 0, prefListeners, 0, old.length); | |
| prefListeners[old.length] = pcl; | |
| } | |
| startEventDispatchThreadIfNecessary(); | |
| } | |
| public void removePreferenceChangeListener(PreferenceChangeListener pcl) { | |
| synchronized(lock) { | |
| if (removed) | |
| throw new IllegalStateException("Node has been removed."); | |
| if ((prefListeners == null) || (prefListeners.length == 0)) | |
| throw new IllegalArgumentException("Listener not registered."); | |
| // Copy-on-write | |
| PreferenceChangeListener[] newPl = | |
| new PreferenceChangeListener[prefListeners.length - 1]; | |
| int i = 0; | |
| while (i < newPl.length && prefListeners[i] != pcl) | |
| newPl[i] = prefListeners[i++]; | |
| if (i == newPl.length && prefListeners[i] != pcl) | |
| throw new IllegalArgumentException("Listener not registered."); | |
| while (i < newPl.length) | |
| newPl[i] = prefListeners[++i]; | |
| prefListeners = newPl; | |
| } | |
| } | |
| public void addNodeChangeListener(NodeChangeListener ncl) { | |
| if (ncl==null) | |
| throw new NullPointerException("Change listener is null."); | |
| synchronized(lock) { | |
| if (removed) | |
| throw new IllegalStateException("Node has been removed."); | |
| // Copy-on-write | |
| if (nodeListeners == null) { | |
| nodeListeners = new NodeChangeListener[1]; | |
| nodeListeners[0] = ncl; | |
| } else { | |
| NodeChangeListener[] old = nodeListeners; | |
| nodeListeners = new NodeChangeListener[old.length + 1]; | |
| System.arraycopy(old, 0, nodeListeners, 0, old.length); | |
| nodeListeners[old.length] = ncl; | |
| } | |
| } | |
| startEventDispatchThreadIfNecessary(); | |
| } | |
| public void removeNodeChangeListener(NodeChangeListener ncl) { | |
| synchronized(lock) { | |
| if (removed) | |
| throw new IllegalStateException("Node has been removed."); | |
| if ((nodeListeners == null) || (nodeListeners.length == 0)) | |
| throw new IllegalArgumentException("Listener not registered."); | |
| // Copy-on-write | |
| int i = 0; | |
| while (i < nodeListeners.length && nodeListeners[i] != ncl) | |
| i++; | |
| if (i == nodeListeners.length) | |
| throw new IllegalArgumentException("Listener not registered."); | |
| NodeChangeListener[] newNl = | |
| new NodeChangeListener[nodeListeners.length - 1]; | |
| if (i != 0) | |
| System.arraycopy(nodeListeners, 0, newNl, 0, i); | |
| if (i != newNl.length) | |
| System.arraycopy(nodeListeners, i + 1, | |
| newNl, i, newNl.length - i); | |
| nodeListeners = newNl; | |
| } | |
| } | |
| // "SPI" METHODS | |
| /** | |
| * Put the given key-value association into this preference node. It is | |
| * guaranteed that {@code key} and {@code value} are non-null and of | |
| * legal length. Also, it is guaranteed that this node has not been | |
| * removed. (The implementor needn't check for any of these things.) | |
| * | |
| * <p>This method is invoked with the lock on this node held. | |
| * @param key the key | |
| * @param value the value | |
| */ | |
| protected abstract void putSpi(String key, String value); | |
| /** | |
| * Return the value associated with the specified key at this preference | |
| * node, or {@code null} if there is no association for this key, or the | |
| * association cannot be determined at this time. It is guaranteed that | |
| * {@code key} is non-null. Also, it is guaranteed that this node has | |
| * not been removed. (The implementor needn't check for either of these | |
| * things.) | |
| * | |
| * <p> Generally speaking, this method should not throw an exception | |
| * under any circumstances. If, however, if it does throw an exception, | |
| * the exception will be intercepted and treated as a {@code null} | |
| * return value. | |
| * | |
| * <p>This method is invoked with the lock on this node held. | |
| * | |
| * @param key the key | |
| * @return the value associated with the specified key at this preference | |
| * node, or {@code null} if there is no association for this | |
| * key, or the association cannot be determined at this time. | |
| */ | |
| protected abstract String getSpi(String key); | |
| /** | |
| * Remove the association (if any) for the specified key at this | |
| * preference node. It is guaranteed that {@code key} is non-null. | |
| * Also, it is guaranteed that this node has not been removed. | |
| * (The implementor needn't check for either of these things.) | |
| * | |
| * <p>This method is invoked with the lock on this node held. | |
| * @param key the key | |
| */ | |
| protected abstract void removeSpi(String key); | |
| /** | |
| * Removes this preference node, invalidating it and any preferences that | |
| * it contains. The named child will have no descendants at the time this | |
