Introduction to AtomPub Web Services

Introduction to AtomPub Web Services Ben Ramsey • International PHP Conference • 11 Oct 2010

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

Atom & AtomPub?

What’s the difference?

Atom: RFC 4287 Introduction to AtomPub Web Services • Ben Ramsey 5

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

Atom is an XML language.

AtomPub: RFC 5023 Introduction to AtomPub Web Services • Ben Ramsey 8

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

AtomPub is a publishing protocol.

What about RSS? Introduction to AtomPub Web Services • Ben Ramsey 11

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

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

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

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

Atom was created to solve the RSS problems.

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

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

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

Terminology ‣ Entry ‣ Feed/Collection ‣ Category Document ‣ Service Document Introduction to AtomPub Web Services • Ben Ramsey 20

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

Designing an AtomPub Service Introduction to AtomPub Web Services • Ben Ramsey 22

What will our service do? ‣ Expose users ‣ Expose content ‣ Allow users to manipulate content Introduction to AtomPub Web Services • Ben Ramsey 23

Step 1: Deﬁne our URIs

Users ‣ /user ‣ /user/{username} ‣ For example: /user/ramsey Introduction to AtomPub Web Services • Ben Ramsey 25

Content ‣ /content ‣ /content/{id} ‣ For example: /content/1234 Introduction to AtomPub Web Services • Ben Ramsey 26

Step 2: Deﬁne the relationships

Relationship Building ‣ user ⇛ content: one to many ‣ content ⇛ user: one to one Introduction to AtomPub Web Services • Ben Ramsey 28

Step 3: Deﬁne the interface

Methods Cut & Paste GET Copy PUT Paste Over POST Paste After DELETE Cut

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

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

Other Actions ‣ Service discovery: GET / ‣ Retrieve content for a particular user: GET /user/ramsey/content Introduction to AtomPub Web Services • Ben Ramsey 33

Let’s see it in action Introduction to AtomPub Web Services • Ben Ramsey 34

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

<?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>

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

<?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>

Manipulating a User Introduction to AtomPub Web Services • Ben Ramsey 39

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

<?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>

Modify the Entry Locally Introduction to AtomPub Web Services • Ben Ramsey 42

<?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>

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

Add Some Content Introduction to AtomPub Web Services • Ben Ramsey 45

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

That’s out of scope.

But I’ll show you the basics.

<?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>

Get the Categories Introduction to AtomPub Web Services • Ben Ramsey 51

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

<?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>

Create the Entry Document Locally Introduction to AtomPub Web Services • Ben Ramsey 54

<?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>

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}

Authentication? ‣ Atom doesn’t specify a preference ‣ WSSE Username Token ‣ OAuth ‣ Basic authentication ‣ Digest authentication ‣ ??? Introduction to AtomPub Web Services • Ben Ramsey 57

Did I miss anything?

Oh, yeah. Where’s the PHP code?

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

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

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

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.

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

Introduction to AtomPub Web Services

by Ben Ramsey

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