REST Architecture

REST stands for Representational State Transfer. It is not a programming language or a tool; it is an architectural style.

Think of REST as the "Traffic Rules" for the internet. If everyone follows the same rules, communication between different systems (like a Mobile App and a Java Server) becomes seamless.

The 5 Core Principles of REST

To be called a RESTful API, a system must follow these specific constraints:

☁️ Statelessness

No Memory

The server does not store any info about your previous requests. Every single request must contain all the information (like a Token or ID) needed to understand it.

• Analogy: It's like a vending machine. It doesn't care if you bought a soda 5 minutes ago; you must put in the money and press the button every single time.

📱 Client-Server

Separation of Concerns

The Frontend (Client) and Backend (Server) are independent.

• You can completely redesign your Android app without ever touching your database code. As long as the API "Contract" stays the same, everything works!

🛤️ Uniform Interface

Consistency

Every resource (User, Post, Product) must have a unique URL. You should always use standard HTTP methods (GET, POST, etc.) to interact with them.

• Standard: GET /users/1 should always return user data, no matter which company built the API.

The REST Communication Flow

In a RESTful system, the communication is always initiated by the Client. The server just waits, listens, and responds.

Resources: The Heart of REST

In REST, everything is a Resource. A resource is any piece of data that the API can provide.

• Collections: A list of items (e.g., /products)
• Individual Items: One specific item (e.g., /products/101)

How we identify them:

We use URIs (Uniform Resource Identifiers). A good RESTful URI should use nouns, not verbs.

• Bad (Action-based): https://api.com/getNewOrders
• Good (Resource-based): https://api.com/orders

Summary Checklist

• I understand that REST is an architectural style, not a language.
• I know that Statelessness means every request is independent.
• I understand that Client and Server are separate entities.
• I recognize that resources should be named with Nouns.