REST Foundations: Core Concepts, HTTP Methods, Status Codes, and Tooling

REST (Representational State Transfer) is an architectural style that treats information as a first‑class citizen, enabling high performance, scalability, and simplicity for web services.

The article begins with an overview of REST’s philosophy, emphasizing that it is a worldview rather than a library, and references Roy Fielding’s doctoral dissertation as the seminal source.

Key concepts include stateless communication, resource identification via URLs, and content negotiation using the Accept header. Example URLs such as http://fakelibrary.org/library and http://fakelibrary.org/book/isbn/978-0596801687 illustrate how resources can be accessed, created, updated, or deleted.

HTTP verbs are detailed: GET retrieves resources without side effects; POST creates new resources or submits queries; PUT replaces a known resource; DELETE removes a resource; additional verbs HEAD , OPTIONS , and PATCH are explained with their typical use‑cases and idempotency properties.

Response codes are grouped into informational (1xx), success (2xx), redirection (3xx), client error (4xx), and server error (5xx) categories, with examples such as 200, 201, 204, 404, and 418.

The Richardson Maturity Model is introduced to classify RESTful services into three levels of sophistication, guiding incremental adoption of hypermedia controls.

API description languages such as RAML, Swagger, Apiary.io, and Hydra‑Cg are surveyed, highlighting their role in generating documentation and client/server code.

Popular server‑side frameworks and libraries are listed, including JAX‑RS, Restlet, NetKernel, Play, Spray, Express, Hapi, and Sinatra, each with a brief note on language support and URLs.

Client tools for testing and interacting with REST APIs are presented: curl (e.g., curl http://fakelibrary.org/library and

curl -H "Accept:application/json" http://fakelibrary.org/library

), httpie, and Postman.

Finally, the article provides additional reading links on related architectural topics and encourages readers to follow the author for more practical content.