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From-SVN: r102074

libjava/classpath/java/beans/PropertyChangeSupport.java

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+/* PropertyChangeSupport.java -- support to manage property change listeners
+   Copyright (C) 1998, 1999, 2000, 2002, 2005  Free Software Foundation, Inc.
+
+This file is part of GNU Classpath.
+
+GNU Classpath is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2, or (at your option)
+any later version.
+
+GNU Classpath 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 for more details.
+
+You should have received a copy of the GNU General Public License
+along with GNU Classpath; see the file COPYING.  If not, write to the
+Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+02110-1301 USA.
+
+Linking this library statically or dynamically with other modules is
+making a combined work based on this library.  Thus, the terms and
+conditions of the GNU General Public License cover the whole
+combination.
+
+As a special exception, the copyright holders of this library give you
+permission to link this library with independent modules to produce an
+executable, regardless of the license terms of these independent
+modules, and to copy and distribute the resulting executable under
+terms of your choice, provided that you also meet, for each linked
+independent module, the terms and conditions of the license of that
+module.  An independent module is a module which is not derived from
+or based on this library.  If you modify this library, you may extend
+this exception to your version of the library, but you are not
+obligated to do so.  If you do not wish to do so, delete this
+exception statement from your version. */
+
+
+package java.beans;
+
+import java.io.IOException;
+import java.io.ObjectInputStream;
+import java.io.ObjectOutputStream;
+import java.io.Serializable;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Hashtable;
+import java.util.Iterator;
+import java.util.Map.Entry;
+import java.util.Vector;
+
+/**
+ * PropertyChangeSupport makes it easy to fire property change events and
+ * handle listeners. It allows chaining of listeners, as well as filtering
+ * by property name. In addition, it will serialize only those listeners
+ * which are serializable, ignoring the others without problem. This class
+ * is thread-safe.
+ *
+ * @author John Keiser
+ * @author Eric Blake (ebb9@email.byu.edu)
+ * @since 1.1
+ * @status updated to 1.4
+ */
+public class PropertyChangeSupport implements Serializable
+{
+  /**
+   * Compatible with JDK 1.1+.
+   */
+  private static final long serialVersionUID = 6401253773779951803L;
+
+  /**
+   * Maps property names (String) to named listeners (PropertyChangeSupport).
+   * If this is a child instance, this field will be null.
+   *
+   * @serial the map of property names to named listener managers
+   * @since 1.2
+   */
+  private Hashtable children;
+
+  /**
+   * The non-null source object for any generated events.
+   *
+   * @serial the event source
+   */
+  private final Object source;
+
+  /**
+   * A field to compare serialization versions - this class uses version 2.
+   *
+   * @serial the serialization format
+   */
+  private static final int propertyChangeSupportSerializedDataVersion = 2;
+
+  /**
+   * The list of all registered property listeners. If this instance was
+   * created by user code, this only holds the global listeners (ie. not tied
+   * to a name), and may be null. If it was created by this class, as a
+   * helper for named properties, then this vector will be non-null, and this
+   * instance appears as a value in the <code>children</code> hashtable of
+   * another instance, so that the listeners are tied to the key of that
+   * hashtable entry.
+   */
+  private transient Vector listeners;
+
+  /**
+   * Create a PropertyChangeSupport to work with a specific source bean.
+   *
+   * @param source the source bean to use
+   * @throws NullPointerException if source is null
+   */
+  public PropertyChangeSupport(Object source)
+  {
+    this.source = source;
+    if (source == null)
+      throw new NullPointerException();
+  }
+
+  /**
+   * Adds a PropertyChangeListener to the list of global listeners. All
+   * property change events will be sent to this listener. The listener add
+   * is not unique: that is, <em>n</em> adds with the same listener will
+   * result in <em>n</em> events being sent to that listener for every
+   * property change. Adding a null listener may cause a NullPointerException
+   * down the road. This method will unwrap a PropertyChangeListenerProxy,
+   * registering the underlying delegate to the named property list.
