What is API?

This note provides an overview of key concepts related to APIs, HTTP, REST, headers, stateless protocols, CRUD operations, JSON, cacheability, layered systems, and Curl.

API

• Definition: API stands for Application Programming Interface. It refers to a set of rules and protocols that allow different software applications to communicate with each other.
• Types of APIs:
  • Framework APIs: APIs provided by frameworks that allow developers to extend and customize the functionality of the framework.
  • Package and Library APIs: APIs provided by packages and libraries that solve common problems and provide reusable code.
  • Remote APIs: APIs like REST and GraphQL that allow communication with remote servers over a network.
  • Web-based APIs: APIs that are accessed through web protocols, typically using HTTP.

HTTP and Verbs

• HTTP: HTTP stands for Hypertext Transfer Protocol. It is a protocol that defines the expectations for communication between clients and servers.
• HTTP Verbs:
  • GET: Used to receive information and retrieve data from the server (read operation).
  • POST: Used to submit data to the server and receive a response (create operation).
  • PUT: Used to update existing data on the server.
  • PATCH: Used to partially update existing data on the server.
  • DELETE: Used to delete specific resources from the server.

Stateless Protocol

• Definition: A stateless protocol is a type of communication protocol in which each transaction between a client and a server is independent and self-contained. The server does not retain any information about the client’s previous interactions or the current state of the client.
• Advantages: Stateless protocols are scalable, lightweight, and promote fault tolerance.
• Limitations: They are not suitable for scenarios that require maintaining a continuous session or context across multiple requests.

Headers

• Definition: Headers are specific sections of data that precede the main content or payload of a message or packet.
• Function: Headers provide important information and metadata about the message, facilitating its interpretation and processing by the receiving entity.
• Examples: In the context of HTTP, headers include fields like “Host,” “User-Agent,” and “Content-Type.”

REST and CRUD

• REST: REST stands for Representational State Transfer. It is an architectural style for designing networked applications and APIs.
• CRUD: CRUD stands for Create, Read, Update, and Delete, which are the basic operations performed on data.
• Relationship: RESTful APIs map the CRUD operations to appropriate HTTP methods (POST, GET, PUT/PATCH, DELETE) to provide a consistent and intuitive interface for interacting with resources.

JSON

• Definition: JSON (JavaScript Object Notation) is a lightweight data-interchange format. It is commonly used for structuring data in APIs and exchanging information between a client and a server.

Layered System

• Definition: A layered system is an architectural style where components are organized in layers, and each layer has specific responsibilities. Communication between layers is well-defined and follows certain protocols.

Cacheability

• Definition: Cacheability refers to the capability of storing and reusing previously obtained responses from a server. Caching can improve performance by reducing the need for repeated requests to the server.

Curl

• Definition: Curl is a command-line tool and library used for making requests to web servers and transferring data using various protocols such as HTTP, HTTPS, FTP, SMTP, and more.
• Use Cases: Curl is used for sending HTTP requests, testing APIs, downloading/uploading files, scripting and automation, and debugging network connectivity issues.