Creating Controller, Model, and ViewResolvers

Spring MVC framework enables the separation of modules, namely Model, View, and Controller, and seamlessly handles application integration. This enables the developer to create complex applications using plain Java classes. The model object can be passed between the view and the controller using maps.

Spring MVC Framework Components

Model

• A model can be an object or a collection of objects that contains the application's data.
• Example: A User object with name, email, and age

View

• A view is used for displaying information to the user in a specific format.
• Technologies like Thymeleaf, JSP, and FreeMarker are used.
• Example: An HTML page showing user details.

Controller

• It contains the logical part of the application.
• The @Controller annotation is used to mark a class as a controller.
• It takes input from the user, works with the model, and returns a view.

Front Controller

• It is responsible for managing the flow of the web application.
• DispatcherServlet acts as a front controller in Spring MVC.

Spring MVC Request Flow: From Client to View

Prerequisites

• Eclipse (EE version).
• Tomcat Apache latest version

Steps to Build Spring MVC App with Java-Based Configuration

Step 1: Create a Maven Project

Go to File menu > Click on New > Select Maven Project. 

Step 2: Search for Maven Project 

In the search bar, type maven, select Maven Project, and click Next.

Step 3: Keep Default Settings 

Ensure the default settings remain unchanged and click Next.

Step 4: Select Maven Archetype 

Select maven-archetype-webapp for web applications and click Next.

Step 5: Configure Group ID and Artifact ID 

Provide a Group ID and Artifact ID.

Step 6: Configure Tomcat Runtime 

Right-click on the project > Properties

Click on Targeted Runtimes > Select the installed Apache Tomcat > Click Apply and Close. 

Step 7: Create Java Folder 

Ensure Java files are in src/main/java to build a Spring MVC project.

• Go to the src folder in the project.
• Right-click on main and select New Folder.

Name the folder as java. 

Step 8: Create Java Class 

Create a Java class named "AddController" inside com.geeksforgeeks.springmvc under src/main/java.

Step 9: Add Dependencies in pom.xml

This file contains the Maven dependencies for the Spring framework.

<project xmlns="https://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="https://maven.apache.org/POM/4.0.0
                             https://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>

  <groupId>com.example.springmvc</groupId>
  <artifactId>SpringMVCApp</artifactId>
  <packaging>war</packaging>
  <version>0.0.1-SNAPSHOT</version>

  <dependencies>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-webmvc</artifactId>
      <version>5.3.34</version>
    </dependency>
    <dependency>
      <groupId>javax.servlet</groupId>
      <artifactId>javax.servlet-api</artifactId>
      <version>4.0.1</version>
      <scope>provided</scope>
    </dependency>
    <dependency>
      <groupId>jstl</groupId>
      <artifactId>jstl</artifactId>
      <version>1.2</version>
    </dependency>
  </dependencies>

  <build>
    <finalName>SpringMVCApp</finalName>
  </build>
</project>

Step 10: Create Java Configuration Files

WebInitializer replaces with web.xml. The getServletMappings() function receives requests corresponding to the '/' URL mapping. getServletConfigClasses() configures the dispatcher servlet and transfers the handler to MVCconfig.class.

WebInitializer.java

package com.geeksforgeeks.web;

import org.springframework.web.servlet.support.AbstractAnnotationConfigDispatcherServletInitializer;

public class WebInitializer extends AbstractAnnotationConfigDispatcherServletInitializer {
    
    @Override
    protected Class<?>[] getRootConfigClasses() {
        return null;
    }

    @Override
    protected Class<?>[] getServletConfigClasses() {
        return new Class[] { MVCconfig.class };
    }

    @Override
    protected String[] getServletMappings() {
        return new String[] { "/" };
    }
}

Step 10: Create MVCconfig.java 

This file replaces the dispatcher servlet. The @ComponentScan annotation enables component scanning.

package com.geeksforgeeks.web;

import org.springframework.context.annotation.Bean;
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.view.InternalResourceViewResolver;

@Configuration
@EnableWebMvc
@ComponentScan("com.geeksforgeeks.web")
public class MVCconfig {

    @Bean
    public InternalResourceViewResolver viewResolver() {
        InternalResourceViewResolver resolver = new InternalResourceViewResolver();
        resolver.setPrefix("/WEB-INF/views/");
        resolver.setSuffix(".jsp");
        return resolver;
    }
}

Step 11: Create GreetController.java

This controller handles the /greet request.

package com.geeksforgeeks.web;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.servlet.ModelAndView;

@Controller
public class GreetController {

    @RequestMapping("/greet")
    public ModelAndView showView() {
        ModelAndView mv = new ModelAndView();
        mv.setViewName("result"); // Logical view name
        mv.addObject("result", "GeeksForGeeks Welcomes you to Spring!");
        return mv;
    }
}

Step 12: Create index.jsp

This is the landing page of the application.

<html>
<body>
    <h2>Hello World!</h2>
    <form action="greet">
        <input type="submit" value="Press to greet">
    </form>
</body>
</html>

Step 13: Create result.jsp 

This page is displayed when the button in index.jsp is pressed.

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1" isELIgnored="false"%>
<!DOCTYPE html>
<html>
<head>
    <meta charset="ISO-8859-1">
    <title>Insert title here</title>
</head>
<body>
    <h1>${result}</h1>
</body>
</html>

Run Application

Open browser type below URL:

http://localhost:8080/SpringMVCApp/index.jsp

We will see a simple HTML page with:

• A heading: "Hello World!"
• A form with a submit button labeled "Press to greet"

Output:

When you click "Press to greet", it sends a request to the /greet endpoint, which is handled by the GreetController which loads result.jsp and displays.

_shreya_garg_

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Article Tags :

• Java
• java-advanced
• Java-Spring
• Java-Spring-MVC