APIs Introduction

Client-server computing is everywhere and the architectural styles for client-server interactions are many.

The dominant style however is APIs based on the HTTP protocol and what are known as RESTful principles.

In this lesson we’ll cover some basics like data serialization and review HTTP to ensure we’re ready to use it for designing APIs.

The principles of REST guide the API design so that we create client-server interactions that are loosely coupled.

In this lesson we’ll also see how to specify APIs using a standard language called swagger.

We’ll see how to create APIs that support multiple users, a technique called multi-tenancy, and authorize access to user data in a standard way.

Finally, we’ll look at how applications get authorization to use an API from a user.

Lesson Objectives

After completing this lesson, you should be able to

Identify the three most common serialization formats and explain why serialization is necessary.
Explain the parts of an HTTP transaction and the interaction of resources, HTTP methods, bodies, and headers.
Explain why RESTful APIs are different from RPC over HTTP.
Demonstrate a simple URI structure for an API including collections, items, and identifiers and explain how methods work with URIs to implement transactional workflow.
Read an API specification written in Swagger and explain it.
Describe multi-tenancy and explain why it’s necessary for many APIs.
Explain the importance of sessions and how authentication is used to re-establish them.
Show how the Authorization Code Grant in OAuth works for both getting and using an authorization token.