org.apache.commons.vfs.impl
Class DefaultFileMonitor

java.lang.Object
  org.apache.commons.vfs.impl.DefaultFileMonitor

All Implemented Interfaces:

FileMonitor, Runnable

public class DefaultFileMonitor

extends Object

implements Runnable, FileMonitor

A polling FileMonitor implementation.

The DefaultFileMonitor is a Thread based polling file system monitor with a 1 second delay.

Design:

There is a Map of monitors known as FileMonitorAgents. With the thread running, each FileMonitorAgent object is asked to "check" on the file it is responsible for. To do this check, the cache is cleared.

• If the file existed before the refresh and it no longer exists, a delete event is fired.
• If the file existed before the refresh and it still exists, check the last modified timestamp to see if that has changed.
• If it has, fire a change event.

With each file delete, the FileMonitorAgent of the parent is asked to re-build its list of children, so that they can be accurately checked when there are new children.
New files are detected during each "check" as each file does a check for new children. If new children are found, create events are fired recursively if recursive descent is enabled.

For performance reasons, added a delay that increases as the number of files monitored increases. The default is a delay of 1 second for every 1000 files processed.

Example usage:

 FileSystemManager fsManager = VFS.getManager();
 FileObject listendir = fsManager.resolveFile("/home/username/monitored/");
 

 DefaultFileMonitor fm = new DefaultFileMonitor(new CustomFileListener());
 fm.setRecursive(true);
 fm.addFile(listendir);
 fm.start();
 

(where CustomFileListener is a class that implements the FileListener interface.)

Version:

$Revision: 484943 $ $Date: 2006-12-09 08:42:06 +0100 (Sa, 09 Dez 2006) $

Author:

Christopher Ottley

Constructor Summary

DefaultFileMonitor(FileListener listener)

Method Summary

void	addFile(FileObject file) Adds a file to be monitored.
int	getChecksPerRun() get the number of files to check per run
long	getDelay() Get the delay between runs
boolean	isRecursive() Access method to get the recursive setting when adding files for monitoring.
protected void	queueAddFile(FileObject file) Queues a file for addition to be monitored.
protected void	queueRemoveFile(FileObject file) Queues a file for removal from being monitored.
void	removeFile(FileObject file) Removes a file from being monitored.
void	run() Asks the agent for each file being monitored to check its file for changes.
void	setChecksPerRun(int checksPerRun) set the number of files to check per run.
void	setDelay(long delay) Set the delay between runs
void	setRecursive(boolean newRecursive) Access method to set the recursive setting when adding files for monitoring.
void	start() Starts monitoring the files that have been added.
void	stop() Stops monitoring the files that have been added.

Methods inherited from class java.lang.Object

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

Constructor Detail

DefaultFileMonitor

public DefaultFileMonitor(FileListener listener)

Method Detail

isRecursive

public boolean isRecursive()

Access method to get the recursive setting when adding files for monitoring.

setRecursive

public void setRecursive(boolean newRecursive)

Access method to set the recursive setting when adding files for monitoring.

addFile

public void addFile(FileObject file)

Adds a file to be monitored.

Specified by:

addFile in interface FileMonitor

removeFile

public void removeFile(FileObject file)

Removes a file from being monitored.

Specified by:

removeFile in interface FileMonitor

queueRemoveFile

protected void queueRemoveFile(FileObject file)

Queues a file for removal from being monitored.

getDelay

public long getDelay()

Get the delay between runs

setDelay

public void setDelay(long delay)

Set the delay between runs

getChecksPerRun

public int getChecksPerRun()

get the number of files to check per run

setChecksPerRun

public void setChecksPerRun(int checksPerRun)

set the number of files to check per run. a additional delay will be added if there are more files to check

Parameters:

checksPerRun - a value less than 1 will disable this feature

queueAddFile

protected void queueAddFile(FileObject file)

Queues a file for addition to be monitored.

start

public void start()

Starts monitoring the files that have been added.

stop

public void stop()

Stops monitoring the files that have been added.

run

public void run()

Asks the agent for each file being monitored to check its file for changes.

Specified by:

run in interface Runnable