Building Java Web Applications with Spring Web MVC - Learn Java for Web Development - page 227

The DispatcherServlet
Like any servlet, DispatcherServlet needs to be configured in web.xml to be able to handle requests.
Configuring and using the DispatcherServlet requires the following:

You have to indicate to the container to load DispatcherServlet and map it to
URL patterns.

1.

2. After the DispatcherServlet is loaded, it creates its own
org.springframework.web.context.WebApplicationContext .
3. The DispatcherServlet then detects the SpringMVC components from this
application context, and if not found, it will use the default. These SpringMVC
components and their defaults will be explained later.
4. DispatcherServlet then delegates tasks to each of the SpringMVC
components (or their defaults) depending on the request.

Note DispatcherServlet creates its own WebApplicationContext , which contains the web-specific
components such as Controllers and ViewResolver . This WebApplicationContext is then nested inside
the root WebApplicationContext , which is loaded before the DispatcherServlet is initialized to ensure
that the web components in WebApplicationContext of DispatcherServlet can find their dependencies.

DispatcherServlet , like any other servlet, is declared in the web.xml file of your web application.
You need to map requests that you want DispatcherServlet to handle, by using a URL mapping in
the same web.xml file. Listing 5-34 illustrates a DispatcherServlet declaration and mapping.

Listing 5-34. Declaring and Mapping DispatcherServlet

<web-app>
<servlet>
<servlet-name>bookstore</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>bookstore</servlet-name>
<url-pattern>/bookstore/*</url-pattern>
</servlet-mapping>
</web-app>

In a Servlet 3.0 and newer environment, you can also use WebApplicationInitializer , an interface
provided by the Spring MVC framework, to configure the servlet container programmatically.
Listing 5-35 illustrates the programmatic equivalent of the previous web.xml example.