Model-View-Controller (MVC) Design Pattern
The Model-View-Controller (MVC) design pattern is an architectural pattern that separates an application into three main components:
1. Model
- Represents the application’s data and business logic.
- Manages the data, logic, and rules of the application.
- Notifies the view of any changes in the data.
2. View
- Â Represents the presentation layer (UI) of the application.
- Â Displays the data from the model to the user.
- Â Sends user actions to the controller.
3. Controller
- Â Acts as an intermediary between the model and the view.
- Â Receives user input from the view and processes it.
- Â Updates the model based on user input and logic.
- Â Determines which view to display based on the model’s state.

Table of Contents
Project Structure
Java Example Using Spring MVC
1. Project Structure
```
src
└── main
└── java
└── com
└── example
└── config
└── WebConfig.java
└── controller
└── HomeController.java
└── model
└── Message.java
└── resources
└── application.properties
└── webapp
└── WEB-INF
└── views
└── home.jsp
└── web.xml
```
Maven Dependencies (pom.xml)
2. Maven Dependencies (pom.xml)
```xml
<dependencies>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-webmvc</artifactId>
<version>5.3.10</version>
</dependency>
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
<version>4.0.1</version>
<scope>provided</scope>
</dependency>
</dependencies>
```
Web Configuration (WebConfig.java)
3. Web Configuration (WebConfig.java)
```java
package com.example.config;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.EnableWebMvc;
import org.springframework.web.servlet.config.annotation.ViewResolverRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
@Configuration
@EnableWebMvc
@ComponentScan(basePackages = "com.example.controller")
public class WebConfig implements WebMvcConfigurer {
@Override
public void configureViewResolvers(ViewResolverRegistry registry) {
registry.jsp("/WEB-INF/views/", ".jsp");
}
}
```
Model (Message.java)
4. Model (Message.java)
```java
package com.example.model;
public class Message {
private String content;
public Message(String content) {
this.content = content;
}
public String getContent() {
return content;
}
public void setContent(String content) {
this.content = content;
}
}
```
Controller (HomeController.java)
5. Controller (HomeController.java)
```java
package com.example.controller;
import com.example.model.Message;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.GetMapping;
@Controller
public class HomeController {
@GetMapping("/")
public String home(Model model) {
Message message = new Message("Hello, Spring MVC!");
model.addAttribute("message", message.getContent());
return "home"; // returns the view name "home"
}
}
```
View (home.jsp)
6. View (home.jsp)
```jsp
<!DOCTYPE html>
<html>
<head>
<title>Home</title>
</head>
<body>
<h1>${message}</h1>
</body>
</html>
```
web.xml Configuration
7. web.xml Configuration
```xml
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee
http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
version="4.0">
<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>
<servlet-mapping>
<servlet-name>dispatcher</servlet-name>
<url-pattern>/</url-pattern>
</servlet-mapping>
</web-app>
```