531 lines
20 KiB
Java
531 lines
20 KiB
Java
/* VetoableChangeSupport.java -- support to manage vetoable change listeners
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Copyright (C) 1998, 1999, 2000, 2002, 2005 Free Software Foundation, Inc.
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This file is part of GNU Classpath.
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GNU Classpath is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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GNU Classpath is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GNU Classpath; see the file COPYING. If not, write to the
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Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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02110-1301 USA.
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Linking this library statically or dynamically with other modules is
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making a combined work based on this library. Thus, the terms and
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conditions of the GNU General Public License cover the whole
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combination.
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As a special exception, the copyright holders of this library give you
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permission to link this library with independent modules to produce an
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executable, regardless of the license terms of these independent
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modules, and to copy and distribute the resulting executable under
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terms of your choice, provided that you also meet, for each linked
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independent module, the terms and conditions of the license of that
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module. An independent module is a module which is not derived from
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or based on this library. If you modify this library, you may extend
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this exception to your version of the library, but you are not
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obligated to do so. If you do not wish to do so, delete this
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exception statement from your version. */
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package java.beans;
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import java.io.IOException;
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import java.io.ObjectInputStream;
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import java.io.ObjectOutputStream;
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import java.io.Serializable;
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import java.util.ArrayList;
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import java.util.Arrays;
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import java.util.Hashtable;
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import java.util.Iterator;
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import java.util.Map.Entry;
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import java.util.Vector;
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/**
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* VetoableChangeSupport makes it easy to fire vetoable change events and
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* handle listeners. It allows chaining of listeners, as well as filtering
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* by property name. In addition, it will serialize only those listeners
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* which are serializable, ignoring the others without problem. This class
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* is thread-safe.
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*
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* @author John Keiser
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* @author Eric Blake (ebb9@email.byu.edu)
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* @since 1.1
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* @status updated to 1.4
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*/
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public class VetoableChangeSupport implements Serializable
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{
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/**
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* Compatible with JDK 1.1+.
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*/
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private static final long serialVersionUID = -5090210921595982017L;
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/**
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* Maps property names (String) to named listeners (VetoableChangeSupport).
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* If this is a child instance, this field will be null.
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*
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* @serial the map of property names to named listener managers
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* @since 1.2
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*/
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private Hashtable children;
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/**
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* The non-null source object for any generated events.
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*
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* @serial the event source
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*/
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private final Object source;
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/**
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* A field to compare serialization versions - this class uses version 2.
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*
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* @serial the serialization format
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*/
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private static final int vetoableChangeSupportSerializedDataVersion = 2;
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/**
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* The list of all registered vetoable listeners. If this instance was
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* created by user code, this only holds the global listeners (ie. not tied
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* to a name), and may be null. If it was created by this class, as a
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* helper for named properties, then this vector will be non-null, and this
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* instance appears as a value in the <code>children</code> hashtable of
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* another instance, so that the listeners are tied to the key of that
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* hashtable entry.
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*/
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private transient Vector listeners;
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/**
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* Create a VetoableChangeSupport to work with a specific source bean.
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*
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* @param source the source bean to use
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* @throws NullPointerException if source is null
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*/
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public VetoableChangeSupport(Object source)
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{
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this.source = source;
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if (source == null)
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throw new NullPointerException();
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}
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/**
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* Adds a VetoableChangeListener to the list of global listeners. All
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* vetoable change events will be sent to this listener. The listener add
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* is not unique: that is, <em>n</em> adds with the same listener will
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* result in <em>n</em> events being sent to that listener for every
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* vetoable change. Adding a null listener may cause a NullPointerException
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* down the road. This method will unwrap a VetoableChangeListenerProxy,
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* registering the underlying delegate to the named property list.
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*
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* @param l the listener to add
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*/
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public synchronized void addVetoableChangeListener(VetoableChangeListener l)
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{
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if (l instanceof VetoableChangeListenerProxy)
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{
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VetoableChangeListenerProxy p = (VetoableChangeListenerProxy) l;
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addVetoableChangeListener(p.propertyName,
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(VetoableChangeListener) p.getListener());
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}
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else
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{
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if (listeners == null)
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listeners = new Vector();
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listeners.add(l);
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}
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}
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/**
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* Removes a VetoableChangeListener from the list of global listeners. If
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* any specific properties are being listened on, they must be deregistered
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* by themselves; this will only remove the general listener to all
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* properties. If <code>add()</code> has been called multiple times for a
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* particular listener, <code>remove()</code> will have to be called the
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* same number of times to deregister it. This method will unwrap a
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* VetoableChangeListenerProxy, removing the underlying delegate from the
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* named property list.
