org.openbase.jul.pattern

Class AbstractObservable<T>

java.lang.Object

org.openbase.jul.pattern.AbstractObservable<T>

Type Parameters:

T - the data type on whose changes is notified

All Implemented Interfaces:

Shutdownable, Observable<T>

Direct Known Subclasses:

ObservableImpl

public abstract class AbstractObservable<T>
extends Object
implements Observable<T>

Author:

Divine Threepwood

Nested Class Summary

Nested classes/interfaces inherited from interface org.openbase.jul.iface.Shutdownable

Shutdownable.ShutdownDeamon

Field Summary

Fields

Modifier and Type	Field and Description
protected int	latestValueHash
protected List<Observer<T>>	observers
protected boolean	unchangedValueFilter

Constructor Summary

Constructors

Constructor and Description
AbstractObservable() Construct new Observable.
AbstractObservable(boolean unchangedValueFilter) Construct new Observable
AbstractObservable(boolean unchangedValueFilter, Object source) Construct new Observable.
AbstractObservable(Object source) Construct new Observable.

Method Summary

Modifier and Type	Method and Description
void	addObserver(Observer<T> observer) Method registers the given observer to this observable to get informed about value changes.
protected void	applyValueUpdate(T value) Method is called if a observer notification delivers a new value.
boolean	isNotificationInProgess() Method checks if a notification is currently in progess.
boolean	notifyObservers(Observable<T> source, T observable) Notify all changes of the observable to all observers only if the observable has changed.
boolean	notifyObservers(T observable) Notify all changes of the observable to all observers only if the observable has changed.
void	removeObserver(Observer<T> observer) Method removes the given observer from this observable to finish the observation.
void	setExecutorService(ExecutorService executorService) Set an executor service for the observable.
void	setHashGenerator(HashGenerator<T> hashGenerator)
void	shutdown()
String	toString()
void	waitUntilNotificationIsFinished()

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.openbase.jul.pattern.Observable

getLatestValue, getValue, getValueFuture, isValueAvailable, waitForValue, waitForValue

Methods inherited from interface org.openbase.jul.iface.Shutdownable

registerShutdownHook, registerShutdownHook

Field Detail

unchangedValueFilter

protected final boolean unchangedValueFilter

observers

protected final List<Observer<T>> observers

latestValueHash

protected int latestValueHash

Constructor Detail

AbstractObservable

public AbstractObservable()

Construct new Observable.

AbstractObservable

public AbstractObservable(Object source)

Construct new Observable.

Parameters:

source - the responsible source of the value notifications.

AbstractObservable

public AbstractObservable(boolean unchangedValueFilter)

Construct new Observable

Parameters:

unchangedValueFilter - defines if the observer should be informed even if the value is the same than notified before.

AbstractObservable

public AbstractObservable(boolean unchangedValueFilter,
                          Object source)

Construct new Observable.

If the source is not defined the observable itself will be used as notification source.

Parameters:

unchangedValueFilter - defines if the observer should be informed even if the value is the same than notified before.

source - the responsible source of the value notifications.

Method Detail

addObserver

public void addObserver(Observer<T> observer)

Method registers the given observer to this observable to get informed about value changes.

Specified by:

addObserver in interface Observable<T>

Parameters:

observer -

removeObserver

public void removeObserver(Observer<T> observer)

Method removes the given observer from this observable to finish the observation.

Specified by:

removeObserver in interface Observable<T>

Parameters:

observer -

shutdown

public void shutdown()

Specified by:

shutdown in interface Shutdownable

notifyObservers

public boolean notifyObservers(T observable)
                        throws MultiException,
                               CouldNotPerformException

Notify all changes of the observable to all observers only if the observable has changed. The source of the notification is set as this. Because of data encapsulation reasons this method is not included within the Observer interface. Attention! This method is not thread safe against changes of the observable because the check if the observable has changed is done by computing its hash value. Therefore if the observable is a collection and it is changed while notifying a concurrent modification exception can occur. To avoid this compute the observable hash yourself by setting a hash generator. If this method is interrupted a rollback is done by reseting the latestHashValue. Thus the observable has not changed and false is returned.

Parameters:

observable - the value which is notified

Returns:

true if the observable has changed

Throws:

MultiException - thrown if the notification to at least one observer fails

CouldNotPerformException - thrown if the hash computation fails

notifyObservers

public boolean notifyObservers(Observable<T> source,
                               T observable)
                        throws MultiException,
                               CouldNotPerformException

Notify all changes of the observable to all observers only if the observable has changed. Because of data encapsulation reasons this method is not included within the Observer interface. Attention! This method is not thread safe against changes of the observable because the check if the observable has changed is done by computing its hash value. Therefore if the observable is a collection and it is changed while notifying a concurrent modification exception can occur. To avoid this compute the observable hash yourself by setting a hash generator. If this method is interrupted a rollback is done by reseting the latestHashValue. Thus the observable has not changed and false is returned.

Note: In case the given observable is null this notification will be ignored.

Parameters:

source - the source of the notification

observable - the value which is notified

Returns:

true if the observable has changed

Throws:

MultiException - thrown if the notification to at least one observer fails

CouldNotPerformException - thrown if the hash computation fails

applyValueUpdate

protected void applyValueUpdate(T value)
                         throws NotAvailableException

Method is called if a observer notification delivers a new value.

Parameters:

value - the new value

Note: Overwrite this method for getting informed about value changes.

Throws:

NotAvailableException

setExecutorService

public void setExecutorService(ExecutorService executorService)

Set an executor service for the observable. If it is set the notification will be parallelized using this service.

Parameters:

executorService - the executor service which will be used for parallelization

setHashGenerator

public void setHashGenerator(HashGenerator<T> hashGenerator)

isNotificationInProgess

public boolean isNotificationInProgess()

Method checks if a notification is currently in progess.

Returns:

notificationInProgess returns true if a notification is currently in progess.

waitUntilNotificationIsFinished

public void waitUntilNotificationIsFinished()
                                     throws InterruptedException

Throws:

InterruptedException

toString

public String toString()

Overrides:

toString in class Object