Introduction to AtomPub Web Services (IPC 2010)

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

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Introduction to AtomPub Web Services • Ben Ramsey 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 2

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Atom & AtomPub? 

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What’s the diﬀerence? 

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

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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

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Atom is an XML language.

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

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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

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AtomPub is a publishing protocol.

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

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Introduction to AtomPub Web Services • Ben Ramsey Content Types 12 ‣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

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Introduction to AtomPub Web Services • Ben Ramsey 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 13

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Introduction to AtomPub Web Services • Ben Ramsey 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 14

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Introduction to AtomPub Web Services • Ben Ramsey 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 15

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Atom was created to solve the RSS problems.

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Introduction to AtomPub Web Services • Ben Ramsey 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 17

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Introduction to AtomPub Web Services • Ben Ramsey 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 18

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Introduction to AtomPub Web Services • Ben Ramsey 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 19

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

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Introduction to AtomPub Web Services • Ben Ramsey Content Types ‣Entry:   application/atom+xml;type=entry ‣Feed/Collection:  application/atom+xml ‣Category Document:  application/atomcat+xml ‣Service Document:  application/atomsvc+xml 21

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

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

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Step 1: Deﬁne our URIs

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

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

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Step 2: Deﬁne the relationships

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

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Step 3: Deﬁne the interface

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

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Introduction to AtomPub Web Services • Ben Ramsey 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 31

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Introduction to AtomPub Web Services • Ben Ramsey Actions for Content Resources ‣Retrieve content:  GET /content ‣Create new content:  POST /content ‣Modify content:  PUT /content/1234 ‣Remove content:  DELETE /content/1234 32

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

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

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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

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Our Content Store Users application/atom+xml;type=entry Content application/atom+xml;type=entry

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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

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Users 2009-09-21T05:21:19Z tag:example.org,2009-09:user Users application/atom+xml;type=entry ...

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

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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

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ramsey ramsey tag:example.org,2008:user/ramsey 2009-09-21T13:45:00Z 2008-05-23T16:23:34Z

Ben Ramsey 123-456-7890

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

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ramsey ramsey tag:example.org,2008:user/ramsey 2009-09-22T09:14:58Z 2008-05-23T16:23:34Z

Ben Ramsey Moontoast 123-456-7890

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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

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

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Introduction to AtomPub Web Services • Ben Ramsey First, a Few Notes 46 ‣You need authentication! ‣Perhaps you need encryption ‣You deﬁnitely need validation ‣And I’m not going to tell you how

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That’s out of scope.

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:-)

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But I’ll show you the basics.

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Our Content Store Users application/atom+xml;type=entry Content application/atom+xml;type=entry

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

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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

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

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Perfect Mark Phelps tag:example.org,2009:content/perfect 2009-09-22T20:12:08Z TWFuIGlzIGRpc3Rpbmd1aXNoZWQsIG5vdCBvbmx5IGJ5IGhpcyByZWF IHNpbmd1bGFyIHBhc3Npb24gZnJvbSBvdGhlciBhbmltYWxzLCB3aGl ...

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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}

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

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Did I miss anything?

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Oh, yeah. Where’s the PHP code?

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Introduction to AtomPub Web Services • Ben Ramsey 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 60

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Introduction to AtomPub Web Services • Ben Ramsey 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 61

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Introduction to AtomPub Web Services • Ben Ramsey 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 62

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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.

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Introduction to AtomPub Web Services • Ben Ramsey Photo Credits 64 ‣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