Python Ireland Nov 2010 - RESTing with Django

RESTing with DJANGO Fernando Ciciliati Python Ireland November Meet-up 10/11/2010 – The Science Gallery – Dublin

Contents● Quick review of REST ?● Even quicker review of Django ?● Lets REST with Django...

Practical REST● Building a web for computers ● They (computers) want to find computer-friendly pages ● They love well organised data/information ● They dont mind about ”visual appeal”● Side note: There is no ”Google” for them [yet].

REST Keywords● Resource● ”Resource name” or URI [or URL]● Representation● Methods/Verbs (Uniform Interface)● Links

REST: Resource● Any entity, object or concept we want our application to keep information about● Obvious resources: ● Books, people, employees, cities, blog entries, bank accounts, hotels, flights, ..● Slightly less obvious: ● Money transfers, hotel reservations, flight tickets, …● Even less obvious: ● User session, transaction, ...

REST: Resource Name● Every resource should receive at least one name that identifies it uniquely in its context of usage or existence – ideally, in the world.● This name should be durable, persistent.● Typical naming schemas: URLs, URIs, URNs● It is OK to have more than one name identifying the same resource

REST: Representation● Representations are the materialization, in bytes and bits, of resources.● Resources are ideas, concepts; representations are ”physical”, ”tangible” REPRESENTATIONS of ideas● Multiple formats possible● A single resource can have multiple representations associated to it

REST: Uniform Interface● Minimize number of ”verbs” ● REST x ”WebServices”● Stick to HTTP verbs

Core REST principles● Addressability● State and statelessness● Conectedness● Uniform Interface ● Safety and Idempotence

HTTP● HTTP is your best friend● Requests● Headers● Body● Status (return) codes ● 2xx – Success ● 3xx – ??? ● 4xx – ??? ● 5xx – Server Error

Django + REST

General Approach urls.py urls.py JSON HTML views.py views.py models.pymodels.py templates

Methods● OPTIONS ● Should be always available with any URI ● Returns a list of available methods for that URI in the ”Allow” header of the HTTP response;● GET ● on a collection URI returns a list of items in that collection – for large collections, consider paging ● on an items URI returns a representation of that item (resource) ● ”Safe”

Methods (contd.)● POST ● Points to a collection URI ● Creates a new resource in that collection ● We dont know the resource-id beforehand ● Not idempotent!● PUT ● Points to an item URI ● We KNOW the resource-id ● Creates a new resource or updated an existing one ● Idempotent

Methods (contd.)● DELETE ● Usually points to a resouce URI ● Deletes the resource ● Retry strategy is not a problem● HEAD ● Like GET, but returns only headers, no body ● Good for retrieving information about the resource as its size, language, content type, etc., without transmitting the entire resource.

Recommended Tools● Firefox 3.x ● FireBug (Net tab) or HTTPFox ● Poster ● SQLite Manager ● JSONView ● Modify Headers● Wireshark

Recommended BooksRESTful Web Services, Leonard Pro Django, Marty Alchin, ApressRichardson & Sam Ruby, OReilly

Python Ireland Nov 2010 - RESTing with Django

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