springboot -03 Event Listeners

  In the actual development, often encounter this scenario:

When something is completed, we need to inform other modules perform corresponding processing. We can send a request to a notification, but a better approach is accomplished by an event listener. Event Listener is based on the design pattern of releases - subscription, observer mode to achieve.

Next we springboot to tell the story based on a custom event listeners process.

1. Configure custom event: MyEvent extends ApplicationEvent
2. Configure custom listeners: MyApplicationListener implements ApplicationListener
3. Event publishing: Event publishing using the spring container: context.publishEvent

2 which configure a custom listeners in four ways:

2.1: Inheritance ApplicationEvent rewrite onApplicationEvent, the current must be injected into the spring bean container.

public class MyEvent extends ApplicationEvent {

    public MyEvent(Object source) {
        super(source);
    }
}

@Component
public class MyApplicationListener implements  ApplicationListener{

    public void onApplicationEvent(ApplicationEvent event) {
        System.out.println(event.getSource());
        System.out.println(event.getClass().getName());
    }
}

 

2.2: Inheritance ApplicationEvent rewrite onApplicationEvent, the use of container reprint listener context.addApplicationListener (new MyApplicationListener ());

public class MyEvent extends ApplicationEvent {

    public MyEvent(Object source) {
        super(source);
    }
}

public class MyApplicationListener implements  ApplicationListener{

    public void onApplicationEvent(ApplicationEvent event) {
        System.out.println(event.getSource());
        System.out.println(event.getClass().getName());
    }
}

@SpringBootApplication(scanBasePackages = "com.example.eventListener")
public class SpringbootApplication_listener {

    public static void main(String[] args) {
        SpringApplication springApplication = new SpringApplication(SpringbootApplication_listener.class);
        ConfigurableApplicationContext context = springApplication.run(args);
        context.addApplicationListener(new MyApplicationListener());
        context.publishEvent(new MyEvent("测试事件监听"));

      //  context.close();
    }
}

 

 

2.3: Inheritance ApplicationEvent rewrite onApplicationEvent, the configuration file, add a listener:

public class MyEvent extends ApplicationEvent {

    public MyEvent(Object source) {
        super(source);
    }
}

public class MyApplicationListener implements  ApplicationListener{

    public void onApplicationEvent(ApplicationEvent event) {
        System.out.println(event.getSource());
        System.out.println(event.getClass().getName());
    }
}

application.yml

context:
  listener:
    classes: com.example.eventListener.MyApplicationListener

2.4: utilizing annotation @EventListener, can customize multiple methods, does not require class inherits the ApplicationEvent, current must be injected into the spring type container.

public class MyEvent extends ApplicationEvent {

    public MyEvent(Object source) {
        super(source);
    }
}

@Component
public class MyApplicationListener {

    @EventListener
    public void onApplicationEvent11(ApplicationEvent event) {
        System.out.println(event.getSource());
        System.out.println(event.getClass().getName());
    }
}