🔵 1. Project Setup

✅ Maven dependencies in pom.xml:

<dependencies>
    <!-- Spring Boot Starter Web -->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>

    <!-- Spring Boot Starter Thymeleaf -->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-thymeleaf</artifactId>
    </dependency>
</dependencies>

✅ These two starters are enough!

🔵 2. Create the Main Application Class

File: src/main/java/com/example/demo/DemoApplication.java

package com.example.demo;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class DemoApplication {
    public static void main(String[] args) {
        SpringApplication.run(DemoApplication.class, args);
    }
}

✅ This starts your Spring Boot app.

🔵 3. Create a Controller

File: src/main/java/com/example/demo/controller/HelloController.java

package com.example.demo.controller;

import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.GetMapping;

@Controller
public class HelloController {

    @GetMapping("/hello")
    public String sayHello(Model model) {
        model.addAttribute("username", "Stanley");
        return "hello"; // Return the template name (hello.html)
    }
}

✅ This controller:

Handles GET request to /hello
Adds a username attribute into the model
Returns the view hello.html

🔵 4. Create a Thymeleaf Template

File: src/main/resources/templates/hello.html

<!DOCTYPE html>
<html xmlns:th="http://www.thymeleaf.org">
<head>
    <title>Hello Page</title>
</head>
<body>

<h1 th:text="'Hello, ' + ${username} + '!'">Hello, Guest!</h1>

</body>
</html>

✅ Here:

th:text dynamically replaces the content of <h1> at runtime.
If username = "Stanley", the browser will see:

<h1>Hello, Stanley!</h1>

🔵 5. Run the Application

✅ Run DemoApplication.java (main() method).

Open your browser and go to:

http://localhost:8080/hello

You will see:

Hello, Stanley!

🎉 Congratulations! You have a working Spring Boot + Thymeleaf mini project!

🎯 Quick Full Architecture Overview

Layer	Code
Controller	`HelloController.java` (handles `/hello` request)
Template Engine	Thymeleaf (renders `hello.html`)
View (HTML page)	`hello.html` uses `${username}`

📢 Important Extras:

Thymeleaf templates must be placed inside src/main/resources/templates/.
Thymeleaf automatically resolves .html files — you don’t need to add .html in the controller (return "hello" not "hello.html").
Thymeleaf provides many more features: loops (th:each), conditionals (th:if), fragment reuse (th:fragment), etc.

Java.Thymeleaf.SmallExampleSpringBoot