JSP / Servlet Web应用程序中的后台计时器任务 [英] Background timer task in JSP/Servlet web application

问题描述

我希望每隔6小时从订阅中检索并将订阅源存储到DB。我想在后台有一个计时器线程来完成这个任务。

I want to retrieve from subscription and store feeds to DB from subscription after every 6 hours. I want to have a timer thread in background to accomplish this task.

最好的方法是什么？普通的计时器线程或Quartz API？

What's the best way? A normal timer thread or Quartz API?

推荐答案

首先，我不会使用JSP。它不适用于。

To start, I wouldn't use JSP for this. There it is not for.

当您使用Java EE 5时，请使用容器提供的jobscheduling API。更多细节取决于您正在使用的容器。例如，JBoss AS 5随附了Quartz。或者当您在JSP / Servlet上使用提供jobscheduling API的框架时，例如 Spring ，那么你应该使用它。

When you're on Java EE 5, use the container-provided jobscheduling APIs for this. Further detail depends on the container you're using. JBoss AS 5 for example ships with Quartz out the box. Or when you're using a framework on top of JSP/Servlet which offers jobscheduling APIs, like as Spring, then you should use it.

如果没有（例如你正在使用）只是Tomcat 6），或者你想独立于容器和/或框架，创建一个 ServletContextListener ，带有 ScheduledExecutorService 。有关详细信息，请参阅此答案。

If there are none (e.g. you're using just Tomcat 6), or you want to be independent from the container and/or framework, create a ServletContextListener with a ScheduledExecutorService. Further detail can be found in this answer.

或者当你已经在支持EJB 3.1的Java EE 6容器上时（JBoss AS 6，GlassFish 3，但是不是 Tomcat 7） ），最简单的方法是创建一个 @使用的Singleton EJB @Schedule 方法。

Or when you're already on a Java EE 6 container which supports EJB 3.1 (JBoss AS 6, GlassFish 3, but thus not Tomcat 7), easiest is to create a @Singleton EJB with @Schedule method.

@Singleton
public class UpdateSubscriptions {

    @Schedule(hour="*/6", minute="0", second="0", persistent=false)
    public void run() {
        // Do your job here.
    }

}        

就是这样。无需进一步配置。

That's it. No further configuration is necessary.

更新：根据评论，您正在使用Tomcat（6或7？）。要在webapp启动期间启动一个每6小时运行一次任务的线程，请使用 beforelinked answer 并在 scheduleAtFixedRate（） 方法

Update: as per the comments, you're using Tomcat (6 or 7?). To start a thread during webapp's startup which runs the task every 6 hours, use the example as provided in the beforelinked answer and make the following change in the scheduleAtFixedRate() method

scheduler.scheduleAtFixedRate(new UpdateSubscriptions(), 0, 6, TimeUnit.HOURS);

类 UpdateSubscriptions 必须实现 Runnable 并且实际工作需要在 run（） @Override ，如链接答案中的示例所示。

The class UpdateSubscriptions must implement Runnable and the actual job needs to be done in the run() method which you @Override, like as in the example in the linked answer.

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