path: root/libjava/classpath/javax/swing/event/SwingPropertyChangeSupport.java

/* SwingPropertyChangeSupport.java --
   Copyright (C) 2002, 2004, 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
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As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
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package javax.swing.event;

import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import java.beans.PropertyChangeListenerProxy;
import java.beans.PropertyChangeSupport;
import java.util.ArrayList;
import java.util.EventListener;
import java.util.Hashtable;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;

/**
 * Provides a mechanism for registering {@link PropertyChangeListener}s and
 * forwarding {@link PropertyChangeEvent}s to those listeners.
 * 
 * @author Andrew Selkirk
 */
public final class SwingPropertyChangeSupport
    extends PropertyChangeSupport 
{

  private static final long serialVersionUID = 7162625831330845068L;

  /**
   * Storage for the listeners that are not linked to a specific property.
   */
  private transient EventListenerList listeners;

  /**
   * Storage for the listeners that are linked (by name) to a specific property.
   * The hash table maps <code>String</code> objects (the property names) to 
   * {@link EventListenerList} instances (which record the listener(s) for the 
   * given property).
   */
  private Hashtable propertyListeners;

  /**
   * The object that is used as the default source for the 
   * {@link PropertyChangeEvent}s generated by this class.
   */
  private Object source;

  /**
   * Creates a new instance.
   * 
   * @param source  the source (<code>null</code> not permitted).
   * 
   * @throws NullPointerException if <code>source</code> is <code>null</code>.
   */
  public SwingPropertyChangeSupport(Object source) 
  {
    super(source);
    this.source = source;
    this.listeners = new EventListenerList();
    this.propertyListeners = new Hashtable();
  }

  /**
   * Registers <code>listener</code> to receive notification of any future
   * {@link PropertyChangeEvent}s generated by this instance.
   * 
   * @param listener  the listener (<code>null</code> is ignored).
   * 
   * @see #removePropertyChangeListener(PropertyChangeListener)
   */
  public synchronized void addPropertyChangeListener(PropertyChangeListener 
          listener) 
  {
    listeners.add(PropertyChangeListener.class, listener);
  } 

  /**
   * Registers <code>listener</code> to receive notification of any future
   * {@link PropertyChangeEvent}s generated by this instance for the named
   * property.
   * 
   * @param propertyName  the property name.
   * @param listener  the listener.
   * 
   * @see #removePropertyChangeListener(String, PropertyChangeListener)
   */
  public synchronized void addPropertyChangeListener(String propertyName, 
          PropertyChangeListener listener) 
  {
    EventListenerList list;
    list = (EventListenerList) propertyListeners.get(propertyName);
    if (list == null) 
      {
        list = new EventListenerList();
        propertyListeners.put(propertyName, list);
      }
    list.add(PropertyChangeListener.class, listener);
  }

  /**
   * Removes <code>listener</code> from the list of registered listeners, so 
   * that it will no longer receive notification of property change events.
   * 
   * @param listener  the listener to remove.
   */
  public synchronized void removePropertyChangeListener(PropertyChangeListener 
          listener) 
  {
    listeners.remove(PropertyChangeListener.class, listener);
  }

  /**
   * Removes <code>listener</code> from the list of registered listeners for
   * the named property, so that it will no longer receive notification of 
   * property change events.
   * 
   * @param propertyName  the property name.
   * @param listener  the listener to remove.
   */
  public synchronized void removePropertyChangeListener(String propertyName, 
          PropertyChangeListener listener) 
  {
    EventListenerList list;
    list = (EventListenerList) propertyListeners.get(propertyName);
    if (list == null)
      return;
    list.remove(PropertyChangeListener.class, listener);
    if (list.getListenerCount() == 0) 
      {
        propertyListeners.remove(propertyName);
      } 
  } 

  /**
   * Returns an array of the {@link PropertyChangeListener}s registered with
   * this <code>SwingPropertyChangeSupport</code> instance.
   * 
   * @return The array of listeners.
   * 
   * @since 1.4
   */
  public synchronized PropertyChangeListener[] getPropertyChangeListeners() 
  {
    // fetch the named listeners first so we know how many there are
    List namedListeners = new ArrayList();
    Set namedListenerEntries = propertyListeners.entrySet();
    Iterator iterator = namedListenerEntries.iterator();
    while (iterator.hasNext())
      {
        Map.Entry e = (Map.Entry) iterator.next();
        String propertyName = (String) e.getKey();
        EventListenerList ell = (EventListenerList) e.getValue();
        if (ell != null)
          {
            Object[] list = ell.getListenerList();
            for (int i = 0; i < list.length; i += 2)
              {
                namedListeners.add(new PropertyChangeListenerProxy(propertyName, 
                    (PropertyChangeListener) list[i + 1]));
              }
          }
      }
    
