Spring MVC Behind The Scenes#

Components Of Spring MVC Application#

There are 3 main components of a Spring MVC Application:
- A set of web pages to layout UI components.
- A collection of Spring beans (controllers, services, etc).
- Spring configuration (XML, Annotations or Java).

Let's see the diagram of a Spring MVC Application below then we will go to details for every components.

So the Front Controller known as DispatcherServlet.
- It is a part of the Spring Framework.
- It already developed by Spring Develop Team.
- It incoming HTTP requests and delegate them to the the appropriate controller for processing.

When we work with Spring MVC, we don't need to create it anymore. We will focus on creating:
- Model Objects
- View Templates
- Controller Classes

The DispatcherServlet is the key component of the Spring MVC web framework. It is a servlet that receives incoming HTTP requests and then processes them through a series of handlers, which ultimately generate a response that is sent back to the client. The DispatcherServlet is responsible for managing the entire lifecycle of a request, including handling request mapping, view resolution, and exception handling. It also manages the flow of control between multiple handler components, such as controllers and view resolvers, and provides a unified interface for processing both synchronous and asynchronous requests.
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Controller is the code that is created by developer. It contains our business logic like:
- Handle the request.
- Store / retrieve data (database, web service...).
- Place data in model then send it to the appropriate view template.

The Model contains our data, so when our controller is executed and performs an operation to retrieve data from back-end systems like database, web services or Spring Bean. Then we can take that data and place it in into the Model. So the Model is like our container and we can ship it between various parts in our Spring MVC application and it will be passed over the View Template.

The Spring MVC is flexible, it supports many view templates and there are two most view templates are:
- JSP (Jave Server Page).
- JSTL (JSP Standard Tag Library)
So When the Model data comes to our view template then our JSP page can read that model data and display it.

In case that we don't want to use the JSP template, we can make use of some other templates like Thymeleaf, Groovy, Velocity, Freemarker etc.
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