分别在Tomcat，spring初始化时注册监听器

Tomcat，spring初始化时加载自定义监听器方法

Tomcat初始化时加载自定义监听器方法：

  1.创建一个监听器MyListener继承ServletContextListener

//@Component //监听器是web层的组件，它是tomcat实例化的，不是Spring实例化的。不能放到Spring中   public class MyListener implements ServletContextListener {            private UserService userService = null;//UserService中的相关逻辑            @Override      public void contextDestroyed(ServletContextEvent event) {        }        @Override      public void contextInitialized(ServletContextEvent event) {     项目在启动时，把Spring配置文件通过Spring的监听器加载，存储到ServletContext中，我们只要在ServletContext中获取即可。          ApplicationContext context = (ApplicationContext) event.getServletContext()                                               .getAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE);          userService = (UserService) context.getBean("UserService");          System.out.println(userService);       }    }  、

         2.并在web.xml中配置该监听器：

这是tomcat加载spring容器的配置：

 <listener>  <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>  </listener>    <context-param>  <param-name>contextConfigLocation</param-name>  <param-value>classpath:beans.xml</param-value>  </context-param>

而加载我们自定义监听器也需要配置在web.xml中

<listener>  <listener-class>com.listener.MyListener</listener-class>  </listener>

 2.加载spring监听器方法

@Component//由加载spring容器时实例化该监听器public class CreateDefaultAdminListener implementsApplicationListener<ContextRefreshedEvent> {@Autowiredprivate LoginService loginService;@Overridepublic void onApplicationEvent(ContextRefreshedEvent event) {if(!loginService.hasAdmin()){loginService.createDefaultAdmin();}}}、