What is Representational State Transfer (REST)?

Representational State Transfer (REST) is a paradigm for software architecture with the aim of simplifying communication between machines through a uniform API. REST is applied via the HTTP protocol and is primarily aimed at web services. It was developed around the turn of the millennium by Roy Fielding.
The name Representational State Transfer comes from the goal that REST-compliant services should transmit the representation of their state to the querying party.

The RESTful Philosophy

REST is more of a philosophy than a specific technology. There is no fixed set of rules, only a series of principles that developers are responsible for adhering to in their implementation.

Client-Server

To use REST, a client-server architecture must exist that allows the server to provide a service by transmitting its state to the client.

Statelessness

Every REST message should contain the full state required by the client. For this to work, it is necessary that the server itself does not store any additional state that is not transmitted to the client.
This Statelessnes can be a great advantage, as it makes it very easy to scale a server horizontally and distribute the payload across it. It doesn’t matter which server the client communicates with, as no server stores a state.

Uniform Interface

For a REST interface, it is important that this interface is implemented uniformly so that it is easier to use.

Additionally, endpoints in REST do not represent methods, but the resources the client wants to access. What should be done with a resource is defined by the HTTP method the client uses in his request.

REST does not dictate how resources should be represented, but it is required that a server offers a resource in different languages or formats (HTML, JSON, XML) which the client can request via HTTP headers.

HATEOAS

Hypermedia as the Engine of Application State (HATEOAS) is, according to Fielding, the most important constraint of REST. But is also the least implemented. HATEOAS means that the server not only provides the state of the resource requested, but also links to all possible relations or actions possible with said resource. By doing so, the client can explore and use the entire API even with only knowing a single URL.

Richardson Maturity Model

The by Leonard Richardson developed Richardson Maturity Model is a scale to measure the maturity of a RESTful API. It consists of four levels that describe how mature an API is.

StufeBeschreibung
0The Swamp of POX: The API uses only HTTP as a transport protocol without utilizing the benefits of HTTP.
1Resources: The API uses resources and unique URIs, to identify them.
2HTTP Verbs: The API uses HTTP-Methods (GET, POST, PUT, DELETE) for interaction with the resources.
3Hypermedia Controls (HATEOAS): The API uses Hypermeddia as the Engine for Application State, to guide clients through the application.

Resources

REST - Wikipedia

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Last updated 03 Mar 2025, 09:28 +0100 . history