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A Java library to parse, migrate and validate crons as well as describe them in human readable language

There is a newer version: 9.2.1

/*
 * Copyright 2019 fahmpeermoh
 * Licensed 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 com.cronutils.converter;

import org.apache.commons.lang3.StringUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.time.ZoneId;
import java.util.Calendar;
import java.util.TimeZone;

public class CronConverter {

	private static final Logger LOGGER = LoggerFactory.getLogger(CronConverter.class);

	private static final String CRON_FIELDS_SEPARATOR = " ";
	private String[] cronParts;
	private Calendar fromCalendar;
	private String sourceCron;
	private ZoneId sourceZoneId;
	private ZoneId targetZoneId;

	private CronToCalendarTransformer toCalendarConverter;
	private CalendarToCronTransformer toCronConverter;

	public CronConverter(CronToCalendarTransformer toCalendarConverter, CalendarToCronTransformer toCronConverter){
		this.toCalendarConverter = toCalendarConverter;
		this.toCronConverter = toCronConverter;
	}

	public CronConverter using(String cronExpression) {
		this.sourceCron = cronExpression;
		cronParts = cronExpression.split(CRON_FIELDS_SEPARATOR);
		LOGGER.debug("Cron '{}' split into {}", cronExpression, cronParts);
		return this;
	}

	public CronConverter from(ZoneId zoneId) {
		sourceZoneId = zoneId;
		fromCalendar = getCalendar(zoneId);
		toCalendarConverter.apply(cronParts, fromCalendar);
		LOGGER.debug("Calendar object built using cron :{} and zoneID {} => {}",
				cronParts, zoneId, fromCalendar);
		return this;
	}

	public CronConverter to(ZoneId zoneId) {
		targetZoneId = zoneId;
		Calendar toCalendar = getCalendar(zoneId);
		toCalendar.setTimeInMillis(fromCalendar.getTimeInMillis());
		LOGGER.debug(
				"Calendar object built from calendar {} and zoneID {} => {}",
				fromCalendar, zoneId, toCalendar);
		toCronConverter.apply(cronParts, toCalendar);
		LOGGER.debug("cron after applying calendar {} => {}", toCalendar,
				cronParts);
		return this;
	}

	public String convert() {
		String targetCron = StringUtils.join(cronParts, CRON_FIELDS_SEPARATOR);
		LOGGER.info("Converted CRON -- {} :[{}] => {} :[{}]", sourceZoneId,
				sourceCron, targetZoneId, targetCron);
		return targetCron;
	}

	private Calendar getCalendar(ZoneId id) {
		return Calendar.getInstance(TimeZone.getTimeZone(id));
	}
}