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java.lang.Objectorg.apache.commons.io.FileCleaner
public class FileCleaner
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.
Nested Class Summary | |
---|---|
(package private) static class |
FileCleaner.Reaper
The reaper thread. |
(package private) static class |
FileCleaner.Tracker
Inner class which acts as the reference for a file pending deletion. |
Field Summary | |
---|---|
(package private) static boolean |
exitWhenFinished
Whether to terminate the thread when the tracking is complete. |
(package private) static java.lang.ref.ReferenceQueue |
q
Queue of Tracker instances being watched. |
(package private) static java.lang.Thread |
reaper
The thread that will clean up registered files. |
(package private) static java.util.Collection |
trackers
Collection of Tracker instances in existence. |
Constructor Summary | |
---|---|
FileCleaner()
|
Method Summary | |
---|---|
private static void |
addTracker(java.lang.String path,
java.lang.Object marker,
FileDeleteStrategy deleteStrategy)
Adds a tracker to the list of trackers. |
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 int |
getTrackCount()
Retrieve the number of files currently being tracked, and therefore awaiting deletion. |
static void |
track(java.io.File file,
java.lang.Object marker)
Track the specified file, using the provided marker, deleting the file when the marker instance is garbage collected. |
static void |
track(java.io.File file,
java.lang.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(java.lang.String path,
java.lang.Object marker)
Track the specified file, using the provided marker, deleting the file when the marker instance is garbage collected. |
static void |
track(java.lang.String path,
java.lang.Object marker,
FileDeleteStrategy deleteStrategy)
Track the specified file, using the provided marker, deleting the file when the marker instance is garbage collected. |
Methods inherited from class java.lang.Object |
---|
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Field Detail |
---|
static java.lang.ref.ReferenceQueue q
Tracker
instances being watched.
static java.util.Collection trackers
Tracker
instances in existence.
static volatile boolean exitWhenFinished
static java.lang.Thread reaper
Constructor Detail |
---|
public FileCleaner()
Method Detail |
---|
public static void track(java.io.File file, java.lang.Object marker)
normal
deletion strategy will be used.
file
- the file to be tracked, not nullmarker
- the marker object used to track the file, not null
java.lang.NullPointerException
- if the file is nullpublic static void track(java.io.File file, java.lang.Object marker, FileDeleteStrategy deleteStrategy)
file
- the file to be tracked, not nullmarker
- the marker object used to track the file, not nulldeleteStrategy
- the strategy to delete the file, null means normal
java.lang.NullPointerException
- if the file is nullpublic static void track(java.lang.String path, java.lang.Object marker)
normal
deletion strategy will be used.
path
- the full path to the file to be tracked, not nullmarker
- the marker object used to track the file, not null
java.lang.NullPointerException
- if the path is nullpublic static void track(java.lang.String path, java.lang.Object marker, FileDeleteStrategy deleteStrategy)
path
- the full path to the file to be tracked, not nullmarker
- the marker object used to track the file, not nulldeleteStrategy
- the strategy to delete the file, null means normal
java.lang.NullPointerException
- if the path is nullprivate static void addTracker(java.lang.String path, java.lang.Object marker, FileDeleteStrategy deleteStrategy)
path
- the full path to the file to be tracked, not nullmarker
- the marker object used to track the file, not nulldeleteStrategy
- the strategy to delete the file, null means normalpublic static int getTrackCount()
public static void exitWhenFinished()
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.
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