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*
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* @param l the listener to remove
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*/
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public synchronized void
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removeVetoableChangeListener(VetoableChangeListener l)
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{
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if (l instanceof VetoableChangeListenerProxy)
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{
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VetoableChangeListenerProxy p = (VetoableChangeListenerProxy) l;
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removeVetoableChangeListener(p.propertyName,
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(VetoableChangeListener) p.getListener());
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}
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else if (listeners != null)
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{
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listeners.remove(l);
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if (listeners.isEmpty())
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listeners = null;
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}
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}
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/**
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* Returns an array of all registered vetoable change listeners. Those that
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* were registered under a name will be wrapped in a
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* <code>VetoableChangeListenerProxy</code>, so you must check whether the
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* listener is an instance of the proxy class in order to see what name the
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* real listener is registered under. If there are no registered listeners,
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* this returns an empty array.
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*
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* @return the array of registered listeners
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* @see VetoableChangeListenerProxy
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* @since 1.4
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*/
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public synchronized VetoableChangeListener[] getVetoableChangeListeners()
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{
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ArrayList list = new ArrayList();
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if (listeners != null)
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list.addAll(listeners);
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if (children != null)
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{
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int i = children.size();
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Iterator iter = children.entrySet().iterator();
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while (--i >= 0)
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{
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Entry e = (Entry) iter.next();
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String name = (String) e.getKey();
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Vector v = ((VetoableChangeSupport) e.getValue()).listeners;
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int j = v.size();
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while (--j >= 0)
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list.add(new VetoableChangeListenerProxy
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(name, (VetoableChangeListener) v.get(j)));
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}
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}
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return (VetoableChangeListener[])
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list.toArray(new VetoableChangeListener[list.size()]);
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}
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/**
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* Adds a VetoableChangeListener listening on the specified property. Events
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* will be sent to the listener only if the property name matches. The
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* listener add is not unique; that is, <em>n</em> adds on a particular
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* property for a particular listener will result in <em>n</em> events
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* being sent to that listener when that property is changed. The effect is
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* cumulative, too; if you are registered to listen to receive events on
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* all vetoable changes, and then you register on a particular property,
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* you will receive change events for that property twice. Adding a null
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* listener may cause a NullPointerException down the road. This method
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* will unwrap a VetoableChangeListenerProxy, registering the underlying
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* delegate to the named property list if the names match, and discarding
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* it otherwise.
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*
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* @param propertyName the name of the property to listen on
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* @param l the listener to add
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* @throws NullPointerException if propertyName is null
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*/
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public synchronized void addVetoableChangeListener(String propertyName,
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VetoableChangeListener l)
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{
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while (l instanceof VetoableChangeListenerProxy)
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{
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VetoableChangeListenerProxy p = (VetoableChangeListenerProxy) l;
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if (propertyName == null ? p.propertyName != null
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: ! propertyName.equals(p.propertyName))
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return;
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l = (VetoableChangeListener) p.getListener();
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}
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VetoableChangeSupport s = null;
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if (children == null)
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children = new Hashtable();
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else
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s = (VetoableChangeSupport) children.get(propertyName);
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if (s == null)
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{
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s = new VetoableChangeSupport(source);
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s.listeners = new Vector();
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children.put(propertyName, s);
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}
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s.listeners.add(l);
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}
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/**
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* Removes a VetoableChangeListener from listening to a specific property.
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* If <code>add()</code> has been called multiple times for a particular
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* listener on a property, <code>remove()</code> will have to be called the
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* same number of times to deregister it. This method will unwrap a
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* VetoableChangeListenerProxy, removing the underlying delegate from the
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* named property list if the names match.
