Spring : Configuring web.xml programatically

Spring 3.1introdced the support for Servlet 3's code-based configuration, which can be used as an alternative to the web deployment descriptor file web.xml. For this purpose, Spring has come up with 
an interface namely WebApplicationInitializer. 

The traditional web.xml file I have with me is as follows : 

<?xml version="1.0" encoding="UTF-8"?> <?xml version="1.0" encoding="UTF-8"?> <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" version="3.0"> <servlet> <servlet-name>assortedmind</servlet-name> <servlet-class> org.springframework.web.servlet.DispatcherServlet</servlet-class> <load-on-startup>1</load-on-startup> </servlet> <servlet-mapping> <servlet-name>assortedmind</servlet-name> <url-pattern>/hello/*</url-pattern> </servlet-mapping> </web-app>

And my servlet configuration file assortedmind-servlet.xml is as follows :

<?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:p="http://www.springframework.org/schema/p" xmlns:context="http://www.springframework.org/schema/context" xmlns:mvc="http://www.springframework.org/schema/mvc" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.1.xsd http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-4.1.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.1.xsd"> <context:annotation-config> </context:annotation-config> <mvc:annotation-driven> </mvc:annotation-driven> <context:component-scan base-package="com.assortedmind.controller"> </context:component-scan> </beans>

The servlet configuration is kept simple for the time sake. 

With these traditional xmls in mind, let us try to achieve the same purpose through a code based approach. The following piece of code can be used to replace web.xml

package com.assortedmind.configurations; import javax.servlet.ServletContext; import javax.servlet.ServletException; import javax.servlet.ServletRegistration; import org.springframework.context.annotation.Configuration; import org.springframework.web.WebApplicationInitializer; import org.springframework.web.context.ContextLoaderListener; import org.springframework.web.context.support.AnnotationConfigWebApplicationContext; import org.springframework.web.servlet.DispatcherServlet; @Configuration public class WebapplicationConfig implements WebApplicationInitializer{ //replaces web.xml :) public void onStartup(ServletContext servletContext) throws ServletException { AnnotationConfigWebApplicationContext assortedMindContext = new AnnotationConfigWebApplicationContext(); // Registers the servlet configuraton with the dispatcher servlet context assortedMindContext.register(MVCConfigur.class); assortedMindContext.setServletContext(servletContext); ServletRegistration.Dynamic dispatcher = servletContext.addServlet("assortedmind", new DispatcherServlet(assortedMindContext)); dispatcher.setLoadOnStartup(1); dispatcher.addMapping("/hello/*"); } }

And the assortedmind-servlet.xml can be coded as follows :

package com.assortedmind.configurations; import org.springframework.context.annotation.ComponentScan; import org.springframework.context.annotation.Configuration; import org.springframework.core.Ordered; import org.springframework.web.servlet.config.annotation.EnableWebMvc; import org.springframework.web.servlet.config.annotation.ViewControllerRegistry; import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter; @Configuration @EnableWebMvc @ComponentScan("com.assortedmind.controller") public class MVCConfigur extends WebMvcConfigurerAdapter { }