org.jdesktop.beans

Class AbstractBean

java.lang.Object

org.jdesktop.beans.AbstractBean

Direct Known Subclasses:

AbstractFilter, AbstractPainter, AbstractSerializableBean, CapsLockSupport, CompoundFocusListener, JXGraph.Plot, LoginService, UserNameStore

public abstract class AbstractBean
extends Object

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 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
      }
    }
  }
 

AbstractBean is not Serializable. Special care must be taken when creating Serializable subclasses, as the Serializable listeners will not be saved. Subclasses will need to manually save the serializable listeners. The AbstractSerializableBean is Serializable and already handles the listeners correctly. If possible, it is recommended that Serializable beans should extend AbstractSerializableBean. If it is not possible, the AbstractSerializableBean bean implementation provides details on how to correctly serialize an AbstractBean subclass.

Author:

rbair

See Also:

AbstractSerializableBean

API Status:

REVIEWED

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	AbstractBean() Creates a new instance of AbstractBean
protected	AbstractBean(PropertyChangeSupport pcs, VetoableChangeSupport vcs) Creates a new instance of AbstractBean, using the supplied PropertyChangeSupport and VetoableChangeSupport delegates.

Method Summary

Modifier and Type	Method and Description
void	addPropertyChangeListener(PropertyChangeListener listener) Add a PropertyChangeListener to the listener list.
void	addPropertyChangeListener(String propertyName, PropertyChangeListener listener) Add a PropertyChangeListener for a specific property.
void	addVetoableChangeListener(String propertyName, VetoableChangeListener listener) Add a VetoableChangeListener for a specific property.
void	addVetoableChangeListener(VetoableChangeListener listener) Add a VetoableListener to the listener list.
Object	clone()
protected void	fireIndexedPropertyChange(String propertyName, int index, Object oldValue, Object newValue) Report a bound indexed property update to any registered listeners.
protected void	firePropertyChange(PropertyChangeEvent evt) Fire an existing PropertyChangeEvent to any registered listeners.
protected void	firePropertyChange(String propertyName, Object oldValue, Object newValue) Report a bound property update to any registered listeners.
protected void	fireVetoableChange(PropertyChangeEvent evt) Fire a vetoable property update to any registered listeners.
protected void	fireVetoableChange(String propertyName, Object oldValue, Object newValue) Report a vetoable property update to any registered listeners.
PropertyChangeListener[]	getPropertyChangeListeners() Returns an array of all the listeners that were added to the PropertyChangeSupport object with addPropertyChangeListener().
PropertyChangeListener[]	getPropertyChangeListeners(String propertyName) Returns an array of all the listeners which have been associated with the named property.
VetoableChangeListener[]	getVetoableChangeListeners() Returns the list of VetoableChangeListeners.
VetoableChangeListener[]	getVetoableChangeListeners(String propertyName) Returns an array of all the listeners which have been associated with the named property.
protected boolean	hasPropertyChangeListeners(String propertyName) Check if there are any listeners for a specific property, including those registered on all properties.
protected boolean	hasVetoableChangeListeners(String propertyName) Check if there are any listeners for a specific property, including those registered on all properties.
void	removePropertyChangeListener(PropertyChangeListener listener) Remove a PropertyChangeListener from the listener list.
void	removePropertyChangeListener(String propertyName, PropertyChangeListener listener) Remove a PropertyChangeListener for a specific property.
void	removeVetoableChangeListener(String propertyName, VetoableChangeListener listener) Remove a VetoableChangeListener for a specific property.
void	removeVetoableChangeListener(VetoableChangeListener listener) Remove a VetoableChangeListener from the listener list.

Methods inherited from class java.lang.Object

equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

AbstractBean

protected AbstractBean()

Creates a new instance of AbstractBean

AbstractBean

protected AbstractBean(PropertyChangeSupport pcs,
                       VetoableChangeSupport vcs)

Creates a new instance of AbstractBean, using the supplied PropertyChangeSupport and VetoableChangeSupport delegates. Neither of these may be null.

Method Detail

addPropertyChangeListener

public final void addPropertyChangeListener(PropertyChangeListener listener)

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 listener is null, no exception is thrown and no action is taken.

Parameters:

listener - The PropertyChangeListener to be added

removePropertyChangeListener

public final void removePropertyChangeListener(PropertyChangeListener 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.

