RESTful  Imaginarium  

Jeremy  Deane    h5p://jeremydeane.net/  

Agenda  

   Representa?onal  State  Transfer  (REST)    

   REST  Conceptual  Model  

   Universal  Resource  Indicators  

   Representa?ons  

   State  Transfer  

   HTTP  Protocol  

   Service  Design  Pa5erns    

   REST  Framework  Examples  (Restlet,  Jersey,  Spring  MVC,  NetKernel)  

Why  REST?  

Simple  Integra.on  

REST  is  simple.  

Standards-­‐based  

REST  is  based  on  a  small  set  of  widely-­‐accepted  standards  such  as  HTTP  URI,  and  XML  

REST  requires  far  fewer  development  steps,  toolkits  and  execu?on  engines  than  SOAP  

Fewer  requirements  

Representa?onal  State  Transfer  (REST)    

Web  Principles  

URI  

HTTP  Methods  

REST  is  an  architectural  style  based  on  the  principles  of  the  web  

A  service  provides  access  to  a  resource,  iden?fied  by  a  Universal  Resource  Indicator  (URI),  over  HTTP  

HTTP  methods  (e.g.  GET,  PUT,  POST,  and  DELETE)  define  a  uniform  interface  

Consumer  and  provider  exchange  immutable  representa?ons  of  a  resource  that  may  itself  contain  links  to  other  resources  

Resource  Representa?ons  

«execu?on  environment»  Web  Applica.on  

«execu?on  environment»  Web  Applica.on  

Consumer  Service  Provider  

URI  

HTTP  GET  Request  

HTTP  Response:  200  (ok)  

XML  Representa?on  

REST  Conceptual  Model  

Execu?on  Context  

Service  

Resource  

Resource  Representa?on  

Resource  Provider  

Resource  Iden?fier  

Policies  and  Contracts  

Service  Consumer  

Real-­‐World  Effect  

part  of  

use  

represents  

seeks  

part  of  

provide  access  to  

returns  

constrains  

limits  use  of  

hosts  

iden?fies  

OASIS  SOA  Concepts  

REST  Concepts  

Key  

Examples: Building, Room, floor

Resources  &  Universal  Resource  Iden?fiers  (URI)  

A  resource  is  an  abstract  set  of  data  

/building/{building-id} /building/{building-id}/room/{room-id}

A  resource  representa?on  is  iden?fied  by  a  URI  

A  URI  does  NOT  contain  verbs  or  resource  iden?fying  parameters  

Incorrect   /building/{building-id}?action=update

Correct   /building/{building-id}/room/{room-id}

Incorrect   /building/{building-id}/delete/room/{room-id}

Representa?ons  

Representa.on  

A  representa?on  is  an  immutable  physical  snapshot  of  a  resource  

A  representa?on  is  self-­‐descrip?ve  and  stateless  

The  most  common  resource  representa?ons  are  XML  and  JSON  

A  representa?on  may  contain  links  to  other  resources  (hypermedia)  

State  Transfer  

Applica?on  State  

State  transfer  refers  to  the  Applica5on  state  between  a  consumer  and  provider.  It  does  NOT  refer  to  the  state  of  a  given  resource.  

Maintenance  

Applica5on  state  is  maintained  by  the  consumer  while  Resource  state  is  maintained  by  the  provider.  

No  side  effects  

A  request  for  a  resource  should  not  change  the  state  of  a  resource  (no  side  effects).  

Idempotent  

Duplicate  requests  to  create,  update,  or  delete  a  resource  should  not  result  in  a  change  in  Resource  state.  

HTTP  Uniform  Interface:  Structure  &  Transport  Protocol  

Request  and  response  messages  are  comprised  of  a  command,  headers,  and  a  body  

HTTP  is  stateless  request-­‐response  applica?on  protocol  

Requests  can  be  authen?cated  using    HTTP  Basic  Authen?ca?on  or  Client  Side  Cer?ficates  

The  transport  layer  is  secured  using  Secure  Sockets  Layer  (SSL)  and  the  message  body  is  secured  using  encryp?on  and  digital  signatures  

HTTP  Uniform  Interface:  Methods  

Ac?on   Result  

PUT /building/{building-id} Creates a resource

GET /building/{building-id} Retrieves a resource representation

POST /building/{building-id} Updates a resource

DELETE /building/{building-id} Deletes a resource

Ac?on   Result  

POST /building/ Creates a resource

GET /building/{building-id} Retrieves a resource representation

PUT/building/{building-id} Updates a resource

DELETE /building/{building-id} Deletes a resource

HTTP  Uniform  Interface:  Content  Nego?a?on  

URI  Content  ID  

URI  Content  Extensions  

Accept  Headers  –  Media  Types  

/building/{building-id}/room/pdf/{room-id}

/building/{building-id}/room/{room-id}.xml

Accept Headers = application/xml

Securing  RESTful  Endpoints  

Authen.ca.on  -­‐  assurance  of  consumer  iden?ty  

• HTTP  Basic  Authen?ca?on  (with  SSL)  or  client  side  cer?ficate  

Authoriza.on  -­‐  unauthorized  resource  access  is  prevented  

• A  privilege  is  comprised  of  a  rela?ve  URI  

and  an  ac?on  (C.R.U.D)  

