Likewise, every compliant Servlet container invokes contextDestroyed only after the servlet(s) and filters have finished their last invocation. So this is a good place to shutdown your database, make backups, or do any other clean-up chore appropriate to your web app.

我们正在讨论您的网络应用上下文"的生命周期.该上下文可能涉及一个或多个 servlet.上下文的这个生命周期超出了任何一个 servlet 的生命周期参与这个上下文.背景有点像蜂王，它在一个新的蜂巢中生下了她所有的雄蜂，在它们之前她生活在那里，当它们为她尽职尽责地死去时，她将比它们活得更久(如果这就是蜂巢的方式)有用吗?).

We are discussing the life cycle of your web app’s "context". That context may involve one, or more than one, servlet. This life cycle of the context goes beyond the life cycle of any one of the servlets participating in this context. The context is kinda-sorta like the queen bee who gives birth to all her drones in a new hive, where she was living before them and she will outlive them all as they die off in dutiful service to her (if that is how a hive works?).

制作一个 ServletContextListener 非常简单:用一对方法和一个注解制作一个类.

Making a ServletContextListener is quite easy: Make a class with a pair of methods plus an annotation.

添加一个新的 Java 类作为您的 Vaadin 应用程序的一部分.您可以随意命名课程.

Add a new Java class as part of your Vaadin app. You can name the class anything you want.

我将上下文侦听器添加到与我的主要 Vaadin 应用程序相同的包中 UI 类(MyUI.java 可能由您的 Vaadin 插件或 Maven 原型生成).似乎是一个自然的地方，因为上下文侦听器是我的 Vaadin 应用程序在 any 被处理之前启动的开始，而指定的 UI 类将成为我的 Vaadin 的第一部分为每个用户运行的应用.

I add my context listeners in the same package as my main Vaadin app UI class (MyUI.java may have been generated by your Vaadin plugin or by Maven archetype). Seems like a natural place as the context listener is the beginning of my Vaadin app launching before any user is handled while the designated UI class will then be the first piece of my Vaadin app being run for each user.

将您的类声明为实现 ServleContextListener.添加上面讨论的两个必需的方法；您的 IDE 可能会协助完成这项工作.

Declare your class as implementing ServleContextListener. Add the two required methods discussed above; your IDE may assist with this chore.

还有一个技巧:您必须通知 Servlet 容器有关此上下文侦听器的信息.有不止一种方法可以做到这一点，但我使用最简单的注释 @WebListener 类.

One more trick: You must inform the Servlet container about this context listener. There is more than one way to do this, but I use the simplest, an annotation @WebListener on the class.

这是一个完整的示例类.

Here is an entire example class.

package com.example.amazingapp;

import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import javax.servlet.annotation.WebListener;

/**
 *
 * @author Basil Bourque
 */
@WebListener
public class WebAppListener implements ServletContextListener {

    @Override
    public void contextInitialized ( ServletContextEvent sce ) {
        System.out.println ( "My Vaadin web app is starting. " );
    }

    @Override
    public void contextDestroyed ( ServletContextEvent sce ) {
        System.out.println ( "My Vaadin web app is shutting down." );
    }

}

这篇关于为我的 Vaadin 网络应用程序启动和停止挂钩?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，WP2