Class FileCleaningTracker
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(javax.servlet.ServletContextEvent)
or similar.
-
Nested Class Summary
Nested ClassesModifier and TypeClassDescriptionprivate final class
The reaper thread.private static final class
Inner class which acts as the reference for a file pending deletion. -
Field Summary
FieldsModifier and TypeFieldDescriptionCollection of File paths that failed to delete.(package private) boolean
Whether to terminate the thread when the tracking is complete.(package private) ReferenceQueue<Object>
Queue ofTracker
instances being watched.(package private) Thread
The thread that will clean up registered files.(package private) final Collection<FileCleaningTracker.Tracker>
Collection ofTracker
instances in existence. -
Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptionprivate void
addTracker
(String path, Object marker, FileDeleteStrategy deleteStrategy) Adds a tracker to the list of trackers.void
Call this method to cause the file cleaner thread to terminate when there are no more objects being tracked for deletion.Return the file paths that failed to delete.int
Retrieve the number of files currently being tracked, and therefore awaiting deletion.void
Track the specified file, using the provided marker, deleting the file when the marker instance is garbage collected.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.void
Track the specified file, using the provided marker, deleting the file when the marker instance is garbage collected.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
-
q
Queue ofTracker
instances being watched. -
trackers
Collection ofTracker
instances in existence. -
deleteFailures
Collection of File paths that failed to delete. -
exitWhenFinished
volatile boolean exitWhenFinishedWhether to terminate the thread when the tracking is complete. -
reaper
Thread reaperThe thread that will clean up registered files.
-
-
Constructor Details
-
FileCleaningTracker
public FileCleaningTracker()
-
-
Method Details
-
track
Track the specified file, using the provided marker, deleting the file when the marker instance is garbage collected. Thenormal
deletion strategy will be used.- Parameters:
file
- the file to be tracked, not nullmarker
- the marker object used to track the file, not null- Throws:
NullPointerException
- if the file is null
-
track
Track the specified file, using the provided marker, deleting the file when the marker instance is garbage collected. The specified deletion strategy is used.- Parameters:
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- Throws:
NullPointerException
- if the file is null
-
track
Track the specified file, using the provided marker, deleting the file when the marker instance is garbage collected. Thenormal
deletion strategy will be used.- Parameters:
path
- the full path to the file to be tracked, not nullmarker
- the marker object used to track the file, not null- Throws:
NullPointerException
- if the path is null
-
track
Track the specified file, using the provided marker, deleting the file when the marker instance is garbage collected. The specified deletion strategy is used.- Parameters:
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- Throws:
NullPointerException
- if the path is null
-
addTracker
Adds a tracker to the list of trackers.- Parameters:
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
-
getTrackCount
public int getTrackCount()Retrieve the number of files currently being tracked, and therefore awaiting deletion.- Returns:
- the number of files being tracked
-
getDeleteFailures
Return the file paths that failed to delete.- Returns:
- the file paths that failed to delete
- Since:
- 2.0
-
exitWhenFinished
public 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 constitute 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(javax.servlet.ServletContextEvent)
. Once called, no new objects can be tracked by the file cleaner.
-