* 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. *
* ** 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. *
* ** Here is a simple example bean that contains one property, foo, and the proper * pattern for implementing property change notification: * *
* 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;
* }
* }
* * 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. *
* ** 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() *
* *
* AbstractBean also supports vetoable
* {@link PropertyChangeEvent} events. These events are similar to
* PropertyChange 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:
*
*
* 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 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. *
* * @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. * Iflistener 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 listener was added more than once to the same event
* source, it will be notified one less time after being removed.
* If listener 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().
*
* If some listeners have been added with a named property, then
* the returned array will be a mixture of PropertyChangeListeners
* and PropertyChangeListenerProxys. If the calling
* method is interested in distinguishing the listeners then it must
* test each element to see if it's a
* PropertyChangeListenerProxy, perform the cast, and examine
* the parameter.
*
*
* 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"
* }
* }
* }
*
*
* @see java.beans.PropertyChangeListenerProxy
* @return all of the PropertyChangeListeners 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 propertyName or listener 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 listener 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 propertyName is null, no exception is thrown and no
* action is taken.
* If listener 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 PropertyChangeListeners associated with
* the named property. If no such listeners have been added,
* or if propertyName 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.
*
* * 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. *
* No event is fired if old and new values are equal * and non-null. * *
* 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 propertyName
* 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 propertyName
* 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 listener 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 listener was added more than once to the same event
* source, it will be notified one less time after being removed.
* If listener 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
*
* @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 propertyName or listener 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 listener 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 propertyName is null, no exception is thrown and no
* action is taken.
* If listener 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 VetoableChangeListeners associated with
* the named property. If no such listeners have been added,
* or if propertyName 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.
*
* 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. *
* 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} */ public Object clone() throws CloneNotSupportedException { AbstractBean result = (AbstractBean) super.clone(); result.pcs = new PropertyChangeSupport(result); result.vcs = new VetoableChangeSupport(result); return result; } }