springboot2-监听spring容器初始化完成

Bertha 。 2022-04-24 01:56 565阅读 0赞

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);
            }
        }
    
    }