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JPoint	
  




REST: From GET to HATEOAS
      …	
  or	
  how	
  to	
  create	
  RESTful	
  APIs	
  
2




                                                                Who am I?
                                                                    ~	
  just	
  some	
  java	
  guy	
  ~	
  




 Jos Dirksen                                       Interests                                                                                          Books
 Architect	
  @	
  JPoint	
                       •            Java	
  &	
  Scala	
                                                                   Shameless	
  self	
  promotion:	
  
                                                  •            REST,	
  WS-­‐*	
  
•    Live	
  in	
  Waalwijk	
                     •            HTML5	
                                                                                •           SOA	
  Governance	
  in	
  
•    Married	
                                                	
                                                                                                  Action,	
  Manning,	
  2012	
  
•    Daughter	
  (2.5	
  y/o)	
                   •            Snowboarding	
                                                                         •           Open	
  Source	
  ESBs	
  in	
  
•    Blog	
  at:	
                                •            Reading	
                                                                                          Action,	
  Manning,	
  2008	
  
     www.smartjava.org	
                          •            Cooking	
  



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  TWITTER:	
  @JOSDIRKSEN	
  
3




                                                  Disclaimer
                           ~	
  you	
  will	
  encounter	
  opinionated	
  content	
  ~	
  




Heavily opinionated
•  There are many truths
•  This is mine
•  I’m not a Restafarian




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4




 In the beginning…              ~	
  It	
  was	
  a	
  dark	
  place	
  ~	
  




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5




The world before REST!
                                                                                                     Many different ‘standards’:
                                                                                                     RMI,	
  SOAP,	
  Corba,	
  DCE,	
  DCOM	
  

                                                                                                     From many different parties:
                                                                                                     Sun,	
  Microsoft,	
  IBM,	
  OASIS,	
  OMG	
  

                                                                                                     Caused many problems:
                                                                                                     •  Bad	
  interoperability.	
  
                                                                                                     •  Reinvent	
  the	
  wheel.	
  
                                                                                                     •  Vendor	
  ‘lock-­‐in’.	
  




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6




             And then came REST!

“Representational State Transfer (REST) is a style of
 software architecture for distributed hypermedia
      systems such as the World Wide Web”


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7




REST is based on a set of constraints                              ~	
  Rest	
  101	
  ~	
  




1. Client-server                                                                                                        4. Uniform interface
Separate clients and servers.                                                                                           There is a uniform interface between
                                                                                                                        clients and servers.
2. Stateless server
Each request from a client contains all the                                                                             5. Layered System
information necessary to service the request.                                                                           Must allow concepts such as load
                                                                                                                        balancers, proxies and firewalls.
3. Cacheable
Clients can cache responses, responses
                                                                                                                        6. Code-On-Demand (optional)
                                                                                                                        Client can request code from server and
must indicate if this is allowed.
                                                                                                                        execute it.
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8




             Constraint 4: Uniform interface                               ~	
  Rest	
  101	
  ~	
  



A.  Identification of resources:
     E.g. by using an URI.
B.  Manipulation of resources through representations:
    A representations allows user to modify/delete resource .
C.  Self-descriptive messages:
     Process message based on message and meta-data.
D.  Hypermedia as the engine of application state:
     State transitions are defined in representations.


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9




                And all was good!
                                                                                                                Why do this? Why be RESTful?
                                                                                                                •             Scalable
                                                                                                                •             Fault-tolerant
                                                                                                                •             Recoverable
                                                                                                                •             Secure
                                                                                                                •             Loosely coupled


“Exactly what we want in the applications we are developing!”
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10




      But not everybody understood…
•  GET: /getAllDogs
•  GET: /saveDog?name=brian&age=7
•  GET: /feedDog?food=123&dog=brian
instead of:
•  GET: /dogs
•  PUT: /dog/brian
•  POST: /dog/brian/food/123

     “In your URLs – nouns are good; verbs are (usually) bad”
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11




                                               Twitter API
                     ~	
  just	
  saying	
  your	
  RESTful	
  doesn’t	
  make	
  it	
  so	
  ~	
  




Bad URLs:
•  POST statuses/destroy/:id
•  GET statuses/show/:id
•  POST direct_messages/new
Instead of:
•  DELETE status/:id
•  GET status/:id
•  POST direct_message or PUT direct_message/:id
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12




The maturity levels of REST




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13




Richardson’s Maturity Model




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14




              Level 0: The Swamp of Pox       ~	
  nothing	
  to	
  do	
  with	
  REST	
  ~	
  




    •  One URI, one HTTP method
    •  XML-RPC / SOAP / POX
    •  Giant ‘black box’, is what eBay uses.
POST /appointmentService HTTP/1.1
[various other headers]

<appointmentRequest>
  <slot doctor = "mjones" start = "1400" end = "1450"/>
  <patient id = "jsmith"/>
</appointmentRequest>
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15




                                       Level 0: eBay
                                                ~	
  not	
  an	
  easy	
  to	
  use	
  API	
  ~	
  


POST http://svcs.ebay.com/services/search/FindingService/v1

<findItemsByKeywordsRequest xmlns="http://www.ebay.com/marketplace/
search/v1/services">
  <affiliate>
    <networkId>9</networkId>
    <trackingId>1234567890</trackingId>
    <customId>k-man</customId>
  </affiliate>
  <sortOrder>EndTime</sortOrder>
  <paginationInput>
    <entriesPerPage>2</entriesPerPage>
  </paginationInput>
  <keywords>camalots</keywords>
</findItemsByKeywordsRequest>


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16




                       Level 1: Resources
                                      ~	
  lots	
  of	
  APIs	
  start	
  out	
  this	
  way	
  ~	
  




    •    Each resource has an unique URI
    •    Single HTTP verb (usually POST or GET)
    •    Verbs have no meaning, used to tunnel over HTTP
    •    Early versions of Flickr, del.ico.us and Amazon
POST /slots/1234 HTTP/1.1
[various other headers]

<appointmentRequest>
  <patient id = "jsmith"/>
</appointmentRequest>
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17




                                                   Level 2: HTTP Verbs   ~	
  close	
  but	
  no	
  sigar	
  ~	
  




               •       Many URIs, using multiple verbs
               •       Correct use of response codes
               •       Exposes state, not behavior
               •       Crud services, can be useful e.g Amazon S3
GET /doctors/mjones/slots?date=20100104&status=open HTTP/1.1
Host: royalhope.nhs.uk

HTTP/1.1 200 OK
<openSlotList>
  <slot id = "1234” start = "1400" end = "1450"/>
  <slot id = "5678” start = "1600" end = "1650"/>
</openSlotList>   WWW.JPOINT.NL	
  	
  	
  	
