What is the Dispatcher Servlet?

Dispatcher Servlet is the central component of the Spring MVC web framework. It receives all incoming HTTP requests, acting as the front controller.

Algorithm of Dispatcher Servlet:

1. Receives an incoming request.
2. Determines the appropriate HandlerMapping to find a suitable handler (controller) for the request.
3. Calls the found handler.
4. The handler returns a ModelAndView (containing the logical name of the view and the data model).
5. The Dispatcher Servlet determines the ViewResolver to resolve the logical view name into a specific view object (e.g., JSP file).
6. Passes the data model to the view object.
7. The view object generates a response (e.g., HTML).
8. The Dispatcher Servlet sends the response to the client.

Configuration of the Dispatcher Servlet is usually done in web.xml or using Java configuration.

Example of configuration in web.xml:

<!-- DispatcherServlet configuration -->  
<servlet>
    <servlet-name>dispatcher</servlet-name>
    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
    <init-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>/WEB-INF/spring/dispatcher-config.xml</param-value>
    </init-param>
    <load-on-startup>1</load-on-startup>
</servlet>

<!-- URL mapping to DispatcherServlet -->  
<servlet-mapping>
    <servlet-name>dispatcher</servlet-name>
    <url-pattern>/</url-pattern>  <!-- Handles all requests -->
</servlet-mapping>