|
|
| Line 1: |
Line 1: |
| − | __NOTOC__== RESTful Design Principles ==
| + | ignore |
| − | The term REST - <b>RE</b>presentational <b>S</b>tate <b>T</b>ransfer - was introduced and defined in 2000 by [http://www.ics.uci.edu/~fielding/pubs/dissertation/rest_arch_style.htm Roy Fielding in his doctoral dissertation] (Fielding is one of the principal authors of the HTTP v1.1 protocol). Conforming to Fielding's architecture is referred to as being <b><i>RESTful</i></b>. A RESTful web service (also called a RESTful [http://en.wikipedia.org/wiki/Web_API web API]) is implemented using HTTP and the principles of REST, with emphasis on the following aspects:
| + | |
| − | # definition of URIs for <b>all</b> resources exposed by the web service: e.g. <nowiki>/myproject/entities/</nowiki><b><i>car</i></b>
| + | |
| − | # use of Internet media types for on-the-wire representation. This is often JSON or XML, but can be any valid Internet media type.
| + | |
| − | # use of the HTTP v1.1 operations: POST, GET, PUT, and DELETE - [http://en.wikipedia.org/wiki/Create%2C_read%2C_update_and_delete analogous to the database semantics of CRUD: <b>C</b>reate, <b>R</b>etrieve, <b>U</b>pdate and <b>D</b>elete].
| + | |
| − | # use of hyperlinks to interact with/navigate to resources.
| + | |
| − | | + | |
| − | ===== RESTful URI Design =====
| + | |
| − | A URI is structured as follows: <tt>/[contextual key(s)]/[resource name]/?[query args and modifiers]</tt> and should follow the following Design Principles:
| + | |
| − | # A URI must represent a unique object, permanently: if it becomes necessary to relocate a resource, use the response code <tt>HTTP 301 (redirect)</tt> so that the client can find where the resource has been moved to.
| + | |
| − | # Should be succinct and easy-to-understand: <tt>/some/resource/about</tt> is preferred over <tt>/some/resource/about-acme-corp</tt>.
| + | |
| − | # A URI's structure must be consistent: once the strategy is chosen, follow it. As in 1), if the strategy changes, return <tt>HTTP 301</tt> so that users familiar with resources under the previous structure can find them under the new structure.
| + | |
| − | # A URI must follow the [http://http://en.wikipedia.org/wiki/Principle_of_least_astonishment|<b>P</b>rinciple <b>O</b>f <b>L</b>east <b>A</b>stonishment]: URIs should be structured so that they are intelligibly 'hackable'. For example, if the URI <tt>/events/2010/01</tt> represents the events for January 2010, then it follows that:
| + | |
| − | #: <tt>/events/2009/01</tt> - represents events for January 2009
| + | |
| − | #: <tt>/events/2010</tt> - represents events for the entire year of 2010
| + | |
| − | #: <tt>/events/2010/01/21</tt> - represents events for January 21st, 2010
| + | |
| − | # URIs should be composed of keywords that are important to the context of the resource. Typical contextual keys describe:
| + | |
| − | #: - a resource's type
| + | |
| − | #: - a resource's category - or parent category
| + | |
| − | #: - key resource data/attributes (i.e. the date posted)<div style="line-height:125%"><br/></div>Typically, a URI specifies a categorization that moves from general to specific, e.g. a descending hierarchy like year -> month -> day
| + | |
| − | # A URI should <b>never</b> contain any markers that would allow someone to infer (correctly or otherwise!) what sort of underlying implementation technology is being used. Suffixes such as <tt>.php</tt> or <tt>.aspx</tt> should not be used.
| + | |
| − | # A URI should be lowercase up to the [resource name] - query args and modifiers can be mixed case. In addition, query args and modifiers change only the <b><i>view</i></b> presented for a resource, <b>never</b> its underlying representation. For example a chart service may show some rows from a database; a query modifier may indicate that the chart should be rendered as a <tt>.pdf</tt> file instead of a <tt>.png</tt> image - the presence of the query modifier should in no way alter the information contained in the rows.
| + | |
| − | # A URI that refers to a list of resources should use plural nouns; a URI that refers to a single resource should use singular nouns:
| + | |
| − | #:: GET <tt><nowiki>/myproject/entities/employees</nowiki></tt> - returns a list of employees
| + | |
| − | #:: GET <tt><nowiki>/myproject/entities/employee/1</nowiki></tt> - returns the first employee
| + | |
| − | # Pagination of returned lists of resources is supposed to be managed via HTTP header attributes called HTTP Ranges. Unfortunately, this requires returning response code <tt>HTTP 206 (Partial Content)</tt> which is not universally accepted by clients. Thus pagination is typically accomplished by appending query modifiers to indicate page number and size:
| + | |
| − | #:: GET <tt><nowiki>/myproject/entities/employees/?pgNum=0&pgSize=40</nowiki></tt> - returns the first group of 40 employees
| + | |
| − | #:: GET <tt><nowiki>/myproject/entities/employees/?pgNum=1&pgSize=20</nowiki></tt> - returns the next group of 20 employees
| + | |
| − | :To protect the server from 'greedy' clients that try to query the entire database, use the response code <tt>HTTP 413 (Request Entity Too Large)</tt> if necessary. The Entity tag (ETag) header, when used with <tt>Last-Modified/If-None-Modified/If-Modified-Since</tt> headers, is essential for handling the <i>[http://www.w3.org/1999/04/Editing lost update problem]</i> when editing resources selected from (partial) paginated lists.
| + | |
