写springMvc的Demo时遇到 通配符的匹配很全面, 但无法找到元素 'context:component-scan' 的声明 解决办法

错误原因：

idea生成的命名空间依赖不完整导致报错，修改web.xml的命名空间为

        <beans xmlns="http://www.springframework.org/schema/beans"
             xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             xmlns:context="http://www.springframework.org/schema/context"
             xmlns:mvc="http://www.springframework.org/schema/mvc"
             xsi:schemaLocation="http://www.springframework.org/schema/beans
             http://www.springframework.org/schema/beans/spring-beans-4.2.xsd
             http://www.springframework.org/schema/mvc
             http://www.springframework.org/schema/mvc/spring-mvc-4.2.xsd
             http://www.springframework.org/schema/context
             http://www.springframework.org/schema/context/spring-context-4.2.xsd">