| * invocation is made (i.e., the {@link Preferences#removeNode()} method | |
| * invokes this method repeatedly in a bottom-up fashion, removing each of | |
| * a node's descendants before removing the node itself). | |
| * | |
| * <p>This method is invoked with the lock held on this node and its | |
| * parent (and all ancestors that are being removed as a | |
| * result of a single invocation to {@link Preferences#removeNode()}). | |
| * | |
| * <p>The removal of a node needn't become persistent until the | |
| * {@code flush} method is invoked on this node (or an ancestor). | |
| * | |
| * <p>If this node throws a {@code BackingStoreException}, the exception | |
| * will propagate out beyond the enclosing {@link #removeNode()} | |
| * invocation. | |
| * | |
| * @throws BackingStoreException if this operation cannot be completed | |
| * due to a failure in the backing store, or inability to | |
| * communicate with it. | |
| */ | |
| protected abstract void removeNodeSpi() throws BackingStoreException; | |
| /** | |
| * Returns all of the keys that have an associated value in this | |
| * preference node. (The returned array will be of size zero if | |
| * this node has no preferences.) It is guaranteed that this node has not | |
| * been removed. | |
| * | |
| * <p>This method is invoked with the lock on this node held. | |
| * | |
| * <p>If this node throws a {@code BackingStoreException}, the exception | |
| * will propagate out beyond the enclosing {@link #keys()} invocation. | |
| * | |
| * @return an array of the keys that have an associated value in this | |
| * preference node. | |
| * @throws BackingStoreException if this operation cannot be completed | |
| * due to a failure in the backing store, or inability to | |
| * communicate with it. | |
| */ | |
| protected abstract String[] keysSpi() throws BackingStoreException; | |
| /** | |
| * Returns the names of the children of this preference node. (The | |
| * returned array will be of size zero if this node has no children.) | |
| * This method need not return the names of any nodes already cached, | |
| * but may do so without harm. | |
| * | |
| * <p>This method is invoked with the lock on this node held. | |
| * | |
| * <p>If this node throws a {@code BackingStoreException}, the exception | |
| * will propagate out beyond the enclosing {@link #childrenNames()} | |
| * invocation. | |
| * | |
| * @return an array containing the names of the children of this | |
| * preference node. | |
| * @throws BackingStoreException if this operation cannot be completed | |
| * due to a failure in the backing store, or inability to | |
| * communicate with it. | |
| */ | |
| protected abstract String[] childrenNamesSpi() | |
| throws BackingStoreException; | |
| /** | |
| * Returns the named child if it exists, or {@code null} if it does not. | |
| * It is guaranteed that {@code nodeName} is non-null, non-empty, | |
| * does not contain the slash character ('/'), and is no longer than | |
| * {@link #MAX_NAME_LENGTH} characters. Also, it is guaranteed | |
| * that this node has not been removed. (The implementor needn't check | |
| * for any of these things if he chooses to override this method.) | |
| * | |
| * <p>Finally, it is guaranteed that the named node has not been returned | |
| * by a previous invocation of this method or {@link #childSpi} after the | |
| * last time that it was removed. In other words, a cached value will | |
| * always be used in preference to invoking this method. (The implementor | |
| * needn't maintain his own cache of previously returned children if he | |
| * chooses to override this method.) | |
| * | |
| * <p>This implementation obtains this preference node's lock, invokes | |
| * {@link #childrenNames()} to get an array of the names of this node's | |
| * children, and iterates over the array comparing the name of each child | |
| * with the specified node name. If a child node has the correct name, | |
| * the {@link #childSpi(String)} method is invoked and the resulting | |
| * node is returned. If the iteration completes without finding the | |
| * specified name, {@code null} is returned. | |
| * | |
| * @param nodeName name of the child to be searched for. | |
| * @return the named child if it exists, or null if it does not. | |
| * @throws BackingStoreException if this operation cannot be completed | |
| * due to a failure in the backing store, or inability to | |
| * communicate with it. | |
| */ | |
| protected AbstractPreferences getChild(String nodeName) | |
| throws BackingStoreException { | |
| synchronized(lock) { | |
| // assert kidCache.get(nodeName)==null; | |
| String[] kidNames = childrenNames(); | |
| for (String kidName : kidNames) | |
