net.ion.radon.cload.monitor.FileAlterationMonitor.java Source code

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Here is the source code for net.ion.radon.cload.monitor.FileAlterationMonitor.java

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/*
 * 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.
 */

package net.ion.radon.cload.monitor;

import java.util.List;
import java.util.concurrent.Callable;
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;

import org.apache.commons.io.monitor.FileAlterationObserver;

/**
 * It's a runnable that spawns of a monitoring thread triggering the the observers and managing the their listeners.
 */
public final class FileAlterationMonitor {

    private final long interval;
    private final List<FileAlterationObserver> observers;
    private ScheduledExecutorService ses;
    private transient boolean running = true;

    public FileAlterationMonitor(long interval, ScheduledExecutorService ses, FileAlterationObserver first,
            FileAlterationObserver... observers) {
        this.ses = ses;
        this.observers = new CopyOnWriteArrayList<FileAlterationObserver>();
        this.interval = interval;
        addObserver(first);
        for (FileAlterationObserver observer : observers) {
            addObserver(observer);
        }
    }

    public long getInterval() {
        return interval;
    }

    public void addObserver(FileAlterationObserver observer) {
        observers.add(observer);
    }

    public void removeObserver(FileAlterationObserver observer) {
        while (observers.remove(observer))
            ;
    }

    public Iterable getObservers() {
        return observers;
    }

    public synchronized void start() throws Exception {

        Callable<Void> sjob = new Callable<Void>() {
            @Override
            public Void call() throws Exception {
                try {
                    for (FileAlterationObserver o : observers) {
                        o.checkAndNotify();
                    }
                } catch (Exception e) {
                    e.printStackTrace();
                    throw e;
                } finally {
                    ses.schedule(this, interval, TimeUnit.MILLISECONDS);
                }
                return null;
            }
        };
        ses.schedule(sjob, interval, TimeUnit.MILLISECONDS);
    }

    public synchronized void stop() throws Exception {
        this.running = false;
    }

}