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*
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* @param propertyName the property to stop listening on
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* @param l the listener to remove
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* @throws NullPointerException if propertyName is null
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*/
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public synchronized void
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removeVetoableChangeListener(String propertyName, VetoableChangeListener l)
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{
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if (children == null)
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return;
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VetoableChangeSupport s
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= (VetoableChangeSupport) children.get(propertyName);
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if (s == null)
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return;
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while (l instanceof VetoableChangeListenerProxy)
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{
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VetoableChangeListenerProxy p = (VetoableChangeListenerProxy) l;
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if (propertyName == null ? p.propertyName != null
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: ! propertyName.equals(p.propertyName))
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return;
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l = (VetoableChangeListener) p.getListener();
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}
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s.listeners.remove(l);
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if (s.listeners.isEmpty())
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{
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children.remove(propertyName);
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if (children.isEmpty())
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children = null;
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}
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}
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/**
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* Returns an array of all vetoable change listeners registered under the
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* given property name. If there are no registered listeners, this returns
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* an empty array.
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*
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* @return the array of registered listeners
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* @throws NullPointerException if propertyName is null
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* @since 1.4
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*/
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public synchronized VetoableChangeListener[]
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getVetoableChangeListeners(String propertyName)
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{
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if (children == null)
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return new VetoableChangeListener[0];
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VetoableChangeSupport s
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= (VetoableChangeSupport) children.get(propertyName);
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if (s == null)
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return new VetoableChangeListener[0];
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return (VetoableChangeListener[])
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s.listeners.toArray(new VetoableChangeListener[s.listeners.size()]);
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}
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/**
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* Fire a PropertyChangeEvent containing the old and new values of the
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* property to all the global listeners, and to all the listeners for the
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* specified property name. This does nothing if old and new are non-null
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* and equal. If the change is vetoed, a new event is fired to notify
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* listeners about the rollback before the exception is thrown.
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*
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* @param propertyName the name of the property that changed
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* @param oldVal the old value
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* @param newVal the new value
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* @throws PropertyVetoException if the change is vetoed by a listener
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*/
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public void fireVetoableChange(String propertyName,
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Object oldVal, Object newVal)
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throws PropertyVetoException
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{
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fireVetoableChange(new PropertyChangeEvent(source, propertyName,
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oldVal, newVal));
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}
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/**
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* Fire a PropertyChangeEvent containing the old and new values of the
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* property to all the global listeners, and to all the listeners for the
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* specified property name. This does nothing if old and new are equal.
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* If the change is vetoed, a new event is fired to notify listeners about
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* the rollback before the exception is thrown.
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*
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* @param propertyName the name of the property that changed
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* @param oldVal the old value
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* @param newVal the new value
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* @throws PropertyVetoException if the change is vetoed by a listener
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*/
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public void fireVetoableChange(String propertyName, int oldVal, int newVal)
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throws PropertyVetoException
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{
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if (oldVal != newVal)
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fireVetoableChange(new PropertyChangeEvent(source, propertyName,
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new Integer(oldVal),
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new Integer(newVal)));
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}
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/**
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* Fire a PropertyChangeEvent containing the old and new values of the
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* property to all the global listeners, and to all the listeners for the
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* specified property name. This does nothing if old and new are equal.
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* If the change is vetoed, a new event is fired to notify listeners about
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* the rollback before the exception is thrown.
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*
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* @param propertyName the name of the property that changed
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* @param oldVal the old value
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* @param newVal the new value
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* @throws PropertyVetoException if the change is vetoed by a listener
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*/
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public void fireVetoableChange(String propertyName,
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boolean oldVal, boolean newVal)
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throws PropertyVetoException
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{
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if (oldVal != newVal)
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fireVetoableChange(new PropertyChangeEvent(source, propertyName,
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Boolean.valueOf(oldVal),
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Boolean.valueOf(newVal)));
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}
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/**
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* Fire a PropertyChangeEvent to all the global listeners, and to all the
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* listeners for the specified property name. This does nothing if old and
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* new values of the event are equal. If the change is vetoed, a new event
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* is fired to notify listeners about the rollback before the exception is
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* thrown.
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*
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* @param event the event to fire
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* @throws NullPointerException if event is null
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* @throws PropertyVetoException if the change is vetoed by a listener
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*/
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public void fireVetoableChange(PropertyChangeEvent event)
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throws PropertyVetoException
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{
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if (event.oldValue != null && event.oldValue.equals(event.newValue))
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return;
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Vector v = listeners; // Be thread-safe.
