Package com.pnfsoftware.jeb.util.io

Class FileMonitor

java.lang.Object
com.pnfsoftware.jeb.util.io.FileMonitor
public class FileMonitor extends Object
File monitors can be used to create and retrieve lock on a file for exclusive operations. Locks are implemented as small files alongside the file to be locked.

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    static final long
    CHECK_MS
    Check frequency in ms, that is, the frequency at which a lock-file write-timestamp is verified.
    static final long
    TOUCH_MS
    Touch frequency in ms, that is, the frequency at which a lock-file write-timestamp is updated.

  • Method Summary

    Modifier and Type
    Method
    Description
    static FileMonitor
    create(File file)
    Create a monitor object for the provided file.
    static FileMonitor
    create(File folder, String filename, boolean singlefile)
    Create a monitor object for the provided file or group of files.
    static FileMonitor
    get(File file)
    Retrieve the existing monitor for the provided file.
    static FileMonitor
    get(File folder, String filename, boolean singlefile)
    Retrieve the existing monitor for the provided file or group of files.
    boolean
    isLocked()
    Determine whether a valid lock file exists.
    void
    lock()
    Attempt to create and refresh a valid lock file (per this monitor setting).
    void
    unlock(boolean unregister)
    Stop refreshing the lock file.

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Field Details

    • TOUCH_MS

      public static final long TOUCH_MS
      Touch frequency in ms, that is, the frequency at which a lock-file write-timestamp is updated.
      See Also:

    • CHECK_MS

      public static final long CHECK_MS
      Check frequency in ms, that is, the frequency at which a lock-file write-timestamp is verified.
      See Also:

  • Method Details

    • get

      public static FileMonitor get(File file) throws IOException
      Retrieve the existing monitor for the provided file.
      Parameters:
      file - monitored file
      Returns:
      existing monitor, or null
      Throws:
      IOException - if the file path cannot be canonicalized

    • get

      public static FileMonitor get(File folder, String filename, boolean singlefile) throws IOException
      Retrieve the existing monitor for the provided file or group of files.
      Parameters:
      folder - folder containing lock files
      filename - monitored file name or filename prefix
      singlefile - true for one lock file, false for prefix-based lock files
      Returns:
      existing monitor, or null
      Throws:
      IOException - if the folder path cannot be canonicalized

    • create

      public static FileMonitor create(File file) throws IOException
      Create a monitor object for the provided file. (Note that this method does not create any file.)
      Parameters:
      file - monitored file
      Returns:
      monitor object
      Throws:
      IOException - if the file path cannot be canonicalized

    • create

      public static FileMonitor create(File folder, String filename, boolean singlefile) throws IOException
      Create a monitor object for the provided file or group of files. (Note that this method does not create any file.)
      Parameters:
      folder - folder containing lock files
      filename - monitored file name or filename prefix
      singlefile - true for one lock file, false for prefix-based lock files
      Returns:
      monitor object
      Throws:
      IOException - if the folder path cannot be canonicalized

    • isLocked

      public boolean isLocked()
      Determine whether a valid lock file exists.
      Returns:
      true if a valid lock file (per this monitor settings) exists and is recent enough to be valid

    • lock

      public void lock()
      Attempt to create and refresh a valid lock file (per this monitor setting). This call should be mirrored by a call to unlock(boolean) when monitoring is to stop. This method does not hard fail if the lock file cannot be created (e.g. attempting to create a lock on a read-only partition).

    • unlock

      public void unlock(boolean unregister) throws InterruptedException
      Stop refreshing the lock file.
      Parameters:
      unregister - true to remove this monitor from the monitor registry
      Throws:
      InterruptedException - if interrupted while waiting for the monitor thread to stop