org.knime.core.internal
Class ReferencedFile

java.lang.Object
  org.knime.core.internal.ReferencedFile

public final class ReferencedFile
extends Object

A File wrapper with modifiable parent location. This class is used in cases in which nested elements keep a file reference and the file location (particular of the parent or the parent of the parent) may change.

Author:

Bernd Wiswedel, University of Konstanz

Constructor Summary

ReferencedFile(File rootDir)
Creates new root element.

ReferencedFile(ReferencedFile parent, String base)
Creates new sub-element.

Method Summary

boolean	equals(Object obj)
boolean	fileLockRootForVM()
void	fileUnlockRootForVM()
File	getFile() Get the File representing the full path of this referenced file element.
ReferencedFile	getParent() Get the parent of this element or null if the file's parent is not represented as a ReferencedFile object.
int	hashCode()
boolean	isRootFileLockedForVM()
void	lock() Locks this file location.
boolean	rename(String newBaseName) Renames this (base) element as an atomic operation.
String	toString() Get absolute path of the represented file.
void	unlock() Unlocks this file hierarchy.
void	writeLock() Locks this file location for writing.
void	writeUnlock() Unlocks this file hierarchy.

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

ReferencedFile

public ReferencedFile(File rootDir)

Creates new root element.

Parameters:

rootDir - The parent directory of the referenced file location.

Throws:

NullPointerException - If the argument is null

ReferencedFile

public ReferencedFile(ReferencedFile parent,
                      String base)

Creates new sub-element.

Parameters:

parent - The parent location

base - The name of this file

Throws:

NullPointerException - If either argument is null

Method Detail

lock

public void lock()

Locks this file location. Asynchronous invocations of rename(String) will block until unlock() is called. It will also disable the renaming of any element further up the hierarchy. Parallel reading of the resource is still possibly.

unlock

public void unlock()

Unlocks this file hierarchy. (Counterpart to lock()).

Throws:

IllegalMonitorStateException - If monitor is not held by current thread.

writeLock

public void writeLock()

Locks this file location for writing. See ReentrantReadWriteLock.writeLock().

writeUnlock

public void writeUnlock()

Unlocks this file hierarchy. (Counterpart to writeLock()).

Throws:

IllegalMonitorStateException - If monitor is not held by current thread.

fileLockRootForVM

public boolean fileLockRootForVM()

fileUnlockRootForVM

public void fileUnlockRootForVM()

isRootFileLockedForVM

public boolean isRootFileLockedForVM()

rename

public boolean rename(String newBaseName)

Renames this (base) element as an atomic operation. "This" element refers the current element in the hierarchy. The operation will block until all read/write operations have finished. If the associated file location exists (i.e. the file returned by getFile() exists, it will also be renamed.

Parameters:

newBaseName - The new name

Returns:

whether the rename was successful: it returns true in two cases: (i) the file exists and was successfully renamed or (ii) if it does not exist (being positive that it has not been created just yet)

Throws:

NullPointerException - If argument is null

getFile

public File getFile()

Get the File representing the full path of this referenced file element. Please note that the returned file may be renamed after this method returns. In order to circumvent this, you typically write code as follows:

 ReferencedFile m_refFile = ... // this element
 m_refFile.lock();
 try {
   File file = m_refFile.getFile();
   // do something with this file
 } finally {
   m_refFile.unlock();
 }
 

Returns:

The file representing the full path of this referenced file

getParent

public ReferencedFile getParent()

Get the parent of this element or null if the file's parent is not represented as a ReferencedFile object.

Returns:

The parent or null.

equals

public boolean equals(Object obj)

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object

toString

public String toString()

Get absolute path of the represented file.

Overrides:

toString in class Object