| if (kidName.equals(nodeName)) | |
| return childSpi(kidName); | |
| } | |
| return null; | |
| } | |
| /** | |
| * Returns the named child of this preference node, creating it if it does | |
| * not already exist. It is guaranteed that {@code name} is non-null, | |
| * non-empty, does not contain the slash character ('/'), and is no longer | |
| * than {@link #MAX_NAME_LENGTH} characters. Also, it is guaranteed that | |
| * this node has not been removed. (The implementor needn't check for any | |
| * of these things.) | |
| * | |
| * <p>Finally, it is guaranteed that the named node has not been returned | |
| * by a previous invocation of this method or {@link #getChild(String)} | |
| * after the last time that it was removed. In other words, a cached | |
| * value will always be used in preference to invoking this method. | |
| * Subclasses need not maintain their own cache of previously returned | |
| * children. | |
| * | |
| * <p>The implementer must ensure that the returned node has not been | |
| * removed. If a like-named child of this node was previously removed, the | |
| * implementer must return a newly constructed {@code AbstractPreferences} | |
| * node; once removed, an {@code AbstractPreferences} node | |
| * cannot be "resuscitated." | |
| * | |
| * <p>If this method causes a node to be created, this node is not | |
| * guaranteed to be persistent until the {@code flush} method is | |
| * invoked on this node or one of its ancestors (or descendants). | |
| * | |
| * <p>This method is invoked with the lock on this node held. | |
| * | |
| * @param name The name of the child node to return, relative to | |
| * this preference node. | |
| * @return The named child node. | |
| */ | |
| protected abstract AbstractPreferences childSpi(String name); | |
| /** | |
| * Returns the absolute path name of this preferences node. | |
| */ | |
| public String toString() { | |
| return (this.isUserNode() ? "User" : "System") + | |
| " Preference Node: " + this.absolutePath(); | |
| } | |
| /** | |
| * Implements the {@code sync} method as per the specification in | |
| * {@link Preferences#sync()}. | |
| * | |
| * <p>This implementation calls a recursive helper method that locks this | |
| * node, invokes syncSpi() on it, unlocks this node, and recursively | |
| * invokes this method on each "cached child." A cached child is a child | |
| * of this node that has been created in this VM and not subsequently | |
| * removed. In effect, this method does a depth first traversal of the | |
| * "cached subtree" rooted at this node, calling syncSpi() on each node in | |
| * the subTree while only that node is locked. Note that syncSpi() is | |
| * invoked top-down. | |
| * | |
| * @throws BackingStoreException if this operation cannot be completed | |
| * due to a failure in the backing store, or inability to | |
| * communicate with it. | |
| * @throws IllegalStateException if this node (or an ancestor) has been | |
| * removed with the {@link #removeNode()} method. | |
| * @see #flush() | |
| */ | |
| public void sync() throws BackingStoreException { | |
| sync2(); | |
| } | |
| private void sync2() throws BackingStoreException { | |
| AbstractPreferences[] cachedKids; | |
| synchronized(lock) { | |
| if (removed) | |
| throw new IllegalStateException("Node has been removed"); | |
| syncSpi(); | |
| cachedKids = cachedChildren(); | |
| } | |
| for (AbstractPreferences cachedKid : cachedKids) | |
| cachedKid.sync2(); | |
| } | |
| /** | |
| * This method is invoked with this node locked. The contract of this | |
| * method is to synchronize any cached preferences stored at this node | |
| * with any stored in the backing store. (It is perfectly possible that | |
| * this node does not exist on the backing store, either because it has | |
| * been deleted by another VM, or because it has not yet been created.) | |
| * Note that this method should <i>not</i> synchronize the preferences in | |
| * any subnodes of this node. If the backing store naturally syncs an | |
| * entire subtree at once, the implementer is encouraged to override | |
| * sync(), rather than merely overriding this method. | |
| * | |
| * <p>If this node throws a {@code BackingStoreException}, the exception | |
| * will propagate out beyond the enclosing {@link #sync()} invocation. | |
| * | |
| * @throws BackingStoreException if this operation cannot be completed | |
| * due to a failure in the backing store, or inability to | |
| * communicate with it. | |
| */ | |
| protected abstract void syncSpi() throws BackingStoreException; | |
| /** | |
| * Implements the {@code flush} method as per the specification in | |
| * {@link Preferences#flush()}. | |
