/*
* $Id: AbstractBean.java 3100 2008-10-14 22:33:10Z rah003 $
*
* Copyright 2004 Sun Microsystems, Inc., 4150 Network Circle,
* Santa Clara, California 95054, U.S.A. All rights reserved.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
package org.hdesktop.beans;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import java.beans.PropertyChangeSupport;
import java.beans.PropertyVetoException;
import java.beans.VetoableChangeListener;
import java.beans.VetoableChangeSupport;
/**
* <p>
* A convenience class from which to extend all non-visual AbstractBeans. It
* manages the PropertyChange notification system, making it relatively trivial
* to add support for property change events in getters/setters.
* </p>
*
* <p>
* A non-visual java bean is a Java class that conforms to the AbstractBean
* patterns to allow visual manipulation of the bean's properties and event
* handlers at design-time.
* </p>
*
* <p>
* Here is a simple example bean that contains one property, foo, and the proper
* pattern for implementing property change notification:
*
* <pre><code>
* public class ABean extends AbstractBean {
* private String foo;
*
* public void setFoo(String newFoo) {
* String old = getFoo();
* this.foo = newFoo;
* firePropertyChange("foo", old, getFoo());
* }
*
* public String getFoo() {
* return foo;
* }
* }
* </code></pre>
*
* </p>
*
* <p>
* You will notice that "getFoo()" is used in the setFoo method rather than
* accessing "foo" directly for the gets. This is done intentionally so that if
* a subclass overrides getFoo() to return, for instance, a constant value the
* property change notification system will continue to work properly.
* </p>
*
* <p>
* The firePropertyChange method takes into account the old value and the new
* value. Only if the two differ will it fire a property change event. So you
* can be assured from the above code fragment that a property change event will
* only occur if old is indeed different from getFoo()
* </p>
*
* <p>
* <code>AbstractBean</code> also supports vetoable
* {@link PropertyChangeEvent} events. These events are similar to
* <code>PropertyChange</code> events, except a special exception can be used
* to veto changing the property. For example, perhaps the property is changing
* from "fred" to "red", but a listener deems that "red" is unexceptable. In
* this case, the listener can fire a veto exception and the property must
* remain "fred". For example:
*
* <pre><code>
* public class ABean extends AbstractBean {
* private String foo;
*
* public void setFoo(String newFoo) throws PropertyVetoException {
* String old = getFoo();
* this.foo = newFoo;
* fireVetoableChange("foo", old, getFoo());
* }
* public String getFoo() {
* return foo;
* }
* }
*
* public class Tester {
* public static void main(String... args) {
* try {
* ABean a = new ABean();
* a.setFoo("fred");
* a.addVetoableChangeListener(new VetoableChangeListener() {
* public void vetoableChange(PropertyChangeEvent evt) throws PropertyVetoException {
* if ("red".equals(evt.getNewValue()) {
* throw new PropertyVetoException("Cannot be red!", evt);
* }
* }
* }
* a.setFoo("red");
* } catch (Exception e) {
* e.printStackTrace(); // this will be executed
* }
* }
* }
* </code></pre>
*
* </p>
* <p>
* {@code AbstractBean} is not {@link java.io.Serializable}. Special care must
* be taken when creating {@code Serializable} subclasses, as the
* {@code Serializable} listeners will not be saved. Subclasses will need to
* manually save the serializable listeners. The {@link AbstractSerializableBean}
* is {@code Serializable} and already handles the listeners correctly. If
* possible, it is recommended that {@code Serializable} beans should extend
* {@code AbstractSerializableBean}. If it is not possible, the
* {@code AbstractSerializableBean} bean implementation provides details on
* how to correctly serialize an {@code AbstractBean} subclass.
* </p>
*
* @see AbstractSerializableBean
* @status REVIEWED
* @author rbair
*/
public abstract class AbstractBean {
/**
* Helper class that manages all the property change notification machinery.
* PropertyChangeSupport cannot be extended directly because it requires
* a bean in the constructor, and the "this" argument is not valid until
* after super construction. Hence, delegation instead of extension
*/
private transient PropertyChangeSupport pcs;
/**
* Helper class that manages all the veto property change notification machinery.
*/
private transient VetoableChangeSupport vcs;
/** Creates a new instance of AbstractBean */
protected AbstractBean() {
pcs = new PropertyChangeSupport(this);
vcs = new VetoableChangeSupport(this);
}
/**
* Creates a new instance of AbstractBean, using the supplied PropertyChangeSupport and
* VetoableChangeSupport delegates. Neither of these may be null.
*/
protected AbstractBean(PropertyChangeSupport pcs, VetoableChangeSupport vcs) {
if (pcs == null) {
throw new NullPointerException("PropertyChangeSupport must not be null");
}
if (vcs == null) {
throw new NullPointerException("VetoableChangeSupport must not be null");
}
this.pcs = pcs;
this.vcs = vcs;
}
/**
* Add a PropertyChangeListener to the listener list.
* The listener is registered for all properties.
* The same listener object may be added more than once, and will be called
* as many times as it is added.
* If <code>listener</code> is null, no exception is thrown and no action
* is taken.
