001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements. See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache license, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License. You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the license for the specific language governing permissions and
015 * limitations under the license.
016 */
017package org.apache.logging.log4j.core.util;
018
019import java.io.File;
020import java.util.List;
021
022import org.apache.logging.log4j.core.config.Configuration;
023import org.apache.logging.log4j.core.config.ConfigurationListener;
024import org.apache.logging.log4j.core.config.Reconfigurable;
025
026/**
027 * Watcher for configuration files. Causes a reconfiguration when a file changes.
028 */
029public abstract class AbstractWatcher implements Watcher {
030
031    private final Reconfigurable reconfigurable;
032    private final List<ConfigurationListener> configurationListeners;
033    private final Log4jThreadFactory threadFactory;
034    private final Configuration configuration;
035    private Source source;
036
037    public AbstractWatcher(final Configuration configuration, final Reconfigurable reconfigurable,
038            final List<ConfigurationListener> configurationListeners) {
039        this.configuration = configuration;
040        this.reconfigurable = reconfigurable;
041        this.configurationListeners = configurationListeners;
042        this.threadFactory = configurationListeners != null ?
043            Log4jThreadFactory.createDaemonThreadFactory("ConfiguratonFileWatcher") : null;
044    }
045
046    @Override
047    public List<ConfigurationListener> getListeners() {
048        return configurationListeners;
049    }
050
051    @Override
052    public void modified() {
053        for (final ConfigurationListener configurationListener : configurationListeners) {
054            final Thread thread = threadFactory.newThread(new ReconfigurationRunnable(configurationListener, reconfigurable));
055            thread.start();
056        }
057    }
058
059    public Configuration getConfiguration() {
060        return configuration;
061    }
062
063    public abstract long getLastModified();
064
065    public abstract boolean isModified();
066
067    @Override
068    public void watching(Source source) {
069        this.source = source;
070    }
071
072    @Override
073    public Source getSource() {
074        return source;
075    }
076
077    /**
078     * Helper class for triggering a reconfiguration in a background thread.
079     */
080    public static class ReconfigurationRunnable implements Runnable {
081
082        private final ConfigurationListener configurationListener;
083        private final Reconfigurable reconfigurable;
084
085        public ReconfigurationRunnable(final ConfigurationListener configurationListener, final Reconfigurable reconfigurable) {
086            this.configurationListener = configurationListener;
087            this.reconfigurable = reconfigurable;
088        }
089
090        @Override
091        public void run() {
092            configurationListener.onChange(reconfigurable);
093        }
094    }
095}