What is REST API?

REST API is an architectural style for building distributed systems. The main principles of REST:

• Statelessness: Each request from the client to the server must contain all the information needed to process the request. The server does not store the client's state between requests.
• Client-Server: Clear separation of responsibilities between the client and the server. The client sends requests, and the server processes them.
• Cacheable: The server should indicate whether responses can be cached by the client or intermediary.
• Layered System: The client does not necessarily interact directly with the end server; it can interact through intermediate layers (proxies, load balancers).
• Uniform Interface: A single and standardized way of interaction between the client and the server. This principle includes:
  • Identification of Resources: Resources (data) are identified by URLs.
  • Manipulation of Resources Through Representations: The client interacts with resources by obtaining their representations (e.g., JSON, XML) and sending new representations to modify them.
  • Self-descriptive Messages: Each message contains enough information to understand how to process it.
  • HATEOAS (Hypertext As The Engine Of Application State): Resources should contain links (hyperlinks) to related resources and available actions.

REST API typically uses standard HTTP methods to perform operations on resources:

• GET: Retrieve a resource or a collection of resources.
• POST: Create a new resource.
• PUT: Fully update an existing resource.
• PATCH: Partially update an existing resource.
• DELETE: Remove a resource.

Example of a JSON representation of a resource:

{
  "id": 1, // Identifier
  "name": "Resource Name", // Resource name
  "description": "Detailed description of the resource." // Resource description
}

Testing REST API includes checking:

• Functionality (correct responses to requests).
• Error handling.
• Performance.
• Security.
• Compliance with documentation.