REST APIs offer an easy way of communication between applications. Big companies like Amazon, Twitter, Facebook and MercadoLibre implement Restful APIs to provide their services. This talk is an introduction to understand how this technology works and how can be consumed by our apps.

1. REST 101
An Overview to Representational State Transfer API

2. Fernando Zafe
Systems Engineer Student
Universidad Tecnológica Nacional
Tucumán, Argentina
🌎 ZAFE.COM.AR
🐙 GITHUB.COM/zafe

3. What is a Web Service?
• A Web Service is a service offered by an electronic device
to another electronic device, communicating with each
other via World Wide Web. Source: Wikipedia

4. What is an API
• API stands for Application Programming Interface
• Is a contract provided by a piece of software to another
• Examples: C++ API, YouTube API,

5. What is REST
• REST stands for REpresentational State Transfer
• It’s a software architectural style
• Proposed by Roy Fielding in 2000

6. HTTP
• Stands for Hyper Text Transfer Protocol
• Application layer protocol used by the World Wide Web
• Used by web browsers and web servers to communicate

7. HTTP Verbs
• HEAD: This method asks for a response identical to that
of a GET request, but without the response body.
• GET: Used for requesting data. It doesn’t modify data
from the server
• POST: Used for changing a state on the server.
Something has change after this operation. Usually
initiated by a web form

8. HTTP Verbs
• PATCH: requests that the enclosed entity be stored
under the supplied URI. If the URI refers to an already
existing resource, it is modified; if the URI does not point
to an existing resource, then the server can create the
resource with that URI
• DELETE: Deletes the specified resource

9. Constraints
• Client-Server
• Stateless
• Cache
• Interface / Uniform Contract
• Layered System

10. HATEOAS

11. HTTP Status Code

13. 2xx
• 200 OK Standard response for successful HTTP requests. The actual
response will depend on the request method used. In a GET request, the
response will contain an entity corresponding to the requested resource.
In a POST request, the response will contain an entity describing or
containing the result of the action.[7]
• 201 Created The request has been fulfilled, resulting in the creation of a
new resource.[8]
• 202 Accepted The request has been accepted for processing, but the
processing has not been completed. The request might or might not be
eventually acted upon, and may be disallowed when processing occurs
• 204 No Content The server successfully processed the request and is
not returning any content.[12]

14. 3xx
• 301 Moved Permanently This and all future requests
should be directed to the given URI.
• 304 Not Modified Indicates that the resource has not
been modified since the version specified by the request
headers If-Modified-Since or If-None-Match. In such
case, there is no need to retransmit the resource since
the client still has a previously-downloaded copy.

15. 4xx
• 400 Bad Request The server cannot or will not process the request due to an
apparent client error (e.g., malformed request syntax, too large size, invalid request
message framing, or deceptive request routing).
• 401 Unauthorized Similar to 403 Forbidden, but specifically for use when
authentication is required and has failed or has not yet been provided. The
response must include a WWW-Authenticate header field containing a challenge
applicable to the requested resource. See Basic access authentication and Digest
access authentication. 401 semantically means "unauthenticated", i.e. the user
does not have the necessary credentials.
• 403 Forbidden The request was a valid request, but the server is refusing to
respond to it. The user might be logged in but does not have the necessary
permissions for the resource.
• 404 Not Found The requested resource could not be found but may be available
in the future. Subsequent requests by the client are permissible

16. 5xx
• 500 Internal Server Error A generic error message,
given when an unexpected condition was encountered
and no more specific message is suitable.
• 501 Not Implemented The server either does not
recognize the request method, or it lacks the ability to
fulfill the request. Usually this implies future availability
(e.g., a new feature of a web-service API)

17. The Richardson Maturity Model (RMM)

18. Level 0

19. Level 1

20. Level 2

21. Level 3

22. Example

23. Thank you!