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org.ematgine.utils.concurrent
Class VetoableChangeMulticaster  

java.lang.Object
  org.ematgine.utils.concurrent.VetoableChangeMulticaster

All Implemented Interfaces:

java.io.Serializable

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public class VetoableChangeMulticaster

extends java.lang.Object

implements java.io.Serializable

This class is interoperable with java.beans.VetoableChangeSupport, but relies on a streamlined copy-on-write scheme similar to that used in CopyOnWriteArrayList. It also adheres to clarified semantics of add, remove, and fireVetoableChange operations.

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;
   }

 }
 

[ Introduction to this package. ]

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Field Summary
protected  java.util.HashMap	children           HashMap for managing listeners for specific properties.
protected  java.beans.VetoableChangeListener[]	listeners           The array of listeners.
protected  java.lang.Object	source           The object to be provided as the "source" for any generated events.

 

Constructor Summary

VetoableChangeMulticaster(java.lang.Object sourceBean)           Constructs a VetoableChangeMulticaster object.

 

Method Summary
void	addVetoableChangeListener(java.lang.String propertyName, java.beans.VetoableChangeListener listener)           Add a VetoableChangeListener for a specific property.
void	addVetoableChangeListener(java.beans.VetoableChangeListener listener)           Add a VetoableChangeListener to the listener list.
void	addVetoableChangeListenerIfAbsent(java.lang.String propertyName, java.beans.VetoableChangeListener listener)           Add a VetoableChangeListener for a specific property, if it is not already registered.
void	addVetoableChangeListenerIfAbsent(java.beans.VetoableChangeListener listener)           Add a PropertyChangeListener to the listener list if it is not already present.
void	fireVetoableChange(java.beans.PropertyChangeEvent evt)           Report a vetoable property update to any registered listeners.
void	fireVetoableChange(java.lang.String propertyName, boolean oldValue, boolean newValue)           Report a vetoable property update to any registered listeners.
void	fireVetoableChange(java.lang.String propertyName, int oldValue, int newValue)           Report a vetoable property update to any registered listeners.
void	fireVetoableChange(java.lang.String propertyName, java.lang.Object oldValue, java.lang.Object newValue)           Report a vetoable property update to any registered listeners.
protected  VetoableChangeMulticaster	getChild(java.lang.String propertyName)           Return the child associated with property, or null if no such
boolean	hasListeners(java.lang.String propertyName)           Check if there are any listeners for a specific property.
protected  void	multicast(java.beans.PropertyChangeEvent evt)           Helper method to relay evt to all listeners.
private  void	readObject(java.io.ObjectInputStream s)
void	removeVetoableChangeListener(java.lang.String propertyName, java.beans.VetoableChangeListener listener)           Remove a VetoableChangeListener for a specific property.
void	removeVetoableChangeListener(java.beans.VetoableChangeListener listener)           Remove an occurrence of a VetoableChangeListener from the listener list.
private  void	writeObject(java.io.ObjectOutputStream s)

 

Methods inherited from class java.lang.Object

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

 

Field Detail

listeners

protected transient java.beans.VetoableChangeListener[] listeners

The array of listeners. Copied on each update

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source

protected final java.lang.Object source

The object to be provided as the "source" for any generated events.

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children

protected java.util.HashMap children

HashMap for managing listeners for specific properties. Maps property names to VetoableChangeMulticaster objects.

Constructor Detail

VetoableChangeMulticaster

public VetoableChangeMulticaster(java.lang.Object sourceBean)

Constructs a VetoableChangeMulticaster object.

Method Detail

getChild

protected VetoableChangeMulticaster getChild(java.lang.String propertyName)

Return the child associated with property, or null if no such

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addVetoableChangeListener

public void addVetoableChangeListener(java.beans.VetoableChangeListener listener)

Add a VetoableChangeListener to the listener list. The listener is registered for all properties. If the listener is added multiple times, it will receive multiple change notifications upon any fireVetoableChange.

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addVetoableChangeListenerIfAbsent

public void addVetoableChangeListenerIfAbsent(java.beans.VetoableChangeListener listener)

Add a PropertyChangeListener to the listener list if it is not already present. The listener is registered for all properties. The operation maintains Set semantics: If the listener is already registered, the operation has no effect.

