EDU.oswego.cs.dl.util.concurrent
public class VetoableChangeMulticaster extends Object implements Serializable
Sample usage.
class Thing { protected Color myColor = Color.red; // an example property protected boolean changePending; // track whether in midst of change // vetoable listeners: protected VetoableChangeMulticaster vetoers = new VetoableChangeMulticaster(this); // Possibly also some ordinary listeners: protected PropertyChangeMulticaster listeners = new PropertyChangeMulticaster(this); // registration methods, including: void addVetoer(VetoableChangeListener l) { // Use the `ifAbsent' version to avoid duplicate notifications vetoers.addVetoableChangeListenerIfAbsent(l); } public synchronized Color getColor() { // accessor return myColor; } // Simple transactional control for vetos public void setColor(int newColor) throws PropertyVetoException { Color oldColor = prepareSetColor(newColor); try { vetoers.fireVetoableChange("color", oldColor, newColor); commitColor(newColor); listeners.firePropertyChange("color", oldColor, newColor); } catch(PropertyVetoException ex) { abortSetColor(); throw ex; } } // Called on entry to proposed vetoable change from setColor. // Throws exception if there is already another change in progress. // Returns current color synchronized int prepareSetColor(Color c) throws PropertyVetoException { // only support one transaction at a time if (changePending) throw new PropertyVetoException("Concurrent modification"); // (Could alternatively wait out other transactions via // a wait/notify construction based on changePending.) // perhaps some other screenings, like: else if (c == null) throw new PropertyVetoException("Cannot change color to Null"); else { changePending = true; return myColor; } } synchronized void commitColor(Color newColor) { myColor = newColor; changePending = false; } synchronized void abortSetColor() { changePending = false; } }
Field Summary | |
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protected HashMap | children
HashMap for managing listeners for specific properties.
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protected VetoableChangeListener[] | listeners
The array of listeners. |
protected Object | source
The object to be provided as the "source" for any generated events. |
Constructor Summary | |
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VetoableChangeMulticaster(Object sourceBean)
Constructs a VetoableChangeMulticaster object.
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Method Summary | |
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void | addVetoableChangeListener(VetoableChangeListener listener)
Add a VetoableChangeListener to the listener list.
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void | addVetoableChangeListener(String propertyName, VetoableChangeListener listener)
Add a VetoableChangeListener for a specific property. |
void | addVetoableChangeListenerIfAbsent(VetoableChangeListener listener)
Add a PropertyChangeListener to the listener list if it is
not already present.
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void | addVetoableChangeListenerIfAbsent(String propertyName, VetoableChangeListener listener)
Add a VetoableChangeListener for a specific property, if it is not
already registered. |
void | fireVetoableChange(String propertyName, Object oldValue, Object newValue)
Report a vetoable property update to any registered listeners.
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void | fireVetoableChange(String propertyName, int oldValue, int newValue)
Report a vetoable property update to any registered listeners.
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void | fireVetoableChange(String propertyName, boolean oldValue, boolean newValue)
Report a vetoable property update to any registered listeners.
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void | fireVetoableChange(PropertyChangeEvent evt)
Report a vetoable property update to any registered listeners.
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protected VetoableChangeMulticaster | getChild(String propertyName)
Return the child associated with property, or null if no such
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boolean | hasListeners(String propertyName)
Check if there are any listeners for a specific property.
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protected void | multicast(PropertyChangeEvent evt)
Helper method to relay evt to all listeners.
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void | removeVetoableChangeListener(VetoableChangeListener listener)
Remove an occurrence of a VetoableChangeListener from the listener list.
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void | removeVetoableChangeListener(String propertyName, VetoableChangeListener listener)
Remove a VetoableChangeListener for a specific property.
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Serial:
Serial:
VetoableChangeMulticaster
object.
Parameters: sourceBean The bean to be given as the source for any events.
Throws: NullPointerException if sourceBean is null
Parameters: listener The VetoableChangeListener to be added
Parameters: propertyName The name of the property to listen on. listener The VetoableChangeListener to be added
Throws: NullPointerException If listener is null
Parameters: listener The PropertyChangeListener to be added
Throws: NullPointerException If listener is null
Parameters: propertyName The name of the property to listen on. listener The VetoableChangeListener to be added
Throws: NullPointerException If listener is null
No event is fired if old and new are equal non-null.
Parameters: propertyName The programmatic name of the property that was changed. oldValue The old value of the property. newValue The new value of the property.
Throws: PropertyVetoException if a recipient wishes the property change to be rolled back.
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.
Parameters: propertyName The programmatic name of the property that was changed. oldValue The old value of the property. newValue The new value of the property.
Throws: PropertyVetoException if the recipient wishes the property change to be rolled back.
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.
Parameters: propertyName The programmatic name of the property that was changed. oldValue The old value of the property. newValue The new value of the property.
Throws: PropertyVetoException if the recipient wishes the property change to be rolled back.
No event is fired if old and new are equal and non-null. equal and non-null.
Parameters: evt The PropertyChangeEvent object.
Throws: PropertyVetoException if the recipient wishes the property change to be rolled back.
Parameters: propertyName the property name.
Returns: true if there are one or more listeners for the given property
Parameters: listener The VetoableChangeListener to be removed
Parameters: propertyName The name of the property that was listened on. listener The VetoableChangeListener to be removed