  	
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18




            Level 3: Hypermedia controls                      ~	
  True	
  RESTful	
  ~	
  




     •  Resources are self-describing
     •  Hypermedia As The Engine Of Application State (HATEOAS)
     •  Exposes state and behavior
<appointment>
  <slot id = "1234" doctor = "mjones" start = "1400"
       end = "1450"/>
  <patient id = "jsmith"/>
  <link rel = "/linkrels/appointment/addTest"
        uri = "/slots/1234/appointment/tests"/>
  <link rel = "/linkrels/appointment/updateContactInfo"
        uri = "/patients/jsmith/contactInfo"/>
</appointment>
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19




           So, are level 0, 1 and 2 RESTful?
“What needs to be done to make the REST architectural style clear on
the notion that hypertext is a constraint? In other words, if the engine
    of application state (and hence the API) is not being driven by
hypertext, then it cannot be RESTful and cannot be a REST API. Period.
  Is there some broken manual somewhere that needs to be fixed?”
                                                                                                                                                           Roy T. Fielding
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20




Level 2 is easy, how do we do HATEOAS?~	
  Worst	
  acronym	
  ever!	
  ~	
  




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21




                                                     HATEOAS?
  “The next control state of an application resides in the representation of the
  first requested resource, … The application state is controlled and stored by
      the user agent … anticipate changes to that state (e.g., link maps and
prefetching of representations) … The model application is therefore an engine
 that moves from one state to the next by examining and choosing from among
     the alternative state transitions in the current set of representations.”
                                                                                                                                                              Roy T. Fielding
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22




                            Say what?




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23




                  The key to HATEOAS is simple
    •  Hypermedia / Mime-types / Media-types :
            •    Describes a current state
            •    Compare it with a web page
            •    Can be seen as the contract
    •  Links:
            •    Describe the transition to the next state
            •    Compare it with hyperlinks
    •  HATEOAS makes surfing the web possible
    •  Jim Webber: “Hypermedia Describes Protocols” (HYDEPR)
“In each response message, include the links for the next request message”
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24




                  HATEOAS Part 1: Links                           ~	
  AtomPub	
  ~	
  
<feed xmlns="http://www.w3.org/2005/Atom">!
        <title>Example Feed</title>!
        <subtitle>A subtitle.</subtitle>!
        <link href="http://example.org/feed/" !
              rel="self" />!
        <link href="http://example.org/" />!
        <id>urn:uuid:60a76c80-d399-11d9-b91C-0003939e0af6</id>!
        <updated>2003-12-13T18:30:02Z</updated>!
        <author>!
                 <name>John Doe</name>!
                 <email>johndoe@example.com</email>!
        </author>!
        <entry>!
                 <title>Atom-Powered Robots Run Amok</title>!
                 <link href="http://example.org/2003/12/13/atom03" />!
                 <link rel="alternate" type="text/html" !
                      href="http://example.org/2003/12/13/atom03.html"/>!
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25




                                       HATEOAS Part 1: Links     ~	
  NetGlix	
  API	
  ~	
  

<link
  href="http://.../catalog/titles/series/70023522/cast”
   rel="http://schemas.netflix.com/catalog/people"
 title="cast">
 <cast>
  <link href="http://api.netflix.com/catalog/people/30011713"
         rel="http://schemas.netflix.com/catalog/person"
       title="Steve Carell"/>
  <link href="http://api.netflix.com/catalog/people/30014922"
         rel="http://schemas.netflix.com/catalog/person"
       title="John Krasinski"/>
  <link href="http://api.netflix.com/catalog/people/20047634"
         rel="http://schemas.netflix.com/catalog/person"
       title="Jenna Fischer"/>
</cast>
</link>           WWW.JPOINT.NL	
  	
  	
  	
  	
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26




        HATEOAS Part 1: Twitter Example            ~	
  Before	
  using	
  links~	
  

GET .../followers/ids.json?cursor=-1&screen_name=josdirksen

{
 “previous_cursor”: 0,
 “previous_cursor_str”: 0,
 “ids”: [
    12345678,
    87654321,
    11223344
 ],
 “next_cursor”: 0,
 “next_cursor_str”: “0”
}


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27




        HATEOAS Part 1: Twitter Example                        ~	
  With	
  links~	
  

GET .../followers/ids.json?cursor=-1&screen_name=josdirksen

{
 “previous_cursor”: 0,
 “id”: {
   “name”: “John Smit”,
   “id”: “12345678”
   “links” : [
   { “rel”: “User info”,
     “href”: “https://.../user/12345678”},
   { “rel”: “Follow user”,
     “href”: “https://.../friendship/12345678”}
   ]
  } // and add other links: tweet to, send direct message,
  ..// block, report for spam, add or remove from list
}                 WWW.JPOINT.NL	
  	
  	
  	
  	
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28




HATEOAS Part 2: Media-types
                                                                                                       WHERE:
                                                                                                       People	
  know	
  where	
  to	
  `ind	
  your	
  
                                                                                                       resource	
  using	
  URIs.	
  

                                                                                                       HOW:
                                                                                                       They	
  know	
  how	
  to	
  interact	
  by	
  
                                                                                                       following	
  links.	
  

                                                                                                       WHAT:
                                                                                                       But	
  what	
  do	
  the	
  resources	
  look	
  
                                                                                                       like,	
  what	
  do	
  they	
  need	
  to	
  post?	
  



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29




              HATEOAS Part 2: Media-types
               ~	
  not	
  all	
  media-­‐types	
  are	
  equal,	
  some	
  are	
  more	
  equal	
  than	
  others	
  ~	
  



•  Standard formats
        •    Easy to use and understand.
        •    Clients already know how to use them
        •    Don’t always match with what you want to do
        •    XHTML and AtomPub
•  Self created
        •    Very domain specific
        •    Can have rich semantics
        •    Client specific implementation required
        •    Often described using XML Schema
        •    or in plain text, or not at all…

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30




            HATEOAS Part 2: Media-types           ~	
  Custom	
  media	
  types	
  ~	
  
200 OK!
Content-Type: application/vnd.bank.org.account+xml;charset=UTF-8!
!
<accounts xmlns="urn:org:bank:accounts">!
    <account>!
        <id>AZA12093</id>!
        <link href="http://bank.org/account/AZA12093" rel="self"/>!
        <link rel="http://bank.org/rel/transfer"!
               type="application/vnd.bank.org.transfer+xml"!
               href="http://bank.org/transfers"/>!
        <link rel="http://bank.org/rel/customer"!
               type="application/vnd.bank.org.customer+xml"!
               href="http://bank.org/customer/7t676323a"/>!
        <balance currency="USD">993.95</balance>!
    </account>!
</accounts>!

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31




         And that is what HATEOAS means!
•  Media-types describe the resources.
•  Actions are executed by following links.
•  Each new response reflects a state.

