--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/jdk/src/share/classes/java/util/prefs/AbstractPreferences.java Sat Dec 01 00:00:00 2007 +0000
@@ -0,0 +1,1615 @@
+/*
+ * Copyright 2000-2006 Sun Microsystems, Inc. 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. Sun designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ */
+
+package java.util.prefs;
+
+import java.util.*;
+import java.io.*;
+import java.security.AccessController;
+import java.security.PrivilegedAction;
+// These imports needed only as a workaround for a JavaDoc bug
+import java.lang.Integer;
+import java.lang.Long;
+import java.lang.Float;
+import java.lang.Double;
+
+/**
+ * This class provides a skeletal implementation of the {@link Preferences}
+ * class, greatly easing the task of implementing it.
+ *
+ * <p><strong>This class is for <tt>Preferences</tt> implementers only.
+ * Normal users of the <tt>Preferences</tt> 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 <tt>getSpi</tt> 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 <tt>removeNodeSpi, keysSpi,
+ * childrenNamesSpi, syncSpi</tt> and <tt>flushSpi</tt> 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
+ * <tt>BackingStoreException</tt>, 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, all subsequent invocations
+ * of <tt>flush()</tt> and <tt>sync</tt> should return <tt>false</tt>, as
+ * returning <tt>true</tt> would imply that all previous operations had
+ * successfully been made permanent.
+ *
+ * <p>There is one circumstance under which <tt>putSpi, removeSpi and
+ * childSpi</tt> <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 <tt>Preferences</tt>
+ * 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 <tt>Preferences</tt>
+ * implementations may have the user identity change from request to request,
+ * implicitly passed to <tt>Preferences</tt> 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 <tt>Preferences</tt> instance. The latter behavior conflicts
+ * with normal <tt>Preferences</tt> usage and would lead to great confusion.
+ *
+ * @author Josh Bloch
+ * @see Preferences
+ * @since 1.4
+ */
+public abstract class AbstractPreferences extends Preferences {
+ /**
+ * 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 <tt>true</tt> 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 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 <tt>""</tt> if this is the root.
+ * @throws IllegalArgumentException if <tt>name</tt> contains a slash
+ * (<tt>'/'</tt>), or <tt>parent</tt> is <tt>null</tt> and
+ * name isn't <tt>""</tt>.
+ */
+ protected AbstractPreferences(AbstractPreferences parent, String name) {
+ if (parent==null) {
+ if (!name.equals(""))
+ 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.equals(""))
+ 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 <tt>put</tt> 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 <tt>null</tt>.
+ * @throws IllegalArgumentException if <tt>key.length()</tt> exceeds
+ * <tt>MAX_KEY_LENGTH</tt> or if <tt>value.length</tt> exceeds
+ * <tt>MAX_VALUE_LENGTH</tt>.
+ * @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);
+
+ synchronized(lock) {
+ if (removed)
+ throw new IllegalStateException("Node has been removed.");
+
+ putSpi(key, value);
+ enqueuePreferenceChangeEvent(key, value);
+ }
+ }
+
+ /**
+ * Implements the <tt>get</tt> method as per the specification in
+ * {@link Preferences#get(String,String)}.
+ *
+ * <p>This implementation first checks to see if <tt>key</tt> is
+ * <tt>null</tt> throwing a <tt>NullPointerException</tt> 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 <tt>getSpi</tt>
+ * invocation returns <tt>null</tt> or throws an exception, in which case
+ * this invocation returns <tt>def</tt>.
+ *
+ * @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 <tt>key</tt>.
+ * @return the value associated with <tt>key</tt>, or <tt>def</tt>
+ * if no value is associated with <tt>key</tt>.
+ * @throws IllegalStateException if this node (or an ancestor) has been
+ * removed with the {@link #removeNode()} method.
+ * @throws NullPointerException if key is <tt>null</tt>. (A
+ * <tt>null</tt> default <i>is</i> permitted.)
+ */
+ public String get(String key, String def) {
+ if (key==null)
+ throw new NullPointerException("Null key");
+ 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 <tt>remove(String)</tt> 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.
+ */
+ public void remove(String key) {
+ synchronized(lock) {
+ if (removed)
+ throw new IllegalStateException("Node has been removed.");
+
+ removeSpi(key);
+ enqueuePreferenceChangeEvent(key, null);
+ }
+ }
+
+ /**
+ * Implements the <tt>clear</tt> 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) {
+ String[] keys = keys();
+ for (int i=0; i<keys.length; i++)
+ remove(keys[i]);
+ }
+ }
+
+ /**
+ * Implements the <tt>putInt</tt> method as per the specification in
+ * {@link Preferences#putInt(String,int)}.
