Understanding spring dispatcher servlet initialization

Question

Here is how spring documentation recomends to initialize dispatcherServlet:

<web-app>
    <context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>/WEB-INF/root-context.xml</param-value>
    </context-param>
    <servlet>
        <servlet-name>dispatcher</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        <init-param>
            <param-name>contextConfigLocation</param-name>
            <param-value></param-value>
        </init-param>
        <load-on-startup>1</load-on-startup>
    </servlet>
    <servlet-mapping>
        <servlet-name>dispatcher</servlet-name>
        <url-pattern>/*</url-pattern>
    </servlet-mapping>
    <listener>
        <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
    </listener>
</web-app>

My question is about providing an empty param-value inside the init-param tag. Despite defining that param as context-param we still provide the empty value. Therefore contextConfigLocation should be null when passes to servlet's init() method. What's wrong, correct me please.

Answer 1

In Spring Web Applications, there are two types of container, each of which is configured and initialized differently.

• Application Context
• Web Application Context

Application context is inialised by config file's that you specified in as context-params and picked up by ContextLoaderListener. This is purely i would consider as business logic related beans.

Web application context is child of application context which may or may not be present. Each DispatcherServlet will have associated WebApplicationContext and which takes spring beans from your init-params to create context.

Whatever beans are available in the ApplicationContext can be referred to from each WebApplicationContext.

Reason why we have two different bean configurations is to keep a clear separation between middle-tier services such as business logic components and data access classes (that are typically defined in the ApplicationContext) and web- related components such as controllers and view resolvers (that are defined in the WebApplicationContext per Dispatcher Servlet).