+   *
+   * @param l the listener to add
+   */
+  public synchronized void addPropertyChangeListener(PropertyChangeListener l)
+  {
+    if (l instanceof PropertyChangeListenerProxy)
+      {
+        PropertyChangeListenerProxy p = (PropertyChangeListenerProxy) l;
+        addPropertyChangeListener(p.propertyName,
+                                  (PropertyChangeListener) p.getListener());
+      }
+    else
+      {
+        if (listeners == null)
+          listeners = new Vector();
+        listeners.add(l);
+      }
+  }
+
+  /**
+   * Removes a PropertyChangeListener from the list of global listeners. If
+   * any specific properties are being listened on, they must be deregistered
+   * by themselves; this will only remove the general listener to all
+   * properties. If <code>add()</code> has been called multiple times for a
+   * particular listener, <code>remove()</code> will have to be called the
+   * same number of times to deregister it. This method will unwrap a
+   * PropertyChangeListenerProxy, removing the underlying delegate from the
+   * named property list.
+   *
+   * @param l the listener to remove
+   */
+  public synchronized void
+    removePropertyChangeListener(PropertyChangeListener l)
+  {
+    if (l instanceof PropertyChangeListenerProxy)
+      {
+        PropertyChangeListenerProxy p = (PropertyChangeListenerProxy) l;
+        removePropertyChangeListener(p.propertyName,
+                                     (PropertyChangeListener) p.getListener());
+      }
+    else if (listeners != null)
+      {
+        listeners.remove(l);
+        if (listeners.isEmpty())
+          listeners = null;
+      }
+  }
+
+  /**
+   * Returns an array of all registered property change listeners. Those that
+   * were registered under a name will be wrapped in a
+   * <code>PropertyChangeListenerProxy</code>, so you must check whether the
+   * listener is an instance of the proxy class in order to see what name the
+   * real listener is registered under. If there are no registered listeners,
+   * this returns an empty array.
+   *
+   * @return the array of registered listeners
+   * @see PropertyChangeListenerProxy
+   * @since 1.4
+   */
+  public synchronized PropertyChangeListener[] getPropertyChangeListeners()
+  {
+    ArrayList list = new ArrayList();
+    if (listeners != null)
+      list.addAll(listeners);
+    if (children != null)
+      {
+        int i = children.size();
+        Iterator iter = children.entrySet().iterator();
+        while (--i >= 0)
+          {
+            Entry e = (Entry) iter.next();
+            String name = (String) e.getKey();
+            Vector v = ((PropertyChangeSupport) e.getValue()).listeners;
+            int j = v.size();
+            while (--j >= 0)
+              list.add(new PropertyChangeListenerProxy
+                (name, (PropertyChangeListener) v.get(j)));
+          }
+      }
+    return (PropertyChangeListener[])
+      list.toArray(new PropertyChangeListener[list.size()]);
+  }
+
+  /**
+   * Adds a PropertyChangeListener listening on the specified property. Events
+   * will be sent to the listener only if the property name matches. The
+   * listener add is not unique; that is, <em>n</em> adds on a particular
+   * property for a particular listener will result in <em>n</em> events
+   * being sent to that listener when that property is changed. The effect is
+   * cumulative, too; if you are registered to listen to receive events on
+   * all property changes, and then you register on a particular property,
+   * you will receive change events for that property twice. Adding a null
+   * listener may cause a NullPointerException down the road. This method
+   * will unwrap a PropertyChangeListenerProxy, registering the underlying
+   * delegate to the named property list if the names match, and discarding
+   * it otherwise.
+   *
+   * @param propertyName the name of the property to listen on
+   * @param l the listener to add
+   * @throws NullPointerException if propertyName is null
+   */
+  public synchronized void addPropertyChangeListener(String propertyName,
+                                                     PropertyChangeListener l)
+  {
+    while (l instanceof PropertyChangeListenerProxy)
+      {
+        PropertyChangeListenerProxy p = (PropertyChangeListenerProxy) l;
+        if (propertyName == null ? p.propertyName != null
+            : ! propertyName.equals(p.propertyName))
+          return;
+        l = (PropertyChangeListener) p.getListener();
+      }
+    PropertyChangeSupport s = null;
+    if (children == null)
+      children = new Hashtable();
+    else
+      s = (PropertyChangeSupport) children.get(propertyName);
+    if (s == null)
+      {
+        s = new PropertyChangeSupport(source);
+        s.listeners = new Vector();
+        children.put(propertyName, s);
+      }
+    s.listeners.add(l);
+  }
+
+  /**
+   * Removes a PropertyChangeListener from listening to a specific property.
