springboot定时任务

 简单使用：

类上加上@EnableScheduling注解

方法上加上 @Scheduled注解（参数会指定定时时间，corn表达式...）

---

 springboot定时任务学习 @EnableScheduling  @Scheduled 简单例子

---

 

@EnableScheduling

 

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Import(SchedulingConfiguration.class)
@Documented
public @interface EnableScheduling {

}

 @EnableScheduling 要求在类上使用。

 @EnableScheduling 引入了 SchedulingConfiguration 类，属于 org.springframework.context 模块。

---

@Scheduled

@Target({ElementType.METHOD, ElementType.ANNOTATION_TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Repeatable(Schedules.class)
public @interface Scheduled {

 @Scheduled 要求在方法、注解中使用。

 @Scheduled 要求方法参数为空，返回值类型为void。

 @Scheduled 参数：corn...

 @Scheduled 源码：

/*
 * Copyright 2002-2016 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
 *
 *      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 org.springframework.scheduling.annotation;

import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Repeatable;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

/**
 * An annotation that marks a method to be scheduled. Exactly one of
 * the {@link #cron()}, {@link #fixedDelay()}, or {@link #fixedRate()}
 * attributes must be specified.
 *
 * <p>The annotated method must expect no arguments. It will typically have
 * a {@code void} return type; if not, the returned value will be ignored
 * when called through the scheduler.
 *
 * <p>Processing of {@code @Scheduled} annotations is performed by
 * registering a {@link ScheduledAnnotationBeanPostProcessor}. This can be
 * done manually or, more conveniently, through the {@code <task:annotation-driven/>}
 * element or @{@link EnableScheduling} annotation.
 *
 * <p>This annotation may be used as a <em>meta-annotation</em> to create custom
 * <em>composed annotations</em> with attribute overrides.
 *
 * @author Mark Fisher
 * @author Dave Syer
 * @author Chris Beams
 * @since 3.0
 * @see EnableScheduling
 * @see ScheduledAnnotationBeanPostProcessor
 * @see Schedules
 */
@Target({ElementType.METHOD, ElementType.ANNOTATION_TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Repeatable(Schedules.class)
public @interface Scheduled {

    /**
     * A cron-like expression, extending the usual UN*X definition to include
     * triggers on the second as well as minute, hour, day of month, month
     * and day of week.  e.g. {@code "0 * * * * MON-FRI"} means once per minute on
     * weekdays (at the top of the minute - the 0th second).
     * @return an expression that can be parsed to a cron schedule
     * @see org.springframework.scheduling.support.CronSequenceGenerator
     */
    String cron() default "";

    /**
     * A time zone for which the cron expression will be resolved. By default, this
     * attribute is the empty String (i.e. the server's local time zone will be used).
     * @return a zone id accepted by {@link java.util.TimeZone#getTimeZone(String)},
     * or an empty String to indicate the server's default time zone
     * @since 4.0
     * @see org.springframework.scheduling.support.CronTrigger#CronTrigger(String, java.util.TimeZone)
     * @see java.util.TimeZone
     */
    String zone() default "";

    /**
     * Execute the annotated method with a fixed period in milliseconds between the
     * end of the last invocation and the start of the next.
     * @return the delay in milliseconds
     */
    long fixedDelay() default -1;

    /**
     * Execute the annotated method with a fixed period in milliseconds between the
     * end of the last invocation and the start of the next.
     * @return the delay in milliseconds as a String value, e.g. a placeholder
     * @since 3.2.2
     */
    String fixedDelayString() default "";

    /**
     * Execute the annotated method with a fixed period in milliseconds between
     * invocations.
     * @return the period in milliseconds
     */
    long fixedRate() default -1;

    /**
     * Execute the annotated method with a fixed period in milliseconds between
     * invocations.
     * @return the period in milliseconds as a String value, e.g. a placeholder
     * @since 3.2.2
     */
    String fixedRateString() default "";

    /**
     * Number of milliseconds to delay before the first execution of a
     * {@link #fixedRate()} or {@link #fixedDelay()} task.
     * @return the initial delay in milliseconds
     * @since 3.2
     */
    long initialDelay() default -1;

    /**
     * Number of milliseconds to delay before the first execution of a
     * {@link #fixedRate()} or {@link #fixedDelay()} task.
     * @return the initial delay in milliseconds as a String value, e.g. a placeholder
     * @since 3.2.2
     */
    String initialDelayString() default "";

}

---

简单例子

启动类：

package com.wang.pp;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class PPApplicationStarter {

    public static void main(String[] args) {
        SpringApplication.run(PPApplicationStarter.class, args);
    }
}

配置类：

@Configuration
@EnableScheduling
public class PpSchedualTask {
    
    SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
    
    @Scheduled(cron = "${limitTime.corn}")
    public void runTask(){
        try {
            Date ss = new Date();
            System.out.println(sdf.format(ss)+":"+"定时任务执行");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

配置文件：5秒定时执行

limitTime.corn=*/5 * * * * ?

结果打印：

2020-12-18 15:02:55:定时任务执行
2020-12-18 15:03:00:定时任务执行
2020-12-18 15:03:05:定时任务执行
2020-12-18 15:03:10:定时任务执行