Spring MVC is a framework for building web applications in Java. It is based on the Model-View-Controller (MVC) architecture, which separates the application into three components: the Model, the View, and the Controller.
Model
The model represents the data and the business logic of the application. In Spring MVC, the model is represented by POJO (Plain Old Java Object) classes that contain the data and the methods to access and manipulate it.
View
The view represents the presentation of the data to the user. In Spring MVC, the view is usually implemented using JSP (Java Server Pages) or Thymeleaf templates.
Controller
The controller is responsible for handling user requests and returning the appropriate response. In Spring MVC, the controller is implemented as a Java class that handles HTTP requests using annotations or XML configuration.
The following diagram shows the high-level architecture of Spring MVC:
+----------+ +-----------+ +----------+
| | | | | |
+----> Client +-----> Dispatcher +-----> Handler |
| | | | | | |
| +----------+ +-----------+ +----------+
|
| +-----------------+ +----------+
| | | | |
+----> View Resolver +-----> View |
| | | |
+-----------------+ +----------+The client sends a request to the Dispatcher servlet, which acts as the front controller for the Spring MVC application. The Dispatcher servlet delegates the request to a Handler, which processes the request and returns a ModelAndView object. The ModelAndView object contains the data to be displayed and the name of the view that will be used to render it.
The View Resolver is responsible for locating the appropriate view template based on the name specified in the ModelAndView object. The View then renders the data using the template and returns the response to the client.
Here is an example of a simple Spring MVC controller:
@Controller
public class MyController {
@RequestMapping("/hello")
public ModelAndView hello() {
ModelAndView mav = new ModelAndView("hello");
mav.addObject("message", "Hello World!");
return mav;
}
}This controller maps the URL “/hello” to the hello() method, which returns a ModelAndView object with the view name “hello” and a message attribute with the value “Hello World!”. The View Resolver then locates the “hello” view template and renders it with the message attribute value. The resulting response is sent back to the client.
Overall, Spring MVC provides a powerful and flexible framework for building web applications in Java. Its modular design and support for various view technologies make it easy to develop and maintain complex web applications.