| * | |
| * <p>This implementation calls a recursive helper method that locks this | |
| * node, invokes flushSpi() on it, unlocks this node, and recursively | |
| * invokes this method on each "cached child." A cached child is a child | |
| * of this node that has been created in this VM and not subsequently | |
| * removed. In effect, this method does a depth first traversal of the | |
| * "cached subtree" rooted at this node, calling flushSpi() on each node in | |
| * the subTree while only that node is locked. Note that flushSpi() is | |
| * invoked top-down. | |
| * | |
| * <p> If this method is invoked on a node that has been removed with | |
| * the {@link #removeNode()} method, flushSpi() is invoked on this node, | |
| * but not on others. | |
| * | |
| * @throws BackingStoreException if this operation cannot be completed | |
| * due to a failure in the backing store, or inability to | |
| * communicate with it. | |
| * @see #flush() | |
| */ | |
| public void flush() throws BackingStoreException { | |
| flush2(); | |
| } | |
| private void flush2() throws BackingStoreException { | |
| AbstractPreferences[] cachedKids; | |
| synchronized(lock) { | |
| flushSpi(); | |
| if(removed) | |
| return; | |
| cachedKids = cachedChildren(); | |
| } | |
| for (AbstractPreferences cachedKid : cachedKids) | |
| cachedKid.flush2(); | |
| } | |
| /** | |
| * This method is invoked with this node locked. The contract of this | |
| * method is to force any cached changes in the contents of this | |
| * preference node to the backing store, guaranteeing their persistence. | |
| * (It is perfectly possible that this node does not exist on the backing | |
| * store, either because it has been deleted by another VM, or because it | |
| * has not yet been created.) Note that this method should <i>not</i> | |
| * flush the preferences in any subnodes of this node. If the backing | |
| * store naturally flushes an entire subtree at once, the implementer is | |
| * encouraged to override flush(), rather than merely overriding this | |
| * method. | |
| * | |
| * <p>If this node throws a {@code BackingStoreException}, the exception | |
| * will propagate out beyond the enclosing {@link #flush()} invocation. | |
| * | |
| * @throws BackingStoreException if this operation cannot be completed | |
| * due to a failure in the backing store, or inability to | |
| * communicate with it. | |
| */ | |
| protected abstract void flushSpi() throws BackingStoreException; | |
| /** | |
| * Returns {@code true} iff this node (or an ancestor) has been | |
| * removed with the {@link #removeNode()} method. This method | |
| * locks this node prior to returning the contents of the private | |
| * field used to track this state. | |
| * | |
| * @return {@code true} iff this node (or an ancestor) has been | |
| * removed with the {@link #removeNode()} method. | |
| */ | |
| protected boolean isRemoved() { | |
| synchronized(lock) { | |
| return removed; | |
| } | |
| } | |
| /** | |
| * Queue of pending notification events. When a preference or node | |
| * change event for which there are one or more listeners occurs, | |
| * it is placed on this queue and the queue is notified. A background | |
| * thread waits on this queue and delivers the events. This decouples | |
| * event delivery from preference activity, greatly simplifying | |
| * locking and reducing opportunity for deadlock. | |
| */ | |
| private static final List<EventObject> eventQueue = new LinkedList<>(); | |
| /** | |
| * These two classes are used to distinguish NodeChangeEvents on | |
| * eventQueue so the event dispatch thread knows whether to call | |
| * childAdded or childRemoved. | |
| */ | |
| private static class NodeAddedEvent extends NodeChangeEvent { | |
| private static final long serialVersionUID = -6743557530157328528L; | |
| NodeAddedEvent(Preferences parent, Preferences child) { | |
| super(parent, child); | |
| } | |
| } | |
| private static class NodeRemovedEvent extends NodeChangeEvent { | |
| private static final long serialVersionUID = 8735497392918824837L; | |
| NodeRemovedEvent(Preferences parent, Preferences child) { | |
| super(parent, child); | |
| } | |
| } | |
| /** | |
| * A single background thread ("the event notification thread") monitors | |
| * the event queue and delivers events that are placed on the queue. | |
| */ | |
| private static class EventDispatchThread extends Thread { | |
| private EventDispatchThread() { | |
| super(null, null, "Event Dispatch Thread", 0, false); | |
| } | |
| public void run() { | |
| while(true) { | |
| // Wait on eventQueue till an event is present | |
| EventObject event = null; | |
| synchronized(eventQueue) { | |
| try { | |
