uk.ac.vamsas.client.simpleclient
Class Lock

java.lang.Object
  uk.ac.vamsas.client.simpleclient.Lock

Direct Known Subclasses:

FileLock, NativeLock

public abstract class Lock

extends java.lang.Object

transient object representing a file lock This lock should hold for all processes interacting in a session.

Author:

jimp

Field Summary

protected org.apache.commons.logging.Log	log
protected java.io.RandomAccessFile	rafile

Constructor Summary

protected

Lock(java.io.File lockfile) creates a valid Lock (test with isLocked) if a lock could be obtained for lockfile

Method Summary

protected void	finalize()
java.io.BufferedInputStream	getBufferedInputStream(boolean atStart) return buffered input stream for locked file.
abstract java.io.BufferedOutputStream	getBufferedOutputStream(boolean clear) return buffered output stream to locked file.
abstract java.io.FileInputStream	getFileInputStream(boolean atStart) gets Locked Stream for reading from
abstract java.io.FileOutputStream	getFileOutputStream(boolean clear) gets Locked stream to write to FileInput always starts at the *end* of the file (after any truncation)
abstract java.nio.channels.FileChannel	getRaChannel()
abstract java.io.RandomAccessFile	getRaFile()
abstract boolean	isLocked()
abstract boolean	isTargetLockFile(java.io.File afile) test whether the given file is a target or related to the lock on the target file.
abstract long	length() safe lock target length() function.
abstract void	release() release lock and close all managed channels to file
abstract void	release(boolean closeChannel) optionally close the open random access channel on the file when releasing lock

Methods inherited from class java.lang.Object

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

Field Detail

log

protected org.apache.commons.logging.Log log

rafile

protected java.io.RandomAccessFile rafile

Constructor Detail

Lock

protected Lock(java.io.File lockfile)

creates a valid Lock (test with isLocked) if a lock could be obtained for lockfile

Parameters:

lockfile -

Method Detail

isTargetLockFile

public abstract boolean isTargetLockFile(java.io.File afile)

test whether the given file is a target or related to the lock on the target file.

Parameters:

afile - a file

Returns:

true if target is locked and afile is related to target

isLocked

public abstract boolean isLocked()

Returns:

true if lock is held on the target

release

public abstract void release()

release lock and close all managed channels to file

release

public abstract void release(boolean closeChannel)

optionally close the open random access channel on the file when releasing lock

Parameters:

closeChannel -

getFileInputStream

public abstract java.io.FileInputStream getFileInputStream(boolean atStart)
                                                    throws java.io.IOException

gets Locked Stream for reading from

Parameters:

atStart - true to start reading at beginning of file.

Returns:

null if file not locked

Throws:

java.io.IOException

getFileOutputStream

public abstract java.io.FileOutputStream getFileOutputStream(boolean clear)
                                                      throws java.io.IOException

gets Locked stream to write to FileInput always starts at the *end* of the file (after any truncation)

Parameters:

clear - true means file will be cleared to zero length

Returns:

null if file is not locked

Throws:

java.io.IOException

getBufferedOutputStream

public abstract java.io.BufferedOutputStream getBufferedOutputStream(boolean clear)
                                                              throws java.io.IOException

return buffered output stream to locked file.

Parameters:

clear - - true means file is truncated to 0 length before writing

Returns:

Throws:

java.io.IOException

finalize

protected void finalize()
                 throws java.lang.Throwable

Throws:

java.lang.Throwable

getBufferedInputStream

public java.io.BufferedInputStream getBufferedInputStream(boolean atStart)
                                                   throws java.io.IOException

return buffered input stream for locked file.

Parameters:

atStart - - true means read from begining of file

Returns:

null if file is not locked.

Throws:

java.io.IOException

length

public abstract long length()

safe lock target length() function.

Returns:

-1 for non-lockable target, otherwise target's file length

getRaFile

public abstract java.io.RandomAccessFile getRaFile()
                                            throws java.io.IOException

Throws:

java.io.IOException

getRaChannel

public abstract java.nio.channels.FileChannel getRaChannel()
                                                    throws java.io.IOException

Throws:

java.io.IOException