+   * If <code>add()</code> has been called multiple times for a particular
+   * listener on a property, <code>remove()</code> will have to be called the
+   * same number of times to deregister it. This method will unwrap a
+   * PropertyChangeListenerProxy, removing the underlying delegate from the
+   * named property list if the names match.
+   *
+   * @param propertyName the property to stop listening on
+   * @param l the listener to remove
+   * @throws NullPointerException if propertyName is null
+   */
+  public synchronized void
+    removePropertyChangeListener(String propertyName, PropertyChangeListener l)
+  {
+    if (children == null)
+      return;
+    PropertyChangeSupport s
+      = (PropertyChangeSupport) children.get(propertyName);
+    if (s == null)
+      return;
+    while (l instanceof PropertyChangeListenerProxy)
+      {
+        PropertyChangeListenerProxy p = (PropertyChangeListenerProxy) l;
+        if (propertyName == null ? p.propertyName != null
+            : ! propertyName.equals(p.propertyName))
+          return;
+        l = (PropertyChangeListener) p.getListener();
+      }
+    s.listeners.remove(l);
+    if (s.listeners.isEmpty())
+      {
+        children.remove(propertyName);
+        if (children.isEmpty())
+          children = null;
+      }
+  }
+
+  /**
+   * Returns an array of all property change listeners registered under the
+   * given property name. If there are no registered listeners, this returns
+   * an empty array.
+   *
+   * @return the array of registered listeners
+   * @throws NullPointerException if propertyName is null
+   * @since 1.4
+   */
+  public synchronized PropertyChangeListener[]
+    getPropertyChangeListeners(String propertyName)
+  {
+    if (children == null)
+      return new PropertyChangeListener[0];
+    PropertyChangeSupport s
+      = (PropertyChangeSupport) children.get(propertyName);
+    if (s == null)
+      return new PropertyChangeListener[0];
+    return (PropertyChangeListener[])
+      s.listeners.toArray(new PropertyChangeListener[s.listeners.size()]);
+  }
+
+  /**
+   * Fire a PropertyChangeEvent containing the old and new values of the
+   * property to all the global listeners, and to all the listeners for the
+   * specified property name. This does nothing if old and new are non-null
+   * and equal.
+   *
+   * @param propertyName the name of the property that changed
+   * @param oldVal the old value
+   * @param newVal the new value
+   */
+  public void firePropertyChange(String propertyName,
+                                 Object oldVal, Object newVal)
+  {
+    firePropertyChange(new PropertyChangeEvent(source, propertyName,
+                                               oldVal, newVal));
+  }
+
+  /**
+   * Fire a PropertyChangeEvent containing the old and new values of the
+   * property to all the global listeners, and to all the listeners for the
+   * specified property name. This does nothing if old and new are equal.
+   *
+   * @param propertyName the name of the property that changed
+   * @param oldVal the old value
+   * @param newVal the new value
+   */
+  public void firePropertyChange(String propertyName, int oldVal, int newVal)
+  {
+    if (oldVal != newVal)
+      firePropertyChange(new PropertyChangeEvent(source, propertyName,
+                                                 new Integer(oldVal),
+                                                 new Integer(newVal)));
+  }
+
+  /**
+   * Fire a PropertyChangeEvent containing the old and new values of the
+   * property to all the global listeners, and to all the listeners for the
+   * specified property name. This does nothing if old and new are equal.
+   *
+   * @param propertyName the name of the property that changed
+   * @param oldVal the old value
+   * @param newVal the new value
+   */
+  public void firePropertyChange(String propertyName,
+                                 boolean oldVal, boolean newVal)
+  {
+    if (oldVal != newVal)
+      firePropertyChange(new PropertyChangeEvent(source, propertyName,
+                                                 Boolean.valueOf(oldVal),
+                                                 Boolean.valueOf(newVal)));
+  }
+
+  /**
+   * Fire a PropertyChangeEvent to all the global listeners, and to all the
+   * listeners for the specified property name. This does nothing if old and
+   * new values of the event are equal.
