FileDocCategorySizeDatePackage
VetoableChangeSupport.javaAPI DocJava SE 6 API15675Tue Jun 10 00:25:32 BST 2008java.beans

VetoableChangeSupport

public class VetoableChangeSupport extends Object implements Serializable
This is a utility class that can be used by beans that support constrained properties. You can use an instance of this class as a member field of your bean and delegate various work to it. 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.

Fields Summary
private transient Vector
listeners
"listeners" lists all the generic listeners. This is transient - its state is written in the writeObject method.
private Hashtable
children
Hashtable for managing listeners for specific properties. Maps property names to VetoableChangeSupport objects.
private Object
source
The object to be provided as the "source" for any generated events.
private int
vetoableChangeSupportSerializedDataVersion
Internal version number
static final long
serialVersionUID
Serialization version ID, so we're compatible with JDK 1.1
Constructors Summary
public VetoableChangeSupport(Object sourceBean)
Constructs a VetoableChangeSupport object.

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

	if (sourceBean == null) {
	    throw new NullPointerException();
	}
	source = sourceBean;
    
Methods Summary
public synchronized voidaddVetoableChangeListener(java.beans.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.

param
listener The VetoableChangeListener to be added

        if (listener == null) {
            return;
        }
        if (listener instanceof VetoableChangeListenerProxy) {
            VetoableChangeListenerProxy proxy =
                    (VetoableChangeListenerProxy)listener;
            // Call two argument add method.
            addVetoableChangeListener(proxy.getPropertyName(),
                    (VetoableChangeListener)proxy.getListener());
        } else {
            if (listeners == null) {
                listeners = new java.util.Vector();
            }
        }
        listeners.addElement(listener);
    
public synchronized voidaddVetoableChangeListener(java.lang.String propertyName, java.beans.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.

param
propertyName The name of the property to listen on.
param
listener The VetoableChangeListener to be added

        if (listener == null || propertyName == null) {
            return;
        }
        if (children == null) {
            children = new java.util.Hashtable();
        }
        VetoableChangeSupport child = (VetoableChangeSupport)children.get(propertyName);
        if (child == null) {
            child = new VetoableChangeSupport(source);
            children.put(propertyName, child);
        }
        child.addVetoableChangeListener(listener);
    
public voidfireVetoableChange(java.lang.String propertyName, boolean oldValue, boolean newValue)
Report a boolean vetoable property update to any registered listeners. No event is fired if old and new are equal.

This is merely a convenience wrapper around the more general fireVetoableChange method that takes Object values.

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.

	if (oldValue == newValue) {
	    return;
	}
	fireVetoableChange(propertyName, Boolean.valueOf(oldValue), Boolean.valueOf(newValue));
    
public voidfireVetoableChange(java.beans.PropertyChangeEvent evt)
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.


	Object oldValue = evt.getOldValue();
	Object newValue = evt.getNewValue();
	String propertyName = evt.getPropertyName();
	if (oldValue != null && newValue != null && oldValue.equals(newValue)) {
	    return;
	}

	java.util.Vector targets = null;
	VetoableChangeSupport child = null;
	synchronized (this) {
	    if (listeners != null) {
	        targets = (java.util.Vector) listeners.clone();
	    }
	    if (children != null && propertyName != null) {
		child = (VetoableChangeSupport)children.get(propertyName);
	    }
	}

	if (listeners != null) {
	    try {
	        for (int i = 0; i < targets.size(); i++) {
	            VetoableChangeListener target = 
				(VetoableChangeListener)targets.elementAt(i);
	            target.vetoableChange(evt);
	        }
	    } catch (PropertyVetoException veto) {
	        // Create an event to revert everyone to the old value.
       	        evt = new PropertyChangeEvent(source, propertyName, newValue, oldValue);
	        for (int i = 0; i < targets.size(); i++) {
		    try {
	                VetoableChangeListener target =
				(VetoableChangeListener)targets.elementAt(i);
	                target.vetoableChange(evt);
		    } catch (PropertyVetoException ex) {
		         // We just ignore exceptions that occur during reversions.
		    }
	        }
	        // And now rethrow the PropertyVetoException.
	        throw veto;
	    }
	}

	if (child != null) {
	    child.fireVetoableChange(evt);
	}
    
public voidfireVetoableChange(java.lang.String propertyName, java.lang.Object oldValue, java.lang.Object newValue)
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.

	if (listeners == null && children == null) {
	    return;
	}

       	PropertyChangeEvent evt = new PropertyChangeEvent(source, propertyName,
							    oldValue, newValue);
	fireVetoableChange(evt);
    
public voidfireVetoableChange(java.lang.String propertyName, int oldValue, int newValue)
Report a int vetoable property update to any registered listeners. No event is fired if old and new are equal.

