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<TITLE>Implementing a Constrained Property
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<h3>
e3.
Implementing a Constrained Property</h3>
A constrained property fires a <code>PropertyChangeEvent</code> whenever its
value is about to be changed. Any listener can veto the event,
thereby preventing the change. This example bean implements a single
constrained integer property called <code>myProperty</code>.
<pre>
<font color="#0066ff"><i>int myProperty</i></font>;
public <font color="#0066ff"><i>int</i></font> get<font color="#0066ff"><i>MyProperty</i></font>() {
return <font color="#0066ff"><i>myProperty</i></font>;
}
public void set<font color="#0066ff"><i>MyProperty</i></font>(<font color="#0066ff"><i>int</i></font> newValue) throws PropertyVetoException {
try {
vceListeners.fireVetoableChange(
"<font color="#0066ff"><i>myProperty</i></font>", <font color="#0066ff"><i>new Integer(myProperty)</i></font>, <font color="#0066ff"><i>new Integer</i></font>(newValue));
<font color="#0066ff"><i>myProperty</i></font> = newValue;
} catch (PropertyVetoException e) {
throw e;
}
}
// Create the listener list.
VetoableChangeSupport vceListeners = new VetoableChangeSupport(this);
// The listener list wrapper methods.
public synchronized void addVetoableChangeListener(VetoableChangeListener listener) {
vceListeners.addVetoableChangeListener(listener);
}
public synchronized void removeVetoableChangeListener(VetoableChangeListener listener) {
vceListeners.removeVetoableChangeListener(listener);
}
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Related Examples
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e1. <a class="eglink" href="BasicBean.html?l=rel">
The Quintessential Bean
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e2. <a class="eglink" href="Bound.html?l=rel">
Implementing a Bound Property
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e4. <a class="eglink" href="NewBean.html?l=rel">
Instantiating a Bean
</a>
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e5. <a class="eglink" href="GetProps.html?l=rel">
Listing the Property Names of a Bean
</a>
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e6. <a class="eglink" href="GetSetProp.html?l=rel">
Getting and Setting a Property of a Bean
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See also:
<a class="eglink" href="/egs/java.beans/pkg.html?l=rel#Events">
Events
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<a class="eglink" href="/egs/java.beans/pkg.html?l=rel#Serialization">
Serialization
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