Flask Web Development, 2nd Edition

Chapter 14. Application Programming Interfaces

In recent years, there has been a trend in web applications to move more and more of the business logic to the client side, producing an architecture that is known as Rich Internet Applications (RIAs). In RIAs, the server’s main (and sometimes only) function is to provide the client application with data retrieval and storage services. In this model, the server becomes a web service or application programming interface (API).

There are several protocols by which RIAs can communicate with a web service. Remote procedure call (RPC) protocols such as XML-RPC or its derivative, the Simplified Object Access Protocol (SOAP), were popular choices a few years ago. More recently, the Representational State Transfer (REST) architecture has emerged as the favorite for web applications due to its being built on the familiar model of the World Wide Web.

Flask is an ideal framework to build RESTful web services, thanks to its lightweight nature. In this chapter, you will learn how to implement a Flask-based RESTful API.

Introduction to REST

Roy Fielding’s PhD dissertation describes the REST architectural style for web services in terms of its six defining characteristics:

Client–server

There must be a clear separation between clients and servers.

Stateless

A client request must contain all the information that is necessary to carry it out. The server must not store any state about the client that persists from one request to the next.

Cache ...