Spring boot开启定时任务

Cron表达式生成器

基于接口的方式 

   使用@Scheduled 注解很方便，但缺点是当我们调整了执行周期的时候，需要重启应用才能生效，这多少有些不方便。为了达到实时生效的效果，那么可以使用接口来完成定时任务，统一将定时器信息存放在数据库中。

1. 在mysql中执行一下脚本插入定时任务：

drop table if exists `scheduled`;
create table `scheduled` (`cron_id` varchar(30) NOT NULL primary key,`cron_name` varchar(30) NULL,`cron` varchar(30) NOT NULL
);
insert into `scheduled` values ('1','定时器任务一','0/6 * * * * ?');

2. Mapper层

@Repository
@Mapper
public interface CronMapper {@Select("select cron from scheduled where cron_id = #{id}")public String getCron(int id);
}

3. task类：

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.scheduling.annotation.EnableScheduling;
import org.springframework.scheduling.annotation.SchedulingConfigurer;
import org.springframework.scheduling.config.ScheduledTaskRegistrar;
import org.springframework.scheduling.support.CronTrigger;
import org.springframework.stereotype.Component;/*** @Description* @ClassName MyTask* @Author User* @date 2020.06.07 15:23*/
@Component
@EnableScheduling
public class MyTask implements SchedulingConfigurer {@Autowiredprotected CronMapper cronMapper;@Overridepublic void configureTasks(ScheduledTaskRegistrar scheduledTaskRegistrar) {scheduledTaskRegistrar.addTriggerTask(() -> process(),triggerContext -> {String cron = cronMapper.getCron(1);if (cron.isEmpty()) {System.out.println("cron is null");}return new CronTrigger(cron).nextExecutionTime(triggerContext);});}private void process() {System.out.println("这里实现定时任务具体操作");}
}