How does the web work?aka HTTP 101

by Guilherme Cavalcanti@guiocavalcanti

Schedule

1. Some Web Principles2. REST3. HTTP

VerbsIdempotencySide effectsGET and POST Vs. PUT and DELETE

4. Rails5. AJAX vs. Accessibility

Some Web Principles

UniversalityAny resource anywhere can be given a URIAny resource of significance should be given a URI.

Resources are documentsAs well as concepts and abstract ideias (Semantic Web)

Global ScopeIt doesn't matter to whom or where you specify that URI, it will have the same meaning.

REST

Architectural style coined by Roy Fielding (phd dissertation)5

State transferenceAt any particular time, a client can either be in transition between application states or "at rest". A client in a rest state is able to interact with its user, but creates no load and consumes no per-client storage on the servers or on the network4

The HTTP portocols uses the rest style

HTTP Verbs

Side effectchange or not the state of the world

Idempotencythe side-effects of N > 0 identical requests is the same as for a single request

HTTP Verbs

Idempotent Cacheable Side effects

GET x x

POST x

PUT x x

DELETE x

HTTP: RESTful services vs lack of verbs

PUTPut ssomething at some placeUpdates somethingPUT http://redu.com.br/spaces/my-spaceContent: My new Space

POSTThe server decides which action gonna be takenPOST http://redu.com.br/spaces/filterContent: name=my;audience=[higher-edu,sat]

DELETEDeletes some resourceDELETE http://redu.com.br/spaces/my-space

HTTP: RESTful services vs lack of verbs

Doesn't work on6

< HTML 4< XHTML 1.0

It works onXMLHttpRequests (aka AJAX)3

HTTP: RESTful services vs lack of verbs

POST acting as PUTPOST http://redu.com.br/spacesContent: name=My Space;path=my-space

POST acting as PUT when updatingPOST http://redu.com.br/spaces/my-spaceContent: _method=PUT

POST acting as DELETEPOST http://redu.com.br/spaces/my-spaceContent: _method=DELETE

How Rails deals with it?

Edit:

References

1. Why put and delete?2. HTTP RFC3. Verbs support4. REST5. Roy's dissertation6. Useful question at Stackoverflow