•  It is good to create custom media-types.
•  Creates self-describing APIs.
•  Clients ‘explore’ your API just as they browse the web.
  “Media-types describes a domain specific
           application protocol”
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32




        HATEOAS Part 2: Twitter Example
                                  ~	
  With	
  links,	
  but	
  no	
  media-­‐type	
  ~	
  

GET .../followers/ids.json?cursor=-1&screen_name=josdirksen

{
 “previous_cursor”: 0,
 “id”: {
    “name”: “John Smit”,
    “id”: “12345678”
   “links” : [
    { “rel”: “User info”,
      “href”: “https://.../user/12345678”},
    { “rel”: “Follow user”,
      “href”: “https://.../friendship/12345678”}
    ]
  }
  ...
}                 WWW.JPOINT.NL	
  	
  	
  	
  	
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  JOS@JPOINT.NL	
  	
  	
  	
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  TWITTER:	
  @JOSDIRKSEN	
  
33




         HATEOAS Part 2: Twitter Example    ~	
  With	
  links	
  &	
  media-­‐type	
  ~	
  
GET .../followers/ids.json?cursor=-1&screen_name=josdirksen

{
 “previous_cursor”: 0,
 “id”: {
   “name”: “John Smit”,
   “id”: “12345678”
   “links” : [
   { “type: “application/vnd.twitter.com.user”,
     “rel”: “User info”,
     “href”: “https://.../user/12345678”},
   { “type”: “application/vnd.twitter.com.user.follow”,
     “rel”: “Follow user”,
     “href”: “https://.../friendship/12345678”}
   ] // and add other options: tweet to, send direct message,
     // block, report for spam, add or remove from list
  } // This is how you create a self-describing API.
}
                     WWW.JPOINT.NL	
  	
  	
  	
  	
  |	
  	
  	
  	
  	
  JOS@JPOINT.NL	
  	
  	
  	
  |	
  	
  	
  	
  	
  TWITTER:	
  @JOSDIRKSEN	
  
34




                          Case: eBay
                     ~	
  API	
  should	
  guide	
  the	
  user	
  ~	
  


                                                                                                             Common scenario: bidding on item
                                                                                                             1.  Add	
  item	
  to	
  watch	
  list:	
  keep	
  
                                                                                                                 track	
  of	
  the	
  item.	
  
                                                                                                                 	
  
                                                                                                             2.  Get	
  user	
  details:	
  `ind	
  out	
  more	
  
                                                                                                                 about	
  the	
  buyer.	
  
                                                                                                                 	
  
                                                                                                             3.  Get	
  user	
  feedback:	
  is	
  seller	
  
                                                                                                                 trustworthy?	
  
                                                                                                                 	
  
                                                                                                             4.  Make	
  a	
  bid:	
  place	
  a	
  bid	
  for	
  the	
  
                                                                                                                 item.	
  


WWW.JPOINT.NL	
  	
  	
  	
  	
  |	
  	
  	
  	
  	
  JOS@JPOINT.NL	
  	
  	
  	
  |	
  	
  	
  	
  	
  TWITTER:	
  @JOSDIRKSEN	
  
35




eBay: API should help the client
             ~	
  just	
  like	
  a	
  browser	
  does	
  using	
  links	
  ~	
  




      WWW.JPOINT.NL	
  	
  	
  	
  	
  |	
  	
  	
  	
  	
  JOS@JPOINT.NL	
  	
  	
  	
  |	
  	
  	
  	
  	
  TWITTER:	
  @JOSDIRKSEN	
  
36




                   eBay: add to watchlist
                                        ~	
  API	
  should	
  tell	
  us	
  what	
  to	
  do	
  ~	
  

GET .../item/180881974947
{
  “name” : “Monty Python and the Holy Grail white rabbit big pointy teeth”,
  “id” : “180881974947”,
  “start-price” : “6.50”,
  “currency” : “GBP”,
  ...
 “links” : [
    { “type: “application/vnd.ebay.item”,
      “rel”: “Add item to watchlist”,
      “href”: “https://.../user/12345678/watchlist/180881974947”},
    {
      // and a whole lot of other operations
    ]
}


                       WWW.JPOINT.NL	
  	
  	
  	
  	
  |	
  	
  	
  	
  	
  JOS@JPOINT.NL	
  	
  	
  	
  |	
  	
  	
  	
  	
  TWITTER:	
  @JOSDIRKSEN	
  
37




                    eBay: get user details
                            ~	
  Follow	
  links	
  to	
  get	
  more	
  information	
  ~	
  

GET .../item/180881974947
{
  “name” : “Monty Python and the Holy Grail white rabbit big pointy teeth”,
  “id” : “180881974947”,
  “start-price” : “6.50”,
  “currency” : “GBP”,
  // whole lot of other general item data
  “bidder” : {
     “name” : “dangermouse_rm”,
     “link” : {
       “type” : “application/vnd.ebay.user”,
       “rel : “Get user details”,
       “href : “https://.../user/314512346523”
     }
  }
}

                       WWW.JPOINT.NL	
  	
  	
  	
  	
  |	
  	
  	
  	
  	
  JOS@JPOINT.NL	
  	
  	
  	
  |	
  	
  	
  	
  	
  TWITTER:	
  @JOSDIRKSEN	
  
38




                  eBay: get user feedback
                      ~	
  Depending	
  on	
  rights	
  we	
  get	
  different	
  links	
  ~	
  

GET .../user/314512346523
{
  “name” : “dangermouse_rm”,
  “location” : “united kingdom”,
  // whole lot of other general user data
  “feedbacks” : {
     “last_month” : “7,0,0”
     “last_6_month” : “19,0,0”,
     “feedback” : {
       “title” : “Great communication and quick delivery. +++”
       “link” : {
         “type” : “application/vnd.ebay.feedback”,
         “rel : “Show feedback”,
         “href : “https://.../user/314512346523/feedback/1234567”
       }
   ...

                       WWW.JPOINT.NL	
  	
  	
  	
  	
  |	
  	
  	
  	
  	
  JOS@JPOINT.NL	
  	
  	
  	
  |	
  	
  	
  	
  	
  TWITTER:	
  @JOSDIRKSEN	
  
39




                                  eBay: place bid
                      ~	
  Depending	
  on	
  rights	
  we	
  get	
  different	
  links	
  ~	
  

GET .../item/180881974947
{
  “name” : “Monty Python and the Holy Grail white rabbit big pointy teeth”,
  “id” : “180881974947”,
  “start-price” : “6.50”,
  “currency” : “GBP”,
  ...
 “links” : [
    { “type: “application/vnd.ebay.bid”,
      “rel”: “Place bid”,
      “href”: “https://.../user/12345678/bid/180881974947”},
    {
      // and a whole lot of other operations
    ]
}


                       WWW.JPOINT.NL	
  	
  	
  	
  	
  |	
  	
  	
  	
  	
  JOS@JPOINT.NL	
  	
  	
  	
  |	
  	
  	
  	
