rest/urls

URL Conventions

These are the recommended conventions for RESTful URLs, based on work pioneered by Ruby on Rails, which again is closely modelled over Atompub . Following these conventions for both HTTP method names and URL construction will allow your application to be consumed by ActiveResource, Jester, and other RESTful clients. Note that Rails 1.x used ";edit" and ";new" in place of the simpler "/edit" and "/new" recommended going forward.

Methods

One of the key aspects of REST is using the HTTP Verbs to implement the standard Create-Retrieve-Update-Delete (CRUD) database semantics. The primary ones are:

POST

Create a resource within a given collection

GET

Retrieve a resource

PUT

Update a resource

DELETE

Delete a resource

Most browsers do not currently support PUT and DELETE (HTML forms only allow "get" and "post", links are always "get"). The other methods can be emulated by providing a "method" parameter with a value of "PUT" and "DELETE", respectively.

Routing

The principal unit of operation is the "collection", which typically corresponds to a database table or (in Rails) an ActiveRecord class. For a collection named "people", the primary routes would be:

Operate on the Collection

GET /people

return a list of all records

GET /people/new

return a form for creating a new record

POST /people

submit fields for creating a new record

Operate on a Record

GET /people/1

return the first record

DELETE /people/1

destroy the first record

POST /people/1?_method=DELETE

alias for DELETE, to compensate for browser limitations

GET /people/1/edit

return a form to edit the first record

PUT /people/1

submit fields for updating the first record

POST /people/1?_method=PUT

alias for PUT, to compensate for browser limitations

Follow a Relationship

GET /people/1/phones

return the collection of phone numbers associated with the first person

GET /people/1/phones/23

return the phone number with id #23 associated with the first person

GET /people/1/phones/new

return a form for creating a new phone number for the first person

POST /people/1/phones/

submit fields for creating a new phone number for the first person

Invoke Custom Actions

It isn't always possible to map everything into CRUD. Thus, there is also a syntax for specifying custom actions:

POST /people/1/promote

run the "promote" action against the first record

These should be used sparingly, as they are unlikely to be supported by most clients.

File Formats

Data types are extremely important in REST. While it is ideal to specify the appropriate MIME type as an HTTP header, developers are encouraged to follow Rails in allowing extension-based typing, e.g.:

HTML

GET /people/1

return the first record in HTML format

GET /people/1.html

return the first record in HTML format

XML

GET /people/1.xml

return the first record in XML format

JSON

GET /people/1.json

return the first record in JSON format

While the JSON mapping should be trivially obvious, the best practice for XML is to:

1. use the column name as the element name
2. include an appropriate "type" field

See the Highrise reference for an example of how this works in practice.

Response Codes

Another important aspect of REST is returning the appropriate HTTP Response Codes. Some common ones are:

Successful

200 OK

The request has succeeded.

201 Created

The request has been fulfilled and resulted in a new resource being created. The newly created resource can be referenced by the URI(s) returned in the entity of the response, with the most specific URI for the resource given by a Location header field.

204 No Content

The server has fulfilled the request but does not need to return an entity-body, and might want to return updated metainformation.

Redirection

303 See Other

The response to the request can be found under a different URI and SHOULD be retrieved using a GET method on that resource. This method exists primarily to allow the output of a POST-activated script to redirect the user agent to a selected resource.

Client Error

400 Bad Request

The request could not be understood by the server due to malformed syntax.

401 Unauthorized

The request requires user authentication. The response MUST include a WWW-Authenticate header field (14.47) containing a challenge applicable to the requested resource.

404 Not Found

The requested resource could not be found(section 10.4.5).

405 Method Not Allowed

The method specified in the Request-Line is not allowed for the resource identified by the Request-URI. The response MUST include an Allow header containing a list of valid methods for the requested resource.

422 Unprocessable Entity

The server understands the media type of the request entity, but was unable to process the contained instructions.

Examples in the Wild

Ruby

• Ruby on Rails
• Highrise

PHP

• RestfulRails An extendable PHP library to communicate with RESTful rails applications

Perl

• Catalyst CRUD and REST

Java

• Java

Python

• Python Routes
• Pylons REST Decorators

JavaScript

• Jester (JavaScript)
• DOM-Resource (JavaScript)
• ....