# 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 `PropertyChangeEvent`s 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.

Since:
  1.1
See Also:
  - `PropertyChangeSupport`
  - Serialized Form

- ## Constructor Summary

  Constructors
  Constructor
  Description
  `VetoableChangeSupport(Object sourceBean)`
  Constructs a `VetoableChangeSupport` object.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `void`
  `addVetoableChangeListener(VetoableChangeListener listener)`
  Add a VetoableChangeListener to the listener list.
  `void`
  `addVetoableChangeListener(String propertyName, VetoableChangeListener listener)`
  Add a VetoableChangeListener for a specific property.
  `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(VetoableChangeListener listener)`
  Remove a VetoableChangeListener from the listener list.
  `void`
  `removeVetoableChangeListener(String propertyName, VetoableChangeListener listener)`
  Remove a VetoableChangeListener for a specific property.

  ### Methods declared in class Object

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

- ## Constructor Details

  - ### VetoableChangeSupport

    public VetoableChangeSupport(Object sourceBean)
    Constructs a `VetoableChangeSupport` object.
    Parameters:
      `sourceBean` - The bean to be given as the source for any events.

- ## Method Details

  - ### 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 `VetoableChangeListenerProxy`s. 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
    Since:
      1.2

  - ### 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
    Since:
      1.2

  - ### 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
    Since:
      1.2

  - ### 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
    Since:
      1.2

  - ### 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
    Since:
      1.2

  - ### 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
    Since:
      1.2