Class PropertyChangeSupport

This is a utility class that can be used by beans that support bound properties. It manages a list of listeners and dispatches PropertyChangeEvents to them. You can use an instance of this class as a member field of your bean and delegate these types of work to it. The PropertyChangeListener can be registered for all properties or for a property specified by name.

Here is an example of PropertyChangeSupport usage that follows the rules and recommendations laid out in the JavaBeans™ specification:

public class MyBean {
     private final PropertyChangeSupport pcs = new PropertyChangeSupport(this);

     public void addPropertyChangeListener(PropertyChangeListener listener) {
         this.pcs.addPropertyChangeListener(listener);
     }

     public void removePropertyChangeListener(PropertyChangeListener listener) {
         this.pcs.removePropertyChangeListener(listener);
     }

     private String value;

     public String getValue() {
         return this.value;
     }

     public void setValue(String newValue) {
         String oldValue = this.value;
         this.value = newValue;
         this.pcs.firePropertyChange("value", oldValue, newValue);
     }

     [...]
 }

A PropertyChangeSupport instance is thread-safe.

This class is serializable. When it is serialized it will save (and restore) any listeners that are themselves serializable. Any non-serializable listeners will be skipped during serialization.

Constructors

PropertyChangeSupport

public PropertyChangeSupport(Object sourceBean)

Constructs a PropertyChangeSupport object.

Parameters:

sourceBean - The bean to be given as the source for any events.

Methods

addPropertyChangeListener

public 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 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 PropertyChangeListener[] getPropertyChangeListeners()

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

Since:

1.4

See Also:

PropertyChangeListenerProxy

addPropertyChangeListener

public 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 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 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.

Since:

1.4

firePropertyChange

public void firePropertyChange(String propertyName,
                               Object oldValue,
                               Object newValue)

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

public void firePropertyChange(String propertyName,
                               int oldValue,
                               int newValue)

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

public void firePropertyChange(String propertyName,
                               boolean oldValue,
                               boolean newValue)

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

public void firePropertyChange(PropertyChangeEvent event)

Parameters:

event - the PropertyChangeEvent to be fired

fireIndexedPropertyChange

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

Parameters:

propertyName - the programmatic name of the property that was changed

index - the index of the property element that was changed

oldValue - the old value of the property

newValue - the new value of the property

Since:

1.5

fireIndexedPropertyChange

public void fireIndexedPropertyChange(String propertyName,
                                      int index,
                                      int oldValue,
                                      int newValue)

Parameters:

propertyName - the programmatic name of the property that was changed

index - the index of the property element that was changed

oldValue - the old value of the property

newValue - the new value of the property

Since:

1.5

fireIndexedPropertyChange

public void fireIndexedPropertyChange(String propertyName,
                                      int index,
                                      boolean oldValue,
                                      boolean newValue)

Parameters:

propertyName - the programmatic name of the property that was changed

index - the index of the property element that was changed

oldValue - the old value of the property

newValue - the new value of the property

Since:

1.5

hasListeners

public boolean hasListeners(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