• Accounts  are  associated  with  privileges  or  roles  (sets  of  privileges)  

Audi.ng  –  state  change  of  a  resource  is  logged  

Confiden.ality  -­‐  securing  resource  representa?ons  

Create,  Update  or  Delete  ac?ons  are  audited  

Encryp?on  of  resource  representa?ons  

SOAP  vs.  RESTful  Web  Service  

HTTP  Request  or  Response  

HTTP  Body  

HTTP  HEADERS  

XML  Document  

HTTP  Request  or  Response  

HTTP  Body  

HTTP  HEADERS  

SOAP  Envelope  

SOAP  Body  

XML  Document  

SOAP  HEADERS  

SOAP  vs.  RESTful  Web  Services  

REST-­‐XML  

SOAP-­‐XML  

• Simplicity  

• Proven  architectural  style  (Web)  

• Fewer  development  steps,  toolkits  and  execu?on  engines  

• Transport  Independence  • Intelligent  messages  

• Transport  Independence  • Message  Intelligence  

• Complexity  

• Ever-­‐changing,  vendor-­‐driven  specifica?ons  

• Requires  complex  tools  and  frameworks  

Advantage   Disadvantage  

(Web)  Service  Design  Pa5erns  

h5p://www.servicedesignpa5erns.com  

Jersey  Overview  

Open  source  framework  

Web  services  

Jersey  is  a  reference  implementa?on  of  JAX-­‐RS  (JSR  311)  

Jersey  web  services  are  created  by  configuring  a  Servlet  in  the  web.xml  and  annota?ng  classes  

The  Servlet  delegates  to  resources  in  the  same  way  that  a  Struts  controller  delegates  to  ac?ons  

Annota?on  based  URI  mappings  and  templates  

Delega.on  

URI  

Guar  

Restlet  Overview  

Open  source  framework  

Web  services  

Restlet  is  a  lightweight  open  source  framework  for  implemen?ng  REST  concepts  in  Java  

Restlet  web  services  are  created  by  configuring  the  web.xml  and  implemen?ng  abstract  classes  

A  router  delegates  to  resources  in  the  same  way  that  a  Struts  controller  delegates  to  ac?ons  

The  router  maps  external  requests  to  resources  based  on  a  Universal  Resource  Indicator  (URI)  

A  guard  is  also  associated  to  a  router  and  provides  a  mechanism  for  client  authen?ca?on.  

Delega.on  

URI  

Guard  

Spring  MVC  Overview  

Open  source  framework  

REST  WS  

Spring  MVC  is  a  key  part  of  the  Spring  Framework  

Spring  MVC  provides  advanced  features  for  implemen?ng  RESTful  web  services  such  as  URI  Templates  

Spring  MVC  provides  advanced  features  for  implemen?ng  RESTful  web  services  such  as  URI  Templates  

A  Dispatcher  delegates  a  request  to  Controller  based  on  advice  from  a  Mapping  Handler.  The  Dispatcher  then  consults  a  View  Resolver  before  returning  a  View  (response)  

Dependency  Injec.on  

Components  

Guard  

NetKernel  Overview  

ROC    plaPorm  

Netkernel  is  a  Resource-­‐Oriented  Compu?ng  (ROC)  plahorm  that  runs  within  a  Java  Virtual  Machine  (JVM)  

Transports  

Transports  are  used  to  

• Capture  external  request  or  events  • Map  request  or  event  data  to  a  logical  address  (URI)  and  ac?on  (C.R.U.D)  

• Issue  sub-­‐request  to  a  RESTful  Microkernel  

RESTful  microkernel  

The  RESTful  microkernel  

• Resolves  requests  to  the  address  space  to  physical  code  

• Schedules  request  to  run  on  available  core  allowing  processing  to  scale  linearly  

NetKernel  Middleware  Server  

Transports  HTTP,  JMS,  FTP  

Logical  Address  Space  URI  

RESTful  Microkernel  

Physical  Code  (Java,  Ruby,  Scala)  

Ques?ons  &  Feedback  

My  Contact  informa.on:  

Jeremy  Deane    Director  of  Sojware  Architecture  NaviNet  jeremy.deane@gmail.com  h5p://jeremydeane.net/  

h5ps://github.com/jtdeane/demo-­‐spring-­‐auditor  

h5ps://github.com/jtdeane/demo-­‐jersey-­‐auditor  

h5ps://github.com/jtdeane/demo-­‐restlet-­‐auditor  

h5ps://github.com/jtdeane/demo-­‐netkernel-­‐auditor