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REST API in Spring Boot Explained Clearly (With Examples)

July 13, 2025Posted inJava
REST API in Spring Boot Explained Clearly (With Examples)

Spring Boot makes it super easy to build RESTful web services in Java. If you’re working on any kind of backend application — like a blog, e-commerce site, or mobile app backend — chances are you’ll need to build a REST API.

In this article, I’ll explain what REST APIs are and how to create one using Spring Boot — with clear examples and no unnecessary theory.

🔍 What is a REST API?

REST stands for Representational State Transfer. It’s an architectural style for building APIs that work over HTTP.

A REST API allows your application to Create, Read, Update, and Delete data using HTTP methods like:

HTTP MethodPurpose
GETRead data
POSTCreate data
PUTUpdate data
DELETEDelete data

🚀 Getting Started with Spring Boot REST API

✅ Step 1: Create a Spring Boot Project

You can create a Spring Boot project using Spring Initializr.

Choose:

  • Spring Web (for REST APIs)
  • Spring Boot DevTools (optional for hot reload)
  • Spring Data JPA and H2 Database (for database access)

Download and import it into your IDE (like IntelliJ or Eclipse).

✅ Step 2: Create a Model Class

Let’s say we’re building a simple User API.

package com.example.demo.model;

public class User {
    private Long id;
    private String name;
    private String email;

    // Getters and Setters
}

✅ Step 3: Create a REST Controller

This is where we define the API endpoints.

package com.example.demo.controller;

import com.example.demo.model.User;
import org.springframework.web.bind.annotation.*;

import java.util.*;

@RestController
@RequestMapping("/api/users")
public class UserController {

    private List<User> users = new ArrayList<>();

    @GetMapping
    public List<User> getAllUsers() {
        return users;
    }

    @PostMapping
    public User createUser(@RequestBody User user) {
        users.add(user);
        return user;
    }

    @GetMapping("/{id}")
    public User getUserById(@PathVariable Long id) {
        return users.stream().filter(u -> u.getId().equals(id)).findFirst().orElse(null);
    }

    @PutMapping("/{id}")
    public User updateUser(@PathVariable Long id, @RequestBody User updatedUser) {
        for (User user : users) {
            if (user.getId().equals(id)) {
                user.setName(updatedUser.getName());
                user.setEmail(updatedUser.getEmail());
                return user;
            }
        }
        return null;
    }

    @DeleteMapping("/{id}")
    public String deleteUser(@PathVariable Long id) {
        users.removeIf(u -> u.getId().equals(id));
        return "User deleted successfully";
    }
}

✅ That’s it — you’ve just built a basic REST API in Spring Boot!

🧪 Test Your API

You can use tools like:

Or even test directly in the browser using http://localhost:8080/api/users.

💡 Real-World Tip

In a real application, you’d use:

  • Database + JPA Repository instead of a List
  • DTOs for clean API communication
  • Validation with @Valid
  • Service Layer for business logic
  • Exception handling using @ControllerAdvice

📌 Summary

With Spring Boot, creating a REST API is super simple and fast. You just need:

  1. A model class
  2. A REST controller
  3. Optional: service and database layer

This structure is great for building everything from small tools to large enterprise apps.

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📎 External Resource

Last updated on July 13, 2025