springboot2-监听spring容器初始化完成

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在使用Spring框架开发时, 有时我们需要在spring容器初始化完成后做一些操作, 那么我们可以通过自定义ApplicationListener 来实现.

自定义监听器

@Component
public class MyApplicationListener implements ApplicationListener<ContextRefreshedEvent> {

    @Override
    public void onApplicationEvent(ContextRefreshedEvent contextRefreshedEvent) {

        // 获取spring 上下文
        ApplicationContext applicationContext = contextRefreshedEvent.getApplicationContext();

        // do your work...
}

源码分析

1. springboot 启动应用, 执行 SpringApplication.run(String… args) 方法
2. run方法中执行完初始化上下文方法后, 会执行this.refreshContext方法, 刷新
3. 经过一堆方法跳转, 执行 AbstractApplicationContextl类的publishEvent(Object event, @Nullable ResolvableType eventType) 方法
4. 然后执行 SimpleApplicationEventMulticaster.multicastEvent(ApplicationEvent event, @Nullable ResolvableType eventType)
5. 然后依次执行所有监听器的onApplicationEvent()方法

// 遍历所有ApplicationListeners, 依次执行ApplicationListener 的onApplicationEvent()方法
public void multicastEvent(ApplicationEvent event, @Nullable ResolvableType eventType) {
    ResolvableType type = eventType != null ? eventType : this.resolveDefaultEventType(event);
    Iterator var4 = this.getApplicationListeners(event, type).iterator();

    while(var4.hasNext()) {
        ApplicationListener<?> listener = (ApplicationListener)var4.next();
        Executor executor = this.getTaskExecutor();
        if (executor != null) {
            executor.execute(() -> {
                this.invokeListener(listener, event);
            });
        } else {
            this.invokeListener(listener, event);
        }
    }

}