Spring built-in event and custom event

1. Spring built-in event What?

• Spring events is a subclass of class ApplicationEvent, sent by the realization ApplicationEventPublisherAware interface class that implements the class monitor ApplicationListener interface.
• Spring has defined a set of built of events issued by the ApplicationContext container. (ContextRefreshedEvent, ContextStartedEvent, ContextStoppedEvent, ContextClosedEvent, RequestHandledEvent)
• To listen ApplicationContext event listener class should implement the interface and override ApplicationListener onApplicationEvent () method.

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. how to use custom events?

• Create an event class - Extended ApplicationEvent class, create event class.

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";
    }
}

• Create a send class - Send the class instance get ApplicationEventPublisher send events.

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");
    }
}

• Create a listener class - ApplicationListener implement the interface, create a listener class.

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());
    }
}