com.antelmann.util
Class Placeholder<T>

java.lang.Object
  com.antelmann.util.Placeholder<T>

All Implemented Interfaces:

ValueRetriever<T>, ValueSetter<T>, Wrapped<T>, Serializable

@Warning(value="the instance is only serializable if T is serializable")
public class Placeholder<T>
extends Object
implements ValueSetter<T>, ValueRetriever<T>, Serializable, Wrapped<T>

useful for storing immutable objects in local variables which are used in inner classes when the value may change or to enable 'call by reference' on methods with otherwise primitive parameters. A Placeholder supports PropertyChangeListeners and the ValueSetter interface implemented here additionally supports VetoableChangeListeners. Note that for the Placeholder to actually be serializable, the value of T itself must be serializable.

Since:

04/18/08

Author:

Holger Antelmann

See Also:

ImageHolder, BinaryData, Serialized Form

Constructor Summary

Placeholder()

Placeholder(T value)

Method Summary

void	addPropertyChangeListener(PropertyChangeListener listener)
void	addVetoableChangeListener(VetoableChangeListener listener) note that the given listener is only applied if setRelevantValue(Object) is called while setValue(Object) merely fires a PropertyChangeEvent.
PropertyChangeListener[]	getPropertyChangeListeners()
T	getRelevantValue() calls getValue()
T	getValue()
VetoableChangeListener[]	getVetoableChangeListeners()
boolean	isEmpty()
void	removePropertyChangeListener(PropertyChangeListener listener)
void	removeVetoableChangeListener(VetoableChangeListener listener)
void	setRelevantValue(T value) calls setValue(Object) after checking any VetoableChangeListener
void	setValue(T value) sets the value directly (VetoableChangeListeners are bypassed) and fires a PropertyChangeEvent to the listeners.
T	unwrap() simply returns getValue()

Methods inherited from class java.lang.Object

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

Constructor Detail

Placeholder

public Placeholder()

Placeholder

public Placeholder(T value)

Method Detail

getValue

public T getValue()

isEmpty

public boolean isEmpty()

setValue

public void setValue(T value)

sets the value directly (VetoableChangeListeners are bypassed) and fires a PropertyChangeEvent to the listeners.

setRelevantValue

public void setRelevantValue(T value)
                      throws PropertyVetoException

calls setValue(Object) after checking any VetoableChangeListener

Specified by:

setRelevantValue in interface ValueSetter<T>

Throws:

PropertyVetoException - if a VetoableChangeListener throws it

getRelevantValue

public T getRelevantValue()
                   throws IOException

calls getValue()

Specified by:

getRelevantValue in interface ValueRetriever<T>

Throws:

IOException - if any resource to fulfill the request is not accessible

unwrap

public T unwrap()

simply returns getValue()

Specified by:

unwrap in interface Wrapped<T>

addPropertyChangeListener

public void addPropertyChangeListener(PropertyChangeListener listener)

getPropertyChangeListeners

public PropertyChangeListener[] getPropertyChangeListeners()

removePropertyChangeListener

public void removePropertyChangeListener(PropertyChangeListener listener)

addVetoableChangeListener

public void addVetoableChangeListener(VetoableChangeListener listener)

note that the given listener is only applied if setRelevantValue(Object) is called while setValue(Object) merely fires a PropertyChangeEvent.

getVetoableChangeListeners

public VetoableChangeListener[] getVetoableChangeListeners()

removeVetoableChangeListener

public void removeVetoableChangeListener(VetoableChangeListener listener)