  	
  TWITTER:	
  @JOSDIRKSEN	
  
40




eBay: much easier!
                ~	
  and	
  there	
  was	
  much	
  rejoicing	
  ~	
  




WWW.JPOINT.NL	
  	
  	
  	
  	
  |	
  	
  	
  	
  	
  JOS@JPOINT.NL	
  	
  	
  	
  |	
  	
  	
  	
  	
  TWITTER:	
  @JOSDIRKSEN	
  
41




Versioning without breaking




    WWW.JPOINT.NL	
  	
  	
  	
  	
  |	
  	
  	
  	
  	
  JOS@JPOINT.NL	
  	
  	
  	
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  TWITTER:	
  @JOSDIRKSEN	
  
42




              Three options for versioning                       ~	
  Media-­‐types	
  ~	
  




      •  Media-type is versioned, directly in its name
Request:
GET /opengov/garbageschedule?location=Main%20Street HTTP/1.1
Accept: application/vnd.opengov.org.garbageschedule-v2+json
 
Response:
HTTP/1.1 200 OK
Content-Type: application/vnd.opengov.org.garbageschedule-v2+json

{"schedule"
     "self": "schedule-2423",
     "dayOfWeek": "Monday",
     "oddOrEvenWeeks": "Odd"}
                        WWW.JPOINT.NL	
  	
  	
  	
  	
  |	
  	
  	
  	
  	
  JOS@JPOINT.NL	
  	
  	
  	
  |	
  	
  	
  	
  	
  TWITTER:	
  @JOSDIRKSEN	
  
43




              Three options for versioning         ~	
  Add	
  version	
  qualiGier	
  ~	
  




      •  Media-type stays the same, add a qualifier.
Request:
GET /opengov/garbageschedule?location=Main%20Street HTTP/1.1
Accept: application/vnd.opengov.org.garbageschedule+json;v=1
 
Response:
HTTP/1.1 200 OK
Content-Type: application/vnd.opengov.org.garbageschedule+json;v=1
 
{"schedule"
     "self": "schedule-2423",
     "dayOfWeek": "Monday",
     "oddOrEvenWeeks": "Odd"}
                       WWW.JPOINT.NL	
  	
  	
  	
  	
  |	
  	
  	
  	
  	
  JOS@JPOINT.NL	
  	
  	
  	
  |	
  	
  	
  	
  	
  TWITTER:	
  @JOSDIRKSEN	
  
44




               Three options for versioning           ~	
  The	
  URI	
  is	
  versioned	
  ~	
  




       •  The version is added in the URI path
Request:
GET /opengov/v1/garbageschedule?location=Main%20Street HTTP/1.1
Accept: application/vnd.opengov.org.garbageschedule+json
 
Response:
HTTP/1.1 200 OK
Content-Type: application/vnd.opengov.org.garbageschedule+json
 
{"schedule"
     "self": "schedule-2423",
     "dayOfWeek": "Monday",
     "oddOrEvenWeeks": "Odd"}
                         WWW.JPOINT.NL	
  	
  	
  	
  	
  |	
  	
  	
  	
  	
  JOS@JPOINT.NL	
  	
  	
  	
  |	
  	
  	
  	
  	
  TWITTER:	
  @JOSDIRKSEN	
  
45




Which one is the best?              ~	
  personal	
  opinion	
  ~	
  


                                                                                                     Matter of taste:
                                                                                                     1.  Media-­‐type	
  approach	
  most	
  
                                                                                                         RESTful,	
  but	
  requires	
  work	
  on	
  
                                                                                                         client	
  and	
  server	
  side.	
  
                                                                                                         	
  
                                                                                                     2.  Quali`ier,	
  second	
  best,	
  easier	
  
                                                                                                         to	
  implement.	
  Less	
  media-­‐
                                                                                                         types	
  to	
  keep	
  track	
  off.	
  
                                                                                                         	
  
                                                                                                     3.  URI,	
  most	
  often	
  used.	
  
                                                                                                         Personally	
  don’t	
  like	
  it.	
  Can	
  
                                                                                                         have	
  two	
  URIs	
  point	
  to	
  same	
  
                                                                                                         resource.	
  

  WWW.JPOINT.NL	
  	
  	
  	
  	
  |	
  	
  	
  	
  	
  JOS@JPOINT.NL	
  	
  	
  	
  |	
  	
  	
  	
  	
  TWITTER:	
  @JOSDIRKSEN	
  
46




When HTTPS isn’t enough




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  JOS@JPOINT.NL	
  	
  	
  	
  |	
  	
  	
  	
  	
  TWITTER:	
  @JOSDIRKSEN	
  
47




   General idea about authentication in REST

“REST means working with the standards of the web, and the standard for
 "secure" transfer on the web is SSL. Anything else is going to be kind of
funky and require extra deployment effort for clients, which will have to
                   have encryption libraries available.”

                                                                                Highest rated answer on stackoverflow
                                                                               regarding REST authentication schemes
                     WWW.JPOINT.NL	
  	
  	
  	
  	
  |	
  	
  	
  	
  	
  JOS@JPOINT.NL	
  	
  	
  	
  |	
  	
  	
  	
  	
  TWITTER:	
  @JOSDIRKSEN	
  
48




                   Why do we need more?
•  HTTPS doesn’t fix man-in-the-middle attack
•  It provides only transport level security
•  Has no support for message integrity or authenticity
•  REST assumes “Layered System”
•  OAuth is nice (and complex) for authentication
   doesn’t handle message integrity.
•  REST doesn’t have a WS-Security standard



                       WWW.JPOINT.NL	
  	
  	
  	
  	
  |	
  	
  	
  	
  	
  JOS@JPOINT.NL	
  	
  	
  	
  |	
  	
  	
  	
  	
  TWITTER:	
  @JOSDIRKSEN	
  
49




                 HMAC based authentication                    ~	
  de	
  facto	
  standard	
  ~	
  

•    Used by Google, Amazon AWS, Yahoo etc.
•    Create a signature of the complete request, using shared secret.
•    Add custom header with signature and signing user.
•    Encrypt the following with this shared secret:
         •    URI, to avoid executing on different resource,
         •    Verb, indicates what we want to do with a resource,
         •    MD5-Header, to detect changes to the content body
         •    Content-type, indicates the type of resource
         •    Date header, to avoid replay


                            WWW.JPOINT.NL	
  	
  	
  	
  	
  |	
  	
  	
  	
  	
  JOS@JPOINT.NL	
  	
  	
  	
  |	
  	
  	
  	
