org.apache.commons.vfs2.impl

Class DefaultFileMonitor

java.lang.Object

org.apache.commons.vfs2.impl.DefaultFileMonitor

All Implemented Interfaces:

Runnable, FileMonitor

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.)

Constructor Summary

Constructors

Constructor and Description
DefaultFileMonitor(FileListener listener) Creates a new instance with the given listener.

Method Summary

Modifier and Type	Method and Description
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)

Creates a new instance with the given listener.

Parameters:

listener - the listener.

Method Detail

isRecursive

public boolean isRecursive()

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

Returns:

true if monitoring is enabled for children.

setRecursive

public void setRecursive(boolean newRecursive)

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

Parameters:

newRecursive - true if monitoring should be enabled for children.

addFile

public void addFile(FileObject file)

Adds a file to be monitored.

Specified by:

addFile in interface FileMonitor

Parameters:

file - The FileObject to monitor.

removeFile

public void removeFile(FileObject file)

Removes a file from being monitored.

Specified by:

removeFile in interface FileMonitor

Parameters:

file - The FileObject to remove from monitoring.

queueRemoveFile

protected void queueRemoveFile(FileObject file)

Queues a file for removal from being monitored.

Parameters:

file - The FileObject to be removed from being monitored.

getDelay

public long getDelay()

Get the delay between runs.

Returns:

The delay period.

setDelay

public void setDelay(long delay)

Set the delay between runs.

Parameters:

delay - The delay period.

getChecksPerRun

public int getChecksPerRun()

get the number of files to check per run.

Returns:

The number of files to check per iteration.

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.

Parameters:

file - The FileObject to add.

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