Introduction to AtomPub Web Services

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Since 2003, the Atom format has been used as yet another feed format like RSS, but the Atom protocol opens the door to far more uses of Atom as both a means for distribution and publication. Ben Ramsey introduces the Atom format and protocol, explaining how these can form the foundation of any publishing service and serve as a platform for rich Internet applications.

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Introduction to AtomPub Web Services

  1. 1. Introduction to AtomPub Web Services Ben Ramsey • International PHP Conference • 11 Oct 2010
  2. 2. Hi, I’m Ben. ‣ VP of Engineering at Moontoast ‣ Co-founder and organizer emeritus of the Atlanta PHP user group ‣ Current organizer of the Nashville PHP user group ‣ I blog at benramsey.com ‣ I tweet at @ramsey ‣ Please rate this presentation: http://joind.in/2185 Introduction to AtomPub Web Services • Ben Ramsey 2
  3. 3. Atom & AtomPub?
  4. 4. What’s the difference?
  5. 5. Atom: RFC 4287 Introduction to AtomPub Web Services • Ben Ramsey 5
  6. 6. Atom is an XML-based document format that describes lists of related information known as “feeds”. Feeds are composed of a number of items, known as “entries”, each with an extensible set of attached metadata. For example, each entry has a title. The primary use case that Atom addresses is the syndication of Web content such as weblogs and news headlines to Web sites as well as directly to user agents. —RFC 4287, §1
  7. 7. Atom is an XML language.
  8. 8. AtomPub: RFC 5023 Introduction to AtomPub Web Services • Ben Ramsey 8
  9. 9. The Atom Publishing Protocol is an application-level protocol for publishing and editing Web Resources using HTTP and XML 1.0. The protocol supports the creation of Web Resources and provides facilities for: Collections: Sets of Resources, which can be retrieved in whole or in part. Services: Discovery and description of Collections. Editing: Creating, editing, and deleting Resources. The Atom Publishing Protocol is different from many contemporary protocols in that the server is given wide latitude in processing requests from clients. —RFC 5023, §1
  10. 10. AtomPub is a publishing protocol.
  11. 11. What about RSS? Introduction to AtomPub Web Services • Ben Ramsey 11
  12. 12. Content Types ‣ RSS allows only for plain text and escaped HTML content types ‣ Atom provides for plain text, escaped HTML, XHTML, XML, and Base64-encoded binary data Introduction to AtomPub Web Services • Ben Ramsey 12
  13. 13. Internationalization ‣ RSS may have a language set for a feed, but doesn’t have a way to indicate language for items in the feed ‣ Atom uses the xml:lang attribute to specify language on a per-element basis ‣ Atom uses IRIs, which allow the usage of characters in identifiers outside of ASCII Introduction to AtomPub Web Services • Ben Ramsey 13
  14. 14. Modularity ‣ RSS vocabulary elements aren’t reusable in other XML vocabularies ‣ Atom was designed to allow its vocabulary to be mixed with other XML vocabularies ‣ Namespaces! Atom has one; RSS does not Introduction to AtomPub Web Services • Ben Ramsey 14
  15. 15. Other Things ‣ RSS has no schema; Atom has a RelaxNG schema ‣ RSS defines no mechanism for handling relative URIs; Atom uses xml:base ‣ Various implementations in RSS leads to interoperability problems ‣ No standard protocol for publishing; RSS is read only Introduction to AtomPub Web Services • Ben Ramsey 15
  16. 16. Atom was created to solve the RSS problems.