  	
  TWITTER:	
  @JOSDIRKSEN	
  
50




             HMAC based authentication                            ~	
  example	
  ~	
  




POST /resources/rest/geo/comment HTTP/1.1[r][n]!
hmac: jos:+9tn0CLfxXFbzPmbYwq/KYuUSUI=[r][n]!
Date: Mon, 26 Mar 2012 21:34:33 CEST[r][n]!
Content-Md5: r52FDQv6V2GHN4neZBvXLQ==[r][n]!
Content-Length: 69[r][n]!
Content-Type: application/vnd.geo.comment+json;
charset=UTF-8[r][n]!
Host: localhost:9000[r][n]!
Connection: Keep-Alive[r][n]!
User-Agent: Apache-HttpClient/4.1.3 (java 1.5)[r][n]!
[r][n]!
{"comment" : {"message":"blaat" , "from":"blaat" , "commentFor":
123}}!
                   WWW.JPOINT.NL	
  	
  	
  	
  	
  |	
  	
  	
  	
  	
  JOS@JPOINT.NL	
  	
  	
  	
  |	
  	
  	
  	
  	
  TWITTER:	
  @JOSDIRKSEN	
  
51




                        Parting guidelines
                             ~	
  you	
  may	
  forget	
  everything	
  else	
  I	
  said	
  ~	
  


•  Just doing URIs and Verbs doesn’t make it RESTful
      •  But that isn’t necessary a bad thing.
•  Use “Links” to describe “HOW” your service is used.
•  Describe “WHAT” is expected using media-types.
      •  This isn’t a complete replacement of documentation
      •  Don’t use WADL
•  Use media-types for versioning.
•  Forget what HATEOAS stands for.
                        WWW.JPOINT.NL	
  	
  	
  	
  	
  |	
  	
  	
  	
  	
  JOS@JPOINT.NL	
  	
  	
  	
  |	
  	
  	
  	
  	
  TWITTER:	
  @JOSDIRKSEN	
  
52




                                                  Q&A




WWW.JPOINT.NL	
  	
  	
  	
  	
  |	
  	
  	
  	
  	
  JOS@JPOINT.NL	
  	
  	
  	
  |	
  	
  	
  	
  	
  TWITTER:	
  @JOSDIRKSEN	
  
JPoint	
  




       THANKS FOR COMING
More	
  information;	
  look	
  at	
  http://www.jpoint.nl	
  or	
  contact	
  me.	
  

