org.apache.commons.io

Class FileCleaner


public class FileCleaner
extends java.lang.Object

Keeps track of files awaiting deletion, and deletes them when an associated marker object is reclaimed by the garbage collector.

This utility creates a background thread to handle file deletion. Each file to be deleted is registered with a handler object. When the handler object is garbage collected, the file is deleted.

In an environment with multiple class loaders (a servlet container, for example), you should consider stopping the background thread if it is no longer needed. This is done by invoking the method exitWhenFinished(), typically in javax.servlet.ServletContextListener.contextDestroyed or similar.

Version:
$Id: FileCleaner.java 551002 2007-06-27 01:33:05Z jochen $
Authors:
Noel Bergman
Martin Cooper

Field Summary

(package private) static FileCleaningTracker
theInstance
The instance to use for the deprecated, static methods.

Method Summary

static void
exitWhenFinished()
Call this method to cause the file cleaner thread to terminate when there are no more objects being tracked for deletion.
static FileCleaningTracker
getInstance()
Returns the singleton instance, which is used by the deprecated, static methods.
static int
getTrackCount()
Retrieve the number of files currently being tracked, and therefore awaiting deletion.
static void
track(File file, Object marker)
Track the specified file, using the provided marker, deleting the file when the marker instance is garbage collected.
static void
track(File file, Object marker, FileDeleteStrategy deleteStrategy)
Track the specified file, using the provided marker, deleting the file when the marker instance is garbage collected.
static void
track(String path, Object marker)
Track the specified file, using the provided marker, deleting the file when the marker instance is garbage collected.
static void
track(String path, Object marker, FileDeleteStrategy deleteStrategy)
Track the specified file, using the provided marker, deleting the file when the marker instance is garbage collected.

Field Details

theInstance

(package private) static final FileCleaningTracker theInstance
The instance to use for the deprecated, static methods.

Method Details

exitWhenFinished

public static void exitWhenFinished()
Call this method to cause the file cleaner thread to terminate when there are no more objects being tracked for deletion.

In a simple environment, you don't need this method as the file cleaner thread will simply exit when the JVM exits. In a more complex environment, with multiple class loaders (such as an application server), you should be aware that the file cleaner thread will continue running even if the class loader it was started from terminates. This can consitute a memory leak.

For example, suppose that you have developed a web application, which contains the commons-io jar file in your WEB-INF/lib directory. In other words, the FileCleaner class is loaded through the class loader of your web application. If the web application is terminated, but the servlet container is still running, then the file cleaner thread will still exist, posing a memory leak.

This method allows the thread to be terminated. Simply call this method in the resource cleanup code, such as javax.servlet.ServletContextListener.contextDestroyed. One called, no new objects can be tracked by the file cleaner.


getInstance

public static FileCleaningTracker getInstance()
Returns the singleton instance, which is used by the deprecated, static methods. This is mainly useful for code, which wants to support the new FileCleaningTracker class while maintain compatibility with the deprecated FileCleaner.

getTrackCount

public static int getTrackCount()
Retrieve the number of files currently being tracked, and therefore awaiting deletion.
Returns:
the number of files being tracked

track

public static void track(File file,
                         Object marker)
Parameters:
file - the file to be tracked, not null
marker - the marker object used to track the file, not null

track

public static void track(File file,
                         Object marker,
                         FileDeleteStrategy deleteStrategy)
Track the specified file, using the provided marker, deleting the file when the marker instance is garbage collected. The speified deletion strategy is used.
Parameters:
file - the file to be tracked, not null
marker - the marker object used to track the file, not null
deleteStrategy - the strategy to delete the file, null means normal

track

public static void track(String path,
                         Object marker)
Parameters:
path - the full path to the file to be tracked, not null
marker - the marker object used to track the file, not null

track

public static void track(String path,
                         Object marker,
                         FileDeleteStrategy deleteStrategy)
Track the specified file, using the provided marker, deleting the file when the marker instance is garbage collected. The speified deletion strategy is used.
Parameters:
path - the full path to the file to be tracked, not null
marker - the marker object used to track the file, not null
deleteStrategy - the strategy to delete the file, null means normal