  17. 17. Profile of Atom ‣ Atom Syndication Format ‣ An XML-based web content and metadata syndication format ‣ Defined by IETF RFC 4287 ‣ Fixes the “problems” of RSS ‣ XML namespace: http://www.w3.org/2005/Atom Introduction to AtomPub Web Services • Ben Ramsey 17
  18. 18. Profile of AtomPub ‣ Atom Publishing Protocol or APP ‣ A protocol for publishing and editing web resources using HTTP and XML ‣ Defined by IETF RFC 5023 ‣ Uses Atom as it’s XML syntax ‣ XML namespace: http://www.w3.org/2007/app Introduction to AtomPub Web Services • Ben Ramsey 18
  19. 19. Basics of AtomPub ‣ Each resource has a unique identifier ‣ The resources are well-connected ‣ Resources share the same interface ‣ There is no state; requests are atomic ‣ Follows a resource-oriented architecture Introduction to AtomPub Web Services • Ben Ramsey 19
  20. 20. Terminology ‣ Entry ‣ Feed/Collection ‣ Category Document ‣ Service Document Introduction to AtomPub Web Services • Ben Ramsey 20
  21. 21. Content Types ‣ Entry: application/atom+xml;type=entry ‣ Feed/Collection: application/atom+xml ‣ Category Document: application/atomcat+xml ‣ Service Document: application/atomsvc+xml Introduction to AtomPub Web Services • Ben Ramsey 21
  22. 22. Designing an AtomPub Service Introduction to AtomPub Web Services • Ben Ramsey 22
  23. 23. What will our service do? ‣ Expose users ‣ Expose content ‣ Allow users to manipulate content Introduction to AtomPub Web Services • Ben Ramsey 23
  24. 24. Step 1: Define our URIs
  25. 25. Users ‣ /user ‣ /user/{username} ‣ For example: /user/ramsey Introduction to AtomPub Web Services • Ben Ramsey 25
  26. 26. Content ‣ /content ‣ /content/{id} ‣ For example: /content/1234 Introduction to AtomPub Web Services • Ben Ramsey 26
  27. 27. Step 2: Define the relationships
  28. 28. Relationship Building ‣ user ⇛ content: one to many ‣ content ⇛ user: one to one Introduction to AtomPub Web Services • Ben Ramsey 28
  29. 29. Step 3: Define the interface
  30. 30. Methods Cut & Paste GET Copy PUT Paste Over POST Paste After DELETE Cut
  31. 31. Actions for User Resources ‣ Retrieve user collection: GET /user ‣ Create a new user: POST /user ‣ Modify an existing user: PUT /user/ramsey ‣ Delete a user: DELETE /user/ramsey Introduction to AtomPub Web Services • Ben Ramsey 31
  32. 32. Actions for Content Resources ‣ Retrieve content: GET /content ‣ Create new content: POST /content ‣ Modify content: PUT /content/1234 ‣ Remove content: DELETE /content/1234 Introduction to AtomPub Web Services • Ben Ramsey 32
  33. 33. Other Actions ‣ Service discovery: GET / ‣ Retrieve content for a particular user: GET /user/ramsey/content Introduction to AtomPub Web Services • Ben Ramsey 33
  34. 34. Let’s see it in action Introduction to AtomPub Web Services • Ben Ramsey 34
  35. 35. GET / HTTP/1.1 Host: atom.example.org HTTP/1.x 200 OK Date: Mon, 21 Sep 2009 16:33:45 GMT Content-Type: application/atomsvc+xml