| while (eventQueue.isEmpty()) | |
| eventQueue.wait(); | |
| event = eventQueue.remove(0); | |
| } catch (InterruptedException e) { | |
| // XXX Log "Event dispatch thread interrupted. Exiting" | |
| return; | |
| } | |
| } | |
| // Now we have event & hold no locks; deliver evt to listeners | |
| AbstractPreferences src=(AbstractPreferences)event.getSource(); | |
| if (event instanceof PreferenceChangeEvent) { | |
| PreferenceChangeEvent pce = (PreferenceChangeEvent)event; | |
| PreferenceChangeListener[] listeners = src.prefListeners(); | |
| for (PreferenceChangeListener listener : listeners) | |
| listener.preferenceChange(pce); | |
| } else { | |
| NodeChangeEvent nce = (NodeChangeEvent)event; | |
| NodeChangeListener[] listeners = src.nodeListeners(); | |
| if (nce instanceof NodeAddedEvent) { | |
| for (NodeChangeListener listener : listeners) | |
| listener.childAdded(nce); | |
| } else { | |
| // assert nce instanceof NodeRemovedEvent; | |
| for (NodeChangeListener listener : listeners) | |
| listener.childRemoved(nce); | |
| } | |
| } | |
| } | |
| } | |
| } | |
| private static Thread eventDispatchThread = null; | |
| /** | |
| * This method starts the event dispatch thread the first time it | |
| * is called. The event dispatch thread will be started only | |
| * if someone registers a listener. | |
| */ | |
| private static synchronized void startEventDispatchThreadIfNecessary() { | |
| if (eventDispatchThread == null) { | |
| // XXX Log "Starting event dispatch thread" | |
| eventDispatchThread = new EventDispatchThread(); | |
| eventDispatchThread.setDaemon(true); | |
| eventDispatchThread.start(); | |
| } | |
| } | |
| /** | |
| * Return this node's preference/node change listeners. Even though | |
| * we're using a copy-on-write lists, we use synchronized accessors to | |
| * ensure information transmission from the writing thread to the | |
| * reading thread. | |
| */ | |
| PreferenceChangeListener[] prefListeners() { | |
| synchronized(lock) { | |
| return prefListeners; | |
| } | |
| } | |
| NodeChangeListener[] nodeListeners() { | |
| synchronized(lock) { | |
| return nodeListeners; | |
| } | |
| } | |
| /** | |
| * Enqueue a preference change event for delivery to registered | |
| * preference change listeners unless there are no registered | |
| * listeners. Invoked with this.lock held. | |
| */ | |
| private void enqueuePreferenceChangeEvent(String key, String newValue) { | |
| if (prefListeners.length != 0) { | |
| synchronized(eventQueue) { | |
| eventQueue.add(new PreferenceChangeEvent(this, key, newValue)); | |
| eventQueue.notify(); | |
| } | |
| } | |
| } | |
| /** | |
| * Enqueue a "node added" event for delivery to registered node change | |
| * listeners unless there are no registered listeners. Invoked with | |
| * this.lock held. | |
| */ | |
| private void enqueueNodeAddedEvent(Preferences child) { | |
| if (nodeListeners.length != 0) { | |
| synchronized(eventQueue) { | |
| eventQueue.add(new NodeAddedEvent(this, child)); | |
| eventQueue.notify(); | |
| } | |
| } | |
| } | |
| /** | |
| * Enqueue a "node removed" event for delivery to registered node change | |
| * listeners unless there are no registered listeners. Invoked with | |
| * this.lock held. | |
| */ | |
| private void enqueueNodeRemovedEvent(Preferences child) { | |
| if (nodeListeners.length != 0) { | |
| synchronized(eventQueue) { | |
| eventQueue.add(new NodeRemovedEvent(this, child)); | |
| eventQueue.notify(); | |
| } | |
| } | |
| } | |
| /** | |
| * Implements the {@code exportNode} method as per the specification in | |
| * {@link Preferences#exportNode(OutputStream)}. | |
| * | |
| * @param os the output stream on which to emit the XML document. | |
| * @throws IOException if writing to the specified output stream | |
| * results in an {@code IOException}. | |
| * @throws BackingStoreException if preference data cannot be read from | |
| * backing store. | |
| */ | |
| public void exportNode(OutputStream os) | |
| throws IOException, BackingStoreException | |
| { | |
| XmlSupport.export(os, this, false); | |
| } | |
| /** | |
| * Implements the {@code exportSubtree} method as per the specification in | |
| * {@link Preferences#exportSubtree(OutputStream)}. | |
| * | |
| * @param os the output stream on which to emit the XML document. | |
| * @throws IOException if writing to the specified output stream | |
| * results in an {@code IOException}. | |
| * @throws BackingStoreException if preference data cannot be read from | |
| * backing store. | |
| */ | |
| public void exportSubtree(OutputStream os) | |
| throws IOException, BackingStoreException | |
| { | |
| XmlSupport.export(os, this, true); | |
| } | |
| } |