在使用spring+springMVC的web工程中，我们一般会在web.xml中做如下配置：
<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>classpath:application.xml</param-value>
</context-param>
<!-- spring context listener -->
<listener>
<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>
<!-- spring mvc dispatcher servlet -->
<servlet>
<servlet-name>spring</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<init-param>
<param-name>contextConfigLocation</param-name>
<param-value>classpath:spring-servlet.xml</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>spring</servlet-name>
<url-pattern>/</url-pattern>
</servlet-mapping>
这样就会产生两个spring容器，一个父容器，一个子容器。
父容器Root WebApplicationContext由ContextLoaderListener加载
子容器WebApplicationContext for namespace ‘spring-servlet‘由DispatcherServlet加载（‘spring-servlet‘子容器的contextConfigLocation，web.xml中配置的）
从容器里面getBean的时候，先从本容器取，如果取不到再从父容器取
原码跟踪得到如下结果：
ContextLoaderListener:
beanFactory : org.s[email protected]501af69e: defining beans [commonService,org.springframework.context.annotation.internalConfigurationAnnotationProcessor,org.springframework.context.annotation.internalAutowiredAnnotationProcessor,org.springframework.context.annotation.internalRequiredAnnotationProcessor,org.springframework.context.annotation.internalCommonAnnotationProcessor,propertyConfigurer,messageSource,exceptionHandler,compositeFilter,dataSource,sqlSessionFactory,transactionManager,org.springframework.aop.config.internalAutoProxyCreator,org.springframework.transaction.annotation.AnnotationTransactionAttributeSource#0,org.springframework.transaction.interceptor.TransactionInterceptor#0,org.springframework.transaction.config.internalTransactionAdvisor,org.mybatis.spring.mapper.MapperScannerConfigurer#0,tokenClient,formTokenManager,formTokenAspect,formTokenPointCut,org.springframework.aop.aspectj.AspectJPointcutAdvisor#0,responseAspect,responsePointCut,org.springframework.aop.aspectj.AspectJPointcutAdvisor#1,multiViewResolver,excelView]; root of factory hierarchy
applicationContext:（对象地址：6be04fe1，父容器：null）
(o[email protected]6be04fe1) Root WebApplicationContext: startup date [Thu Feb 16 09:42:54 CST 2017]; root of context hierarchy
contextId : org.springframework.web.context.WebApplicationContext:
beanFactory.registerResolvableDependency(ApplicationContext.class, this);将父容器（根容器）注册到父容器的beanFactory中
DispatcherServlet:
ServletContext : [email protected]
applicationContext : （ 对象地址：8323ee8，父容器：ContextLoaderListener加载的 applicationContext，即 Root WebApplicationContext）
(o[email protected]8323ee8) WebApplicationContext for namespace ‘spring-servlet‘: startup date [Thu Jan 01 08:00:00 CST 1970]; parent: Root WebApplicationContext
contextId : org.springframework.web.context.WebApplicationContext:/spring
beanFactory.registerResolvableDependency(ApplicationContext.class, this); 将子容器注册到子容器的beanFactory中
父容器的ListableBeanFactory中注册的bean：（由ContextLoadListener初始化的容器）
(java.lang.String[]) [commonService initService pageService org.springframework.context.annotation.internalConfigurationAnnotationProcessor org.springframework.context.annotation.internalAutowiredAnnotationProcessor org.springframework.context.annotation.internalRequiredAnnotationProcessor org.springframework.context.annotation.internalCommonAnnotationProcessor propertyConfigurer messageSource exceptionHandler compositeFilter dataSource sqlSessionFactory transactionManager org.springframework.aop.config.internalAutoProxyCreator org.springframework.transaction.annotation.AnnotationTransactionAttributeSource#0 org.springframework.transaction.interceptor.TransactionInterceptor#0 org.springframework.transaction.config.internalTransactionAdvisor org.mybatis.spring.mapper.MapperScannerConfigurer#0 tokenClient formTokenManager formTokenAspect formTokenPointCut org.springframework.aop.aspectj.AspectJPointcutAdvisor#0 responseAspect responsePointCut org.springframework.aop.aspectj.AspectJPointcutAdvisor#1 multiViewResolver excelView org.springframework.context.annotation.ConfigurationClassPostProcessor.importAwareProcessor org.springframework.context.annotation.ConfigurationClassPostProcessor.enhancedConfigurationProcessor ICommonDao IPageDao]
子容器的ListableBeanFactory中注册的bean：（由DispatcherServlet初始化的容器）
(java.lang.String[]) [baseTestController captchaController errorPageTestController excelExportController exceptionHandlerTestController paramProcessController tokenTestController validatorTestController org.springframework.context.annotation.internalConfigurationAnnotationProcessor org.springframework.context.annotation.internalAutowiredAnnotationProcessor org.springframework.context.annotation.internalRequiredAnnotationProcessor org.springframework.context.annotation.internalCommonAnnotationProcessor org.springframework.aop.config.internalAutoProxyCreator mvcContentNegotiationManager org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping#0 org.springframework.format.support.FormattingConversionServiceFactoryBean#0 org.springframework.validation.beanvalidation.OptionalValidatorFactoryBean#0 org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter#0 mvcUriComponentsContributor org.springframework.web.servlet.handler.MappedInterceptor#0 org.springframework.web.servlet.mvc.method.annotation.ExceptionHandlerExceptionResolver#0 org.springframework.web.servlet.mvc.annotation.ResponseStatusExceptionResolver#0 org.springframework.web.servlet.mvc.support.DefaultHandlerExceptionResolver#0 org.springframework.web.servlet.handler.BeanNameUrlHandlerMapping org.springframework.web.servlet.mvc.HttpRequestHandlerAdapter org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter org.springframework.web.servlet.resource.DefaultServletHttpRequestHandler#0 org.springframework.web.servlet.handler.SimpleUrlHandlerMapping#0 org.springframework.web.servlet.view.InternalResourceViewResolver#0]