/*
* Copyright (C) The Apache Software Foundation. All rights reserved.
*
* This software is published under the terms of the Apache Software License
* version 1.1, a copy of which has been included with this distribution in
* the LICENSE file.
*/
// Contributors: Mathias Bogaert
package org.apache.log4j.helpers;
import java.io.File;
import org.apache.log4j.helpers.LogLog;
/**
Check every now and then that a certain file has not changed. If it
has, then call the {@link #doOnChange} method.
@author Ceki Gülcü
@since version 0.9.1 */
public abstract class FileWatchdog extends Thread {
/**
The default delay between every file modification check, set to 60
seconds. */
static final public long DEFAULT_DELAY = 60000;
/**
The name of the file to observe for changes.
*/
protected String filename;
/**
The delay to observe between every check. By default set {@link
#DEFAULT_DELAY}. */
protected long delay = DEFAULT_DELAY;
File file;
long lastModif = 0;
boolean warnedAlready = false;
boolean interrupted = false;
protected
FileWatchdog(String filename) {
this.filename = filename;
file = new File(filename);
setDaemon(true);
checkAndConfigure();
}
/**
Set the delay to observe between each check of the file changes.
*/
public
void setDelay(long delay) {
this.delay = delay;
}
abstract
protected
void doOnChange();
protected
void checkAndConfigure() {
boolean fileExists;
try {
fileExists = file.exists();
} catch(SecurityException e) {
LogLog.warn("Was not allowed to read check file existance, file:["+
filename+"].");
interrupted = true; // there is no point in continuing
return;
}
if(fileExists) {
long l = file.lastModified(); // this can also throw a SecurityException
if(l > lastModif) { // however, if we reached this point this
lastModif = l; // is very unlikely.
doOnChange();
warnedAlready = false;
}
} else {
if(!warnedAlready) {
LogLog.debug("["+filename+"] does not exist.");
warnedAlready = true;
}
}
}
public
void run() {
while(!interrupted) {
try {
Thread.currentThread().sleep(delay);
} catch(InterruptedException e) {
// no interruption expected
}
checkAndConfigure();
}
}
}
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