CronSchedule.java

/*
 * The MIT License (MIT)
 *
 * Copyright (c) 2013 Anders Wisch
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
package cron;

import com.google.common.collect.HashMultimap;
import com.google.common.collect.Multimap;
import com.google.common.collect.Multimaps;

import java.time.ZonedDateTime;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.ScheduledFuture;
import java.util.concurrent.TimeUnit;

public class CronSchedule {
    private static final int ONE_MINUTE_IN_MILLISECONDS = 60000,
            ONE_SECOND_IN_MILLISECONDS = 1000;

    private final ScheduledExecutorService executor;
    private final Multimap<CronExpression, Runnable> runnables;
    private final int periodInMilliseconds;

    private ScheduledFuture<?> future;

    public CronSchedule(ScheduledExecutorService s) {
        this(s, false);
    }

    public CronSchedule(ScheduledExecutorService s, boolean seconds) {
        executor = s;
        Multimap<CronExpression, Runnable> wrapped = HashMultimap.create();
        runnables = Multimaps.synchronizedMultimap(wrapped);
        periodInMilliseconds = seconds ? ONE_SECOND_IN_MILLISECONDS : ONE_MINUTE_IN_MILLISECONDS;
    }

    public void add(CronExpression expression, Runnable runnable) {
        runnables.put(expression, runnable);
    }

    public void remove(CronExpression expression) {
        runnables.removeAll(expression);
    }

    public void remove(CronExpression expression, Runnable runnable) {
        runnables.remove(expression, runnable);
    }

    public boolean isStarted() {
        return future != null && !future.isCancelled() && !future.isDone();
    }

    public synchronized void start() {
        if (!isStarted()) {
            long untilNextPeriod = System.currentTimeMillis() % periodInMilliseconds;
            future = executor.scheduleAtFixedRate(new Runnable() {
                @Override
                public void run() {
                    CronSchedule.this.run();
                }
            }, untilNextPeriod, periodInMilliseconds, TimeUnit.MILLISECONDS);
        }
    }

    public void run() {
        run(ZonedDateTime.now());
    }

    public void run(ZonedDateTime time) {
        for (CronExpression expression : runnables.keySet())
            if (expression.matches(time))
                for (Runnable runnable : runnables.get(expression))
                    executor.submit(runnable);
    }

    public synchronized void stop() {
        if (future != null) {
            future.cancel(true);
            future = null;
        }
    }
}