为什么applicationContext.xml和spring-servlet.xml中都有注解过滤<context:component-scan base-package="myp

Posted 2020-08-10

在刚学习SpringMVC框架整合时，你也许会产生疑问为什么Spring.xml和SpringMVC.xml中都有注解过滤。

<context:component-scan base-package="myproject"> 和<context:component-scan base-package="myproject.controller" />

在这里有一个比较有意思的问题，初学者也会产生困惑，那么他究竟有何不同？我思考和查询很久，话不多说，也实践做起：

（1）只在applicationContext.xml中配置如下

<context:component-scan base-package="myproject">

启动不报错，，但@Controller失效

 

（2）只在spring-servlet.xml中配置上述配置

 Error creating bean with name ‘org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping#0‘ defined in ServletContext resource [/WEB-INF/spring-mvc-......

Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name ‘commonController‘: Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: private eis.service.ICollegeServer eis.controller.CommonController.collService; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No matching bean of type [eis.service.ICollegeServer] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}
 

（3）在applicationContext.xml和spring-servlet.xml中都配置过滤<context:component-scan base-package="myproject"> 和<context:component-scan base-package="myproject.controller" />，

不报错，请求正常，

总结：由此可以分析<context:component-scan base-package="myproject">主要过滤@Controller，同时还查资料了解<context:component-scan base-package="myproject.controller" /> 配置项不但启用了对类包进行扫描以实施注释驱动 Bean 定义的功能，同时还启用了注释驱动自动注入的功能。