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if (v != null)
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{
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int i = v.size();
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try
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{
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while (--i >= 0)
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((VetoableChangeListener) v.get(i)).vetoableChange(event);
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}
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catch (PropertyVetoException e)
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{
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event = event.rollback();
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int limit = i;
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i = v.size();
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while (--i >= limit)
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((VetoableChangeListener) v.get(i)).vetoableChange(event);
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throw e;
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}
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}
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Hashtable h = children; // Be thread-safe.
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if (h != null && event.propertyName != null)
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{
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VetoableChangeSupport s
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= (VetoableChangeSupport) h.get(event.propertyName);
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if (s != null)
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{
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Vector v1 = s.listeners; // Be thread-safe.
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int i = v1 == null ? 0 : v1.size();
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try
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{
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while (--i >= 0)
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((VetoableChangeListener) v1.get(i)).vetoableChange(event);
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}
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catch (PropertyVetoException e)
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{
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event = event.rollback();
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int limit = i;
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i = v.size();
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while (--i >= 0)
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((VetoableChangeListener) v.get(i)).vetoableChange(event);
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i = v1.size();
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while (--i >= limit)
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((VetoableChangeListener) v1.get(i)).vetoableChange(event);
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throw e;
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}
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}
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}
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}
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/**
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* Tell whether the specified property is being listened on or not. This
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* will only return <code>true</code> if there are listeners on all
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* properties or if there is a listener specifically on this property.
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*
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* @param propertyName the property that may be listened on
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* @return whether the property is being listened on
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* @throws NullPointerException if propertyName is null
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*/
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public synchronized boolean hasListeners(String propertyName)
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{
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return listeners != null || (children != null
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&& children.get(propertyName) != null);
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}
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/**
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* Saves the state of the object to the stream.
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*
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* @param s the stream to write to
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* @throws IOException if anything goes wrong
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* @serialData this writes out a null-terminated list of serializable
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* global vetoable change listeners (the listeners for a named
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* property are written out as the global listeners of the
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* children, when the children hashtable is saved)
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*/
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private synchronized void writeObject(ObjectOutputStream s)
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throws IOException
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{
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s.defaultWriteObject();
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if (listeners != null)
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{
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int i = listeners.size();
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while (--i >= 0)
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if (listeners.get(i) instanceof Serializable)
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s.writeObject(listeners.get(i));
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}
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s.writeObject(null);
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}
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/**
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* Reads the object back from stream (deserialization).
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*
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* XXX Since serialization for 1.1 streams was not documented, this may
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* not work if vetoableChangeSupportSerializedDataVersion is 1.
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*
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* @param s the stream to read from
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* @throws IOException if reading the stream fails
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* @throws ClassNotFoundException if deserialization fails
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* @serialData this reads in a null-terminated list of serializable
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* global vetoable change listeners (the listeners for a named
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* property are written out as the global listeners of the
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* children, when the children hashtable is saved)
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*/
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private void readObject(ObjectInputStream s)
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throws IOException, ClassNotFoundException
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{
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s.defaultReadObject();
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VetoableChangeListener l = (VetoableChangeListener) s.readObject();
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while (l != null)
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{
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addVetoableChangeListener(l);
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l = (VetoableChangeListener) s.readObject();
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}
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// Sun is not as careful with children as we are, and lets some proxys
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// in that can never receive events. So, we clean up anything that got
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// serialized, to make sure our invariants hold.
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if (children != null)
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{
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int i = children.size();
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Iterator iter = children.entrySet().iterator();
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while (--i >= 0)
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{
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Entry e = (Entry) iter.next();
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String name = (String) e.getKey();
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VetoableChangeSupport vcs = (VetoableChangeSupport) e.getValue();
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if (vcs.listeners == null)
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vcs.listeners = new Vector();
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if (vcs.children != null)
|
|
vcs.listeners.addAll
|
|
(Arrays.asList(vcs.getVetoableChangeListeners(name)));
|
|
if (vcs.listeners.size() == 0)
|
|
iter.remove();
|
|
else
|
|
vcs.children = null;
|
|
}
|
|
if (children.size() == 0)
|
|
children = null;
|
|
}
|
|
}
|
|
} // class VetoableChangeSupport
|