Springboot使用@WebListener 作为web监听器的过程解析

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

@WebListener
public class SessionListener  implements HttpSessionAttributeListener, HttpSessionListener {
    // ... ... 省略实现方法
}

@WebListener
public class ContextListener  implements ServletContextAttributeListener,ServletContextListener {
      // ... ... 省略实现方法
}

@Component
public class BeanContextListener implements ServletContextListener {
     // ... ... 省略实现方法
}

public class ConfigContextListener implements ServletContextListener {
    // ... .... 省略实现方法
}

@Bean
public ServletListenerRegistrationBean configContextListener() {
    ServletListenerRegistrationBean bean = new ServletListenerRegistrationBean();
    bean.setListener(new ConfigContextListener());
    return bean;
}

public class SelfContextListener implements ServletContextListener {
    // ... ... 省略实现方法
}

@Component
public class ExtendServletConfigInitializer implements ServletContextInitializer {
    @Override
    public void onStartup(ServletContext servletContext) throws ServletException {
        servletContext.addListener(SelfContextListener.class);
    }
}