Spring ApplicationListener在webapp上被触发了两次 [英] Spring ApplicationListener gets fired twice on webapp

问题描述

我有一个应用程序侦听器，由于它会加载基本的用户信息数据，因此应该在每次webapp启动时仅执行一次.

I have an application listener that's supposed to execute only once per webapp startup, since it loads basic user info data.

public class DefaultUsersDataLoader implements ApplicationListener<ContextRefreshedEvent> {
  @Override
  @Transactional
  public void onApplicationEvent(ContextRefreshedEvent e) {...}
}

以某种方式，它执行两次:在应用程序启动时以及第一个请求到达服务器时.为什么会发生这种情况，我该如何预防呢?

Somehow, it gets executed twice: on app startup and when the first request arrives to the server. Why is this happening and how can I prevent it?

推荐答案

通常在Spring MVC应用程序中，您同时具有ContextLoaderListener和DispatcherServlet.这两个组件都创建了自己的ApplicationContext，这又触发了ContextRefreshedEvent.

Generally in a Spring MVC application you have both a ContextLoaderListener and DispatcherServlet. Both components create their own ApplicationContext which in turn both fire a ContextRefreshedEvent.

DispatcherServlet使用由ContextLoaderListener创建的ApplicationContext作为其父级.从子上下文触发的事件将传播到父上下文.

The DispatcherServlet uses the ApplicationContext as created by the ContextLoaderListener as its parent. Events fired from child contexts are propagated to the parent context.

现在，如果您在根上下文中定义了ApplicationListener<ContextRefreshedEvent>(由ContextLoaderListener加载的那个)，它将收到两次事件.

Now if you have an ApplicationListener<ContextRefreshedEvent> defined in the root context (the one loaded by the ContextLoaderListener) it will receive an event twice.

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