原文网址：Spring定时任务--手动执行定时任务（替代@Scheduled）
简介
本文介绍SpringBoot如何手动执行定时任务。
之前此文已经介绍过，直接用@Scheduled即可使用Spring的定时任务，但有时需要手动去提交定时任务，比如：
- 从其他位置获取cron配置，无法写到注解。
- 有不确定个数的任务，不能在代码中写死。
方案1：实现 SchedulingConfigurer 接口
本处从数据库读取配置，然后提交定时任务。
创建定时器
编写定时任务，这里添加的是TriggerTask，循环读取我们在数据库设置好的执行周期，以及执行相关定时任务的内容。
@Configuration
@EnableScheduling
public class DynamicScheduleTask implements SchedulingConfigurer {@Autowiredprivate CronMapper cronMapper;/*** 执行定时任务.*/@Overridepublic void configureTasks(ScheduledTaskRegistrar taskRegistrar) {taskRegistrar.addTriggerTask(//1.添加任务内容(Runnable)() -> System.out.println("执行动态定时任务: " + LocalDateTime.now().toLocalTime()),//2.设置执行周期(Trigger)triggerContext -> {//2.1 从数据库获取执行周期String cron = cronMapper.getCron();//2.2 合法性校验.if (StringUtils.isEmpty(cron)) {// Omitted Code ..}//2.3 返回执行周期(Date)return new CronTrigger(cron).nextExecutionTime(triggerContext);});}}表结构与数据
开启本地数据库mysql，随便打开查询窗口，然后执行脚本内容，如下
DROP DATABASE IF EXISTS `socks`;
CREATE DATABASE `socks`;
USE `SOCKS`;
DROP TABLE IF EXISTS `cron`;
CREATE TABLE `cron` (`cron_id` varchar(30) NOT NULL PRIMARY KEY,`cron` varchar(30) NOT NULL
);
INSERT INTO `cron` VALUES ('1', '0/5 * * * * ?');
项目中的application.yml 添加数据源
spring:datasource:url: jdbc:mysql://localhost:3306/socksusername: rootpassword: 123456启动测试
启动应用后，查看控制台，打印时间是我们预期的每10秒一次：
打开Navicat ，将执行周期修改为每6秒执行一次，如图
如果在数据库修改时格式出现错误，则定时任务会停止，即使重新修改正确；此时只能重新启动项目才能恢复。
方案2：ThreadPoolTaskScheduler
上边的实例的定时任务在SprinBoot在启动时就启动，也可以在代码中任意启动/关闭/调整时间。如下：
package com.example.demo.task;import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Bean;
import org.springframework.scheduling.concurrent.ThreadPoolTaskScheduler;
import org.springframework.scheduling.support.CronTrigger;
import org.springframework.stereotype.Component;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;import java.util.Date;
import java.util.concurrent.ScheduledFuture;@RestController
@Component
public class TestScheduler {@Autowiredprivate ThreadPoolTaskScheduler threadPoolTaskScheduler;private ScheduledFuture<?> future;@Beanpublic ThreadPoolTaskScheduler threadPoolTaskScheduler() {return new ThreadPoolTaskScheduler();}@RequestMapping("/startCron")public String startCron() {future = threadPoolTaskScheduler.schedule(new MyRunnable(), new CronTrigger("0/5 * * * * *"));System.out.println("DynamicTask.startCron()");return "startCron";}@RequestMapping("/stopCron")public String stopCron() {if (future != null) {future.cancel(true);}System.out.println("DynamicTask.stopCron()");return "stopCron";}@RequestMapping("/changeCron10")public String startCron10() {stopCron();// 先停止，在开启.future = threadPoolTaskScheduler.schedule(new MyRunnable(), new CronTrigger("*/10 * * * * *"));System.out.println("DynamicTask.startCron10()");return "changeCron10";}private class MyRunnable implements Runnable {@Overridepublic void run() {System.out.println("DynamicTask.MyRunnable.run()，" + new Date());}}
}
浏览器分别输入：http://localhost:8080/startCron、http://localhost:8080/stopCron
执行结果
. ____ _ __ _ _/\\ / ___'_ __ _ _(_)_ __ __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \\\/ ___)| |_)| | | | | || (_| | ) ) ) )' |____| .__|_| |_|_| |_\__, | / / / /=========|_|==============|___/=/_/_/_/:: Spring Boot :: (v2.3.0.RELEASE)2020-05-27 19:48:02.370 INFO 6804 --- [ main] com.example.demo.DemoApplication : Starting DemoApplication on liu-PC with PID 6804 (E:\work\idea_proj\test-SpringBoot\target\classes started by liu in E:\work\idea_proj\test-SpringBoot)
2020-05-27 19:48:02.373 INFO 6804 --- [ main] com.example.demo.DemoApplication : No active profile set, falling back to default profiles: default
2020-05-27 19:48:03.675 INFO 6804 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat initialized with port(s): 8080 (http)
2020-05-27 19:48:03.684 INFO 6804 --- [ main] o.apache.catalina.core.StandardService : Starting service [Tomcat]
2020-05-27 19:48:03.684 INFO 6804 --- [ main] org.apache.catalina.core.StandardEngine : Starting Servlet engine: [Apache Tomcat/9.0.35]
2020-05-27 19:48:03.941 INFO 6804 --- [ main] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring embedded WebApplicationContext
2020-05-27 19:48:03.941 INFO 6804 --- [ main] o.s.web.context.ContextLoader : Root WebApplicationContext: initialization completed in 1523 ms
2020-05-27 19:48:04.001 INFO 6804 --- [ main] o.s.s.c.ThreadPoolTaskScheduler : Initializing ExecutorService 'threadPoolTaskScheduler'
2020-05-27 19:48:04.405 INFO 6804 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat started on port(s): 8080 (http) with context path ''
2020-05-27 19:48:04.419 INFO 6804 --- [ main] com.example.demo.DemoApplication : Started DemoApplication in 3.328 seconds (JVM running for 8.111)
2020-05-27 19:48:39.380 INFO 6804 --- [nio-8080-exec-1] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring DispatcherServlet 'dispatcherServlet'
2020-05-27 19:48:39.380 INFO 6804 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet : Initializing Servlet 'dispatcherServlet'
2020-05-27 19:48:39.405 INFO 6804 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet : Completed initialization in 25 ms
DynamicTask.startCron()
DynamicTask.MyRunnable.run()，Wed May 27 19:48:50 CST 2020
DynamicTask.MyRunnable.run()，Wed May 27 19:48:55 CST 2020
DynamicTask.MyRunnable.run()，Wed May 27 19:49:00 CST 2020
DynamicTask.MyRunnable.run()，Wed May 27 19:49:05 CST 2020
DynamicTask.MyRunnable.run()，Wed May 27 19:49:10 CST 2020
DynamicTask.stopCron()
