73

对于常规的 Servlet,我想您可以声明一个上下文侦听器,但对于 Spring MVC,Spring 会让这变得更容易吗?

此外,如果我定义了一个上下文侦听器,然后需要访问我的servlet.xmlor中定义的 bean,我applicationContext.xml将如何访问它们?

4

5 回答 5

109

Spring 有一些您可以处理的标准事件。

为此,您必须创建并注册一个实现ApplicationListener接口的 bean,如下所示:

package test.pack.age;

import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationEvent;
import org.springframework.context.ApplicationListener;
import org.springframework.context.event.ContextRefreshedEvent;

public class ApplicationListenerBean implements ApplicationListener {

    @Override
    public void onApplicationEvent(ApplicationEvent event) {
        if (event instanceof ContextRefreshedEvent) {
            ApplicationContext applicationContext = ((ContextRefreshedEvent) event).getApplicationContext();
            // now you can do applicationContext.getBean(...)
            // ...
        }
    }
}

servlet.xml然后在orapplicationContext.xml文件中注册这个 bean :

<bean id="eventListenerBean" class="test.pack.age.ApplicationListenerBean" />

当应用程序上下文初始化时,Spring 会通知它。

在 Spring 3 中(如果您使用的是该版本),ApplicationListener该类是泛型的,您可以声明您感兴趣的事件类型,并且该事件将被相应地过滤。您可以像这样简化您的 bean 代码:

public class ApplicationListenerBean implements ApplicationListener<ContextRefreshedEvent> {

    @Override
    public void onApplicationEvent(ContextRefreshedEvent event) {
        ApplicationContext applicationContext = event.getApplicationContext();
        // now you can do applicationContext.getBean(...)
        // ...
    }
}
于 2011-12-31T10:46:25.000 回答
90

从 Spring 4.2 开始,您可以使用@EventListener文档

@Component
class MyClassWithEventListeners {

    @EventListener({ContextRefreshedEvent.class})
    void contextRefreshedEvent() {
        System.out.println("a context refreshed event happened");
    }
}
于 2015-10-27T14:08:58.070 回答
7

创建您的注释

  @Retention(RetentionPolicy.RUNTIME)
    public @interface AfterSpringLoadComplete {
    }

创建类

    public class PostProxyInvokerContextListener implements ApplicationListener<ContextRefreshedEvent> {

    @Autowired
    ConfigurableListableBeanFactory factory;

    @Override
    public void onApplicationEvent(ContextRefreshedEvent event) {
        ApplicationContext context = event.getApplicationContext();
        String[] names = context.getBeanDefinitionNames();
        for (String name : names) {
            try {
                BeanDefinition definition = factory.getBeanDefinition(name);
                String originalClassName = definition.getBeanClassName();
                Class<?> originalClass = Class.forName(originalClassName);
                Method[] methods = originalClass.getMethods();
                for (Method method : methods) {
                    if (method.isAnnotationPresent(AfterSpringLoadComplete.class)){
                        Object bean = context.getBean(name);
                        Method currentMethod = bean.getClass().getMethod(method.getName(), method.getParameterTypes());
                        currentMethod.invoke(bean);
                    }
                }
            } catch (Exception ignored) {
            }
        }
    }
}

通过@Component注解或者在xml中注册这个类

<bean class="ua.adeptius.PostProxyInvokerContextListener"/>

并在您想要在上下文初始化后运行的任何方法上使用注释,例如:

   @AfterSpringLoadComplete
    public void init() {}
于 2017-08-03T17:36:24.180 回答
1

我在输入 URL 时有一个单页应用程序,它正在创建一个包含来自多个数据库的数据的 HashMap(由我的网页使用)。我做了以下事情以在服务器启动期间加载所有内容-

1- 创建 ContextListenerClass

public class MyAppContextListener implements ServletContextListener
    @Autowired

    private  MyDataProviderBean myDataProviderBean; 

    public MyDataProviderBean getMyDataProviderBean() {

        return MyDataProviderBean;

