RESTrepresentational state transfer

David Krmpotić

WHAT IS IT?

Architectural style that builds on the existing protocols of the web.

Roy Fielding

http://app.com/pics/show/1 http://app.com/pics/destroy/1

RESTful style knocks the verbs out of the urls

http://app.com/pics/1

What remains:

a (unique) resource identifier

an “abstract thing” that lives in the clouda.k.a. ”the intended conceptual target of ahypertext reference” :]

a representation of the resource (you can never access the resource itself, only various representations of it)

http:// GET app.com/pics/1

We have nouns (resources), but what happened to the verbs?

http:// DELETE app.com/pics/1

they moved from the URL to the HTTP request method !

IS THIS A GOOD THING?

simplicity and abstraction

GETPUTPOSTDELETE

Yes!

} uniforminterface

REST is about resourcesNounsURIs

(unconstrained)

VerbsGET, PUT, POST, DELETE

(constrained)

Content TypesHTML, JPEG, XML etc.

(constrained)

GET /pics/1 Accept: JPEG

or GET /pics/1.jpg

Requesting different resource representations

GET /pics/1 Accept: XML

or GET /pics/1.xml

<picture><place>Axe Lake</place><size>1024x768</size><date>2008-05-01</date>

</picture>

GET /people Accept: XML

Plural resources

GET /people/1 Accept: JPEG

<people><person>

<id>1</id><name>Ann</name><age>28</age>

</person><person>

<id>2</id><name>Bruce</name><age>32</age>

</person>...

</people>

It relies on the following standards though:

HTTP

URL

XML/HTML/GIF/JPEG/etc (resource representations)

text/xml, text/html, image/gif, image/jpeg, etc. (content types)

remember

REST is not a standard!

REST in

Before enlightenment

http://app.com/clients/show/1

After

controller action

http://app.com/clients/1 + HTTP method

controllermap.resources

action

map.resources

action where the request lands is shown with gray background

edit and new are helper actions for showing the form

We also get a few named routes:

clients_path new_client_pathedit_client_path(id)client_path(id)

Custom actions

GET /tasks/completed PUT /tasks/12/complete

you should add custom actions carefully and never more than two or three

Responder block

takes care of different resource representations

Nested resources (in Rails 2)

http://adam.blog.heroku.com/past/2007/12/20/nested_resources_in_rails_2/

/events/1/tickets

A resource is not always a one-to-one mapping to a Rails model or database table.

Sometimes a resource is "virtual" and exists in your domain vocabulary and application logic, but is not backed by a database table. [2]

GOOD TO KNOW

models != resources

To create a website that is:

• easy to use• easy to maintain • easy to cache• easy to scale

Why use REST?

Thank you!

Resources (n.p.i.)

[1] Roy Fielding’s dissertation (2000)www.ics.uci.edu/~fielding/pubs/dissertation/top.htm

[2] REST 101 www.softiesonrails.com/search?q=rest+101

[3] A Brief Introduction to RESTwww.infoq.com/articles/rest-introduction

[4] How I Explained REST to My Wifetomayko.com/writings/rest-to-my-wife