REST API

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A REST API (Representational State Transfer Application Programming Interface) is a set of rules and conventions for building and interacting with web services. REST APIs allow different systems to communicate with each other over the internet using HTTP methods. Here are the key concepts and components of REST APIs:

Key Concepts

1. Statelessness:

   • Each request from a client to a server must contain all the information needed to understand and process the request.

   • The server does not store any client context between requests.

2. Client-Server Architecture:

   • The client (front-end) and the server (back-end) are separate, allowing them to evolve independently.

3. Uniform Interface:

   • RESTful systems have a uniform interface that simplifies and decouples the architecture, allowing each part to evolve independently.

   • It is achieved through the use of standard HTTP methods and consistent URIs.

4. Cacheability:

   • Responses must define themselves as cacheable or non-cacheable, to prevent clients from reusing stale or inappropriate data in response to further requests.

5. Layered System:

   • The architecture can be composed of multiple layers, where each layer has specific functions, enhancing flexibility and scalability.

6. Code on Demand (optional):

   • Servers can extend the functionality of a client by transferring executable code.

Core Components

1. Resources and URIs:

   • Resources are objects or representations of data accessible via a URI (Uniform Resource Identifier).

   • Example: https://api.example.com/users represents a collection of user resources.

2. HTTP Methods:

   • GET: Retrieve a resource.

   • POST: Create a new resource.

   • PUT: Update an existing resource.

   • DELETE: Remove a resource.

   • PATCH: Partially update a resource.

3. HTTP Status Codes:

   • Indicate the result of the request.

   • Common codes include:

     • 200 OK: Successful GET, PUT, PATCH, or DELETE.

     • 201 Created: Successful POST that results in a new resource.

     • 204 No Content: Successful request that does not return data (e.g., DELETE).

     • 400 Bad Request: The request was invalid or cannot be processed.

     • 401 Unauthorized: Authentication is required.

     • 404 Not Found: The resource could not be found.

     • 500 Internal Server Error: The server encountered an error.

4. Headers and Query Parameters:

   • Headers: Provide metadata about the request/response (e.g., Content-Type, Authorization).

   • Query Parameters: Allow for additional parameters in the URL (e.g., https://api.example.com/users?sort=asc).

5. Request and Response Bodies:

   • Request Body: Data sent by the client to the server, typically in POST or PUT requests (e.g., JSON, XML).

   • Response Body: Data sent by the server to the client, typically in JSON or XML format.

Example of a REST API Interaction

1. Retrieve a list of users (GET request):

   GET /users HTTP/1.1
   Host: api.example.com

   Response:

   [
     {"id": 1, "name": "John Doe"},
     {"id": 2, "name": "Jane Smith"}
   ]

2. Create a new user (POST request):

   POST /users HTTP/1.1
   Host: api.example.com
   Content-Type: application/json
   
   {
     "name": "New User"
   }

   Response:

   {
     "id": 3,
     "name": "New User"
   }

3. Update a user (PUT request):

   PUT /users/1 HTTP/1.1
   Host: api.example.com
   Content-Type: application/json
   
   {
     "name": "Updated User"
   }

   Response:

   {
     "id": 1,
     "name": "Updated User"
   }

4. Delete a user (DELETE request):

   DELETE /users/1 HTTP/1.1
   Host: api.example.com

   Response:

   HTTP/1.1 204 No Content

REST APIs are widely used due to their simplicity, scalability, and flexibility, making them a standard choice for web services and applications.

Introduction to REST API

Application Programming Interface

Postman