*
* @param listener The PropertyChangeListener to be added
*/
public final void addPropertyChangeListener(PropertyChangeListener listener) {
pcs.addPropertyChangeListener(listener);
}
/**
* Remove a PropertyChangeListener from the listener list.
* This removes a PropertyChangeListener that was registered
* for all properties.
* If <code>listener</code> was added more than once to the same event
* source, it will be notified one less time after being removed.
* If <code>listener</code> is null, or was never added, no exception is
* thrown and no action is taken.
*
* @param listener The PropertyChangeListener to be removed
*/
public final void removePropertyChangeListener(PropertyChangeListener listener) {
pcs.removePropertyChangeListener(listener);
}
/**
* Returns an array of all the listeners that were added to the
* PropertyChangeSupport object with addPropertyChangeListener().
* <p>
* If some listeners have been added with a named property, then
* the returned array will be a mixture of PropertyChangeListeners
* and <code>PropertyChangeListenerProxy</code>s. If the calling
* method is interested in distinguishing the listeners then it must
* test each element to see if it's a
* <code>PropertyChangeListenerProxy</code>, perform the cast, and examine
* the parameter.
*
* <pre>
* PropertyChangeListener[] listeners = bean.getPropertyChangeListeners();
* for (int i = 0; i < listeners.length; i++) {
* if (listeners[i] instanceof PropertyChangeListenerProxy) {
* PropertyChangeListenerProxy proxy =
* (PropertyChangeListenerProxy)listeners[i];
* if (proxy.getPropertyName().equals("foo")) {
* // proxy is a PropertyChangeListener which was associated
* // with the property named "foo"
* }
* }
* }
*</pre>
*
* @see java.beans.PropertyChangeListenerProxy
* @return all of the <code>PropertyChangeListeners</code> added or an
* empty array if no listeners have been added
*/
public final PropertyChangeListener[] getPropertyChangeListeners() {
return pcs.getPropertyChangeListeners();
}
/**
* Add a PropertyChangeListener for a specific property. The listener
* will be invoked only when a call on firePropertyChange names that
* specific property.
* The same listener object may be added more than once. For each
* property, the listener will be invoked the number of times it was added
* for that property.
* If <code>propertyName</code> or <code>listener</code> is null, no
* exception is thrown and no action is taken.
*
* @param propertyName The name of the property to listen on.
* @param listener The PropertyChangeListener to be added
*/
public final void addPropertyChangeListener(String propertyName, PropertyChangeListener listener) {
pcs.addPropertyChangeListener(propertyName, listener);
}
/**
* Remove a PropertyChangeListener for a specific property.
* If <code>listener</code> was added more than once to the same event
* source for the specified property, it will be notified one less time
* after being removed.
* If <code>propertyName</code> is null, no exception is thrown and no
* action is taken.
* If <code>listener</code> is null, or was never added for the specified
* property, no exception is thrown and no action is taken.
*
* @param propertyName The name of the property that was listened on.
* @param listener The PropertyChangeListener to be removed
*/
public final void removePropertyChangeListener(String propertyName, PropertyChangeListener listener) {
pcs.removePropertyChangeListener(propertyName, listener);
}
/**
* Returns an array of all the listeners which have been associated
* with the named property.
*
* @param propertyName The name of the property being listened to
* @return all of the <code>PropertyChangeListeners</code> associated with
* the named property. If no such listeners have been added,
* or if <code>propertyName</code> is null, an empty array is
* returned.
*/
public final PropertyChangeListener[] getPropertyChangeListeners(String propertyName) {
return pcs.getPropertyChangeListeners(propertyName);
}
/**
* Report a bound property update to any registered listeners.
* No event is fired if old and new are equal and non-null.
*
* <p>
* This is merely a convenience wrapper around the more general
* firePropertyChange method that takes {@code
* PropertyChangeEvent} value.
*
* @param propertyName The programmatic name of the property
* that was changed.
* @param oldValue The old value of the property.
* @param newValue The new value of the property.
*/
protected final void firePropertyChange(String propertyName, Object oldValue, Object newValue) {
pcs.firePropertyChange(propertyName, oldValue, newValue);
}
/**
* Fire an existing PropertyChangeEvent to any registered listeners.
* No event is fired if the given event's old and new values are
* equal and non-null.
* @param evt The PropertyChangeEvent object.
*/
protected final void firePropertyChange(PropertyChangeEvent evt) {
pcs.firePropertyChange(evt);
}
/**
* Report a bound indexed property update to any registered
* listeners.
* <p>
* No event is fired if old and new values are equal
* and non-null.
*
* <p>
* This is merely a convenience wrapper around the more general
* firePropertyChange method that takes {@code PropertyChangeEvent} value.
*
* @param propertyName The programmatic name of the property that
* was changed.
* @param index index of the property element that was changed.
* @param oldValue The old value of the property.
* @param newValue The new value of the property.
*/
protected final void fireIndexedPropertyChange(String propertyName, int index,
Object oldValue, Object newValue) {
pcs.fireIndexedPropertyChange(propertyName, index, oldValue, newValue);
}
/**
* Check if there are any listeners for a specific property, including
* those registered on all properties. If <code>propertyName</code>
* is null, only check for listeners registered on all properties.