This is merely a convenience wrapper around the more general fireVetoableChange method that takes Object values.

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.

	if (oldValue == newValue) {
	    return;
	}
	fireVetoableChange(propertyName, new Integer(oldValue), new Integer(newValue));
    
public synchronized java.beans.VetoableChangeListener[]getVetoableChangeListeners()
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.
since
1.4

        List returnList = new ArrayList();

        // Add all the VetoableChangeListeners
        if (listeners != null) {
            returnList.addAll(listeners);
        }

        // Add all the VetoableChangeListenerProxys
        if (children != null) {
            Iterator iterator = children.keySet().iterator();
            while (iterator.hasNext()) {
                String key = (String)iterator.next();
                VetoableChangeSupport child =
                        (VetoableChangeSupport)children.get(key);
                VetoableChangeListener[] childListeners =
                    child.getVetoableChangeListeners();
                for (int index = childListeners.length - 1; index >= 0;
                        index--) {
                    returnList.add(new VetoableChangeListenerProxy(
                            key, childListeners[index]));
                }
            }
        }
	return (VetoableChangeListener[])(returnList.toArray(
                new VetoableChangeListener[0]));
    
public synchronized java.beans.VetoableChangeListener[]getVetoableChangeListeners(java.lang.String propertyName)
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.
since
1.4

        List returnList = new ArrayList();

        if (children != null && propertyName != null) {
            VetoableChangeSupport support =
                    (VetoableChangeSupport)children.get(propertyName);
            if (support != null) {
                returnList.addAll(
                        Arrays.asList(support.getVetoableChangeListeners()));
            }
        }
        return (VetoableChangeListener[])(returnList.toArray(new
                VetoableChangeListener[0]));
    
public synchronized booleanhasListeners(java.lang.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.

param
propertyName the property name.
return
true if there are one or more listeners for the given property

	if (listeners != null && !listeners.isEmpty()) {
	    // there is a generic listener
	    return true;
	}
	if (children != null && propertyName != null) {
	    VetoableChangeSupport child = (VetoableChangeSupport)children.get(propertyName);
	    if (child != null && child.listeners != null) {
		return !child.listeners.isEmpty();
	    }
	}
	return false;
    
private voidreadObject(java.io.ObjectInputStream s)

        s.defaultReadObject();
      
        Object listenerOrNull;
        while(null != (listenerOrNull = s.readObject())) {
	    addVetoableChangeListener((VetoableChangeListener)listenerOrNull);
        }
    
public synchronized voidremoveVetoableChangeListener(java.beans.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.

param
listener The VetoableChangeListener to be removed

        if (listener == null) {
            return;
        }
        if (listener instanceof VetoableChangeListenerProxy) {
            VetoableChangeListenerProxy proxy =
                    (VetoableChangeListenerProxy)listener;
            // Call two argument remove method.
            removeVetoableChangeListener(proxy.getPropertyName(),
                    (VetoableChangeListener)proxy.getListener());
        } else {
            if (listeners == null) {
                return;
            }
            listeners.removeElement(listener);
        }
    
public synchronized voidremoveVetoableChangeListener(java.lang.String propertyName, java.beans.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.

param
propertyName The name of the property that was listened on.
param
listener The VetoableChangeListener to be removed

        if (listener == null || propertyName == null) {
            return;
        }
        if (children == null) {
            return;
        }
        VetoableChangeSupport child = (VetoableChangeSupport)children.get(propertyName);
        if (child == null) {
            return;
        }
        child.removeVetoableChangeListener(listener);
    
private voidwriteObject(java.io.ObjectOutputStream s)

serialData
Null terminated list of VetoableChangeListeners.

At serialization time we skip non-serializable listeners and only serialize the serializable listeners.

        s.defaultWriteObject();

	java.util.Vector v = null;
	synchronized (this) {
	    if (listeners != null) {
	        v = (java.util.Vector) listeners.clone();
            }
	}

	if (v != null) {
	    for(int i = 0; i < v.size(); i++) {
	        VetoableChangeListener l = (VetoableChangeListener)v.elementAt(i);
	        if (l instanceof Serializable) {
	            s.writeObject(l);
	        }
            }
        }
        s.writeObject(null);