// Copyright (c) 2003-2012, Jodd Team (jodd.org). All Rights Reserved.
package jodd.io;
import java.io.File;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import java.util.Timer;
import java.util.TimerTask;
import java.util.HashSet;
/**
* Monitoring disk files changes. Change event is broadcasted to all registered listeners.
*
* @see jodd.io.FileChangeListener
*/
public class FileMonitor {
protected final Map<File, Long> files;
protected final Set<FileChangeListener> listeners;
protected final long pollingInterval;
protected Timer timer;
protected final Object lock = new Object();
/**
* Creates a file monitor instance with specified polling interval in ms.
*/
public FileMonitor(long pollingInterval) {
this.pollingInterval = pollingInterval;
files = new HashMap<File, Long>();
listeners = new HashSet<FileChangeListener>();
start();
}
/**
* Starts the file monitoring polling, after it was stopped.
*/
public void start() {
if (timer == null) {
timer = new Timer(true);
timer.schedule(new FileMonitorNotifier(), 0, pollingInterval);
}
}
/**
* Stops the file monitor polling.
*/
public void stop() {
if (timer != null) {
timer.cancel();
timer = null;
}
}
/**
* Adds file to listen for. File may be any file or folder,
* including a non-existing file in the case where the
* creating of the file is to be trapped.
*/
public void monitorFile(File file) {
synchronized (lock) {
if (files.containsKey(file) == false) {
long modifiedTime = file.exists() ? file.lastModified() : -1;
files.put(file, new Long(modifiedTime));
}
}
}
/**
* Removes specified file for listening.
*/
public void releaseFile(File file) {
synchronized (lock) {
files.remove(file);
}
}
/**
* Adds listener to this file monitor.
*/
public void registerListener(FileChangeListener fileChangeListener) {
synchronized (lock) {
for (FileChangeListener listener : listeners) {
if (listener == fileChangeListener) {
return;
}
}
listeners.add(fileChangeListener);
}
}
/**
* Removes listener from this file monitor.
*/
public void removeListener(FileChangeListener fileChangeListener) {
synchronized (lock) {
Iterator<FileChangeListener> i = listeners.iterator();
while(i.hasNext()) {
FileChangeListener listener = i.next();
if (listener == fileChangeListener) {
i.remove();
break;
}
}
}
}
/**
* Removes all file listeners/
*/
public void removeAllListeners() {
synchronized (lock) {
listeners.clear();
}
}
/**
* Actual file monitor timer task.
*/
protected class FileMonitorNotifier extends TimerTask {
@Override
public void run() {
synchronized (lock) {
for (Map.Entry<File, Long> entry : files.entrySet()) {
File file = entry.getKey();
long lastModifiedTime = entry.getValue().longValue();
long newModifiedTime = file.exists() ? file.lastModified() : -1;
// check if file has been changed
if (newModifiedTime != lastModifiedTime) {
// store new modified time
entry.setValue(new Long(newModifiedTime));
// notify listeners
for (FileChangeListener listener : listeners) {
listener.onFileChange(file);
}
}
}
}
}
}
}
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