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REST: From GET to HATEOAS

  • 1. JPoint   REST: From GET to HATEOAS …  or  how  to  create  RESTful  APIs  
  • 2. 2 Who am I? ~  just  some  java  guy  ~   Jos Dirksen Interests Books Architect  @  JPoint   •  Java  &  Scala   Shameless  self  promotion:   •  REST,  WS-­‐*   •  Live  in  Waalwijk   •  HTML5   •  SOA  Governance  in   •  Married     Action,  Manning,  2012   •  Daughter  (2.5  y/o)   •  Snowboarding   •  Open  Source  ESBs  in   •  Blog  at:   •  Reading   Action,  Manning,  2008   www.smartjava.org   •  Cooking   WWW.JPOINT.NL          |          JOS@JPOINT.NL        |          TWITTER:  @JOSDIRKSEN  
  • 3. 3 Disclaimer ~  you  will  encounter  opinionated  content  ~   Heavily opinionated •  There are many truths •  This is mine •  I’m not a Restafarian WWW.JPOINT.NL          |          JOS@JPOINT.NL        |          TWITTER:  @JOSDIRKSEN  
  • 4. 4 In the beginning… ~  It  was  a  dark  place  ~   WWW.JPOINT.NL          |          JOS@JPOINT.NL        |          TWITTER:  @JOSDIRKSEN  
  • 5. 5 The world before REST! Many different ‘standards’: RMI,  SOAP,  Corba,  DCE,  DCOM   From many different parties: Sun,  Microsoft,  IBM,  OASIS,  OMG   Caused many problems: •  Bad  interoperability.   •  Reinvent  the  wheel.   •  Vendor  ‘lock-­‐in’.   WWW.JPOINT.NL          |          JOS@JPOINT.NL        |          TWITTER:  @JOSDIRKSEN  
  • 6. 6 And then came REST! “Representational State Transfer (REST) is a style of software architecture for distributed hypermedia systems such as the World Wide Web” WWW.JPOINT.NL          |          JOS@JPOINT.NL        |          TWITTER:  @JOSDIRKSEN  
  • 7. 7 REST is based on a set of constraints ~  Rest  101  ~   1. Client-server 4. Uniform interface Separate clients and servers. There is a uniform interface between clients and servers. 2. Stateless server Each request from a client contains all the 5. Layered System information necessary to service the request. Must allow concepts such as load balancers, proxies and firewalls. 3. Cacheable Clients can cache responses, responses 6. Code-On-Demand (optional) Client can request code from server and must indicate if this is allowed. execute it. WWW.JPOINT.NL          |          JOS@JPOINT.NL        |          TWITTER:  @JOSDIRKSEN  
  • 8. 8 Constraint 4: Uniform interface ~  Rest  101  ~   A.  Identification of resources: E.g. by using an URI. B.  Manipulation of resources through representations: A representations allows user to modify/delete resource . C.  Self-descriptive messages: Process message based on message and meta-data. D.  Hypermedia as the engine of application state: State transitions are defined in representations. WWW.JPOINT.NL          |          JOS@JPOINT.NL        |          TWITTER:  @JOSDIRKSEN  
  • 9. 9 And all was good! Why do this? Why be RESTful? •  Scalable •  Fault-tolerant •  Recoverable •  Secure •  Loosely coupled “Exactly what we want in the applications we are developing!” WWW.JPOINT.NL          |          JOS@JPOINT.NL        |          TWITTER:  @JOSDIRKSEN  
  • 10. 10 But not everybody understood… •  GET: /getAllDogs •  GET: /saveDog?name=brian&age=7 •  GET: /feedDog?food=123&dog=brian instead of: •  GET: /dogs •  PUT: /dog/brian •  POST: /dog/brian/food/123 “In your URLs – nouns are good; verbs are (usually) bad” WWW.JPOINT.NL          |          JOS@JPOINT.NL        |          TWITTER:  @JOSDIRKSEN  
  • 11. 11 Twitter API ~  just  saying  your  RESTful  doesn’t  make  it  so  ~   Bad URLs: •  POST statuses/destroy/:id •  GET statuses/show/:id •  POST direct_messages/new Instead of: •  DELETE status/:id •  GET status/:id •  POST direct_message or PUT direct_message/:id WWW.JPOINT.NL          |          JOS@JPOINT.NL        |          TWITTER:  @JOSDIRKSEN  
  • 12. 12 The maturity levels of REST WWW.JPOINT.NL          |          JOS@JPOINT.NL        |          TWITTER:  @JOSDIRKSEN  
  • 13. 13 Richardson’s Maturity Model WWW.JPOINT.NL          |          JOS@JPOINT.NL        |          TWITTER:  @JOSDIRKSEN  
  • 14. 14 Level 0: The Swamp of Pox ~  nothing  to  do  with  REST  ~   •  One URI, one HTTP method •  XML-RPC / SOAP / POX •  Giant ‘black box’, is what eBay uses. POST /appointmentService HTTP/1.1 [various other headers] <appointmentRequest> <slot doctor = "mjones" start = "1400" end = "1450"/> <patient id = "jsmith"/> </appointmentRequest> WWW.JPOINT.NL          |          JOS@JPOINT.NL        |          TWITTER:  @JOSDIRKSEN  
  • 15. 15 Level 0: eBay ~  not  an  easy  to  use  API  ~   POST http://svcs.ebay.com/services/search/FindingService/v1 <findItemsByKeywordsRequest xmlns="http://www.ebay.com/marketplace/ search/v1/services"> <affiliate> <networkId>9</networkId> <trackingId>1234567890</trackingId> <customId>k-man</customId> </affiliate> <sortOrder>EndTime</sortOrder> <paginationInput> <entriesPerPage>2</entriesPerPage> </paginationInput> <keywords>camalots</keywords> </findItemsByKeywordsRequest> WWW.JPOINT.NL          |          JOS@JPOINT.NL        |          TWITTER:  @JOSDIRKSEN  
  • 16. 16 Level 1: Resources ~  lots  of  APIs  start  out  this  way  ~   •  Each resource has an unique URI •  Single HTTP verb (usually POST or GET) •  Verbs have no meaning, used to tunnel over HTTP •  Early versions of Flickr, del.ico.us and Amazon POST /slots/1234 HTTP/1.1 [various other headers] <appointmentRequest> <patient id = "jsmith"/> </appointmentRequest> WWW.JPOINT.NL          |          JOS@JPOINT.NL        |          TWITTER:  @JOSDIRKSEN  
  • 17. 17 Level 2: HTTP Verbs ~  close  but  no  sigar  ~   •  Many URIs, using multiple verbs •  Correct use of response codes •  Exposes state, not behavior •  Crud services, can be useful e.g Amazon S3 GET /doctors/mjones/slots?date=20100104&status=open HTTP/1.1 Host: royalhope.nhs.uk HTTP/1.1 200 OK <openSlotList> <slot id = "1234” start = "1400" end = "1450"/> <slot id = "5678” start = "1600" end = "1650"/> </openSlotList> WWW.JPOINT.NL          |          JOS@JPOINT.NL        |          TWITTER:  @JOSDIRKSEN  
  • 18. 18 Level 3: Hypermedia controls ~  True  RESTful  ~   •  Resources are self-describing •  Hypermedia As The Engine Of Application State (HATEOAS) •  Exposes state and behavior <appointment> <slot id = "1234" doctor = "mjones" start = "1400" end = "1450"/> <patient id = "jsmith"/> <link rel = "/linkrels/appointment/addTest" uri = "/slots/1234/appointment/tests"/> <link rel = "/linkrels/appointment/updateContactInfo" uri = "/patients/jsmith/contactInfo"/> </appointment> WWW.JPOINT.NL          |          JOS@JPOINT.NL        |          TWITTER:  @JOSDIRKSEN  
  • 19. 19 So, are level 0, 1 and 2 RESTful? “What needs to be done to make the REST architectural style clear on the notion that hypertext is a constraint? In other words, if the engine of application state (and hence the API) is not being driven by hypertext, then it cannot be RESTful and cannot be a REST API. Period. Is there some broken manual somewhere that needs to be fixed?” Roy T. Fielding WWW.JPOINT.NL          |          JOS@JPOINT.NL        |          TWITTER:  @JOSDIRKSEN  
  • 20. 20 Level 2 is easy, how do we do HATEOAS?~  Worst  acronym  ever!  ~   WWW.JPOINT.NL          |          JOS@JPOINT.NL        |          TWITTER:  @JOSDIRKSEN  
