org.xins.common.io
Class FileWatcher

java.lang.Object
  java.lang.Thread
      org.xins.common.io.FileWatcher

All Implemented Interfaces:

Runnable

public final class FileWatcher

extends Thread

File watcher thread. This thread checks if a file changed and if it has, it notifies the listener. The check is performed every n seconds, where n can be configured.

Initially this thread will be a daemon thread. This can be changed by calling Thread.setDaemon(boolean).

Since:

XINS 1.0.0

Version:

$Revision: 1.31 $ $Date: 2006/08/28 09:12:34 $

Author:

Ernst de Haan

Nested Class Summary

static interface

FileWatcher.Listener Interface for file watcher listeners.

Field Summary

Fields inherited from class java.lang.Thread

MAX_PRIORITY, MIN_PRIORITY, NORM_PRIORITY

Constructor Summary

FileWatcher(String file, FileWatcher.Listener listener)
Creates a new FileWatcher for the specified file.

FileWatcher(String file, int interval, FileWatcher.Listener listener)
Creates a new FileWatcher for the specified file, with the specified interval.

Method Summary

void	check() Checks if the file changed.
void	end() Stops this thread.
int	getInterval() Returns the current interval.
void	run() Runs this thread.
void	setInterval(int newInterval) Changes the file check interval.

Methods inherited from class java.lang.Thread

activeCount, checkAccess, countStackFrames, currentThread, destroy, dumpStack, enumerate, getContextClassLoader, getName, getPriority, getThreadGroup, holdsLock, interrupt, interrupted, isAlive, isDaemon, isInterrupted, join, join, join, resume, setContextClassLoader, setDaemon, setName, setPriority, sleep, sleep, start, stop, stop, suspend, toString, yield

Methods inherited from class java.lang.Object

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

Constructor Detail

FileWatcher

public FileWatcher(String file,
                   int interval,
                   FileWatcher.Listener listener)
            throws IllegalArgumentException

Creates a new FileWatcher for the specified file, with the specified interval.

Parameters:

file - the name of the file to watch, cannot be null.

interval - the interval in seconds, must be greater than or equal to 1.

listener - the object to notify on events, cannot be null.

Throws:

IllegalArgumentException - if file == null || listener == null || interval < 1

FileWatcher

public FileWatcher(String file,
                   FileWatcher.Listener listener)
            throws IllegalArgumentException

Creates a new FileWatcher for the specified file.

The interval must be set before the thread can be started.

Parameters:

file - the name of the file to watch, cannot be null.

listener - the object to notify on events, cannot be null.

Throws:

IllegalArgumentException - if file == null || listener == null

Since:

XINS 1.2.0

Method Detail

run

public void run()
         throws IllegalStateException

Runs this thread. This method should not be called directly, call Thread.start() instead. That method will call this method.

Throws:

IllegalStateException - if Thread.currentThread() != this, if the thread is already running or should stop, or if the interval was not set yet.

getInterval

public int getInterval()

Returns the current interval.

Returns:

interval the current interval in seconds, always greater than or equal to 1, except if the interval is not initialized yet, in which case 0 is returned.

setInterval

public void setInterval(int newInterval)
                 throws IllegalArgumentException

Changes the file check interval.

Parameters:

newInterval - the new interval in seconds, must be greater than or equal to 1.

Throws:

IllegalArgumentException - if interval < 1

end

public void end()
         throws IllegalStateException

Stops this thread.

Throws:

IllegalStateException - if the thread is currently not running or already stopping.

check

public void check()

Checks if the file changed. The following algorithm is used:

• check if the file is readable;
• if so, then determine when the file was last modified;
• if either the file existence check or the file modification check causes a SecurityException to be thrown, then FileWatcher.Listener.securityException(SecurityException) is called and the method returns;
• otherwise if the file is not readable (it may not exist), then FileWatcher.Listener.fileNotFound() is called and the method returns;
• otherwise if the file is readable, but previously was not, then FileWatcher.Listener.fileFound() is called and the method returns;
• otherwise if the file was modified, then FileWatcher.Listener.fileModified() is called and the method returns;
• otherwise the file was not modified, then FileWatcher.Listener.fileNotModified() is called and the method returns.

Since:

XINS 1.2.0