/**
 * SpringBoot使用 Listener
 */
@WebListener
public class OneListener implements ServletContextListener {

    @Override
    public void contextInitialized(ServletContextEvent servletContextEvent) {
        System.out.println("OneListener init ...");
    }

    @Override
    public void contextDestroyed(ServletContextEvent servletContextEvent) {
    }
}

@SpringBootApplication
//在 springBoot 启动时会扫描@WebListener并实例化
@ServletComponentScan
public class OneListenerApp {
    public static void main(String[] args) {
        SpringApplication.run(OneListenerApp.class, args);
    }
}

/**
 * SpringBoot使用 Listener
 */
public class TwoListener implements ServletContextListener {

    @Override
    public void contextInitialized(ServletContextEvent servletContextEvent) {
        System.out.println("TwoListener init ...");
    }

    @Override
    public void contextDestroyed(ServletContextEvent servletContextEvent) {

    }
}

@SpringBootApplication
public class TwoListenerApp {
    public static void main(String[] args) {
        SpringApplication.run(TwoListenerApp.class, args);
    }

    @Bean
    public ServletListenerRegistrationBean registrationListenerBean(){
        ServletListenerRegistrationBean bean = new ServletListenerRegistrationBean(new TwoListener());
        return bean;
    }
}