为啥Spring和Spring MVC包扫描要分开

开始学习springmvc各种小白问题

根据例子配置了spring扫描包，但是一直提示404错误，经过大量搜索，发现，扫描包的配置应该写在springmvc的配置文件中，而不是springmvc

配置成功的applicationContext 即 spring配置

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:aop="http://www.springframework.org/schema/aop"
       xmlns:c="http://www.springframework.org/schema/c"
       xmlns:context="http://www.springframework.org/schema/context"
       xmlns:flow="http://www.springframework.org/schema/webflow-config"
       xmlns:jee="http://www.springframework.org/schema/jee"
       xmlns:jms="http://www.springframework.org/schema/jms"
       xmlns:lang="http://www.springframework.org/schema/lang"
       xmlns:osgi="http://www.springframework.org/schema/osgi"
       xmlns:p="http://www.springframework.org/schema/p"
       xmlns:tx="http://www.springframework.org/schema/tx"
       xmlns:util="http://www.springframework.org/schema/util"

       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
          http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-4.3.xsd
          http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.3.xsd
          http://www.springframework.org/schema/webflow-config http://www.springframework.org/schema/webflow-config/spring-webflow-config-2.0.xsd
          http://www.springframework.org/schema/jee http://www.springframework.org/schema/jee/spring-jee-4.3.xsd
          http://www.springframework.org/schema/jms http://www.springframework.org/schema/jms/spring-jms-4.3.xsd
          http://www.springframework.org/schema/lang http://www.springframework.org/schema/lang/spring-lang-4.3.xsd
          http://www.springframework.org/schema/osgi http://www.springframework.org/schema/osgi/spring-osgi-1.2.xsd
          http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-4.3.xsd
          http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-4.3.xsd
">
   
     
      
         
</beans>

自动生成的，什么也没写

springMvc的配置spring-servlet

<?xml version="1.0" encoding="UTF-8"?>

<web-app xmlns="http://java.sun.com/xml/ns/javaee"
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
     version="3.0">
    <session-config>
        <session-timeout>
            30
        </session-timeout>
    </session-config>
 

 <listener>
        <listener-class>
            org.springframework.web.context.ContextLoaderListener
        </listener-class>
    </listener>
    <!-- 指定Spring Bean的配置文件所在目录。默认配置在WEB-INF目录下 -->
    <context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>WEB-INF/config/applicationContext.xml</param-value>
    </context-param>
    <!--SPRING MVC 配置-->
    <servlet>
        <servlet-name>spring</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        <init-param>
            <param-name>contextConfigLocation</param-name>
            <param-value>WEB-INF/config/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>
        <!--注意/和/*的区别-->
    </servlet-mapping>
    
    
</web-app>

 然后在web.xml中引入spring和springmvc的配置

 <listener>
        <listener-class>
            org.springframework.web.context.ContextLoaderListener
        </listener-class>
    </listener>
    <!-- 指定Spring Bean的配置文件所在目录。默认配置在WEB-INF目录下 -->
    <context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>WEB-INF/config/applicationContext.xml</param-value>
    </context-param>
    <!--SPRING MVC 配置-->
    <servlet>
        <servlet-name>spring</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        <init-param>
            <param-name>contextConfigLocation</param-name>
            <param-value>WEB-INF/config/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>
        <!--注意/和/*的区别-->
    </servlet-mapping>

这就成功了。为何扫描包不能写在spring的配置中呢

我查了一下

原理：   

      原来Spring 是父容器， Spring MVC是子容器， 子容器可以访问父容器的bean,父容器不能访问子容器的bean。 

     具体参照：

    Spring和SpringMVC父子容器关系初窥

      Spring为什么不做全局包扫描

      Spring与SpringMVC的容器关系分析

具体测试，后边跟进。

当前做法就是springmvc加载所有bean就行了