    }

    public void setMyDataProviderBean(MyDataProviderBean MyDataProviderBean) {

        this.myDataProviderBean = MyDataProviderBean;

    }

    @Override
    public void contextDestroyed(ServletContextEvent arg0) {

        System.out.println("ServletContextListener destroyed");

    }


    @Override

    public void contextInitialized(ServletContextEvent context) {

        System.out.println("ServletContextListener started");

        ServletContext sc = context.getServletContext();

        WebApplicationContext springContext = WebApplicationContextUtils.getWebApplicationContext(sc);

        MyDataProviderBean MyDataProviderBean = (MyDataProviderBean)springContext.getBean("myDataProviderBean");

        Map<String, Object> myDataMap = MyDataProviderBean.getDataMap();

        sc.setAttribute("myMap", myDataMap);

    }

2- 在 web.xml 中添加以下条目

<listener>
    <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener> 
<listener>
    <listener-class>com.context.listener.MyAppContextListener</listener-class>
</listener>

3-在我的控制器类中更新代码以首先检查 servletContext 中的 Map

    @RequestMapping(value = "/index", method = RequestMethod.GET)
        public String index(@ModelAttribute("model") ModelMap model) {

            Map<String, Object> myDataMap = new HashMap<String, Object>();
            if (context != null && context.getAttribute("myMap")!=null)
            {

                myDataMap=(Map<String, Object>)context.getAttribute("myMap");
            }

            else
            {

                myDataMap = myDataProviderBean.getDataMap();
            }

            for (String key : myDataMap.keySet())
            {
                model.addAttribute(key, myDataMap.get(key));
            }
            return "myWebPage";

        }

当我启动我的 tomcat 时有这么大的变化,它会在 startTime 期间加载 dataMap 并将所有内容放在 servletContext 中,然后控制器类使用它从已经填充的 servletContext 中获取结果。

于 2016-04-20T11:03:05.573 回答
0

请按照以下步骤在应用程序上下文加载后进行一些处理,即应用程序准备好服务。

  1. 创建下面的注释即

    @Retention(RetentionPolicy.RUNTIME) @Target(value= {ElementType.METHOD, ElementType.TYPE}) 公共@interface AfterApplicationReady {}

2.创建Below Class,它是一个监听器,可以在应用程序就绪状态下调用。

    @Component
    public class PostApplicationReadyListener implements ApplicationListener<ApplicationReadyEvent> {

    public static final Logger LOGGER = LoggerFactory.getLogger(PostApplicationReadyListener.class);
    public static final String MODULE = PostApplicationReadyListener.class.getSimpleName();

    @Override
    public void onApplicationEvent(ApplicationReadyEvent event) {
        try {
            ApplicationContext context = event.getApplicationContext();
            String[] beans = context.getBeanNamesForAnnotation(AfterAppStarted.class);

            LOGGER.info("bean found with AfterAppStarted annotation are : {}", Arrays.toString(beans));

            for (String beanName : beans) {
                Object bean = context.getBean(beanName);
                Class<?> targetClass = AopUtils.getTargetClass(bean);
                Method[] methods = targetClass.getMethods();
                for (Method method : methods) {
                    if (method.isAnnotationPresent(AfterAppStartedComplete.class)) {

                        LOGGER.info("Method:[{} of Bean:{}] found with AfterAppStartedComplete Annotation.", method.getName(), beanName);

                        Method currentMethod = bean.getClass().getMethod(method.getName(), method.getParameterTypes());

                        LOGGER.info("Going to invoke method:{} of bean:{}", method.getName(), beanName);

                        currentMethod.invoke(bean);

                        LOGGER.info("Invocation compeleted method:{} of bean:{}", method.getName(), beanName);
                    }
                }
            }
        } catch (Exception e) {
            LOGGER.warn("Exception occured : ", e);
        }
    }
}

最后,当您在日志说明应用程序启动之前启动 Spring 应用程序时,将调用您的侦听器。

于 2018-07-04T16:43:45.543 回答