（五）如何动态修改定时器的下次执行时间

package com.example.demo.javaConfig;

import org.springframework.context.annotation.Configuration;
import org.springframework.scheduling.Trigger;
import org.springframework.scheduling.TriggerContext;
import org.springframework.scheduling.annotation.SchedulingConfigurer;
import org.springframework.scheduling.config.ScheduledTaskRegistrar;
import org.springframework.scheduling.support.CronTrigger;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import java.text.SimpleDateFormat;
import java.util.Date;

@RestController
@Configuration
public class ScheduleDynamicTest implements SchedulingConfigurer {

    private String cron = "0 0/1 * * * ?";

    @RequestMapping("changeCron")
    public String changeCron(){
        cron = "0 0/3 * * * ?";
        return "ok" ;
    }

    @Override
    public void configureTasks(ScheduledTaskRegistrar scheduledTaskRegistrar) {

        // 构建一个线程来执行job
        Runnable job = new Runnable() {
            @Override
            public void run() {
                SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");
                String nowStr = sdf.format(new Date());
                System.out.println(nowStr);
            }
        };

        // 构建一个trigger ,并且设置重写trigger的下一次执行时间
        Trigger trigger = new Trigger(){

            @Override
            public Date nextExecutionTime(TriggerContext triggerContext) {
                CronTrigger ct = new CronTrigger(cron);
                return ct.nextExecutionTime(triggerContext);
            }
        };

        scheduledTaskRegistrar.addTriggerTask(job,trigger);

    }
}