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| − | __NOTOC__== DBRS Design ==
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| − | The DBRS utility generates <b><i>RESTful</i></b> applications (see [[#RESTful_URI_Design_Principles|below]] for more details on <b><i>RESTful</i></b> design principles). Of primary importance is the design of the URIs for each resource (a.k.a. entity):
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| − | {|{{BMTableStyle}}
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| − | |-{{BMTHStyle}}
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| − | ! URI
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| − | ! Operation
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| − | ! Result
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| − | | <nowiki>/myproject/entities/employees/</nowiki>
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| − | {|
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| − | |GET
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| − | |-
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| − | |PUT
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| − | |-
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| − | |POST
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| − | |-
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| − | |DELETE
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| − | |}
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| − | {|
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| − | |retrieve list of employees (200 OK)
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| − | |-
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| − | |replace list of employees (201 Created)
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| − | |-
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| − | |add a new employee (201 Created)
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| − | |-
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| − | |unused (400 Bad Request)
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| − | |}
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| − | | <nowiki>/myproject/entities/employees/count</nowiki>
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| − | | GET (with search modifier)
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| − | |retrieve a count of the list of employees (200 OK)
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| − | | <nowiki>/myproject/entities/employees/?pgNum=0&pgSize=40</nowiki>
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| − | | GET (with query parameters)
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| − | |retrieve the first group of 40 employees (200 OK) <br/>
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| − | Message body should include the following additional information:
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| − | * pageNum: reflects the pgNum query parameter
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| − | * pageSize: reflects the pgSz query parameter (or the default page size)
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| − | * itemsInPage: reflects the total number of items in the current page
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| − | * totalItems: reflects the total number of items found for the list
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| − | | <nowiki>/myproject/entities/employee/{id}</nowiki>
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| − | {|
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| − | |GET
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| − | |-
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| − | |PUT
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| − | |-
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| − | |POST
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| − | |-
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| − | |DELETE
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| − | |}
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| − | {|
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| − | |retrieve employee details (200 OK | 404 Not Found)
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| − | |-
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| − | |update employee details (201 Created | 404 Not Found). If the message body is missing an employee attributes, sparse update logic used
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| − | |-
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| − | |add a new employee (201 Created)
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| − | |-
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| − | |remove employee (204 No Content | 404 Not Found)
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| − | |}
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| − | |}
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| − | In addition, the URIs for an entity's <i>meta-resources</i>: the in-memory representation of the ORM and OXM meta-data as specified by the JPA2 spec:
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| − | [[Image:JPA2Metamodel.png]]
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| − | ===== RESTful URI Design Principles =====
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| − | 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 spec). 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:
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| − | # definition of URIs for <b>all</b> resources exposed by the web service: e.g. <nowiki>/myproject/entities/</nowiki><b><i>car</i></b>
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| − | # use of Internet media types for on-the-wire representation. This is often JSON or XML, but can be any valid Internet media type.
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| − | # 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].
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| − | # use of hyperlinks to interact with/navigate to resources.
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| − | A URI is structured as follows: <tt>domainname/[contextual key(s)]/[resource name]/?[query args and modifiers]</tt> and should follow the following Design Principles:
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| − | # 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.
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| − | # should be succinct and easy-to-understand: <tt>/some/resource/about</tt> is preferred over <tt>/some/resource/about-acme-corp</tt>.
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| − | # 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.
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| − | # A URI must follow <b>POLA</b> - [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:
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| − | #: <tt>/events/2009/01</tt> - represents events for January 2009
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| − | #: <tt>/events/2010</tt> - represents events for the entire year of 2010
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| − | #: <tt>/events/2010/01/21</tt> - represents events for January 21st, 2010
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| − | # URIs should be composed of keywords that are important to the context of the resource. Typical contextual keys describe:
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| − | #: a resource's type
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| − | #: a resource's category - or parent category
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| − | #: 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
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| − | # A URI should not 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.
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| − | # 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 PDF file instead of a PNG image - the presence of the query modifier should in no way alter the information contained in the rows.
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| − | # 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:
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| − | #:: GET <tt><nowiki>/myproject/entities/employees</nowiki></tt> - returns a list of employees
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| − | #:: GET <tt><nowiki>/myproject/entities/employee/1</nowiki></tt> - returns the first employee
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| − | # 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:
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| − | #:: GET <tt><nowiki>http://example.com/myproject/entities/employees/?pgNum=0&pgSize=40</nowiki></tt> - returns the first group of 40 employees
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| − | #:: GET <tt><nowiki>http://example.com/myproject/entities/employees/?pgNum=1&pgSize=20</nowiki></tt> - returns the next group of 20 employees
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| − | :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.
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