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removeVetoableChangeListener

public void removeVetoableChangeListener(java.beans.VetoableChangeListener listener)

Remove an occurrence of a VetoableChangeListener from the listener list. It removes at most one occurrence of the given listener. If the listener was added multiple times it must be removed mulitple times. This removes a VetoableChangeListener that was registered for all properties, and has no effect if registered for only one or more specified properties.

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addVetoableChangeListener

public void addVetoableChangeListener(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. However, if a listener is registered both for all properties and a specific property, it will receive multiple notifications upon changes to that property.

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addVetoableChangeListenerIfAbsent

public void addVetoableChangeListenerIfAbsent(java.lang.String propertyName,
                                              java.beans.VetoableChangeListener listener)

Add a VetoableChangeListener for a specific property, if it is not already registered. The listener will be invoked only when a call on fireVetoableChange names that specific property.

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removeVetoableChangeListener

public void removeVetoableChangeListener(java.lang.String propertyName,
                                         java.beans.VetoableChangeListener listener)

Remove a VetoableChangeListener for a specific property. Affects only the given property. If the listener is also registered for all properties, then it will continue to be registered for them.

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multicast

protected void multicast(java.beans.PropertyChangeEvent evt)
                  throws java.beans.PropertyVetoException

Helper method to relay evt to all listeners. Called by all public fireVetoableChange methods.

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fireVetoableChange

public void fireVetoableChange(java.lang.String propertyName,
                               java.lang.Object oldValue,
                               java.lang.Object newValue)
                        throws java.beans.PropertyVetoException

Report a vetoable property update to any registered listeners. Notifications are sent serially (although in no particular order) to the list of listeners, aborting if one throws PropertyVetoException. Upon this exception, fire a new event reverting this change to all listeners that have already been notified (ignoring any further vetos), suppress notifications to all other listeners, and then rethrow the PropertyVetoException.

No event is fired if old and new are equal non-null.

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fireVetoableChange

public void fireVetoableChange(java.lang.String propertyName,
                               int oldValue,
                               int newValue)
                        throws java.beans.PropertyVetoException

Report a vetoable property update to any registered listeners. Notifications are sent serially (although in no particular order) to the list of listeners, aborting if one throws PropertyVetoException. Upon this exception, fire a new event reverting this change to all listeners that have already been notified (ignoring any further vetos), suppress notifications to all other listeners, and then rethrow the PropertyVetoException.

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.

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fireVetoableChange

public void fireVetoableChange(java.lang.String propertyName,
                               boolean oldValue,
                               boolean newValue)
                        throws java.beans.PropertyVetoException

Report a vetoable property update to any registered listeners. Notifications are sent serially (although in no particular order) to the list of listeners, aborting if one throws PropertyVetoException. Upon this exception, fire a new event reverting this change to all listeners that have already been notified (ignoring any further vetos), suppress notifications to all other listeners, and then rethrow the PropertyVetoException.

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.

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fireVetoableChange

public void fireVetoableChange(java.beans.PropertyChangeEvent evt)
                        throws java.beans.PropertyVetoException

Report a vetoable property update to any registered listeners. Notifications are sent serially (although in no particular order) to the list of listeners, aborting if one throws PropertyVetoException. Upon this exception, fire a new event reverting this change to all listeners that have already been notified (ignoring any further vetos), suppress notifications to all other listeners, and then rethrow the PropertyVetoException.

No event is fired if old and new are equal and non-null. equal and non-null.

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hasListeners

public boolean hasListeners(java.lang.String propertyName)

Check if there are any listeners for a specific property. If propertyName is null, return whether there are any listeners at all.

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writeObject

private void writeObject(java.io.ObjectOutputStream s)
                  throws java.io.IOException

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readObject

private void readObject(java.io.ObjectInputStream s)
                 throws java.lang.ClassNotFoundException,
                        java.io.IOException

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Overview  Package   Class  Use  Deprecated  Index
Home >> All >> org >> ematgine >> utils >> [ concurrent overview ]	PREV CLASS  NEXT CLASS
SUMMARY:  JAVADOC |  SOURCE |  DOWNLOAD | NESTED | FIELD | CONSTR | METHOD	DETAIL: FIELD | CONSTR | METHOD

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