Spring-Task的使用

一、动态修改cron表达式

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;

/**
 * Created by lq on 2018/10/7.
 */
@RestController
@Component
public class DynamicTask {

    /**
     * 线程池任务调度类，能够开启线程池进行任务调度。
     */
    @Autowired
    private ThreadPoolTaskScheduler threadPoolTaskScheduler;

    /**
     * 定时计划ScheduledFuture
     */
    private ScheduledFuture<?> future;


    @Bean
    public ThreadPoolTaskScheduler threadPoolTaskScheduler() {
        return new ThreadPoolTaskScheduler();
    }


    /**
     * ThreadPoolTaskScheduler.schedule()方法会创建一个定时计划ScheduledFuture，
     * 在这个方法需要添加两个参数，Runnable（线程接口类） 和CronTrigger（定时任务触发器）
     */
    @RequestMapping("/startCron")
    public String startCron() {
        future = threadPoolTaskScheduler.schedule(new MyRunnable(), new CronTrigger("0/5 * * * * *"));
        System.out.println("DynamicTask.startCron()");
        return "startCron";
    }


    /**
     * 在ScheduledFuture中有一个cancel可以停止定时任务。
     * 参数为true便可以停止
     * @return
     */
    @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 {
        @Override
        public void run() {
            System.out.println("DynamicTask.MyRunnable.run()，" + new Date());
}
    }

}

二、通过数据库修改表达式

(1)、在数据库中建一张表cron

属性：cron_id,cron

(2)、建立一个和表对应的持久化类

import lombok.Data;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;

/**
 * Created by lq on 2018/10/7.
 */
@Data
@Entity
public class Cron {

    @GeneratedValue
    @Id
    private Integer cronId;

    private String cron;


    public Cron() {

    }

    public Cron(String cron) {
        this.cron = cron;
    }
}

(3)、写一个CronRepository接口

import com.lq.bean.Cron;
import org.springframework.data.jpa.repository.JpaRepository;

/**
 * Created by lq on 2018/10/7.
 */
public interface CronRepository extends JpaRepository<Cron,Integer>{

}

(4)、实现

import com.lq.dao.CronRepository;
import org.springframework.context.annotation.Configuration;
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.util.StringUtils;

import javax.annotation.Resource;
import java.time.LocalDateTime;

/**
 * Created by lq on 2018/10/7.
 */
@Configuration
@EnableScheduling
public class CompleteScheduleConfig implements SchedulingConfigurer {


    // 0/5 * * * * *
    // */10 * * * * *
    @Resource
    private CronRepository cronRepository;



    @Override
    public void configureTasks(ScheduledTaskRegistrar scheduledTaskRegistrar) {
        scheduledTaskRegistrar.addTriggerTask(
                //1.添加任务内容(Runnable)
                () -> System.out.println("执行定时任务2: " + 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 = cronRepository.findById(23).get().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);
                }
        );

    }
}