What you know about Application Programming Interface-API

• API: API is the acronym for Application Programming Interface, which is a software intermediary that allows two applications to talk to each other. Each time you use an app like Facebook, send an instant message, or check the weather on your phone, you’re using an API. The “hidden” portion of a website that is meant for computer consumption
• Consuming developers- Merchants to API providing organizations-the Bank.
• An API is very much the same thing as a UI, except that it is geared for consumption by software instead of humans.
• A technology that allows applications (software programs) to talk to one another.
• The significance of APIs to the modern world should not be underestimated. With each day, their importance to three primary constituencies—customers (the public), businesses (and business-like organizations such as government and non-profits) and programmers–seems to grow.
• the server. This is the side that provides the API. It helps to remember that the API is simply another program running on the server
• The same principle applies to websites that are integrated. When one site pulls in data from the other, the site providing the data is acting as the server, and the site fetching the data is the client.

Protocol used in APIs

• Many companies choose HTTP to adopt it as the protocol underlying their APIs
• To make a valid request, the client needs to include four things:
• URL (Uniform Resource Locator) 1
• Method
• List of Headers
• Body

Data Formats

• JSON (JavaScript Object Notation)
• XML (Extensible Markup Language)

Authentication

• Basic Authentication
• API key Authentication
• Open Authentication (OAuth)

Open Authentication v2 (OAuth 2)

• Steps in Authentication
  • Step 1 – User Tells Client to Connect to Server
  • Step 2 – Client Directs User to Server
  • Step 3 – User Logs-in to Server and Grants Client Access
  • Step 4 – Server Sends User Back to Client, Along with Code
  • Step 5 – Client Exchanges Code + Secret Key for Access Token
  • Step 6 – Client Fetches Data from Server

Note:

1. The User – A person who wants to connect two websites they use
2. The Client – The website that will be granted access to the user’s data
3. The Server – The website that has the user’s data

API Design

Architectural Style

1. SOAP
2. REST (Representational State Transfer) uses URL

Integrations

• Server-Driven
• Client-Driven
  • Polling: Repeatedly requesting a resource at a short interval
  • Long Polling: Polling, but with a delayed response (server responds only when certain changes are found); improves efficiency
  • Webhooks: When the client gives the server a Callback URL, so the server can post updates in real time
  • Subscription Webhooks: Informal name for solutions that make setting up webhooks automatic