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<TITLE>Listening for a Vetoable Property Change Event
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<h3>
e12.
Listening for a Vetoable Property Change Event</h3>
A vetoable property change event is fired when a constrained property
is changed. A listener can veto the change by throwing
<code>PropertyVetoException</code> and preventing the change.
<pre>
// Register for property change events on the bean
<font color="#0066ff"><i>bean</i></font>.addVetoableChangeListener(new MyVetoableChangeListener());
class MyVetoableChangeListener implements VetoableChangeListener {
// This method is called every time the property value is changed
public void vetoableChange(PropertyChangeEvent evt) throws PropertyVetoException {
// Get the old value of the property
Object oldValue = evt.getOldValue();
// Get the new value of the property
Object newValue = evt.getNewValue();
// Determine if the change should be vetoed, thereby preventing the change
boolean veto = <font color="#0066ff"><i>false</i></font>;
if (veto) {
throw new PropertyVetoException(<font color="#0066ff"><i>"the reason for the veto"</i></font>, evt);
}
}
}
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Related Examples
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e11. <a class="eglink" href="HandleBound.html?l=rel">
Listening for a Property Change Event
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See also:
<a class="eglink" href="/egs/java.beans/pkg.html?l=rel#Serialization">
Serialization
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