Introduction

Hello everyone, in this article I will discuss the Spring web MVC, the components of this framework, their roles, the architecture as well as the request execution flow in Spring MVC application. So please enjoy reading!

Spring MVC components

The Spring Web MVC framework provides Model-View-Controller (MVC) architecture and a lot of ready components that can be used to develop Web applications. In this section, we will focus mainly on the components:

1-Front controller

The front controller is responsible to perform pre-processing and post-processing of incoming requests.
For example:

• pre-processing request: capturing form data incoming from the client.
• post-processing request: returning data to client.
  

In Spring Web MVC based application we will use the DispatcherServlet as a front controller which is a pre-defined servlet provided by the Spring MVC module.

💡Java Servlet are programs that act as a middle layer between a request coming from a Web browser or HTTP client, and applications on the HTTP server.

2.Handler mapper

The handler mapper is a pre-defined class available in Spring MVC which is responsible to identify the request handler (controller) and return details to the DispatcherServlet.

3.Controller

A controller is a class which is responsible to handle the request, there are some pre-defined controllers available in the Spring MVC like below:

• org.springframework.web.servlet.mvc.SimpleFormController
• org.springframework.web.servlet.mvc.AbstractFormController
• org.springframework.web.servlet.mvc.multiaction.MultiActionController etc…
  

Also, we can define our costume controllers using the @Controller annotation.

4.Model and View

Once the request processing is completed the controller will return the org.springframework.web.servlet.ModelAndView object to the DispatcherServlet.

The model holds data retrieved from the data source.
The view represents a logical view name.

5.View resolvers

In Spring MVC we have multiple view resolver classes that implement the interface org.springframework.web.servlet.ViewResolver :

• org.springframework.web.servlet.view.InternalResourceViewResolver
• org.springframework.web.servlet.view.UrlBasedViewResolver etc…
  

These view resolvers are responsible to identify view files (location and extension).

6.View component

Responsible to render model data on view files.

💡 All the above-mentioned components (i.e. HandlerMapping, Controller, and ViewResolver) are parts of WebApplicationContext, which is an extension of the ApplicationContext with some extra features necessary for web applications.

Request execution flow

The Spring Web MVC framework is designed around the DispatcherServlet.

🔍 What happens behind the scene when an HTTP request is sent to the server:

1. Incoming Http request will be received by the Dispatcher servlet, which will send request URL to the HandlerMapper.
   

2. HandlerMapper will identify the appropriate request handler (controller) which is responsible to handle the request. After the HandlerMapper will send handler request details to DispatcherServlet.
   

3. DispatcherServlet will call the respective Controller class method.
   

4. Controller method will process the request and will send ModelAndView object to DispatcherServlet:
   • Model → Data
   • View → Logical file name

5. DispatcherServlet will send the view name to the ViewResolver.
   

6. ViewResolver will identify the view location & extension and sends data to DispatcherServlet.
   

7. DispatcherServlet will give the model and view details to the view component.
   

8. View component will render the appropriate view which holds the data model.
   

9. DispatcherServlet will send back the response to the browser.
   

Summary

That was all for this blog, I tried to clarify all the components of the Spring Web MVC and their roles as well as the request execution flow, I hope you enjoy it.
Don’t hesitate to share this blog whit your friends!!! 😄 😄