Parameters:

listener - The PropertyChangeListener to be removed

getPropertyChangeListeners

public final PropertyChangeListener[] getPropertyChangeListeners()

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"
     }
   }
 }

Returns:

all of the PropertyChangeListeners added or an empty array if no listeners have been added

See Also:

PropertyChangeListenerProxy

addPropertyChangeListener

public final void addPropertyChangeListener(String propertyName,
                                            PropertyChangeListener listener)

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.

Parameters:

propertyName - The name of the property to listen on.

listener - The PropertyChangeListener to be added

removePropertyChangeListener

public final void removePropertyChangeListener(String propertyName,
                                               PropertyChangeListener 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.

Parameters:

propertyName - The name of the property that was listened on.

listener - The PropertyChangeListener to be removed

getPropertyChangeListeners

public final PropertyChangeListener[] getPropertyChangeListeners(String propertyName)

Returns an array of all the listeners which have been associated with the named property.

Parameters:

propertyName - The name of the property being listened to

Returns:

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.

firePropertyChange

protected final void firePropertyChange(String propertyName,
                                        Object oldValue,
                                        Object newValue)

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 PropertyChangeEvent value.

Parameters:

propertyName - The programmatic name of the property that was changed.

oldValue - The old value of the property.

newValue - The new value of the property.

firePropertyChange

protected final void firePropertyChange(PropertyChangeEvent evt)

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.

Parameters:

evt - The PropertyChangeEvent object.

fireIndexedPropertyChange

protected final void fireIndexedPropertyChange(String propertyName,
                                               int index,
                                               Object oldValue,
                                               Object newValue)

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 PropertyChangeEvent value.

Parameters:

propertyName - The programmatic name of the property that was changed.

index - index of the property element that was changed.

oldValue - The old value of the property.

newValue - The new value of the property.

hasPropertyChangeListeners

protected final boolean hasPropertyChangeListeners(String 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.

Parameters:

propertyName - the property name.

Returns:

true if there are one or more listeners for the given property

hasVetoableChangeListeners

protected final boolean hasVetoableChangeListeners(String 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.

Parameters:

propertyName - the property name.

Returns:

true if there are one or more listeners for the given property

addVetoableChangeListener

public final void addVetoableChangeListener(VetoableChangeListener listener)

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.

Parameters:

listener - The VetoableChangeListener to be added

removeVetoableChangeListener

public final void removeVetoableChangeListener(VetoableChangeListener 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.

Parameters:

listener - The VetoableChangeListener to be removed

getVetoableChangeListeners

public final VetoableChangeListener[] getVetoableChangeListeners()

Returns the list of VetoableChangeListeners. If named vetoable change listeners were added, then VetoableChangeListenerProxy wrappers will returned

Returns:

List of VetoableChangeListeners and VetoableChangeListenerProxys if named property change listeners were added.

addVetoableChangeListener

public final void addVetoableChangeListener(String propertyName,
                                            VetoableChangeListener listener)

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.

Parameters:

propertyName - The name of the property to listen on.

listener - The VetoableChangeListener to be added

removeVetoableChangeListener

public final void removeVetoableChangeListener(String propertyName,
                                               VetoableChangeListener 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.

Parameters:

propertyName - The name of the property that was listened on.

listener - The VetoableChangeListener to be removed

getVetoableChangeListeners

public final VetoableChangeListener[] getVetoableChangeListeners(String propertyName)

Returns an array of all the listeners which have been associated with the named property.

Parameters:

propertyName - The name of the property being listened to

Returns:

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.

fireVetoableChange

protected final void fireVetoableChange(String propertyName,
                                        Object oldValue,
                                        Object newValue)
                                 throws PropertyVetoException

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.

Parameters:

propertyName - The programmatic name of the property that is about to change..

oldValue - The old value of the property.

newValue - The new value of the property.

Throws:

PropertyVetoException - if the recipient wishes the property change to be rolled back.

fireVetoableChange

protected final void fireVetoableChange(PropertyChangeEvent evt)
                                 throws PropertyVetoException

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.

Parameters:

evt - The PropertyChangeEvent to be fired.

Throws:

PropertyVetoException - if the recipient wishes the property change to be rolled back.

clone

public Object clone()
             throws CloneNotSupportedException

Overrides:

clone in class Object

Throws:

CloneNotSupportedException