Cron.java

/*
 * Copyright (c) 2016, Salesforce.com, Inc.
 * All rights reserved.
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 * Redistribution and use in source and binary forms, with or without
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 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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package com.salesforce.dva.argus.util;

import java.util.Date;

import org.apache.commons.lang.exception.ExceptionUtils;
import org.quartz.CronScheduleBuilder;
import org.quartz.TriggerBuilder;

/**
 * CRON utilities.
 *
 * @author  Tom Valine (tvaline@salesforce.com)
 */
public class Cron {

	//~ Static fields/initializers *******************************************************************************************************************

	private static final String ANNUALLY = "@ANNUALLY";
	private static final String YEARLY = "@YEARLY";
	private static final String MONTHLY = "@MONTHLY";
	private static final String WEEKLY = "@WEEKLY";
	private static final String DAILY = "@DAILY";
	private static final String MIDNIGHT = "@MIDNIGHT";
	private static final String HOURLY = "@HOURLY";

	//~ Constructors *********************************************************************************************************************************

	private Cron() { }

	//~ Methods **************************************************************************************************************************************

	/**
	 * Determines if the given CRON entry is runnable at this current moment in time. This mimics the original implementation of the CRON table.
	 *
	 * <p>This implementation supports only the following types of entries:</p>
	 *
	 * <ol>
	 *   <li>Standard Entries having form: &lt;minutes&gt; &lt;hours&gt; &lt;days&gt; &lt;months&gt; &lt;days of week&gt;
	 *
	 *     <ul>
	 *       <li>* : All</li>
	 *       <li>*\/n : Only mod n</li>
	 *       <li>n : Numeric</li>
	 *       <li>n-n : Range</li>
	 *       <li>n,n,...,n : List</li>
	 *       <li>n,n-n,...,n : List having ranges</li>
	 *     </ul>
	 *   </li>
	 *   <li>Special Entries
	 *
	 *     <ul>
	 *       <li>@annually : equivalent to "0 0 1 1 *"</li>
	 *       <li>@yearly : equivalent to "0 0 1 1 *"</li>
	 *       <li>@monthly : equivalent to "0 0 1 * *"</li>
	 *       <li>@weekly : equivalent to "0 0 * * 0"</li>
	 *       <li>@daily : equivalent to "0 0 * * *"</li>
	 *       <li>@midnight : equivalent to "0 0 * * *"</li>
	 *       <li>@hourly : equivalent to "0 * * * *"</li>
	 *     </ul>
	 *   </li>
	 * </ol>
	 *
	 * @param   entry   The CRON entry to evaluate.
	 * @param   atTime  The time at which to evaluate the entry.
	 *
	 * @return  true if the the current time is a valid runnable time with respect to the supplied entry.
	 */
	public static boolean shouldRun(String entry, Date atTime) {
		entry = entry.trim().toUpperCase();
		if (ANNUALLY.equals(entry) || (YEARLY.equals(entry))) {
			entry = "0 0 1 1 *";
		} else if (MONTHLY.equals(entry)) {
			entry = "0 0 1 * *";
		} else if (WEEKLY.equals(entry)) {
			entry = "0 0 * * 0";
		} else if (DAILY.equals(entry) || (MIDNIGHT.equals(entry))) {
			entry = "0 0 * * *";
		} else if (HOURLY.equals(entry)) {
			entry = "0 * * * *";
		}
		return new CronTabEntry(entry).isRunnable(atTime);
	}

	/**
	 * Indicates if a CRON entry should run at the current moment in time.
	 *
	 * @param   entry  The CRON entry to evaluate.
	 *
	 * @return  true if the the current time is a valid runnable time with respect to the supplied entry.
	 */
	public static boolean shouldRun(String entry) {
		return Cron.shouldRun(entry, new Date());
	}

	/**
	 * Determines if an entry is valid CRON syntax.
	 *
	 * @param   entry  The CRON entry.
	 *
	 * @return  True if the entry is valid CRON syntax.
	 */
	public static boolean isValid(String entry) {
		boolean result = true;

		try {
			shouldRun(entry);
		} catch (Exception ex) {
			result = false;
		}
		return result;
	}

	public static boolean isCronEntryValid(String cronEntry) {
		String quartzCronEntry = convertToQuartzCronEntry(cronEntry);

		try {
			// throws runtime exception if the cronEntry is invalid
			TriggerBuilder.newTrigger().withSchedule(CronScheduleBuilder.cronSchedule(quartzCronEntry)).build();
		}catch(Exception e) {
			return false;
		}
		return true;
	}

	public static String convertToQuartzCronEntry(String cronEntry) {
		// adding seconds field
		cronEntry = "0 " + cronEntry.trim();

		// if day of the week is not specified, substitute it with ?, so as to prevent conflict with month field
		if(cronEntry.charAt(cronEntry.length() - 1) == '*') {
			return cronEntry.substring(0, cronEntry.length() - 1) + "?";
		}else {
			return cronEntry;
		}
	}
}
/* Copyright (c) 2016, Salesforce.com, Inc.  All rights reserved. */