  36. 36. <?xml version="1.0" encoding="utf-8"?> <service xmlns="http://www.w3.org/2007/app" xmlns:atom="http://www.w3.org/2005/Atom" xml:base="http://atom.example.org/"> <workspace> <atom:title>Our Content Store</atom:title> <collection href="user"> <atom:title>Users</atom:title> <accept>application/atom+xml;type=entry</accept> <categories href="cat/user"/> </collection> <collection href="content"> <atom:title>Content</atom:title> <accept>application/atom+xml;type=entry</accept> <categories href="cat/content"/> </collection> </workspace> </service>
  37. 37. GET /user HTTP/1.1 Host: atom.example.org HTTP/1.x 200 OK Date: Mon, 21 Sep 2009 16:34:26 GMT Content-Type: application/atom+xml
  38. 38. <?xml version="1.0" encoding="utf-8"?> <feed xmlns="http://www.w3.org/2005/Atom" xmlns:app="http://www.w3.org/2007/app" xml:base="http://atom.example.org/"> <title>Users</title> <updated>2009-09-21T05:21:19Z</updated> <id>tag:example.org,2009-09:user</id> <app:collection href="user"> <title>Users</title> <app:accept>application/atom+xml;type=entry</app:accept> <app:categories href="cat/user"/> </app:collection> <link rel="first" href="user"/> <link rel="last" href="user?p=23"/> <link rel="next" href="user?p=2"/> <entry> ... </entry> </feed>
  39. 39. Manipulating a User Introduction to AtomPub Web Services • Ben Ramsey 39
  40. 40. GET /user/ramsey HTTP/1.1 Host: atom.example.org HTTP/1.x 200 OK Date: Mon, 21 Sep 2009 16:34:26 GMT Content-Type: application/atom+xml;type=entry
  41. 41. <?xml version="1.0" encoding="utf-8"?> <entry xmlns="http://www.w3.org/2005/Atom" xml:base="http://atom.example.org/"> <title>ramsey</title> <author> <name>ramsey</name> </author> <link rel="self" href="user/ramsey"/> <link rel="edit" type="application/atom+xml;type=entry" href="user/ramsey"/> <link rel="related" href="user/ramsey/content"/> <id>tag:example.org,2008:user/ramsey</id> <updated>2009-09-21T13:45:00Z</updated> <published>2008-05-23T16:23:34Z</published> <content type="xhtml"> <div class="vcard"> <a class="fn">Ben Ramsey</a> <span class="tel">123-456-7890</span> </div> </content> </entry>
  42. 42. Modify the Entry Locally Introduction to AtomPub Web Services • Ben Ramsey 42
  43. 43. <?xml version="1.0" encoding="utf-8"?> <entry xmlns="http://www.w3.org/2005/Atom" xml:base="http://atom.example.org/"> <title>ramsey</title> <author> <name>ramsey</name> </author> <link rel="self" href="user/ramsey"/> <link rel="edit" type="application/atom+xml;type=entry" href="user/ramsey"/> <link rel="related" href="user/ramsey/content"/> <id>tag:example.org,2008:user/ramsey</id> <updated>2009-09-22T09:14:58Z</updated> <published>2008-05-23T16:23:34Z</published> <content type="xhtml"> <div class="vcard"> <a class="fn url" href="http://benramsey.com/">Ben Ramsey</a> <span class="org">Moontoast</span> <span class="tel">123-456-7890</span> </div> </content> </entry>
  44. 44. PUT /user/ramsey HTTP/1.1 Host: atom.example.org Content-Type: application/atom+xml;type=entry {body here} HTTP/1.x 200 OK Date: Mon, 22 Sep 2009 09:14:59 GMT Content-Type: application/atom+xml;type=entry
  45. 45. Add Some Content Introduction to AtomPub Web Services • Ben Ramsey 45
  46. 46. First, a Few Notes ‣ You need authentication! ‣ Perhaps you need encryption ‣ You definitely need validation ‣ And I’m not going to tell you how Introduction to AtomPub Web Services • Ben Ramsey 46
  47. 47. That’s out of scope.
  48. 48. :-)
  49. 49. But I’ll show you the basics.
