DispatcherServlet

Spring MVC, like many other web frameworks, is designed using a "single sign-on (front controller)" design pattern, where a central Servlet, DispatcherServlet, provides common algorithm for processing requests, and the actual work is done by custom delegate components. This model is flexible and supports a variety of workflows.

DispatcherServlet, like any other Servlet, must be declared and rendered according to the Servlet specification using Java configuration or in web.xml . In turn, DispatcherServlet uses the Spring configuration to discover the delegate beans it needs to render requests, recognize views, handle exceptions, etc.

The following Java configuration example registers and initializes a DispatcherServlet that is automatically discovered by the servlet container:

public class MyWebApplicationInitializer implements WebApplicationInitializer {
    @Override
    public void onStartup(ServletContext servletContext) {
        // Load the Spring web application configuration
        AnnotationConfigWebApplicationContext context = new AnnotationConfigWebApplicationContext();
        context.register(AppConfig.class);
        // Create and register DispatcherServlet
        DispatcherServlet servlet = new DispatcherServlet(context);
        ServletRegistration.Dynamic registration = servletContext.addServlet("app", servlet);
        registration.setLoadOnStartup(1);
        registration.addMapping("/app/*");
    }
}

class MyWebApplicationInitializer : WebApplicationInitializer {
    override fun onStartup(servletContext: ServletContext) {
        // Load the Spring web application configuration
        val context = AnnotationConfigWebApplicationContext()
        context.register(AppConfig::class.java)
        // Create and register DispatcherServlet
        val servlet = DispatcherServlet(context)
        val registration = servletContext.addServlet("app", servlet)
        registration.setLoadOnStartup(1)
        registration.addMapping("/app/*")
    }
}

The following configuration example web.xml registers and initializes the DispatcherServlet:

<web-app>
    <listener>
        <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
    </listener>
    <context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>/WEB-INF/app-context.xml</param-value>
    </context-param>
    <servlet>
        <servlet-name>app</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>app</servlet-name>
        <url-pattern>/app/*</url-pattern>
    </servlet-mapping>
</web-app>