动态改变Spring定时任务执行频率

@Component
@EnableScheduling
public class updateCronTask implements SchedulingConfigurer {

    public static String cron = "0/2 * * * * ?";
    int i=0;
    @Override
    public void configureTasks(ScheduledTaskRegistrar taskRegistrar) {
        taskRegistrar.addTriggerTask(new Runnable() {
            @Override
            public void run(){
                i++;
                // 任务逻辑  
                System.out.println("第"+(i)+"次开始执行操作... " +"时间：【" + new SimpleDateFormat("yyyy-MM-dd hh:mm:ss.SSS").format(new Date()) + "】");
            }

        }, new Trigger(){
            @Override
            public Date nextExecutionTime(TriggerContext triggerContext) {
                //任务触发，可修改任务的执行周期 
                CronTrigger trigger = new CronTrigger(cron);
                Date nextExec = trigger.nextExecutionTime(triggerContext);
                return nextExec;
            }
        });
    }
}