计划作业上的chedchedExecutorService，timerService和无状态EJB

问题描述

我正在尝试在服务器中实现一个系统，该系统将在数据库的基础上进行一些更新.

I'm trying to implement a system in server that will do some updates on database on a ragular basis.

此处:生成JSF托管Bean中的线程使用计时器进行计划的任务在其他一些类似的问题中，我看到BalusC强烈建议使用Stateless Bean，如果可能的话，请使用SchedulerExecuterService而不是Timer.

Here: Spawning threads in a JSF managed bean for scheduled tasks using a timer and in some other similar questions, I saw that BalusC strongly recommended to use Stateless Beans, if not possible SchedulerExecuterService rather than Timer.

这是我的情况.我需要一个JSF页面，可以在其中配置计划间隔.即，我可以将其规则从 每5分钟运行一次 更改为 每10分钟运行一次

Here is my situation. I need a JSF page in which I can configure the schedule interval. i.e. I can change its rule from run once in every 5 min to run once in 10 min

首先，我尝试使用@Schedule批注，这很棒.但是，我找不到改变间隔的方法.第一个问题，是否可以像我上面所说的那样动态地更改它?

First, I tried to use @Schedule annotation and it was great. However, I couldn't find a way to change interval with that. First question, is it possible to change it dynamically like I told above?

我当前正在使用SchedulerExecutorService，该程序是从无状态Bean的@PostConstruct调用的.第二个问题，强烈建议不使用Timer BalusC是EJB的TimerService吗?

I am currently using SchedulerExecutorService which is called from @PostConstruct of a Stateless Bean.Second question, is the Timer BalusC strongly recommended not to use is the TimerService of EJB?

第三个问题，我喜欢timerService的属性是:使用scheduleExpression 和 timerConfig .ScheduledExecutorService有任何类似的东西吗?

Third Question, I liked the properties of timerService which is:using scheduleExpression and timerConfig. Are there any similar things for ScheduledExecutorService?

其他问题:我走对了吗?我要拉的东西能以更好的方式完成吗?

Additional Question: Am I on right track? Can the thing that I am trying to pull be done in a better way?

推荐答案

我认为@Schedule仅用于固定的cron类计时器，其中EJB容器在EJB启动时部署计时器.显然，您需要与JSF页面关联的更多动态调度.

I think @Schedule is used only for fixed cron-like timers, where the EJB container deploys a timer at EJB startup. You obviously need more dynamic scheduling connected with a JSF page.

如果您在完整的Java EE 6概要文件上运行，为什么不将TimerService与无状态会话EJB一起使用，如下所示:

If you are running on a full Java EE 6 profile, why not use the TimerService with a Stateless Session EJB like this:

@Stateless
public class JobSchedulerBean {
    @Resource
    private TimerService timerService;

    // @PostConstruct
    public void initTimer() {
        // set initial timer
        ScheduleExpression sch = new ScheduleExpression();
        // set cron expression into sch
        timerService.createCalendarTimer(sch, new TimerConfig("myTimer", false));
    }

    public void rescheduleTimer(int interval) {
        // get timer from timer service
        for (Timer timer : timerService.getTimers()) {
            if (timer != null && timer.getInfo().equals("myTimer")) {
                timer.cancel();
            }
        }
        // schedule new timer, like in initTimer() method
    }

    @Timeout
    public void timeout(Timer timer) {
        // do the job
    }
}

@ManagedBean(eager=true)
@ApplicationScoped
public class JobRunner {
    private ScheduledExecutorService scheduler;
    private static final int POOL_SIZE = 1;

    ScheduledFuture<?> runHandle;

    @PostConstruct
    public void init() {
        scheduler = Executors.newScheduledThreadPool(POOL_SIZE);
        // set initial expiry to 5 minutes after 5 minutes delay
        runHandle = scheduler.scheduleAtFixedRate(new MyJob(), 5, 5, TimeUnit.MINUTES);
    }

    @PreDestroy
    public void destroy() {
        scheduler.shutdownNow();
    }

    public void reschedule(int newDelay) {
        // cancel old timer, but do not interrupt it
        runHandle.cancel(false);
        runHandle = scheduler.scheduleAtFixedRate(new MyJob(), newDelay, newDelay, TimeUnit.MINUTES);
    }
}

public class MyJob implements Runnable {
    public void run() { 
        // do the job
    }
}

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