+ *
+ * <p>This implementation translates <tt>value</tt> 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 <tt>null</tt>.
+ * @throws IllegalArgumentException if <tt>key.length()</tt> exceeds
+ * <tt>MAX_KEY_LENGTH</tt>.
+ * @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 <tt>getInt</tt> method as per the specification in
+ * {@link Preferences#getInt(String,int)}.
+ *
+ * <p>This implementation invokes {@link #get(String,String) <tt>get(key,
+ * null)</tt>}. If the return value is non-null, the implementation
+ * attempts to translate it to an <tt>int</tt> with
+ * {@link Integer#parseInt(String)}. If the attempt succeeds, the return
+ * value is returned by this method. Otherwise, <tt>def</tt> 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 <tt>key</tt>
+ * or the associated value cannot be interpreted as an int.
+ * @return the int value represented by the string associated with
+ * <tt>key</tt> in this preference node, or <tt>def</tt> 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 <tt>key</tt> is <tt>null</tt>.
+ */
+ 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 <tt>putLong</tt> method as per the specification in
+ * {@link Preferences#putLong(String,long)}.
+ *
+ * <p>This implementation translates <tt>value</tt> 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 <tt>null</tt>.
+ * @throws IllegalArgumentException if <tt>key.length()</tt> exceeds
+ * <tt>MAX_KEY_LENGTH</tt>.
+ * @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 <tt>getLong</tt> method as per the specification in
+ * {@link Preferences#getLong(String,long)}.
+ *
+ * <p>This implementation invokes {@link #get(String,String) <tt>get(key,
+ * null)</tt>}. If the return value is non-null, the implementation
+ * attempts to translate it to a <tt>long</tt> with
+ * {@link Long#parseLong(String)}. If the attempt succeeds, the return
+ * value is returned by this method. Otherwise, <tt>def</tt> 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 <tt>key</tt>
+ * or the associated value cannot be interpreted as a long.
+ * @return the long value represented by the string associated with
+ * <tt>key</tt> in this preference node, or <tt>def</tt> 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 <tt>key</tt> is <tt>null</tt>.
+ */
+ 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 <tt>putBoolean</tt> method as per the specification in
+ * {@link Preferences#putBoolean(String,boolean)}.
+ *
+ * <p>This implementation translates <tt>value</tt> 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 <tt>null</tt>.
+ * @throws IllegalArgumentException if <tt>key.length()</tt> exceeds
+ * <tt>MAX_KEY_LENGTH</tt>.
+ * @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 <tt>getBoolean</tt> method as per the specification in
+ * {@link Preferences#getBoolean(String,boolean)}.
+ *
+ * <p>This implementation invokes {@link #get(String,String) <tt>get(key,
+ * null)</tt>}. If the return value is non-null, it is compared with
+ * <tt>"true"</tt> using {@link String#equalsIgnoreCase(String)}. If the
+ * comparison returns <tt>true</tt>, this invocation returns
+ * <tt>true</tt>. Otherwise, the original return value is compared with
+ * <tt>"false"</tt>, again using {@link String#equalsIgnoreCase(String)}.
+ * If the comparison returns <tt>true</tt>, this invocation returns
+ * <tt>false</tt>. Otherwise, this invocation returns <tt>def</tt>.
+ *
+ * @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 <tt>key</tt>
+ * or the associated value cannot be interpreted as a boolean.
+ * @return the boolean value represented by the string associated with
+ * <tt>key</tt> in this preference node, or <tt>def</tt> 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 <tt>key</tt> is <tt>null</tt>.
+ */
+ 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 <tt>putFloat</tt> method as per the specification in
+ * {@link Preferences#putFloat(String,float)}.
+ *
+ * <p>This implementation translates <tt>value</tt> 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 <tt>null</tt>.
+ * @throws IllegalArgumentException if <tt>key.length()</tt> exceeds
+ * <tt>MAX_KEY_LENGTH</tt>.
+ * @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 <tt>getFloat</tt> method as per the specification in
+ * {@link Preferences#getFloat(String,float)}.