  • 21. 21 HATEOAS? “The next control state of an application resides in the representation of the first requested resource, … The application state is controlled and stored by the user agent … anticipate changes to that state (e.g., link maps and prefetching of representations) … The model application is therefore an engine that moves from one state to the next by examining and choosing from among the alternative state transitions in the current set of representations.” Roy T. Fielding WWW.JPOINT.NL          |          JOS@JPOINT.NL        |          TWITTER:  @JOSDIRKSEN  
  • 22. 22 Say what? WWW.JPOINT.NL          |          JOS@JPOINT.NL        |          TWITTER:  @JOSDIRKSEN  
  • 23. 23 The key to HATEOAS is simple •  Hypermedia / Mime-types / Media-types : •  Describes a current state •  Compare it with a web page •  Can be seen as the contract •  Links: •  Describe the transition to the next state •  Compare it with hyperlinks •  HATEOAS makes surfing the web possible •  Jim Webber: “Hypermedia Describes Protocols” (HYDEPR) “In each response message, include the links for the next request message” WWW.JPOINT.NL          |          JOS@JPOINT.NL        |          TWITTER:  @JOSDIRKSEN  
  • 24. 24 HATEOAS Part 1: Links ~  AtomPub  ~   <feed xmlns="http://www.w3.org/2005/Atom">! <title>Example Feed</title>! <subtitle>A subtitle.</subtitle>! <link href="http://example.org/feed/" ! rel="self" />! <link href="http://example.org/" />! <id>urn:uuid:60a76c80-d399-11d9-b91C-0003939e0af6</id>! <updated>2003-12-13T18:30:02Z</updated>! <author>! <name>John Doe</name>! <email>johndoe@example.com</email>! </author>! <entry>! <title>Atom-Powered Robots Run Amok</title>! <link href="http://example.org/2003/12/13/atom03" />! <link rel="alternate" type="text/html" ! href="http://example.org/2003/12/13/atom03.html"/>! WWW.JPOINT.NL          |          JOS@JPOINT.NL        |          TWITTER:  @JOSDIRKSEN  
  • 25. 25 HATEOAS Part 1: Links ~  NetGlix  API  ~   <link href="http://.../catalog/titles/series/70023522/cast” rel="http://schemas.netflix.com/catalog/people" title="cast"> <cast> <link href="http://api.netflix.com/catalog/people/30011713" rel="http://schemas.netflix.com/catalog/person" title="Steve Carell"/> <link href="http://api.netflix.com/catalog/people/30014922" rel="http://schemas.netflix.com/catalog/person" title="John Krasinski"/> <link href="http://api.netflix.com/catalog/people/20047634" rel="http://schemas.netflix.com/catalog/person" title="Jenna Fischer"/> </cast> </link> WWW.JPOINT.NL          |          JOS@JPOINT.NL        |          TWITTER:  @JOSDIRKSEN  
  • 26. 26 HATEOAS Part 1: Twitter Example ~  Before  using  links~   GET .../followers/ids.json?cursor=-1&screen_name=josdirksen { “previous_cursor”: 0, “previous_cursor_str”: 0, “ids”: [ 12345678, 87654321, 11223344 ], “next_cursor”: 0, “next_cursor_str”: “0” } WWW.JPOINT.NL          |          JOS@JPOINT.NL        |          TWITTER:  @JOSDIRKSEN  
  • 27. 27 HATEOAS Part 1: Twitter Example ~  With  links~   GET .../followers/ids.json?cursor=-1&screen_name=josdirksen { “previous_cursor”: 0, “id”: { “name”: “John Smit”, “id”: “12345678” “links” : [ { “rel”: “User info”, “href”: “https://.../user/12345678”}, { “rel”: “Follow user”, “href”: “https://.../friendship/12345678”} ] } // and add other links: tweet to, send direct message, ..// block, report for spam, add or remove from list } WWW.JPOINT.NL          |          JOS@JPOINT.NL        |          TWITTER:  @JOSDIRKSEN  
  • 28. 28 HATEOAS Part 2: Media-types WHERE: People  know  where  to  `ind  your   resource  using  URIs.   HOW: They  know  how  to  interact  by   following  links.   WHAT: But  what  do  the  resources  look   like,  what  do  they  need  to  post?   WWW.JPOINT.NL          |          JOS@JPOINT.NL        |          TWITTER:  @JOSDIRKSEN  
  • 29. 29 HATEOAS Part 2: Media-types ~  not  all  media-­‐types  are  equal,  some  are  more  equal  than  others  ~   •  Standard formats •  Easy to use and understand. •  Clients already know how to use them •  Don’t always match with what you want to do •  XHTML and AtomPub •  Self created •  Very domain specific •  Can have rich semantics •  Client specific implementation required •  Often described using XML Schema •  or in plain text, or not at all… WWW.JPOINT.NL          |          JOS@JPOINT.NL        |          TWITTER:  @JOSDIRKSEN  
  • 30. 30 HATEOAS Part 2: Media-types ~  Custom  media  types  ~   200 OK! Content-Type: application/vnd.bank.org.account+xml;charset=UTF-8! ! <accounts xmlns="urn:org:bank:accounts">! <account>! <id>AZA12093</id>! <link href="http://bank.org/account/AZA12093" rel="self"/>! <link rel="http://bank.org/rel/transfer"! type="application/vnd.bank.org.transfer+xml"! href="http://bank.org/transfers"/>! <link rel="http://bank.org/rel/customer"! type="application/vnd.bank.org.customer+xml"! href="http://bank.org/customer/7t676323a"/>! <balance currency="USD">993.95</balance>! </account>! </accounts>! WWW.JPOINT.NL          |          JOS@JPOINT.NL        |          TWITTER:  @JOSDIRKSEN  
  • 31. 31 And that is what HATEOAS means! •  Media-types describe the resources. •  Actions are executed by following links. •  Each new response reflects a state. •  It is good to create custom media-types. •  Creates self-describing APIs. •  Clients ‘explore’ your API just as they browse the web. “Media-types describes a domain specific application protocol” WWW.JPOINT.NL          |          JOS@JPOINT.NL        |          TWITTER:  @JOSDIRKSEN  
  • 32. 32 HATEOAS Part 2: Twitter Example ~  With  links,  but  no  media-­‐type  ~   GET .../followers/ids.json?cursor=-1&screen_name=josdirksen { “previous_cursor”: 0, “id”: { “name”: “John Smit”, “id”: “12345678” “links” : [ { “rel”: “User info”, “href”: “https://.../user/12345678”}, { “rel”: “Follow user”, “href”: “https://.../friendship/12345678”} ] } ... } WWW.JPOINT.NL          |          JOS@JPOINT.NL        |          TWITTER:  @JOSDIRKSEN  
  • 33. 33 HATEOAS Part 2: Twitter Example ~  With  links  &  media-­‐type  ~   GET .../followers/ids.json?cursor=-1&screen_name=josdirksen { “previous_cursor”: 0, “id”: { “name”: “John Smit”, “id”: “12345678” “links” : [ { “type: “application/vnd.twitter.com.user”, “rel”: “User info”, “href”: “https://.../user/12345678”}, { “type”: “application/vnd.twitter.com.user.follow”, “rel”: “Follow user”, “href”: “https://.../friendship/12345678”} ] // and add other options: tweet to, send direct message, // block, report for spam, add or remove from list } // This is how you create a self-describing API. } WWW.JPOINT.NL          |          JOS@JPOINT.NL        |          TWITTER:  @JOSDIRKSEN  
  • 34. 34 Case: eBay ~  API  should  guide  the  user  ~   Common scenario: bidding on item 1.  Add  item  to  watch  list:  keep   track  of  the  item.     2.  Get  user  details:  `ind  out  more   about  the  buyer.     3.  Get  user  feedback:  is  seller   trustworthy?     4.  Make  a  bid:  place  a  bid  for  the   item.   WWW.JPOINT.NL          |          JOS@JPOINT.NL        |          TWITTER:  @JOSDIRKSEN  
  • 35. 35 eBay: API should help the client ~  just  like  a  browser  does  using  links  ~   WWW.JPOINT.NL          |          JOS@JPOINT.NL        |          TWITTER:  @JOSDIRKSEN  
