解决@Autowired在ServletContextListener中失效的一种方法

最新推荐文章于 2023-03-30 16:45:35 发布

sf_suifeng

最新推荐文章于 2023-03-30 16:45:35 发布

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本文介绍了如何在Servlet上下文监听器中使用Spring的自动装配功能。提供了两种方法：一种是通过Spring实用工具类检索Bean；另一种是直接利用Spring的Autowire工具进行注入。为确保这些方法生效，需配置Spring ContextLoaderListener先于其他监听器加载。

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原文是英文，看了好半天才解决了这个问题，mark一下

原文地址：http://stackoverflow.com/questions/17656046/autowired-in-servletcontextlistener

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

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

    }
}

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

    }
}

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).