java.beans

Class VetoableChangeSupport

java.lang.Object

java.beans.VetoableChangeSupport

All Implemented Interfaces:

Serializable

public class VetoableChangeSupport
extends Object
implements Serializable

This is a utility class that can be used by beans that support constrained 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 VetoableChangeListener can be registered for all properties or for a property specified by name.

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

 public class MyBean {
     private final VetoableChangeSupport vcs = new VetoableChangeSupport(this);

     public void addVetoableChangeListener(VetoableChangeListener listener) {
         this.vcs.addVetoableChangeListener(listener);
     }

     public void removeVetoableChangeListener(VetoableChangeListener listener) {
         this.vcs.removeVetoableChangeListener(listener);
     }

     private String value;

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

     public void setValue(String newValue) throws PropertyVetoException {
         String oldValue = this.value;
         this.vcs.fireVetoableChange("value", oldValue, newValue);
         this.value = newValue;
     }

     [...]
 }
 

A VetoableChangeSupport 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.

See Also:

PropertyChangeSupport, Serialized Form

Constructor Summary

Constructors

Constructor and Description
VetoableChangeSupport(Object sourceBean) Constructs a VetoableChangeSupport object.

Method Summary

Modifier and Type	Method and Description
void	addVetoableChangeListener(String propertyName, VetoableChangeListener listener) Add a VetoableChangeListener for a specific property.
void	addVetoableChangeListener(VetoableChangeListener listener) Add a VetoableChangeListener to the listener list.
void	fireVetoableChange(PropertyChangeEvent event) Fires a property change event to listeners that have been registered to track updates of all properties or a property with the specified name.
void	fireVetoableChange(String propertyName, boolean oldValue, boolean newValue) Reports a boolean constrained property update to listeners that have been registered to track updates of all properties or a property with the specified name.
void	fireVetoableChange(String propertyName, int oldValue, int newValue) Reports an integer constrained property update to listeners that have been registered to track updates of all properties or a property with the specified name.
void	fireVetoableChange(String propertyName, Object oldValue, Object newValue) Reports a constrained property update to listeners that have been registered to track updates of all properties or a property with the specified name.
VetoableChangeListener[]	getVetoableChangeListeners() Returns an array of all the listeners that were added to the VetoableChangeSupport object with addVetoableChangeListener().
VetoableChangeListener[]	getVetoableChangeListeners(String propertyName) Returns an array of all the listeners which have been associated with the named property.
boolean	hasListeners(String propertyName) Check if there are any listeners for a specific property, including those registered on all properties.
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

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

Constructor Detail

VetoableChangeSupport

public VetoableChangeSupport(Object sourceBean)

Constructs a VetoableChangeSupport object.

Parameters:

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

Method Detail

addVetoableChangeListener

public void addVetoableChangeListener(VetoableChangeListener listener)

Add a VetoableChangeListener 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 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 VetoableChangeListener[] getVetoableChangeListeners()

Returns an array of all the listeners that were added to the VetoableChangeSupport object with addVetoableChangeListener().

If some listeners have been added with a named property, then the returned array will be a mixture of VetoableChangeListeners and VetoableChangeListenerProxys. If the calling method is interested in distinguishing the listeners then it must test each element to see if it's a VetoableChangeListenerProxy, perform the cast, and examine the parameter.

 VetoableChangeListener[] listeners = bean.getVetoableChangeListeners();
 for (int i = 0; i < listeners.length; i++) {
        if (listeners[i] instanceof VetoableChangeListenerProxy) {
     VetoableChangeListenerProxy proxy =
                    (VetoableChangeListenerProxy)listeners[i];
     if (proxy.getPropertyName().equals("foo")) {
       // proxy is a VetoableChangeListener which was associated
       // with the property named "foo"
     }
   }
 }
 

Returns:

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

Since:

1.4

See Also:

VetoableChangeListenerProxy

addVetoableChangeListener

public 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 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 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.

Since:

1.4

fireVetoableChange

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

Reports a constrained property update to listeners that have been registered to track updates of all properties or a property with the specified name.

Any listener can throw a PropertyVetoException to veto the update. If one of the listeners vetoes the update, this method passes a new "undo" PropertyChangeEvent that reverts to the old value to all listeners that already confirmed this update and throws the PropertyVetoException again.

No event is fired if old and new values are equal and non-null.

This is merely a convenience wrapper around the more general fireVetoableChange(PropertyChangeEvent) method.

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 one of listeners vetoes the property update

fireVetoableChange

public void fireVetoableChange(String propertyName,
                               int oldValue,
                               int newValue)
                        throws PropertyVetoException

Reports an integer constrained property update to listeners that have been registered to track updates of all properties or a property with the specified name.

Any listener can throw a PropertyVetoException to veto the update. If one of the listeners vetoes the update, this method passes a new "undo" PropertyChangeEvent that reverts to the old value to all listeners that already confirmed this update and throws the PropertyVetoException again.

No event is fired if old and new values are equal.

This is merely a convenience wrapper around the more general fireVetoableChange(String, Object, Object) method.

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 one of listeners vetoes the property update

fireVetoableChange

public void fireVetoableChange(String propertyName,
                               boolean oldValue,
                               boolean newValue)
                        throws PropertyVetoException

Reports a boolean constrained property update to listeners that have been registered to track updates of all properties or a property with the specified name.

Any listener can throw a PropertyVetoException to veto the update. If one of the listeners vetoes the update, this method passes a new "undo" PropertyChangeEvent that reverts to the old value to all listeners that already confirmed this update and throws the PropertyVetoException again.

No event is fired if old and new values are equal.

This is merely a convenience wrapper around the more general fireVetoableChange(String, Object, Object) method.

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 one of listeners vetoes the property update

fireVetoableChange

public void fireVetoableChange(PropertyChangeEvent event)
                        throws PropertyVetoException

Fires a property change event to listeners that have been registered to track updates of all properties or a property with the specified name.

Any listener can throw a PropertyVetoException to veto the update. If one of the listeners vetoes the update, this method passes a new "undo" PropertyChangeEvent that reverts to the old value to all listeners that already confirmed this update and throws the PropertyVetoException again.

No event is fired if the given event's old and new values are equal and non-null.

Parameters:

event - the PropertyChangeEvent to be fired

Throws:

PropertyVetoException - if one of listeners vetoes the property update

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