Introduction to Spring MVC

Spring MVC (Model-View-Controller) is a framework within the Spring Framework that facilitates building web applications. It follows the MVC design pattern, which separates the application into three interconnected components: the model, the view, and the controller. This overview covers the key concepts and basic setup of Spring MVC.

Key Concepts of Spring MVC

Model: Represents the application data and business logic.
View: Represents the presentation layer, typically rendered as HTML.
Controller: Handles user requests and maps them to appropriate service methods.
DispatcherServlet: The central servlet that dispatches requests to controllers.

Setting Up Spring MVC

To set up a Spring MVC project, you need to configure the DispatcherServlet and create controller classes. Here is an example of the basic setup:

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<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_3_1.xsd" 
         version="3.1">
    <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>

dispatcher-config.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:mvc="http://www.springframework.org/schema/mvc"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
       http://www.springframework.org/schema/beans/spring-beans.xsd
       http://www.springframework.org/schema/mvc
       http://www.springframework.org/schema/mvc/spring-mvc.xsd">

    <mvc:annotation-driven />

    <!-- Scan for controller classes -->
    <context:component-scan base-package="com.example.springmvc.controllers" />

    <!-- View resolver for JSP pages -->
    <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <property name="prefix" value="/WEB-INF/views/" />
        <property name="suffix" value=".jsp" />
    </bean>
</beans>

HomeController.java

// HomeController.java
package com.example.springmvc.controllers;

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) {
        model.addAttribute("message", "Welcome to Spring MVC!");
        return "home";
    }
}

home.jsp

<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<html>
<head>
    <title>Home</title>
</head>
<body>
    <h1>${message}</h1>
</body>
</html>

Running the Application

Deploy your application to a servlet container such as Apache Tomcat. Access the application in a web browser using the appropriate URL (e.g., http://localhost:8080/). You should see the welcome message rendered by the home.jsp view.

Key Points

Model: Represents application data and business logic.
View: Represents the presentation layer, typically rendered as HTML.
Controller: Handles user requests and maps them to appropriate service methods.
DispatcherServlet: The central servlet that dispatches requests to controllers.
Set up the DispatcherServlet in web.xml.
Configure Spring MVC using a configuration file (e.g., dispatcher-config.xml).
Create controller classes annotated with @Controller.
Create view templates (e.g., JSP pages) to render the response.

Conclusion

Spring MVC is a powerful framework for building web applications. By following the MVC design pattern, it promotes separation of concerns and provides a structured way to develop web applications. Understanding the key concepts and setting up a basic Spring MVC project lays the foundation for building more complex applications. Happy coding!