The scope <context: component-scan ... / "> and <context: property-placeholder ... /"> in hierarchical contexts

Question

I read:

Multiple component scans

What is the difference between ApplicationContext and WebApplicationContext in Spring MVC?

@RequestMapping annotation does not work if <context: component-scan /> in the application context instead of the dispatcher context (more on this later)

and several others, but not one of them answers the question:

Why is a scope <context:component-scan.../>limited if it is present in the ROOT context of a Spring MVC application?

, ​​ beans, @Component (@Repository, @Service @Controller).

:

applicationContext.xml ( )

<beans...>
    ...
    <context:component-scan base-package="com.myproject"/>
    <context:property-placeholder 
               ignore-resource-not-found="true" 
               location="classpath:default.properties, file:///etc/gallery/gallery.properties"/>
</beans>

main-servlet.xml ( )

<beans ...>
    ...
    <mvc:annotation-driven/>
    <mvc:resources mapping="/image/**"   location="file:/${gallery.location}" />
    <mvc:resources mapping="/css/**"     location="/css/"/>
    <mvc:resources mapping="/js/**"      location="/js/"/>
    <mvc:resources mapping="/images/**"  location="/images/"/>
    ...
</beans>

/MyProject//MainController.java

package com.myproject.web;
@Controller
public class MainController 
{
    ...

    @RequestMapping("/gallery/**")
    public String gallery(ModelMap modelMap, HttpServletRequest req, HttpServletResponse resp) throws IOException
    {
        ...
    }
}

Spring , beans, , . , <context:...> beans, . , , . BOTH <context:component-scan.../> <context:property-placeholder.../> .

<context:component-scan.../>

Sep 15, 2015 10:08:16 AM org.springframework.web.servlet.PageNotFound noHandlerFound
WARNING: No mapping found for HTTP request with URI [/gallery/habitat/20150813] in DispatcherServlet with name 'main'
Sep 15, 2015 10:08:16 AM org.springframework.web.servlet.PageNotFound noHandlerFound
WARNING: No mapping found for HTTP request with URI [/error] in DispatcherServlet with name 'main'

, @Controller .

<context:property-placeholder.../> @Value , , .

<context:.../> bean, , beans , . , component-scan, bean?

@RequestMapping, , < context: component-scan/ > , <mvc:annotation-driven /> , , component-scan.

"", , , , , - . , "" " ​​ " .

Answer 1

<context:property-placeholder />

<context:property-placeholder /> PropertySourcesPlaceholderConfigurer, [BeanFactoryPostProcessor]. BeanFactory, BeanFactory (ApplicationContext - ). , BeanFactory, . . , .

2 <context:property-placeholder />, , . , <context:property-placeholder /> <util:properties />. bean , bean <context:property-placeholder /> properties-ref. .

<util:properties id="appProperties" location="classpath:default.properties, file:///etc/gallery/gallery.properties" ignore-resource-not-found="true" />
<context:property-placeholder properties-ref="appProperties" />

<context:property-placeholder properties-ref="appProperties" />

<mvc:annotation-driven />

<mvc:annotation-driven />, , , RequestMappingHandlerMapper, bean , @RequestMapping @Controller . ApplicationContext, NOT . detectHandlerMethodsInAncestorContexts true, .

, , , , , beans, .. ( DispatcherServlet - , @Controllers.).

<context:component-scan />, , ( ) . beans , .. , <tx:annotation-driven />, AOP AOP, BeanFactoryPostProcessor BeanPostProcessor, .

<context:component-scan base-package="com.myproject">
    <context:exclude-filters type="annotation" expression="org.springframework.stereotype.Controller" />
</context:component-scan>

<context:component-scan base-package="com.myproject" use-default-filters="false">
    <context:include-filters type="annotation" expression="org.springframework.stereotype.Controller" />
</context:component-scan>