+ *
+ * <p>This implementation invokes {@link #get(String,String) <tt>get(key,
+ * null)</tt>}. If the return value is non-null, the implementation
+ * attempts to translate it to an <tt>float</tt> with
+ * {@link Float#parseFloat(String)}. If the attempt succeeds, the return
+ * value is returned by this method. Otherwise, <tt>def</tt> 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 <tt>key</tt>
+ * or the associated value cannot be interpreted as a float.
+ * @return the float value represented by the string associated with
+ * <tt>key</tt> in this preference node, or <tt>def</tt> 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 <tt>key</tt> is <tt>null</tt>.
+ */
+ 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 <tt>putDouble</tt> method as per the specification in
+ * {@link Preferences#putDouble(String,double)}.
+ *
+ * <p>This implementation translates <tt>value</tt> 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 <tt>null</tt>.
+ * @throws IllegalArgumentException if <tt>key.length()</tt> exceeds
+ * <tt>MAX_KEY_LENGTH</tt>.
+ * @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 <tt>getDouble</tt> method as per the specification in
+ * {@link Preferences#getDouble(String,double)}.
+ *
+ * <p>This implementation invokes {@link #get(String,String) <tt>get(key,
+ * null)</tt>}. If the return value is non-null, the implementation
+ * attempts to translate it to an <tt>double</tt> with
+ * {@link Double#parseDouble(String)}. If the attempt succeeds, the return
+ * value is returned by this method. Otherwise, <tt>def</tt> 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 <tt>key</tt>
+ * or the associated value cannot be interpreted as a double.
+ * @return the double value represented by the string associated with
+ * <tt>key</tt> in this preference node, or <tt>def</tt> 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 <tt>key</tt> is <tt>null</tt>.
+ */
+ 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 <tt>putByteArray</tt> 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 <tt>null</tt>.
+ * @throws IllegalArgumentException if key.length() exceeds MAX_KEY_LENGTH
+ * or if value.length exceeds MAX_VALUE_LENGTH*3/4.
+ * @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 <tt>getByteArray</tt> 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 <tt>key</tt>
+ * or the associated value cannot be interpreted as a byte array.
+ * @return the byte array value represented by the string associated with
+ * <tt>key</tt> in this preference node, or <tt>def</tt> 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 <tt>key</tt> is <tt>null</tt>. (A
+ * <tt>null</tt> value for <tt>def</tt> <i>is</i> permitted.)
+ */
+ 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 <tt>keys</tt> 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 <tt>children</tt> 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 <tt>TreeSet</tt> 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 <tt>String</tt> array using the <tt>toArray</tt> 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 s = new TreeSet(kidCache.keySet());
+ String[] kids = childrenNamesSpi();
+ for(int i=0; i<kids.length; i++)
+ s.add(kids[i]);
+ return (String[]) 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 (AbstractPreferences[]) kidCache.values().
+ toArray(EMPTY_ABSTRACT_PREFS_ARRAY);
+ }
+
+ private static final AbstractPreferences[] EMPTY_ABSTRACT_PREFS_ARRAY
+ = new AbstractPreferences[0];
+
+ /**
+ * Implements the <tt>parent</tt> 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 <tt>node</tt> 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 <tt>path</tt> is <tt>""</tt>,
+ * this node is returned; if <tt>path</tt> is <tt>"/"</tt>, this node's
+ * root is returned. If the first character in <tt>path</tt> is
+ * not <tt>'/'</tt>, the implementation breaks <tt>path</tt> into
+ * tokens and recursively traverses the path from this node to the
+ * named node, "consuming" a name and a slash from <tt>path</tt> 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 <tt>MAX_NAME_LENGTH</tt>. Then the {@link #childSpi(String)}
+ * method is invoked, and the result stored in this node's child-cache.
+ * If the newly created <tt>Preferences</tt> object's {@link #newNode}
+ * field is <tt>true</tt> 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 <tt>childSpi</tt> is returned by this
+ * method. If during the traversal, two <tt>"/"</tt> tokens occur
+ * consecutively, or the final token is <tt>"/"</tt> (rather than a name),
+ * an appropriate <tt>IllegalArgumentException</tt> is thrown.
+ *
+ * <p> If the first character of <tt>path</tt> is <tt>'/'</tt>
+ * (indicating an absolute path name) this preference node's
+ * lock is dropped prior to breaking <tt>path</tt> 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.equals(""))
+ 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=(AbstractPreferences)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 <tt>nodeExists</tt> 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
+ * <tt>pathname</tt> is not the empty string (<tt>""</tt>).
