org.apache.log4j.helpers.FileWatchdog Maven / Gradle / Ivy
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
// Contributors: Mathias Bogaert
package org.apache.log4j.helpers;
import java.io.File;
/**
* Checks every now and then that a certain file has not changed. If it has, then call the {@link #doOnChange} method.
*
* @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 = 60_000;
/**
* 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 lastModified;
boolean warnedAlready;
boolean interrupted;
protected FileWatchdog(final String fileName) {
super("FileWatchdog");
this.filename = fileName;
this.file = new File(fileName);
setDaemon(true);
checkAndConfigure();
}
protected void checkAndConfigure() {
boolean fileExists;
try {
fileExists = file.exists();
} catch (final 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) {
final long fileLastMod = file.lastModified(); // this can also throw a SecurityException
if (fileLastMod > lastModified) { // however, if we reached this point this
lastModified = fileLastMod; // is very unlikely.
doOnChange();
warnedAlready = false;
}
} else {
if (!warnedAlready) {
LogLog.debug("[" + filename + "] does not exist.");
warnedAlready = true;
}
}
}
abstract protected void doOnChange();
@Override
public void run() {
while (!interrupted) {
try {
Thread.sleep(delay);
} catch (final InterruptedException e) {
// no interruption expected
}
checkAndConfigure();
}
}
/**
* Sets the delay in milliseconds to observe between each check of the file changes.
*
* @param delayMillis the delay in milliseconds
*/
public void setDelay(final long delayMillis) {
this.delay = delayMillis;
}
}