org.apache.ode.utils
Class WatchDog<T>

java.lang.Object
  org.apache.ode.utils.WatchDog<T>

All Implemented Interfaces:

java.lang.Runnable

Direct Known Subclasses:

FileWatchDog

public class WatchDog<T>
extends java.lang.Object
implements java.lang.Runnable

This class is based on org.apache.log4j.helpers.FileWatchdog.

Modifications have been made to support additional abstract ressource and more events (creation, deletion and updates), and to allow "manual" invocations of check() (i.e wihtout having to use a thread) while preserving time checking.

Now two use cases coexist:

1. Pass an instance of WatchDog to a new thread (WatchDog is a Runnable). So that check () will be called automatically every delay milliseconds.
2. Invoke check () only when you feel like it. If the expiration date previously set is lower than NOW then event callback methods will be invoked accordingly.

Nested Class Summary

static interface

WatchDog.Mutable<T> have you said that duck typing would be nice?

Field Summary

static long	DEFAULT_DELAY
protected WatchDog.Mutable<T>	mutable

Constructor Summary

WatchDog(WatchDog.Mutable<T> mutable)

WatchDog(WatchDog.Mutable<T> mutable, long delay)

Method Summary

void	check()
protected void	doOnDelete() Called only if the resource previously existed and now does not exist.
protected void	doOnUpdate() Called only if the resource previously existed but the WatchDog.Mutable.lastModified() timestamp has changed (greater than the previous value).
long	getDelay()
protected void	init() Called by check() if the object is not initialized and the WatchDog.Mutable.exists() resource does not exist}.
protected boolean	isInitialized()
void	run()
void	setDelay(long delay)

Methods inherited from class java.lang.Object

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

Field Detail

DEFAULT_DELAY

public static final long DEFAULT_DELAY

See Also:

Constant Field Values

mutable

protected final WatchDog.Mutable<T> mutable

Constructor Detail

WatchDog

public WatchDog(WatchDog.Mutable<T> mutable,
                long delay)

Parameters:

mutable - the object to watch closely

delay - between two checks

WatchDog

public WatchDog(WatchDog.Mutable<T> mutable)

See Also:

WatchDog(org.apache.ode.utils.WatchDog.Mutable, long)

Method Detail

isInitialized

protected boolean isInitialized()

init

protected void init()

Called by check() if the object is not initialized and the WatchDog.Mutable.exists() resource does not exist}.
This method might called to reset the object.

Throws:

java.lang.Exception

doOnDelete

protected void doOnDelete()

Called only if the resource previously existed and now does not exist.
The default implementation invokes init() .

Throws:

java.lang.Exception

doOnUpdate

protected void doOnUpdate()

Called only if the resource previously existed but the WatchDog.Mutable.lastModified() timestamp has changed (greater than the previous value).
The default implementation invokes init() .

Throws:

java.lang.Exception

getDelay

public long getDelay()

setDelay

public void setDelay(long delay)

run

public void run()

Specified by:

run in interface java.lang.Runnable

check

public final void check()