    // create an array that can hold everything
    int size = listeners.getListenerCount() + namedListeners.size();
    PropertyChangeListener[] result = new PropertyChangeListener[size];
    
    // copy in the general listeners
    Object[] list = listeners.getListenerList();
    int index = 0;
    for (int i = 0; i < list.length; i += 2)
      result[index++] = (PropertyChangeListener) list[i + 1];
    
    // ...and the named listeners
    Iterator iterator2 = namedListeners.iterator();
    while (iterator2.hasNext()) 
      result[index++] = (PropertyChangeListenerProxy) iterator2.next();
    
    return result;
  }
  
  /**
   * Returns an array of all listeners that are registered to receive 
   * notification of changes to the named property.  This includes the general
   * listeners as well as those registered specifically for the named 
   * property.
   * 
   * @param propertyName  the property name.
   * 
   * @return An array of all listeners for the named property.
   */
  public synchronized PropertyChangeListener[] getPropertyChangeListeners(
          String propertyName)
  {
    EventListenerList list 
      = (EventListenerList) propertyListeners.get(propertyName);
    if (list == null)
      return getPropertyChangeListeners();
    int size = listeners.getListenerCount() + list.getListenerCount();
    PropertyChangeListener[] result = new PropertyChangeListener[size];
    
    // copy in the general listeners
    int index = 0;
    for (int i = 0; i < listeners.listenerList.length; i += 2)
      {
        result[index++] 
            = (PropertyChangeListener) listeners.listenerList[i + 1];
      }
    
    // copy in the specific listeners
    Object[] specificListeners = list.getListenerList();
    for (int i = 0; i < specificListeners.length; i += 2)
      {
        result[index++] = (PropertyChangeListener) specificListeners[i + 1];
      }
    return result;
  }

  /**
   * Creates a new {@link PropertyChangeEvent} using the given arguments (and
   * the default <code>source</code> for this 
   * <code>SwingPropertyChangeSupport</code> instance) and forwards it to all 
   * registered listeners via the 
   * {@link PropertyChangeListener#propertyChange(PropertyChangeEvent)} method.
   * <p>
   * Note that if <code>oldValue</code> and <code>newValue</code> are non-null
   * and equal, no listeners will be notified.
   * 
   * @param propertyName  the property name.
   * @param oldValue  the old value
   * @param newValue  the new value.
   */
  public void firePropertyChange(String propertyName, Object oldValue, 
          Object newValue) 
  {
    PropertyChangeEvent event;
    event = new PropertyChangeEvent(source, propertyName, oldValue, newValue);
    firePropertyChange(event);
  } 

  /**
   * Forwards <code>event</code> to registered listeners.
   * <p>
   * Note that if the event's <code>getOldValue()</code> and 
   * <code>getNewValue()</code> methods return non-null and equal values, no 
   * listeners will be notified.
   * 
   * @param event  the event.
   */
  public void firePropertyChange(PropertyChangeEvent event) 
  {
    EventListenerList list;
    EventListener[] listenerList;
    int index;
    PropertyChangeListener listener;

    // Check Values if they are equal
    if (event.getOldValue() == null && event.getNewValue() == null ||
        (event.getOldValue() != null && event.getNewValue() != null &&
              event.getOldValue().equals(event.getNewValue()))) 
      return;

    // Process Main Listener List
    listenerList = listeners.getListeners(PropertyChangeListener.class);
    for (index = 0; index < listenerList.length; index++) 
      {
        listener = (PropertyChangeListener) listenerList[index];
        listener.propertyChange(event);
      } 

    // Process Property Listener List
    list = (EventListenerList) propertyListeners.get(event.getPropertyName());
    if (list != null) 
      {
        listenerList = list.getListeners(PropertyChangeListener.class);
        for (index = 0; index < listenerList.length; index++) 
          {
            listener = (PropertyChangeListener) listenerList[index];
            listener.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) 
  {
    if (listeners.getListenerCount() > 0)
      return true;
    else
      return (propertyListeners.get(propertyName) != null);
  } 

}