Package org.apache.commons.io

Class FileCleaningTracker

  • public class FileCleaningTracker
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(javax.servlet.ServletContextEvent) or similar.

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      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.
      java.util.List<java.lang.String> getDeleteFailures()
      Return the file paths that failed to delete.
      int getTrackCount()
      Retrieve the number of files currently being tracked, and therefore awaiting deletion.
      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.
      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.
      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.
      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

    • Constructor Detail

      • FileCleaningTracker

        public FileCleaningTracker()

    • Method Detail

      • track

        public 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. 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:
        java.lang.NullPointerException - if the file is null

      • track

        public 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. 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:
        java.lang.NullPointerException - if the file is null

      • track

        public 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. 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:
        java.lang.NullPointerException - if the path is null

      • track

        public 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. 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:
        java.lang.NullPointerException - if the path is null

      • getTrackCount

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

      • getDeleteFailures

        public java.util.List<java.lang.String> 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.