+ */
+ public boolean nodeExists(String path)
+ throws BackingStoreException
+ {
+ synchronized(lock) {
+ if (path.equals(""))
+ 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=(AbstractPreferences)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 <tt>removeNode()</tt> 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 <tt>Preferences</tt>
+ * 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 (int i=0; i<kidNames.length; i++)
+ if (!kidCache.containsKey(kidNames[i]))
+ kidCache.put(kidNames[i], childSpi(kidNames[i]));
+
+ // Recursively remove all cached children
+ for (Iterator i = kidCache.values().iterator(); i.hasNext();) {
+ try {
+ ((AbstractPreferences)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 <tt>name</tt> 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 <tt>absolutePath</tt> 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 <tt>isUserNode</tt> 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 <tt>true</tt> if this preference node is in the user
+ * preference tree, <tt>false</tt> if it's in the system
+ * preference tree.
+ */
+ public boolean isUserNode() {
+ Boolean result = (Boolean)
+ AccessController.doPrivileged( new PrivilegedAction() {
+ public Object run() {
+ return Boolean.valueOf(root == Preferences.userRoot());
+ }
+ });
+ return result.booleanValue();
+ }
+
+ 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 <tt>key</tt> and <tt>value</tt> 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.
+ */
+ protected abstract void putSpi(String key, String value);
+
+ /**
+ * Return the value associated with the specified key at this preference
+ * node, or <tt>null</tt> if there is no association for this key, or the
+ * association cannot be determined at this time. It is guaranteed that
+ * <tt>key</tt> 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 <tt>null</tt>
+ * return value.
+ *
+ * <p>This method is invoked with the lock on this node held.
+ *
+ * @return the value associated with the specified key at this preference
+ * node, or <tt>null</tt> 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 <tt>key</tt> 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.
+ */
+ 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
+ * <tt>flush</tt> method is invoked on this node (or an ancestor).
+ *
+ * <p>If this node throws a <tt>BackingStoreException</tt>, 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 <tt>BackingStoreException</tt>, 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 <tt>BackingStoreException</tt>, 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 <tt>null</tt> if it does not.
+ * It is guaranteed that <tt>nodeName</tt> 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, <tt>null</tt> 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 (int i=0; i<kidNames.length; i++)
+ if (kidNames[i].equals(nodeName))
+ return childSpi(kidNames[i]);
+ }
+ return null;
+ }
+
+ /**
+ * Returns the named child of this preference node, creating it if it does
+ * not already exist. It is guaranteed that <tt>name</tt> 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 <tt>AbstractPreferences</tt>
+ * node; once removed, an <tt>AbstractPreferences</tt> node
+ * cannot be "resuscitated."
+ *
+ * <p>If this method causes a node to be created, this node is not
+ * guaranteed to be persistent until the <tt>flush</tt> 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 <tt>sync</tt> 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 (int i=0; i<cachedKids.length; i++)
+ cachedKids[i].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 <tt>BackingStoreException</tt>, 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 <tt>flush</tt> 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 (int i = 0; i < cachedKids.length; i++)
+ cachedKids[i].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 <tt>BackingStoreException</tt>, 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 <tt>true</tt> 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 <tt>true</tt> 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 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 class NodeAddedEvent extends NodeChangeEvent {
+ private static final long serialVersionUID = -6743557530157328528L;
+ NodeAddedEvent(Preferences parent, Preferences child) {
+ super(parent, child);
+ }
+ }
+ private 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 {
+ 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 = (EventObject) 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 (int i=0; i<listeners.length; i++)
+ listeners[i].preferenceChange(pce);
+ } else {
+ NodeChangeEvent nce = (NodeChangeEvent)event;
+ NodeChangeListener[] listeners = src.nodeListeners();
+ if (nce instanceof NodeAddedEvent) {
+ for (int i=0; i<listeners.length; i++)
+ listeners[i].childAdded(nce);
+ } else {
+ // assert nce instanceof NodeRemovedEvent;
+ for (int i=0; i<listeners.length; i++)
+ listeners[i].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 <tt>exportNode</tt> 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 <tt>IOException</tt>.
+ * @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 <tt>exportSubtree</tt> 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 <tt>IOException</tt>.
+ * @throws BackingStoreException if preference data cannot be read from
+ * backing store.
+ */
+ public void exportSubtree(OutputStream os)
+ throws IOException, BackingStoreException
+ {
+ XmlSupport.export(os, this, true);
+ }
+}