Spring内置事件以及自定义事件

1. Spring内置的事件有哪些？

• Spring中的事件是一个 ApplicationEvent类的子类，由实现 ApplicationEventPublisherAware 接口的类发送，实现 ApplicationListener 接口的类监听。
• Spring中已经定义了一组内置事件，这些事件由ApplicationContext容器发出。(ContextRefreshedEvent、ContextStartedEvent、ContextStoppedEvent、ContextClosedEvent、RequestHandledEvent)
• 要监听ApplicationContext事件，监听类应该实现ApplicationListener接口并重写onApplicationEvent()方法。

package tutorialspointEvent;

import org.springframework.context.ApplicationListener;
import org.springframework.context.event.ContextStartedEvent;
import org.springframework.context.event.ContextStoppedEvent;

public class CStartEventHandler implements ApplicationListener<ContextStartedEvent>  {
    @Override
    public void onApplicationEvent(ContextStartedEvent contextStartedEvent) {
        System.out.println("ContextStartedEvent收到了");
    }
}

2. 怎么使用自定义事件？

• 创建事件类 – 扩展ApplicationEvent类，创建事件类。

import org.springframework.context.ApplicationEvent;

/*
自定义事件
 */
public class CustomEvent extends ApplicationEvent {

    public CustomEvent(Object source) {
        super(source);
    }
    public String toString(){
        return "My Custom Event";
    }
}

• 创建发送类 – 发送类获取ApplicationEventPublisher实例发送事件。

import org.springframework.context.ApplicationEventPublisher;
import org.springframework.context.ApplicationEventPublisherAware;

/*
事件发布者
 */
public class CustomEventPublisher implements ApplicationEventPublisherAware {

    private ApplicationEventPublisher publisher;
    @Override
    public void setApplicationEventPublisher(ApplicationEventPublisher applicationEventPublisher) {
        this.publisher = applicationEventPublisher;
    }

    public void publish() {
        CustomEvent ce = new CustomEvent(this);
        publisher.publishEvent(ce);
        System.out.println("发布了一个"+"CustomEvent");
    }
}

• 创建监听类 – 实现ApplicationListener接口，创建监听类。

import org.springframework.context.ApplicationListener;
public class CustomEventHandler implements ApplicationListener<CustomEvent> {
    @Override
    public void onApplicationEvent(CustomEvent customEvent) {
        System.out.println("处理了"+customEvent.toString());
    }
}