Monday, February 2, 2009

RESTful Thoughts - Planned HTTP Headers for the upcoming RESTful API

Here is the HTTP Header map for the upcoming Fellowship One RESTful API. Please comment / ask questions / make suggestions.

Just like the response codes, many decisions made for this map came from RFC2616, Fielding's dissertation, and analysis of several dozen RESTful or REST "like" APIs currently on the programmable web.

Request Headers

Accept : type/subtype

Example - Accept : application/xml (Available types and sub types: application/xml, application/json)

Notes - Defaults to application/xml if one is not passed in, and when a user sends application/* the resulting content sub type will be XML. Multiple types/sub types can be sent in but as per the specification the first match in degree of specificity will be the first used.
i.e. if user sends in: application/*, application/xml, */* the order would be as follows:
1) application/xml
2) application/*
3) */*

If an invalid value is passed in via Accept header the response will result in a 415 Unsupported Media Type

Accept-Charset : charset

Example - Accept-Charset: utf-8

Notes - Accept-Charset will not be used and will always default to utf-8

Accept-Encoding : encoding

Example - Accept-Encoding : deflate, compress, gzip

Notes - If none is sent in then the API will default to no compression.
If an invalid value is passed in via Accept-Encoding header the response will result in a 406 Not acceptable

Authorization : credentials

Example - Authorization : Oauth realm=

Notes - This is where the OAUTH credentials will go

Date : HTTP-date

Example - Date: Thu, 29 Jan 2009 15:28:25 GMT

Notes - Optional, most commonly passed in with PUTs and POSTs

User-Agent : product/comment

Example - User-Agent : MyChurchSite/v123.x

Notes - Used to identify the HTTP library or client library that was used to consume the API

Response Headers

Allow : method

Example - Allow: GET, HEAD, PUT

Notes - An Allow header field MUST be present in a 405 (Method Not Allowed) response.

Content-Encoding : content-coding

Example - Content-Encoding : gzip

Notes - This will tell the client what type of compression was used on the resource

Content-Length : DIGIT

Example - Content-Length : 1254

Notes - Sent back with each request. Will possibly be available via HEAD requests

Content-Location : absoluteURI | relativeURI

Example - Content-Location :

Notes - Sent back with each GET request

Content-Type : media-type

Example - Content-Type : application/xml, utf-8

Notes - Details the type of content being returned to the client

Date : HTTP-date

Example - Date: Thu, 29 Jan 2009 15:28:25 GMT

Notes - Will be returned with every response, possibly excluding responses returning status codes of 500

Location : absoluteURI

Example - Location:

Notes - Applies to 201 and 301 only

WWW-Authenticate : challenge

Example - WWW-Authenticate : Oauth realm:

Notes - The URI will change per environment, per version

Notes on caching
All headers having to do with caching are still being implemented.

This HTTP header map is subject to change, however, in the current build of the API these rules exist as defined.

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