Question

Just a general question, when you define a Java based configuration web app. Ie.e have a class for : ApplicationContext and a WebApplicationInitializer class.

How does Spring know it has to load the beans, as no xml config files exists.. how does tomcat know anything about the webapp without a web.xml

Its a newbie question.. i appreciate that. 🙂

Answer 1

See this blog post from SpringSource blog, important part about web.xml has an example, basically you point to JavaConfigWebApplicationContext instead of default XmlWebApplicationContext in DispatcherServlet‘s <init-param>:

<web-app>
    <!-- Configure ContextLoaderListener to use JavaConfigWebApplicationContext
         instead of the default XmlWebApplicationContext -->
    <context-param>
        <param-name>contextClass</param-name>
        <param-value>org.springframework.config.java.context.JavaConfigWebApplicationContext</param-value>
    </context-param>
    <!-- Configuration locations must consist of one or more comma- or space-delimited
         fully-qualified @Configuration classes -->
    <context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>example.RootApplicationConfig</param-value>
    </context-param>
    <!-- Bootstrap the root application context as usual using ContextLoaderListener -->
    <listener>
        <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
    </listener>
    <!-- Declare a Spring MVC DispatcherServlet as usual -->
    <servlet>
        <servlet-name>dispatcher-servlet</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        <!-- Configure DispatcherServlet to use JavaConfigWebApplicationContext
             instead of the default XmlWebApplicationContext -->
        <init-param>
            <param-name>contextClass</param-name>
            <param-value>org.springframework.config.java.context.JavaConfigWebApplicationContext</param-value>
        </init-param>
        <!-- Again, config locations must consist of one or more comma- or space-delimited
             and fully-qualified @Configuration classes -->
        <init-param>
            <param-name>contextConfigLocation</param-name>
            <param-value>example.web.WebBeansConfig</param-value>
        </init-param>
    </servlet>
</web-app>