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What are REST APIs?

Overview​

Representational State Transfer is known by the acronym REST. It is an architecture approach that Roy Fielding first introduced in his dissertation in 2000, and it is perfect for creating loosely linked applications that communicate via HTTP. It aids applications in more effectively utilising resources that are dispersed across several internet sites and is most frequently used in the construction of web services. A REST API is a service that enables you to use REST protocols to access and modify data on a server.

REST, to put it simply, is a framework for managing communication between various, independent program environments.

What's an API?​

A set of definitions and protocols known as an API are used to create and integrate application software. It’s sometimes referred to as a contract between an information provider and an information user—establishing the content required from the consumer (the call) and the content required by the producer (the response). For instance, the API design for a weather service might mandate that once the user enters a zip code, the producer responds with a two-part response, the first of which contains the high temperature and the second, the low temperature.

Principles of REST​

At a high level, REST utilizes 6 architectural constraints which must be met for an interface to be referred to as a true REST API. They serve as the guiding principles of REST:

  • Client-server model: The client and server applications are independent of one another and can evolve separately without any inter-dependency. This makes REST APIs more flexible and scalable.
  • Uniform interface: Resources should act consistently across the entire API, should have a single identifier to represent them, and should include all of the data that’s necessary to represent it fully while excluding unnecessary data. It also should follow clear naming conventions and link and data formats.
  • Stateless: The server should treat every request as new, and never store anything about the most recent HTTP request. This means no session and no history.
  • Cacheable: Caching is a strategy to improve client-side performance and reduce server load. REST APIs must state whether data is cacheable or not.
  • Layered system: APIs, stored data, and authentication requests must be spread across different interfaces. This architecture helps enhance an application’s security by limiting components in each layer to interact only with the next immediate layer.
  • Code on demand: This is an optional constraint and is used the least. It permits a client to download code from the API to be executed.

REST APIs are useful​

A RESTful API uses commands to obtain resources. The state of a resource at any given timestamp is called a resource representation. A RESTful API uses existing HTTP methodologies defined by the RFC 2616 protocol, such as:

  • GET to retrieve a resource,
  • PUT to change the state of or update a resource, which can be an object, file, or block,
  • POST to create that resource, and
  • DELETE to remove it.
Remember

With REST, networked components are a resource the user requests access to like a black box whose implementation details are unclear. All calls are stateless, nothing can be retained by the RESTful service between executions.

Data formats the REST API supports include:

  • application/json
  • application/xml
  • application/x-wbe+xml
  • application/x-www-form-urlencoded
  • multipart/form-data

Resources: The Fundamental Building Block of REST APIs​

Resources are the fundamental component of a REST API, and specific resources should be returned that match the location the client requested. Any piece of data can be a resource including documents, text files, images, services, collections of other resources, and more. The state of the resource at any particular time is known as resource representation, and this consists of data, metadata describing payload, and links that can help clients get additional related data.

Unless explicitly documented otherwise, REST APIs return UTF-8 encoded JSON objects as the resource. This is designed to be easy for both humans and machines to create and consume.