Package org.apache.commons.io

# Class FileCleaningTracker

java.lang.Object
org.apache.commons.io.FileCleaningTracker

public class FileCleaningTracker extends 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(javax.servlet.ServletContextEvent)` or similar.

- ## Constructor Summary

  Constructors
  Constructor
  Description
  `FileCleaningTracker()`
  Construct a new instance.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `void`
  `exitWhenFinished()`
  Call this method to cause the file cleaner thread to terminate when there are no more objects being tracked for deletion.
  `List<String>`
  `getDeleteFailures()`
  Gets a copy of the file paths that failed to delete.
  `int`
  `getTrackCount()`
  Gets the number of files currently being tracked, and therefore awaiting deletion.
  `void`
  `track(File file, Object marker)`
  Tracks 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)`
  Tracks the specified file, using the provided marker, deleting the file when the marker instance is garbage collected.
  `void`
  `track(String path, Object marker)`
  Tracks 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)`
  Tracks the specified file, using the provided marker, deleting the file when the marker instance is garbage collected.
  `void`
  `track(Path file, Object marker)`
  Tracks the specified file, using the provided marker, deleting the file when the marker instance is garbage collected.
  `void`
  `track(Path file, Object marker, FileDeleteStrategy deleteStrategy)`
  Tracks 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`

- ## Constructor Details

  - ### FileCleaningTracker

    public FileCleaningTracker()
    Construct a new instance.

- ## Method Details

  - ### 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.

  - ### getDeleteFailures

    public List<String> getDeleteFailures()
    Gets a copy of the file paths that failed to delete.
    Returns:
      a copy of the file paths that failed to delete
    Since:
      2.0

  - ### getTrackCount

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

  - ### track

    public void track(File file, Object marker)
    Tracks the specified file, using the provided marker, deleting the file when the marker instance is garbage collected. The `normal` deletion strategy will be used.
    Parameters:
      `file` - the file to be tracked, not null
      `marker` - the marker object used to track the file, not null
    Throws:
      `NullPointerException` - if the file is null

  - ### track

    public void track(File file, Object marker, FileDeleteStrategy deleteStrategy)
    Tracks 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 null
      `marker` - the marker object used to track the file, not null
      `deleteStrategy` - the strategy to delete the file, null means normal
    Throws:
      `NullPointerException` - if the file is null

  - ### track

    public void track(Path file, Object marker)
    Tracks the specified file, using the provided marker, deleting the file when the marker instance is garbage collected. The `normal` deletion strategy will be used.
    Parameters:
      `file` - the file to be tracked, not null
      `marker` - the marker object used to track the file, not null
    Throws:
      `NullPointerException` - if the file is null
    Since:
      2.14.0

  - ### track

    public void track(Path file, Object marker, FileDeleteStrategy deleteStrategy)
    Tracks 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 null
      `marker` - the marker object used to track the file, not null
      `deleteStrategy` - the strategy to delete the file, null means normal
    Throws:
      `NullPointerException` - if the file is null
    Since:
      2.14.0

  - ### track

    public void track(String path, Object marker)
    Tracks the specified file, using the provided marker, deleting the file when the marker instance is garbage collected. The `normal` deletion strategy will be 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
    Throws:
      `NullPointerException` - if the path is null

  - ### track

    public void track(String path, Object marker, FileDeleteStrategy deleteStrategy)
    Tracks 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 null
      `marker` - the marker object used to track the file, not null
      `deleteStrategy` - the strategy to delete the file, null means normal
    Throws:
      `NullPointerException` - if the path is null