  • 36. 36 eBay: add to watchlist ~  API  should  tell  us  what  to  do  ~   GET .../item/180881974947 { “name” : “Monty Python and the Holy Grail white rabbit big pointy teeth”, “id” : “180881974947”, “start-price” : “6.50”, “currency” : “GBP”, ... “links” : [ { “type: “application/vnd.ebay.item”, “rel”: “Add item to watchlist”, “href”: “https://.../user/12345678/watchlist/180881974947”}, { // and a whole lot of other operations ] } WWW.JPOINT.NL          |          JOS@JPOINT.NL        |          TWITTER:  @JOSDIRKSEN  
  • 37. 37 eBay: get user details ~  Follow  links  to  get  more  information  ~   GET .../item/180881974947 { “name” : “Monty Python and the Holy Grail white rabbit big pointy teeth”, “id” : “180881974947”, “start-price” : “6.50”, “currency” : “GBP”, // whole lot of other general item data “bidder” : { “name” : “dangermouse_rm”, “link” : { “type” : “application/vnd.ebay.user”, “rel : “Get user details”, “href : “https://.../user/314512346523” } } } WWW.JPOINT.NL          |          JOS@JPOINT.NL        |          TWITTER:  @JOSDIRKSEN  
  • 38. 38 eBay: get user feedback ~  Depending  on  rights  we  get  different  links  ~   GET .../user/314512346523 { “name” : “dangermouse_rm”, “location” : “united kingdom”, // whole lot of other general user data “feedbacks” : { “last_month” : “7,0,0” “last_6_month” : “19,0,0”, “feedback” : { “title” : “Great communication and quick delivery. +++” “link” : { “type” : “application/vnd.ebay.feedback”, “rel : “Show feedback”, “href : “https://.../user/314512346523/feedback/1234567” } ... WWW.JPOINT.NL          |          JOS@JPOINT.NL        |          TWITTER:  @JOSDIRKSEN  
  • 39. 39 eBay: place bid ~  Depending  on  rights  we  get  different  links  ~   GET .../item/180881974947 { “name” : “Monty Python and the Holy Grail white rabbit big pointy teeth”, “id” : “180881974947”, “start-price” : “6.50”, “currency” : “GBP”, ... “links” : [ { “type: “application/vnd.ebay.bid”, “rel”: “Place bid”, “href”: “https://.../user/12345678/bid/180881974947”}, { // and a whole lot of other operations ] } WWW.JPOINT.NL          |          JOS@JPOINT.NL        |          TWITTER:  @JOSDIRKSEN  
  • 40. 40 eBay: much easier! ~  and  there  was  much  rejoicing  ~   WWW.JPOINT.NL          |          JOS@JPOINT.NL        |          TWITTER:  @JOSDIRKSEN  
  • 41. 41 Versioning without breaking WWW.JPOINT.NL          |          JOS@JPOINT.NL        |          TWITTER:  @JOSDIRKSEN  
  • 42. 42 Three options for versioning ~  Media-­‐types  ~   •  Media-type is versioned, directly in its name Request: GET /opengov/garbageschedule?location=Main%20Street HTTP/1.1 Accept: application/vnd.opengov.org.garbageschedule-v2+json   Response: HTTP/1.1 200 OK Content-Type: application/vnd.opengov.org.garbageschedule-v2+json {"schedule" "self": "schedule-2423", "dayOfWeek": "Monday", "oddOrEvenWeeks": "Odd"} WWW.JPOINT.NL          |          JOS@JPOINT.NL        |          TWITTER:  @JOSDIRKSEN  
  • 43. 43 Three options for versioning ~  Add  version  qualiGier  ~   •  Media-type stays the same, add a qualifier. Request: GET /opengov/garbageschedule?location=Main%20Street HTTP/1.1 Accept: application/vnd.opengov.org.garbageschedule+json;v=1   Response: HTTP/1.1 200 OK Content-Type: application/vnd.opengov.org.garbageschedule+json;v=1   {"schedule" "self": "schedule-2423", "dayOfWeek": "Monday", "oddOrEvenWeeks": "Odd"} WWW.JPOINT.NL          |          JOS@JPOINT.NL        |          TWITTER:  @JOSDIRKSEN  
  • 44. 44 Three options for versioning ~  The  URI  is  versioned  ~   •  The version is added in the URI path Request: GET /opengov/v1/garbageschedule?location=Main%20Street HTTP/1.1 Accept: application/vnd.opengov.org.garbageschedule+json   Response: HTTP/1.1 200 OK Content-Type: application/vnd.opengov.org.garbageschedule+json   {"schedule" "self": "schedule-2423", "dayOfWeek": "Monday", "oddOrEvenWeeks": "Odd"} WWW.JPOINT.NL          |          JOS@JPOINT.NL        |          TWITTER:  @JOSDIRKSEN  
  • 45. 45 Which one is the best? ~  personal  opinion  ~   Matter of taste: 1.  Media-­‐type  approach  most   RESTful,  but  requires  work  on   client  and  server  side.     2.  Quali`ier,  second  best,  easier   to  implement.  Less  media-­‐ types  to  keep  track  off.     3.  URI,  most  often  used.   Personally  don’t  like  it.  Can   have  two  URIs  point  to  same   resource.   WWW.JPOINT.NL          |          JOS@JPOINT.NL        |          TWITTER:  @JOSDIRKSEN  
  • 46. 46 When HTTPS isn’t enough WWW.JPOINT.NL          |          JOS@JPOINT.NL        |          TWITTER:  @JOSDIRKSEN  
  • 47. 47 General idea about authentication in REST “REST means working with the standards of the web, and the standard for "secure" transfer on the web is SSL. Anything else is going to be kind of funky and require extra deployment effort for clients, which will have to have encryption libraries available.” Highest rated answer on stackoverflow regarding REST authentication schemes WWW.JPOINT.NL          |          JOS@JPOINT.NL        |          TWITTER:  @JOSDIRKSEN  
  • 48. 48 Why do we need more? •  HTTPS doesn’t fix man-in-the-middle attack •  It provides only transport level security •  Has no support for message integrity or authenticity •  REST assumes “Layered System” •  OAuth is nice (and complex) for authentication doesn’t handle message integrity. •  REST doesn’t have a WS-Security standard WWW.JPOINT.NL          |          JOS@JPOINT.NL        |          TWITTER:  @JOSDIRKSEN  
  • 49. 49 HMAC based authentication ~  de  facto  standard  ~   •  Used by Google, Amazon AWS, Yahoo etc. •  Create a signature of the complete request, using shared secret. •  Add custom header with signature and signing user. •  Encrypt the following with this shared secret: •  URI, to avoid executing on different resource, •  Verb, indicates what we want to do with a resource, •  MD5-Header, to detect changes to the content body •  Content-type, indicates the type of resource •  Date header, to avoid replay WWW.JPOINT.NL          |          JOS@JPOINT.NL        |          TWITTER:  @JOSDIRKSEN  
  • 50. 50 HMAC based authentication ~  example  ~   POST /resources/rest/geo/comment HTTP/1.1[r][n]! hmac: jos:+9tn0CLfxXFbzPmbYwq/KYuUSUI=[r][n]! Date: Mon, 26 Mar 2012 21:34:33 CEST[r][n]! Content-Md5: r52FDQv6V2GHN4neZBvXLQ==[r][n]! Content-Length: 69[r][n]! Content-Type: application/vnd.geo.comment+json; charset=UTF-8[r][n]! Host: localhost:9000[r][n]! Connection: Keep-Alive[r][n]! User-Agent: Apache-HttpClient/4.1.3 (java 1.5)[r][n]! [r][n]! {"comment" : {"message":"blaat" , "from":"blaat" , "commentFor": 123}}! WWW.JPOINT.NL          |          JOS@JPOINT.NL        |          TWITTER:  @JOSDIRKSEN  
  • 51. 51 Parting guidelines ~  you  may  forget  everything  else  I  said  ~   •  Just doing URIs and Verbs doesn’t make it RESTful •  But that isn’t necessary a bad thing. •  Use “Links” to describe “HOW” your service is used. •  Describe “WHAT” is expected using media-types. •  This isn’t a complete replacement of documentation •  Don’t use WADL •  Use media-types for versioning. •  Forget what HATEOAS stands for. WWW.JPOINT.NL          |          JOS@JPOINT.NL        |          TWITTER:  @JOSDIRKSEN  
  • 52. 52 Q&A WWW.JPOINT.NL          |          JOS@JPOINT.NL        |          TWITTER:  @JOSDIRKSEN  
  • 53. JPoint   THANKS FOR COMING More  information;  look  at  http://www.jpoint.nl  or  contact  me.