Introduction

Spring Boot is a powerful framework for building web applications in Java. It provides a streamlined and opinionated approach to application development, making it easy to create web applications with minimal configuration. In this guide, we'll walk you through the steps of building a basic Spring Boot web application, complete with sample code and explanations.


Prerequisites

Before you start, make sure you have the following prerequisites:


Step 1: Create a Spring Boot Project

The first step is to create a Spring Boot project. You can do this using the Spring Initializr or through your IDE. Let's assume you're using the Spring Initializr:

  1. Go to the Spring Initializr website.
  2. Configure your project by selecting the desired options, such as project type, language, and packaging. For this example, choose "Maven" as the build tool and "Jar" as the packaging.
  3. Add dependencies for "Spring Web" and any other dependencies you need.
  4. Click the "Generate" button to download a ZIP file containing your project template.

Once you have the project template, import it into your IDE and you're ready to start building your web application.


Step 2: Create a Controller

In Spring Boot, controllers are responsible for handling HTTP requests and returning responses. Create a simple controller class:

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;
@Controller
public class HomeController {
    @GetMapping("/")
    public String home() {
        return "index";
    }
}

In this example, the home() method maps to the root URL ("/") and returns the "index" template.


Step 3: Create a Template

To display content to users, you need to create an HTML template. You can use the Thymeleaf templating engine, which is integrated with Spring Boot. Create an "index.html" file in your project's templates directory:

<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml" xmlns:th="http://www.thymeleaf.org">
<head>
    <title>Spring Boot Web Application</title>
</head>
<body>
    <h1>Welcome to Spring Boot Web Application</h1>
    <p>This is a simple web application built with Spring Boot.</p>
</body>
</html>

Step 4: Run the Application

Now, you're ready to run your Spring Boot web application:

  1. Start your Spring Boot application by running the main class with a public static void main(String[] args) method.
  2. Access the application by opening a web browser and navigating to http://localhost:8080/.

You should see the welcome message from your "index.html" template.


Conclusion

Building a Spring Boot web application is straightforward and allows you to quickly create web applications using Java. This guide covered the essential steps, from creating a Spring Boot project to creating a controller and template. You can expand on this foundation to build more complex and feature-rich web applications.