Package net.sf.eBusx.io

Class EFileWatcher

java.lang.Object

net.sf.eBusx.io.EFileWatcher

All Implemented Interfaces:

EObject, EPublisher

public final class EFileWatcher
extends java.lang.Object
implements EPublisher

This class provides an eBus file watcher service, allowing asynchronous notification when a file or directory is created, modified or deleted. This service only supports JVM-local subscribers. This publisher advertises the EFileNotification with the file name as subject. The subject pattern is ".+" which supports any file name.

The file watcher service starts its timer task with the first subscriber and stops the timer task when there are no more subscribers. This means the timer is running only when there are watched files.

Author:

Charles Rapp

Field Summary

Fields

Modifier and Type	Field	Description
static long	DEFAULT_WATCH_RATE	The default watch rate is one minute.
static long	MAX_WATCH_RATE	The maximum watch rate is one hour.
static long	MIN_WATCH_RATE	The minimum watch rate is one half a second.
static java.lang.String	TIMER_NAME	The thread name is "EFileWatcher".

Fields inherited from interface net.sf.eBus.client.EObject

NAME_NOT_SET

Method Summary

Modifier and Type	Method	Description
static boolean	isFileWatcherRunning(java.io.File file)	Returns true if the file watcher service is running for the given subject and false otherwise.
static EMessageKey	key(java.io.File file)	Returns the EFileWatcher message key for the given file or directory.
java.lang.String	name()	Returns absolute file name as the eBus object name.
void	publishStatus(EFeedState fs, IEPublishFeed f)	Starts or stops a file watcher entry depending on upFlag.
void	shutdown()	Shuts down the file watcher thread by stopping the watch timer task, retracting the notification advertisement, and clearing the file watchers collection.
static void	startFileWatcher(java.io.File file)	Creates the eBus file watcher service using the default watch rate.
static EMessageKey	startFileWatcher(java.io.File file, long rate)	Creates an eBus file watcher service for the specified file or directory and checking at a given watch rate.
void	startup()	Advertises the file watcher service to the local JVM only.
static void	stopFileWatcher(java.io.File file)	Stops the watcher thread.

Methods inherited from class java.lang.Object

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

Field Detail

DEFAULT_WATCH_RATE

public static final long DEFAULT_WATCH_RATE

The default watch rate is one minute. Value is in milliseconds.

See Also:

Constant Field Values

MIN_WATCH_RATE

public static final long MIN_WATCH_RATE

The minimum watch rate is one half a second. Value is in milliseconds.

See Also:

Constant Field Values

MAX_WATCH_RATE

public static final long MAX_WATCH_RATE

The maximum watch rate is one hour. Value is in milliseconds.

See Also:

Constant Field Values

TIMER_NAME

public static final java.lang.String TIMER_NAME

The thread name is "EFileWatcher".

See Also:

Constant Field Values

Method Detail

name

public java.lang.String name()

Returns absolute file name as the eBus object name.

Specified by:

name in interface EObject

Returns:

eBus object name.

startup

public void startup()

Advertises the file watcher service to the local JVM only. The timer task is started with the first subscriber and stopped when there are no more subscribers.

Specified by:

startup in interface EObject

See Also:

EObject.shutdown()

shutdown

public void shutdown()

Shuts down the file watcher thread by stopping the watch timer task, retracting the notification advertisement, and clearing the file watchers collection.

Specified by:

shutdown in interface EObject

See Also:

EObject.startup()

publishStatus

public void publishStatus(EFeedState fs,
                          IEPublishFeed f)

Starts or stops a file watcher entry depending on upFlag. The notification subject is the file name.

Specified by:

publishStatus in interface EPublisher

Parameters:

fs - the f state is either up or down.

f - the f state applies to this publish f.

isFileWatcherRunning

public static boolean isFileWatcherRunning(java.io.File file)

Returns true if the file watcher service is running for the given subject and false otherwise.

Parameters:

file - check if this file or directory has a watcher.

Returns:

true if the file watcher service is running.

startFileWatcher

public static void startFileWatcher(java.io.File file)

Creates the eBus file watcher service using the default watch rate.

Parameters:

file - watch this given file or directory.

Throws:

java.lang.IllegalStateException - if the file watcher service is already running.

startFileWatcher

public static EMessageKey startFileWatcher(java.io.File file,
                                           long rate)

Creates an eBus file watcher service for the specified file or directory and checking at a given watch rate. Returns the message key for this watcher. Use the returned key to build a subscription to the newly created file watcher.

Parameters:

file - watch this given file or directory.

rate - check for file updates at this millisecond rate.

Returns:

the file watcher message key used to subscribe to this file watcher.

Throws:

java.lang.IllegalArgumentException - If file is null or if rate is < MIN_WATCH_RATE or > MAX_WATCH_RATE.

java.lang.IllegalStateException - if the file watcher service is already running but at a different watch rate.

stopFileWatcher

public static void stopFileWatcher(java.io.File file)

Stops the watcher thread. This retracts the EFileNotification advertisement and discards all subscribed file watchers.

Parameters:

file - the file or directory. Must be the same as passed to startFileWatcher(File)

See Also:

startFileWatcher(File), startFileWatcher(File, long)

key

public static EMessageKey key(java.io.File file)

Returns the EFileWatcher message key for the given file or directory.

Parameters:

file - generate the message key for this file.

Returns:

file watcher message key for the given file.