The ContextLoaderListener class

The first step of updating the web.xml file is to remove it and replace it with javax.servlet.ServletContainerInitializer, which is the preferred approach to Servlet 3.0+ initialization. Spring MVC provides the o.s.w.WebApplicationInitializer interface, which leverages this mechanism. In Spring MVC, the preferred approach is to extend o.s.w.servlet.support.AbstractAnnotationConfigDispatcherServletInitializer. The WebApplicationInitializer class is polymorphically o.s.w.context.AbstractContextLoaderInitializer and uses the abstract createRootApplicationContext() method to create a root ApplicationContext, then delegates it to ContextLoaderListener, which is registered in the ServletContext instance, as shown in the following code snippet:

    //src/main/java/c/p/s/web/configuration/WebAppInitializer

    public class WebAppInitializer extends   
    AbstractAnnotationConfigDispatcherServletInitializer {
        @Override
        protected Class<?>[] getRootConfigClasses() {
            return new Class[] { JavaConfig.class, SecurityConfig.class,    
            DataSourceConfig.class };
        }
        ...
    }

The updated configuration will now load SecurityConfig.class from the classpath of the WAR file.