Spring Boot RESTful Web Services

🌱 What is Spring Boot?

Spring Boot is a tool in Java that helps you build web apps and APIs quickly. It removes a lot of boring setup and lets you just focus on writing your logic.

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🌐 What are RESTful Web Services?

RESTful Web Services allow computers to talk to each other over the internet using HTTP (like your browser does).

Imagine this:

🧑‍🍳 You ask a restaurant (a server) for a menu item (a resource), like /burger.

The restaurant gives it to you in a standard way (usually JSON format).

That’s a RESTful service!

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🤔 Why Use Spring Boot for REST?

✅ Quick to set up

✅ Less code needed

✅ Easy to test and run

✅ Comes with tools like an embedded server (Tomcat)

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📦 Example: Let's Create a Simple REST API

Let’s say we want to create a REST API for a "Hello World" service.

🧱 Step-by-Step

1. ✅ Create a Spring Boot Project

You can use https://start.spring.io

Choose Spring Web dependency

Click "Generate" and unzip the project

2. ✍️ Create a Controller (The heart of the REST API)

package com.example.demo;

import org.springframework.web.bind.annotation.GetMapping;

import org.springframework.web.bind.annotation.RestController;

@RestController  // This makes it a REST API

public class HelloController {

    @GetMapping("/hello")  // This maps to the URL: http://localhost:8080/hello

    public String sayHello() {

        return "Hello, World!";

    }

}

3. 🚀 Run the Application

Run the project like a normal Java app (using the main method):

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);

}

}

4. 🌍 Try It Out

Open your browser and go to:

http://localhost:8080/hello

You’ll see:

Hello, World!

🎉 That’s your first RESTful service!

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🧠 What's Happening Behind the Scenes?

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🧪 Bonus: Return JSON instead of plain text

@GetMapping("/greet")

public Map<String, String> greet() {

    return Map.of("message", "Hello, JSON!");

}

🔗 Visit /greet and you get:

{

  "message": "Hello, JSON!"

}