/*
* java.beans.VetoableChangeSupport: part of the Java Class Libraries project.
* Copyright (C) 1998 Free Software Foundation
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library 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
* Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public
* License along with this library; if not, write to the
* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
* Boston, MA 02111-1307, USA.
*/
package java.beans;
import java.util.Hashtable;
import java.util.Vector;
/**
** VetoableChangeSupport makes it easy to fire vetoable
** change events and handle listeners as well as reversion
** of old values when things go wrong.
**
** @author John Keiser
** @since JDK1.1
** @version 1.2.0, 15 Mar 1998
**/
public class VetoableChangeSupport implements java.io.Serializable {
Hashtable propertyListeners = new Hashtable();
Vector listeners = new Vector();
Object bean;
/** Create VetoableChangeSupport to work with a specific
** source bean.
** @param bean the source bean to use.
**/
public VetoableChangeSupport(Object bean) {
this.bean = bean;
}
/** Adds a VetoableChangeListener to the list of listeners.
** All property change events will be sent to this listener.
** <P>
**
** 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.
** <P>
**
** Adding a null listener will cause undefined behavior.
**
** @param l the listener to add.
**/
public void addVetoableChangeListener(VetoableChangeListener l) {
listeners.addElement(l);
}
/** Adds a VetoableChangeListener listening on the specified property.
** Events will be sent to the listener for that particular property.
** <P>
**
** 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.
** <P>
**
** 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.
** <P>
**
** Adding a null listener will cause undefined behavior.
**
** @param propertyName the name of the property to listen on.
** @param l the listener to add.
**/
public void addVetoableChangeListener(String propertyName, VetoableChangeListener l) {
synchronized(propertyListeners) {
Vector v = (Vector)propertyListeners.get(propertyName);
try {
v.addElement(l);
} catch(NullPointerException e) {
/* If v is not found, create a new vector. */
v = new Vector();
v.addElement(l);
propertyListeners.put(propertyName, v);
}
}
}
/** Removes a VetoableChangeListener from the list of 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.
** <P>
**
** 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.
**
** @param l the listener to remove.
**/
public void removeVetoableChangeListener(VetoableChangeListener l) {
listeners.removeElement(l);
}
/** Removes a VetoableChangeListener from listening to a specific property.
** <P>
**
** 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.
**
** @param propertyName the property to stop listening on.
** @param l the listener to remove.
**/
public void removeVetoableChangeListener(String propertyName, VetoableChangeListener l) {
synchronized(propertyListeners) {
Vector v = (Vector)propertyListeners.get(propertyName);
try {
v.removeElement(l);
if(v.size() == 0) {
propertyListeners.remove(propertyName);
}
} catch(NullPointerException e) {
/* if v is not found, do nothing. */
}
}
}
/** Fire a VetoableChangeEvent to all the listeners.
** If any listener objects, a reversion event will be sent to
** those listeners who received the initial event.
**
** @param proposedChange the event to send.
** @exception PropertyVetoException if the change is vetoed.
**/
public void fireVetoableChange(PropertyChangeEvent proposedChange) throws PropertyVetoException {
int currentListener=0;
try {
for(;currentListener<listeners.size();currentListener++) {
((VetoableChangeListener)listeners.elementAt(currentListener)).vetoableChange(proposedChange);
}
} catch(PropertyVetoException e) {
PropertyChangeEvent reversion = new PropertyChangeEvent(proposedChange.getSource(),proposedChange.getPropertyName(),proposedChange.getNewValue(),proposedChange.getOldValue());
for(int sendAgain=0;sendAgain<currentListener;sendAgain++) {
try {
((VetoableChangeListener)listeners.elementAt(sendAgain)).vetoableChange(reversion);
} catch(PropertyVetoException e2) {
}
}
throw e;
}
Vector moreListeners = (Vector)propertyListeners.get(proposedChange.getPropertyName());
if(moreListeners != null) {
try {
for(currentListener = 0; currentListener < moreListeners.size(); currentListener++) {
((VetoableChangeListener)moreListeners.elementAt(currentListener)).vetoableChange(proposedChange);
}
} catch(PropertyVetoException e) {
PropertyChangeEvent reversion = new PropertyChangeEvent(proposedChange.getSource(),proposedChange.getPropertyName(),proposedChange.getNewValue(),proposedChange.getOldValue());
for(int sendAgain=0;sendAgain<listeners.size();sendAgain++) {
try {
((VetoableChangeListener)listeners.elementAt(currentListener)).vetoableChange(proposedChange);
} catch(PropertyVetoException e2) {
}
}
for(int sendAgain=0;sendAgain<currentListener;sendAgain++) {
try {
((VetoableChangeListener)moreListeners.elementAt(sendAgain)).vetoableChange(reversion);
} catch(PropertyVetoException e2) {
}
}
throw e;
}
}
}
/** Fire a VetoableChangeEvent containing the old and new values of the property to all the listeners.
** If any listener objects, a reversion event will be sent to
** those listeners who received the initial event.
**
** @param propertyName the name of the property that
** changed.
** @param oldVal the old value.
** @param newVal the new value.
** @exception PropertyVetoException if the change is vetoed.
**/
public void fireVetoableChange(String propertyName, Object oldVal, Object newVal) throws PropertyVetoException {
fireVetoableChange(new PropertyChangeEvent(bean,propertyName,oldVal,newVal));
}
/** Fire a VetoableChangeEvent containing the old and new values of the property to all the listeners.
** If any listener objects, a reversion event will be sent to
** those listeners who received the initial event.
**
** @param propertyName the name of the property that
** changed.
** @param oldVal the old value.
** @param newVal the new value.
** @exception PropertyVetoException if the change is vetoed.
**/
public void fireVetoableChange(String propertyName, boolean oldVal, boolean newVal) throws PropertyVetoException {
fireVetoableChange(new PropertyChangeEvent(bean,propertyName,new Boolean(oldVal),new Boolean(newVal)));
}
/** Fire a VetoableChangeEvent containing the old and new values of the property to all the listeners.
** If any listener objects, a reversion event will be sent to
** those listeners who received the initial event.
**
** @param propertyName the name of the property that
** changed.
** @param oldVal the old value.
** @param newVal the new value.
** @exception PropertyVetoException if the change is vetoed.
**/
public void fireVetoableChange(String propertyName, int oldVal, int newVal) throws PropertyVetoException {
fireVetoableChange(new PropertyChangeEvent(bean,propertyName,new Integer(oldVal),new Integer(newVal)));
}
/** 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
**/
public boolean hasListeners(String propertyName) {
return listeners.size() > 0 || propertyListeners.get(propertyName) != null;
}
}