  50. 50. <?xml version="1.0" encoding="utf-8"?> <service xmlns="http://www.w3.org/2007/app" xmlns:atom="http://www.w3.org/2005/Atom" xml:base="http://atom.example.org/"> <workspace> <atom:title>Our Content Store</atom:title> <collection href="user"> <atom:title>Users</atom:title> <accept>application/atom+xml;type=entry</accept> <categories href="cat/user"/> </collection> <collection href="content"> <atom:title>Content</atom:title> <accept>application/atom+xml;type=entry</accept> <categories href="cat/content"/> </collection> </workspace> </service>
  51. 51. Get the Categories Introduction to AtomPub Web Services • Ben Ramsey 51
  52. 52. GET /cat/content HTTP/1.1 Host: atom.example.org HTTP/1.x 200 OK Date: Mon, 22 Sep 2009 09:39:26 GMT Content-Type: application/atomcat+xml
  53. 53. <?xml version="1.0"?> <app:categories xmlns:app="http://www.w3.org/2007/app" xmlns:atom="http://www.w3.org/2005/Atom" fixed="yes" scheme="http://atom.example.com/cat/content"> <atom:category term="audio"/> <atom:category term="video"/> <atom:category term="game"/> </app:categories>
  54. 54. Create the Entry Document Locally Introduction to AtomPub Web Services • Ben Ramsey 54
  55. 55. <?xml version="1.0" encoding="utf-8"?> <entry xmlns="http://www.w3.org/2005/Atom" xml:base="http://atom.example.org/"> <title>Perfect</title> <author> <name>Mark Phelps</name> </author> <id>tag:example.org,2009:content/perfect</id> <published>2009-09-22T20:12:08Z</published> <category term="audio" scheme="http://atom.example.com/cat/content"/> <content type="application/mp4"> TWFuIGlzIGRpc3Rpbmd1aXNoZWQsIG5vdCBvbmx5IGJ5IGhpcyByZWF IHNpbmd1bGFyIHBhc3Npb24gZnJvbSBvdGhlciBhbmltYWxzLCB3aGl ... </content> </entry>
  56. 56. POST /content HTTP/1.1 Host: atom.example.org Content-Type: application/atom+xml;type=entry {body here} HTTP/1.x 202 Accepted Date: Mon, 22 Sep 2009 09:14:59 GMT {body contains status indicator}
  57. 57. Authentication? ‣ Atom doesn’t specify a preference ‣ WSSE Username Token ‣ OAuth ‣ Basic authentication ‣ Digest authentication ‣ ??? Introduction to AtomPub Web Services • Ben Ramsey 57
  58. 58. Did I miss anything?
  59. 59. Oh, yeah. Where’s the PHP code?
  60. 60. AtomPub in PHP ‣ DOM for reading/writing ‣ SimpleXML for reading ‣ XMLReader for reading ‣ XMLWriter for writing ‣ String concatenation for writing ‣ I recommend XMLReader/XMLWriter; they’re the fastest at parsing and generating XML Introduction to AtomPub Web Services • Ben Ramsey 60
  61. 61. Wrapping Up ‣ You can extend Atom with other XML vocabularies (Dublin Core, etc.) ‣ XML Digital Signature or XML Encryption may be used, or encrypt as a bag of bits ‣ Use your preferred authentication method ‣ Use HTTP in a RESTful fashion ‣ Use DOM or XMLReader/XMLWriter to parse Atom documents Introduction to AtomPub Web Services • Ben Ramsey 61
  62. 62. Questions? ‣ I blog at benramsey.com ‣ I tweet at @ramsey ‣ Please rate this presentation: http://joind.in/2185 ‣ Read the Atom specifications: RFC 4287 RFC 5023 ‣ My company is Moontoast Introduction to AtomPub Web Services • Ben Ramsey 62
  63. 63. Introduction to AtomPub Web Services Copyright © Ben Ramsey. Some rights reserved. This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 United States License. For uses not covered under this license, please contact the author.
  64. 64. Photo Credits ‣ Molecule display, by Christian Guthier ‣ Atom, by jayneandd ‣ Atomium - detail, by Constantin Barbu ‣ Simplicity, by Subterranean Tourist Board ‣ STEREO's Extreme UltraViolet Imager (EUVI), by NASA ‣ Quantum Universe, by Gaurav ‣ Fullerene Nanogears, by NASA ‣ Little Atom, by Marrio ‣ That Atom, by Albert O’Conner ‣ Bokeh Spiral, by Eric Wüstenhagen ‣ Chambered Nautilus Shell - detail, by Jitze Couperus Introduction to AtomPub Web Services • Ben Ramsey 64

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