org.springframework.context.ApplicationListener<ApplicationReadyEvent>

最新推荐文章于 2025-06-13 10:23:04 发布

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最新推荐文章于 2025-06-13 10:23:04 发布

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原文链接：http://www.cnblogs.com/yangfei-beijing/p/9109956.html

本文介绍Spring框架中的事件监听机制，通过实现ApplicationListener接口并重写onApplicationEvent方法，可以定制容器初始化后的各种操作，如数据加载、缓存初始化等。同时讨论了在不同配置环境下可能遇到的多次调用问题及其解决办法。

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**
 * Interface to be implemented by application event listeners.
 * Based on the standard {@code java.util.EventListener} interface
 * for the Observer design pattern.
 *
 * <p>As of Spring 3.0, an ApplicationListener can generically declare the event type
 * that it is interested in. When registered with a Spring ApplicationContext, events
 * will be filtered accordingly, with the listener getting invoked for matching event
 * objects only.
 *
 * @author Rod Johnson
 * @author Juergen Hoeller
 * @param <E> the specific ApplicationEvent subclass to listen to
 * @see org.springframework.context.event.ApplicationEventMulticaster
 */
public interface ApplicationListener<E extends ApplicationEvent> extends EventListener

在一些业务场景中，当容器初始化完成之后，需要处理一些操作，比如一些数据的加载、初始化缓存、特定任务的注册，加载权限，菜单到redis，执行监听的job等等。这个时候我们就可以使用Spring提供的ApplicationListener来进行操作。

实现ApplicationListener接口并实现onApplicationEvent方法。把需要处理的操作放在onApplicationEvent中进行处理

@Override
    public void onApplicationEvent(ContextRefreshedEvent contextRefreshedEvent) {
        System.out.println("我的父容器为：" + contextRefreshedEvent.getApplicationContext().getParent());
        System.out.println("初始化时我被调用了。");
    }

使用Spring boot来进行操作，没有出现二次调用的问题。在使用传统的application.xml和project-servlet.xml配置中会出现二次调用的问题。主要原因是初始化root容器之后，会初始化project-servlet.xml对应的子容器。我们需要的是只执行一遍即可。那么上面打印父容器的代码用来进行判断排除子容器即可。在业务处理之前添加如下判断：

if(contextRefreshedEvent.getApplicationContext().getParent() != null){
            return;
}

代替写法为：

InitializingBean:spring 容器初始化之前执行

org.springframework.beans.factory.InitializingBean

/**
 * Interface to be implemented by beans that need to react once all their
 * properties have been set by a BeanFactory: for example, to perform custom
 * initialization, or merely to check that all mandatory properties have been set.
 *
 * <p>An alternative to implementing InitializingBean is specifying a custom
 * init-method, for example in an XML bean definition.
 * For a list of all bean lifecycle methods, see the BeanFactory javadocs.
 *
 * @author Rod Johnson
 * @see BeanNameAware
 * @see BeanFactoryAware
 * @see BeanFactory
 * @see org.springframework.beans.factory.support.RootBeanDefinition#getInitMethodName
 * @see org.springframework.context.ApplicationContextAware
 */
public interface InitializingBean

@Override
    public void afterPropertiesSet() throws Exception {
        loadParams();
        loadConfig();
    }

转载于:https://www.cnblogs.com/yangfei-beijing/p/9109956.html