com.arjuna.ats.arjuna.utils
Class FileLock

java.lang.Object
  com.arjuna.ats.arjuna.utils.FileLock

public class FileLock
extends Object

Sometimes it is necessary to lock a file at the disk level. Since there is no native Java way of locking a file, we have to implement our own. Unfortunately, it appears as though we can only assume that rename is atomic. We base the locking on this then: rename the lock file and update it with the lock owners. How it works: for every file we want to lock we create an _lock file. This file contains information about who is locking the file, and in what mode. (Single writer, multiple readers.) To guarantee atomicity of update, we move (rename) the actual file each time we want to lock it and update the lock file. When this is done, we move (rename) it back. Almost like a two-phase commit protocol! Currently we don't support re-entrant locking.

Since:

JTS 1.0.

Version:

$Id: FileLock.java 2342 2006-03-30 13:06:17Z $

Author:

Mark Little (mark@arjuna.com)

Field Summary

static int	defaultRetry
static int	defaultTimeout
static int	F_RDLCK
static int	F_WRLCK

Constructor Summary

FileLock(File name)

FileLock(File name, long timeout, long retry)

FileLock(String name)

Method Summary

boolean	lock(int lmode)
boolean	lock(int lmode, boolean create)
static String	modeString(int mode)
boolean	unlock()

Methods inherited from class java.lang.Object

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

Field Detail

F_RDLCK

public static final int F_RDLCK

See Also:

Constant Field Values

F_WRLCK

public static final int F_WRLCK

See Also:

Constant Field Values

defaultTimeout

public static final int defaultTimeout

See Also:

Constant Field Values

defaultRetry

public static final int defaultRetry

See Also:

Constant Field Values

Constructor Detail

FileLock

public FileLock(String name)

FileLock

public FileLock(File name)

FileLock

public FileLock(File name,
                long timeout,
                long retry)

Method Detail

lock

public boolean lock(int lmode)

Since:

JTS 2.1.1.

lock

public boolean lock(int lmode,
                    boolean create)

unlock

public boolean unlock()

modeString

public static String modeString(int mode)