*
* @param propertyName the property name.
* @return true if there are one or more listeners for the given property
*/
protected final boolean hasPropertyChangeListeners(String propertyName) {
return pcs.hasListeners(propertyName);
}
/**
* Check if there are any listeners for a specific property, including
* those registered on all properties. If <code>propertyName</code>
* is null, only check for listeners registered on all properties.
*
* @param propertyName the property name.
* @return true if there are one or more listeners for the given property
*/
protected final boolean hasVetoableChangeListeners(String propertyName) {
return vcs.hasListeners(propertyName);
}
/**
* Add a VetoableListener to the listener list.
* The listener is registered for all properties.
* The same listener object may be added more than once, and will be called
* as many times as it is added.
* If <code>listener</code> is null, no exception is thrown and no action
* is taken.
*
* @param listener The VetoableChangeListener to be added
*/
public final void addVetoableChangeListener(VetoableChangeListener listener) {
vcs.addVetoableChangeListener(listener);
}
/**
* Remove a VetoableChangeListener from the listener list.
* This removes a VetoableChangeListener that was registered
* for all properties.
* If <code>listener</code> was added more than once to the same event
* source, it will be notified one less time after being removed.
* If <code>listener</code> is null, or was never added, no exception is
* thrown and no action is taken.
*
* @param listener The VetoableChangeListener to be removed
*/
public final void removeVetoableChangeListener(VetoableChangeListener listener) {
vcs.removeVetoableChangeListener(listener);
}
/**
* Returns the list of VetoableChangeListeners. If named vetoable change listeners
* were added, then VetoableChangeListenerProxy wrappers will returned
* <p>
* @return List of VetoableChangeListeners and VetoableChangeListenerProxys
* if named property change listeners were added.
*/
public final VetoableChangeListener[] getVetoableChangeListeners(){
return vcs.getVetoableChangeListeners();
}
/**
* Add a VetoableChangeListener for a specific property. The listener
* will be invoked only when a call on fireVetoableChange names that
* specific property.
* The same listener object may be added more than once. For each
* property, the listener will be invoked the number of times it was added
* for that property.
* If <code>propertyName</code> or <code>listener</code> is null, no
* exception is thrown and no action is taken.
*
* @param propertyName The name of the property to listen on.
* @param listener The VetoableChangeListener to be added
*/
public final void addVetoableChangeListener(String propertyName,
VetoableChangeListener listener) {
vcs.addVetoableChangeListener(propertyName, listener);
}
/**
* Remove a VetoableChangeListener for a specific property.
* If <code>listener</code> was added more than once to the same event
* source for the specified property, it will be notified one less time
* after being removed.
* If <code>propertyName</code> is null, no exception is thrown and no
* action is taken.
* If <code>listener</code> is null, or was never added for the specified
* property, no exception is thrown and no action is taken.
*
* @param propertyName The name of the property that was listened on.
* @param listener The VetoableChangeListener to be removed
*/
public final void removeVetoableChangeListener(String propertyName,
VetoableChangeListener listener) {
vcs.removeVetoableChangeListener(propertyName, listener);
}
/**
* Returns an array of all the listeners which have been associated
* with the named property.
*
* @param propertyName The name of the property being listened to
* @return all the <code>VetoableChangeListeners</code> associated with
* the named property. If no such listeners have been added,
* or if <code>propertyName</code> is null, an empty array is
* returned.
*/
public final VetoableChangeListener[] getVetoableChangeListeners(String propertyName) {
return vcs.getVetoableChangeListeners(propertyName);
}
/**
* Report a vetoable property update to any registered listeners. If
* anyone vetos the change, then fire a new event reverting everyone to
* the old value and then rethrow the PropertyVetoException.
* <p>
* No event is fired if old and new are equal and non-null.
*
* @param propertyName The programmatic name of the property
* that is about to change..
* @param oldValue The old value of the property.
* @param newValue The new value of the property.
* @exception PropertyVetoException if the recipient wishes the property
* change to be rolled back.
*/
protected final void fireVetoableChange(String propertyName,
Object oldValue, Object newValue)
throws PropertyVetoException {
vcs.fireVetoableChange(propertyName, oldValue, newValue);
}
/**
* Fire a vetoable property update to any registered listeners. If
* anyone vetos the change, then fire a new event reverting everyone to
* the old value and then rethrow the PropertyVetoException.
* <p>
* No event is fired if old and new are equal and non-null.
*
* @param evt The PropertyChangeEvent to be fired.
* @exception PropertyVetoException if the recipient wishes the property
* change to be rolled back.
*/
protected final void fireVetoableChange(PropertyChangeEvent evt)
throws PropertyVetoException {
vcs.fireVetoableChange(evt);
}
/**
* {@inheritDoc}
*/
@Override
public Object clone() throws CloneNotSupportedException {
AbstractBean result = (AbstractBean) super.clone();
result.pcs = new PropertyChangeSupport(result);
result.vcs = new VetoableChangeSupport(result);
return result;
}
}