@Autowired在ServletContextListener中 [英] @Autowired in ServletContextListener

问题描述

i hava aclass InitApp

i hava aclass InitApp

@Component
public class InitApp implements ServletContextListener {

@Autowired
ConfigrationService weatherConfService;

/** Creates a new instance of InitApp */
public InitApp() {
   }

public void contextInitialized(ServletContextEvent servletContextEvent) {
    System.out.println(weatherConfService);
   }
public void contextDestroyed(ServletContextEvent servletContextEvent) {
   }
}

和web.xml中的监听器：

and listener in web.xml:

    <listener>
        <listener-class>com.web.Utils.InitApp</listener-class>
    </listener>

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

confService打印 - > null
有什么问题？

the confService print --> null what the problem?

推荐答案

当我遇到同样的问题时，我想到了一些想法。

A couple of ideas came to me as I was having the same issue.

一种是使用Spring utils从侦听器中的Spring上下文中检索bean：

First one is to use Spring utils to retrieve the bean from the Spring context within the listener:

Ex：

@WebListener
public class CacheInitializationListener implements ServletContextListener {

    /**
     * Initialize the Cache Manager once the application has started
     */
    @Override
    public void contextInitialized(ServletContextEvent sce) {
        CacheManager cacheManager = WebApplicationContextUtils.getRequiredWebApplicationContext(
                sce.getServletContext()).getBean(CacheManager.class);
        try {
            cacheManager.init();
        } catch (Exception e) {
            // rethrow as a runtime exception
            throw new IllegalStateException(e);
        }
    }

    @Override
    public void contextDestroyed(ServletContextEvent sce) {
        // TODO Auto-generated method stub

    }
}

如果您只有一个或两个bean，这样可以正常工作。否则它会变得单调乏味。另一个选择是显式调用Spring的Autowire实用程序：

This works fine if you only have one or two beans. Otherwise it can get tedious. The other option is to explicitly call upon Spring's Autowire utilities:

@WebListener
public class CacheInitializationListener implements ServletContextListener {

    @Autowired
    private CacheManager cacheManager;

    /**
     * Initialize the Cache once the application has started
     */
    @Override
    public void contextInitialized(ServletContextEvent sce) {
        SpringBeanAutowiringSupport.processInjectionBasedOnCurrentContext(this);
        try {
            cacheManager.init();
        } catch (Exception e) {
            // rethrow as a runtime exception
            throw new IllegalStateException(e);
        }
    }

    @Override
    public void contextDestroyed(ServletContextEvent sce) {
        // TODO Auto-generated method stub

    }
}

这两个解决方案中的警告是Spring上下文必须在这些中的任何一个可以工作之前首先加载。鉴于无法使用 @WebListener 定义监听器顺序，请确保在< c> c> c> c> c> c> c> c>中定义了 ContextLoaderListener 。 code> web.xml 强制首先加载它（Web描述符中定义的侦听器在注释定义的侦听器之前加载）。

The caveat in both these solutions, is that the Spring context must by loaded first before either of these can work. Given that there is no way to define the Listener order using @WebListener, ensure that the Spring ContextLoaderListener is defined in web.xml to force it to be loaded first (listeners defined in the web descriptor are loaded prior to those defined by annotation).

这篇关于@Autowired在ServletContextListener中的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！