Introduction to RESTful APIs

1. What is an API?

API (Application Programming Interface) is a set of rules that allows different software applications to communicate with each other.

Real-World Examples:

• A weather app fetching data from a weather API.
• A payment gateway like Stripe allowing transactions via an API.
• A social media platform providing an API for third-party integrations.

2. What is a RESTful API?

A RESTful API (Representational State Transfer API) is an API that follows REST (Representational State Transfer) principles. It allows clients (like web browsers, mobile apps, or other servers) to interact with a server using standard HTTP methods.

Key Features of REST:

1. Stateless - Each request is independent and does not rely on previous requests.
2. Client-Server Architecture - The client and server operate independently.
3. Uniform Interface - Follows consistent rules for structuring API endpoints.
4. Cacheable - Responses can be cached to improve performance.
5. Layered System - Can be extended using middleware, proxies, or load balancers.
6. Code on Demand (Optional) - The server can send executable code to the client (e.g., JavaScript in a web response).

3. REST vs. Other API Architectures

Feature	REST	SOAP	GraphQL
Protocol	HTTP	HTTP, SMTP	HTTP
Data Format	JSON, XML	XML Only	JSON
Complexity	Simple	Complex	Medium
Flexibility	Fixed Endpoints	Rigid Structure	Flexible Queries
Caching	Supported	Limited	Not Built-In
Performance	High	Lower	Depends on Query

4. Examples of RESTful APIs

• GitHub API: Allows interacting with GitHub repositories, users, and issues.
• OpenWeather API: Provides weather data for cities around the world.
• Spotify API: Fetches music data, playlists, and artist information.

5. Basic Example of a RESTful API Endpoint

A simple API endpoint that returns a list of books:

GET /books
Host: example.com

Response:

[
  { "id": 1, "title": "Clean Code", "author": "Robert C. Martin" },
  { "id": 2, "title": "The Pragmatic Programmer", "author": "Andy Hunt" }
]

6. Summary

• APIs allow communication between applications.
• RESTful APIs follow REST principles, making them scalable and efficient.
• REST uses standard HTTP methods and JSON for communication.
• REST APIs are widely used in modern web and mobile applications.

Next Lesson: Understanding HTTP and Web Communication