🔄 Understanding DispatcherServlet in Spring MVC: The Heart of Spring Web Applications

If you’re diving into Spring MVC, one class you’ll encounter at the very core is DispatcherServlet. It might sound like just another servlet, but it’s actually the central piece of Spring’s web MVC framework.

In this blog post, we’ll demystify the role and working of DispatcherServlet, explain its lifecycle, and show how it fits into the overall request handling process.

📌 What is DispatcherServlet?

DispatcherServlet is the front controller in Spring MVC. That means it’s the entry point for every HTTP request in a Spring web application.

It receives all requests coming to your web application, decides which controller to call, processes the response, and returns it to the user. Think of it as the traffic controller of your application.

📦 Class Information

• Class: org.springframework.web.servlet.DispatcherServlet
• Superclass: FrameworkServlet → HttpServlet

🧭 Why is DispatcherServlet Important?

It simplifies request handling using Spring’s MVC design pattern, which separates:

• Model (data)
• View (UI)
• Controller (business logic)

This makes your code clean, modular, and maintainable.

🔁 How Does DispatcherServlet Work?

1. Request Received: Servlet container (like Tomcat) forwards the HTTP request to DispatcherServlet.
2. Handler Mapping: It finds which controller method should handle the request.
3. Handler Adapter: It delegates the request to that controller method.
4. ModelAndView: The controller returns data + view name.
5. View Resolver: Resolves the view name to an actual page (JSP, Thymeleaf).
6. Response: Final response is rendered and sent to the user.

⚙️ Example Configuration (Without Spring Boot)

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

<servlet-mapping>
  <servlet-name>spring</servlet-name>
  <url-pattern>/</url-pattern>
</servlet-mapping>
  

🚀 With Spring Boot

In Spring Boot, you don’t need to configure DispatcherServlet manually. It is automatically registered and mapped to /.

📊 DispatcherServlet Workflow Diagram

✅ Key Features of DispatcherServlet

• Centralized Request Handling
• Extensible with Interceptors and Filters
• Supports REST and traditional web apps
• Integrates with JSP, Thymeleaf, FreeMarker, etc.

📝 Final Thoughts

DispatcherServlet is the foundation of Spring MVC. It brings together the flexibility of Java Servlets and the power of the MVC pattern. Whether you’re building a traditional web app or a RESTful service, understanding how it works is essential for mastering the Spring Framework.

If you’re using Spring Boot, you’re already benefiting from DispatcherServlet—you just don’t see it!