再谈spring mvc中的root/child WebApplicationContext

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之前的博客介绍了spring mvc里child WebApplicationContext和root ApplicationContext的关系，以及获取方式。最近我遇到了一个问题：按照之前的博客，无法获取child WebApplicationContext。场景是这样的：spring mvc只拦截特定路径的url，web.xml中配置如下：

<servlet><servlet-name>dispatcher</servlet-name><servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class><init-param><param-name>contextConfigLocation</param-name><param-value>/WEB-INF/spring/spring-dispatcher.xml</param-value></init-param><load-on-startup>1</load-on-startup></servlet><servlet-mapping><servlet-name>dispatcher</servlet-name><url-pattern>/mvc/*</url-pattern></servlet-mapping>

项目还提供了一个外部的servlet，给别的子系统调用，这个servlet不在spring mvc拦截路径范围内。

<servlet><servlet-name>none</servlet-name><servlet-class>net.aty.MyServlet</servlet-class></servlet><servlet-mapping><servlet-name>none</servlet-name><url-pattern>/test.do</url-pattern></servlet-mapping>

public class MyServlet extends HttpServlet {private static final long serialVersionUID = -2931357660081416782L;@Overrideprotected void doGet(HttpServletRequest request,HttpServletResponse response) throws ServletException, IOException {WebApplicationContext context = (WebApplicationContext) request.getAttribute(DispatcherServlet.WEB_APPLICATION_CONTEXT_ATTRIBUTE);System.out.println("context==null: " + (context==null));//true}}

我们在这个servlet里面不能获取到spring mvc的WebApplicationContext。我猜测原因是：我们的请求没有经过spring拦截，spring没有将child WebApplicationContext塞入到request对象中。

目前没有想到特别好的解决方式，使用了spring框架的ApplicationContextAware接口，将其存到全局变量中。

@Controllerpublic class FirstController implements ApplicationContextAware{@Autowiredprivate MyService service;@Autowiredprivate HttpServletRequest request;@RequestMapping("/mvc/first/hello.do")@ResponseBodypublic String hello(@RequestParam("userName") String userName) {return service.process(userName);}@Overridepublic void setApplicationContext(ApplicationContext applicationContext)throws BeansException {System.out.println("...........");SpringMvcContextUtils.setApplicationContext(applicationContext);}}

public class SpringMvcContextUtils {private static volatile ApplicationContext applicationContext;public static ApplicationContext getApplicationContext() {return applicationContext;}public static void setApplicationContext(ApplicationContext applicationContext) {SpringMvcContextUtils.applicationContext = applicationContext;}}

由于FirstController是由spring mvc加载的，它存在于child WebApplicationContext，所有我们使用ApplicationContextAware接口，获取到的就是child容器。

这样在外部的servlet中就可以拿到child容器了：

public class MyServlet extends HttpServlet {private static final long serialVersionUID = -2931357660081416782L;@Overrideprotected void doGet(HttpServletRequest request,HttpServletResponse response) throws ServletException, IOException {ApplicationContext another = SpringMvcContextUtils.getApplicationContext();}}

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