Four Ways to Implement Event Listeners in Spring Boot

Spring Boot provides four ways to listen for events:

Manually add a listener to the ApplicationContext.

Load the listener as a Spring bean.

Configure the listener in application.properties.

Use the @EventListener annotation.

Custom events are created by extending ApplicationEvent, and custom listeners implement ApplicationListener<T> or use @EventListener on a method.

Method 1: Manual registration

Create MyListener1 implementing ApplicationListener<MyEvent>:

public class MyListener1 implements ApplicationListener<MyEvent> {
    Logger logger = Logger.getLogger(MyListener1.class);
    public void onApplicationEvent(MyEvent event) {
        logger.info(String.format("%s监听到事件源：%s.", MyListener1.class.getName(), event.getSource()));
    }
}

In the Spring Boot main class, obtain the ConfigurableApplicationContext and add the listener:

@SpringBootApplication
public class LisenterApplication {
    public static void main(String[] args) {
        ConfigurableApplicationContext context = SpringApplication.run(LisenterApplication.class, args);
        // Register listener
        context.addApplicationListener(new MyListener1());
    }
}

Method 2: Component scanning

Annotate the listener with @Component so Spring registers it automatically:

@Component
public class MyListener2 implements ApplicationListener<MyEvent> {
    Logger logger = Logger.getLogger(MyListener2.class);
    public void onApplicationEvent(MyEvent event) {
        logger.info(String.format("%s监听到事件源：%s.", MyListener2.class.getName(), event.getSource()));
    }
}

Method 3: Configuration file

Create MyListener3 (same as above) and add its fully‑qualified class name to application.properties:

context.listener.classes=com.listener.MyListener3

Method 4: @EventListener annotation

Define a bean without implementing ApplicationListener and annotate a method with @EventListener:

@Component
public class MyListener4 {
    Logger logger = Logger.getLogger(MyListener4.class);
    @EventListener
    public void listener(MyEvent event) {
        logger.info(String.format("%s监听到事件源：%s.", MyListener4.class.getName(), event.getSource()));
    }
}

Custom event class example:

@SuppressWarnings("serial")
public class MyEvent extends ApplicationEvent {
    public MyEvent(Object source) {
        super(source);
    }
}

Testing by publishing the event in the main class:

@SpringBootApplication
public class LisenterApplication {
    public static void main(String[] args) {
        ConfigurableApplicationContext context = SpringApplication.run(LisenterApplication.class, args);
        // Register listeners (if not using component scanning)
        context.addApplicationListener(new MyListener1());
        // Publish event
        context.publishEvent(new MyEvent("测试事件."));
    }
}

Running the application prints log messages from each listener, demonstrating that the four implementations are invoked in order.

Full source code is available at https://github.com/ingorewho/springboot-develope/tree/master/springboot-listener .