A Spring WebApplicationInitializer uses a Servlet 3.0+ implementation to configure ServletContext programmatically.

Here's the sample code of the WebApplicationInitializer class, called MyApplicationInitializer.kt:

class MyApplicationInitializer: WebApplicationInitializer {

    @Throws(ServletException::class)
    override fun onStartup(container: ServletContext) {

        val ctx = AnnotationConfigWebApplicationContext()
        ctx.servletContext = container
        
        val servlet = container.addServlet("dispatcher", DispatcherServlet(ctx))
        servlet.setLoadOnStartup(1)
        servlet.addMapping("/")
    }
}

This class will help to map the project URL path, "", using start. As we are using a code-based annotation in place of an XML configuration, we are using AnnotationConfigWebApplicationContext. 

 Then we have created and registered the dispatcher servlet.