Spring调度任务——只运行一次 [英] Spring scheduling task - run only once

问题描述

是否可以在指定的时间只安排一次 Spring 服务方法?例如，当前时间是下午 2 点，但是当我点击操作按钮时，我希望我的服务方法在晚上 8 点开始.我熟悉@Scheduled 注释，但不确定如何编写不定期运行的 cron 表达式.这个 @Scheduled(cron = "0 0 20 * * ?") 每天晚上 8 点触发.
有什么建议吗?

Is it possible to schedule Spring service method only once at exactly specified time? For example, current time is 2pm but when I hit the action button I want that my service method starts at 8pm. I'm familiar with @Scheduled annotation and I'm not sure how to write cron expression not to run periodically. This one @Scheduled(cron = "0 0 20 * * ?") fires every day at 8pm.
Any suggestions?

推荐答案

您可以使用 Spring 的 TaskScheduler 实现之一.我在下面提供了一个不需要太多配置的示例(ConcurrentTaskScheduler 包装了一个单线程调度执行器).

You can use one of Spring's TaskScheduler's implementations. I provided an example below with one which does not require too much configuration (ConcurrentTaskScheduler that wraps a single-threaded scheduled executor).

最简单的方法是一个名为 schedule 的方法，它接受一个 Runnable和日期.这将导致任务在之后运行一次指定时间.所有其他方法都能够调度重复运行的任务.

The simplest method is the one named schedule that takes a Runnable and Date only. That will cause the task to run once after the specified time. All of the other methods are capable of scheduling tasks to run repeatedly.

阅读更多关于任务执行和;调度

简单的工作示例:

private TaskScheduler scheduler;

Runnable exampleRunnable = new Runnable(){
    @Override
    public void run() {
        System.out.println("Works");
    }
};

@Async
public void executeTaskT() {
    ScheduledExecutorService localExecutor = Executors.newSingleThreadScheduledExecutor();
    scheduler = new ConcurrentTaskScheduler(localExecutor);

    scheduler.schedule(exampleRunnable,
            new Date(1432152000000L));//today at 8 pm UTC - replace it with any timestamp in miliseconds to text
}

...

executeTaskT() //call it somewhere after the spring application has been configured

注意:

要启用对@Scheduled 和@Async 批注的支持，请添加@EnableScheduling 和 @EnableAsync 到您的 @Configuration 之一班级

To enable support for @Scheduled and @Async annotations add @EnableScheduling and @EnableAsync to one of your @Configuration classes

<小时>

更新 - 取消预定任务

TaskScheduler 的 schedule 方法返回一个 ScheduledFuture，它是一个可以取消的延迟结果操作.

TaskScheduler's schedule method returns a ScheduledFuture which is a delayed result-bearing action that can be cancelled.

所以为了取消它，你需要保留一个计划任务的句柄(即保留 ScheduledFuture 返回对象).

So in order to cancel it, you need to keep a handle to the scheduled task (i.e. keep the ScheduledFuture return object).

更改上面的代码以取消任务:

Changes to the code above for cancelling the task :

1. 在 executeTaskT 方法之外声明 ScheduledFuture.

    private ScheduledFuture scheduledFuture;

1. 修改您对 schedule 的调用以保持返回对象如下:

    scheduledFuture = scheduler.schedule(exampleRunnable,
                    new Date(1432152000000L));

1. 对代码中某处的 scheduleFuture 对象调用取消

    boolean mayInterruptIfRunning = true;
    scheduledFuture.cancel(mayInterruptIfRunning);

这篇关于Spring调度任务——只运行一次的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！