+   *
+   * @param event the event to fire
+   * @throws NullPointerException if event is null
+   */
+  public void firePropertyChange(PropertyChangeEvent event)
+  {
+    if (event.oldValue != null && event.oldValue.equals(event.newValue))
+      return;
+    Vector v = listeners; // Be thread-safe.
+    if (v != null)
+      {
+        int i = v.size();
+        while (--i >= 0)
+          ((PropertyChangeListener) v.get(i)).propertyChange(event);
+      }
+    Hashtable h = children; // Be thread-safe.
+    if (h != null && event.propertyName != null)
+      {
+        PropertyChangeSupport s
+          = (PropertyChangeSupport) h.get(event.propertyName);
+        if (s != null)
+          {
+            v = s.listeners; // Be thread-safe.
+            int i = v == null ? 0 : v.size();
+            while (--i >= 0)
+              ((PropertyChangeListener) v.get(i)).propertyChange(event);
+          }
+      }
+  }
+
+  /**
+   * Tell whether the specified property is being listened on or not. This
+   * will only return <code>true</code> if there are listeners on all
+   * properties or if there is a listener specifically on this property.
+   *
+   * @param propertyName the property that may be listened on
+   * @return whether the property is being listened on
+   * @throws NullPointerException if propertyName is null
+   */
+  public synchronized boolean hasListeners(String propertyName)
+  {
+    return listeners != null || (children != null
+                                 && children.get(propertyName) != null);
+  }
+
+  /**
+   * Saves the state of the object to the stream.
+   *
+   * @param s the stream to write to
+   * @throws IOException if anything goes wrong
+   * @serialData this writes out a null-terminated list of serializable
+   *             global property change listeners (the listeners for a named
+   *             property are written out as the global listeners of the
+   *             children, when the children hashtable is saved)
+   */
+  private synchronized void writeObject(ObjectOutputStream s)
+    throws IOException
+  {
+    s.defaultWriteObject();
+    if (listeners != null)
+      {
+        int i = listeners.size();
+        while (--i >= 0)
+          if (listeners.get(i) instanceof Serializable)
+            s.writeObject(listeners.get(i));
+      }
+    s.writeObject(null);
+  }
+
+  /**
+   * Reads the object back from stream (deserialization).
+   *
+   * XXX Since serialization for 1.1 streams was not documented, this may
+   * not work if propertyChangeSupportSerializedDataVersion is 1.
+   *
+   * @param s the stream to read from
+   * @throws IOException if reading the stream fails
+   * @throws ClassNotFoundException if deserialization fails
+   * @serialData this reads in a null-terminated list of serializable
+   *             global property change listeners (the listeners for a named
+   *             property are written out as the global listeners of the
+   *             children, when the children hashtable is saved)
+   */
+  private void readObject(ObjectInputStream s)
+    throws IOException, ClassNotFoundException
+  {
+    s.defaultReadObject();
+    PropertyChangeListener l = (PropertyChangeListener) s.readObject();
+    while (l != null)
+      {
+        addPropertyChangeListener(l);
+        l = (PropertyChangeListener) s.readObject();
+      }
+    // Sun is not as careful with children as we are, and lets some proxys
+    // in that can never receive events. So, we clean up anything that got
+    // serialized, to make sure our invariants hold.
+    if (children != null)
+      {
+        int i = children.size();
+        Iterator iter = children.entrySet().iterator();
+        while (--i >= 0)
+          {
+            Entry e = (Entry) iter.next();
+            String name = (String) e.getKey();
+            PropertyChangeSupport pcs = (PropertyChangeSupport) e.getValue();
+            if (pcs.listeners == null)
+              pcs.listeners = new Vector();
+            if (pcs.children != null)
+              pcs.listeners.addAll
+                (Arrays.asList(pcs.getPropertyChangeListeners(name)));
+            if (pcs.listeners.size() == 0)
+              iter.remove();
+            else
+              pcs.children = null;
+          }
+        if (children.size() == 0)
+          children = null;
+      }
+  }
+} // class PropertyChangeSupport