spring CronTrigger 源码

spring CronTrigger 代码

文件路径：/spring-context/src/main/java/org/springframework/scheduling/support/CronTrigger.java

/*
 * Copyright 2002-2022 the original author or authors.
 *
 * 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
 *
 *      https://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 org.springframework.scheduling.support;

import java.time.Instant;
import java.time.ZoneId;
import java.time.ZonedDateTime;
import java.util.TimeZone;

import org.springframework.lang.Nullable;
import org.springframework.scheduling.Trigger;
import org.springframework.scheduling.TriggerContext;
import org.springframework.util.Assert;

/**
 * {@link Trigger} implementation for cron expressions.
 * Wraps a {@link CronExpression}.
 *
 * @author Juergen Hoeller
 * @author Arjen Poutsma
 * @since 3.0
 * @see CronExpression
 */
public class CronTrigger implements Trigger {

	private final CronExpression expression;

	private final ZoneId zoneId;


	/**
	 * Build a {@code CronTrigger} from the pattern provided in the default time zone.
	 * @param expression a space-separated list of time fields, following cron
	 * expression conventions
	 */
	public CronTrigger(String expression) {
		this(expression, ZoneId.systemDefault());
	}

	/**
	 * Build a {@code CronTrigger} from the pattern provided in the given time zone.
	 * @param expression a space-separated list of time fields, following cron
	 * expression conventions
	 * @param timeZone a time zone in which the trigger times will be generated
	 */
	public CronTrigger(String expression, TimeZone timeZone) {
		this(expression, timeZone.toZoneId());
	}

	/**
	 * Build a {@code CronTrigger} from the pattern provided in the given time zone.
	 * @param expression a space-separated list of time fields, following cron
	 * expression conventions
	 * @param zoneId a time zone in which the trigger times will be generated
	 * @since 5.3
	 * @see CronExpression#parse(String)
	 */
	public CronTrigger(String expression, ZoneId zoneId) {
		Assert.hasLength(expression, "Expression must not be empty");
		Assert.notNull(zoneId, "ZoneId must not be null");

		this.expression = CronExpression.parse(expression);
		this.zoneId = zoneId;
	}


	/**
	 * Return the cron pattern that this trigger has been built with.
	 */
	public String getExpression() {
		return this.expression.toString();
	}


	/**
	 * Determine the next execution time according to the given trigger context.
	 * <p>Next execution times are calculated based on the
	 * {@linkplain TriggerContext#lastCompletionTime completion time} of the
	 * previous execution; therefore, overlapping executions won't occur.
	 */
	@Override
	public Instant nextExecution(TriggerContext triggerContext) {
		Instant instant = triggerContext.lastCompletion();
		if (instant != null) {
			Instant scheduled = triggerContext.lastScheduledExecution();
			if (scheduled != null && instant.isBefore(scheduled)) {
				// Previous task apparently executed too early...
				// Let's simply use the last calculated execution time then,
				// in order to prevent accidental re-fires in the same second.
				instant = scheduled;
			}
		}
		else {
			instant = triggerContext.getClock().instant();
		}
		ZonedDateTime dateTime = ZonedDateTime.ofInstant(instant, this.zoneId);
		ZonedDateTime next = this.expression.next(dateTime);
		return (next != null ? next.toInstant() : null);
	}


	@Override
	public boolean equals(@Nullable Object other) {
		return (this == other || (other instanceof CronTrigger &&
				this.expression.equals(((CronTrigger) other).expression)));
	}

	@Override
	public int hashCode() {
		return this.expression.hashCode();
	}

	@Override
	public String toString() {
		return this.expression.toString();
	}

}

相关信息

spring 源码目录

相关文章

spring BitsCronField 源码

spring CompositeCronField 源码

spring CronExpression 源码

spring CronField 源码

spring CronSequenceGenerator 源码

spring DelegatingErrorHandlingRunnable 源码

spring MethodInvokingRunnable 源码

spring PeriodicTrigger 源码

spring QuartzCronField 源码

spring ScheduledMethodRunnable 源码