org.springframework.scheduling.support.CronTrigger Maven / Gradle / Ivy
/*
* 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.
* 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();
}
}