Representational State Transfer (REST)

Representational State Transfer (REST) - Presentation Transcript

Implemen'ng RESTful Web Services Jeremy Deane Director of Research & Architecture h@p://www.jeremydeane.net/

WS-‐* Failure? Increasing Complexity A survey of 278 IT pros found that 32% of those using SOA said those projects fell short of expecta'ons. Of those, 58% said their SOA projects introduced more complexity into their IT environments, and 30% said they cost more than expected. Informa'on Week August 2008 Complex Integra/on As the number of compe'ng (and completed) web services speciﬁca'ons con'nues to grow, tension rises in direct propor'on to the increasing complexity. Dr. Dobbs June 2008

To the RESTcue REST does what [the SOAP stack] was trying to do in a much more viable, elegant, cheap, aﬀordable way except that we've got no tooling around it yet. Tim Bray August 2008 Standards-‐based Fewer requirements REST is based on a small REST requires far fewer set of widely-‐accepted development steps, standards such as HTTP toolkits and execu'on URI, and XML engines than SOAP REST is simple. Simple Integra/on

REST Conceptual Model part of Execu'on constrains Policies and Context Contracts part of use limits use of Service Service Consumer seeks provide access to Real-‐World represents hosts Resource Resource Effect Provider Key returns OASIS SOA Concepts iden'fies Resource Resource REST Representa'on Iden'fier Concepts

Representa'onal State Transfer (REST) «execu'on environment» «execu'on environment» Web Applica/on Web Applica/on HTTP GET Request Service Consumer HTTP Response: 200 (ok) URI Provider XML Representa'on Web Principles REST is an architectural style based on the principles of the web URI A service provides access to a resource, iden'ﬁed by a Universal Resource Indicator (URI), over HTTP HTTP Methods HTTP methods (e.g. GET, PUT, POST, and DELETE) deﬁne a uniform interface Resource Consumer and provider exchange immutable representa'ons Representa'ons of a resource that may itself contain links to other resources

Resources & Universal Resource Iden'ﬁers (URI) A resource is an abstract set of data Examples: Building, Room, floor A resource representa'on is iden'ﬁed by a URI /building/{building-id} /building/{building-id}/room/{room-id} 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 A representa'on is an A representa'on is self-‐ immutable physical descrip've and stateless snapshot of a resource Representa/on The most common resource representa'on A representa'on may is XML but other popular contain links to other formats include JSON resources (hypermedia) and XHTML

State Transfer Applica'on State Maintenance State transfer refers to the ApplicaHon state ApplicaHon state is maintained by the between a consumer and provider. It does consumer while Resource state is NOT refer to the state of a given resource. maintained by the provider. No side eﬀects Idempotent Duplicate requests to create, update, or A request for a resource should not change delete a resource should not result in a the state of a resource (no side eﬀects). change in Resource state.

Hypertext Transfer Protocol (HTTP) Uniform Interface HTTP is stateless request-‐response applica'on protocol The transport layer is Request and response Requests can be secured using Secure messages are comprised authen'cated using Sockets Layer (SSL) and the of a command, headers, HTTP Basic Authen'ca'on message body is secured and a body using encryp'on and digital signatures HTTP deﬁnes a universal interface to resources (CRUD): 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

Content Nego'a'on URI Content ID /building/{building-id}/room/pdf/{room-id} URI Content Extensions /building/{building-id}/room/{room-id}.xml Accept Headers – Media Types Accept Headers = text/xml

SOAP vs. RESTful Web Service HTTP Request or Response HTTP Request or Response HTTP HEADERS HTTP HEADERS HTTP Body HTTP Body SOAP Envelope XML Document SOAP HEADERS SOAP Body XML Document

SOAP vs. RESTful Web Services Advantage Disadvantage • Simplicity • Proven architectural style REST-‐XML (Web) • Lack of speciﬁca'on format • Fewer development steps, (e.g. WSDL) toolkits and execu'on engines • Complexity • Ever-‐changing, vendor-‐driven • Transport Independence SOAP-‐XML speciﬁca'ons • Intelligent messages • Requires complex tools and frameworks

REST Web Service Frameworks h@p://jboss.org/resteasy h@p://blog.springsource.com/ 2009/03/08/rest-‐in-‐spring-‐3-‐mvc/ h@p://www.1060research.com/netkernel/

Restlet Framework Open source Restlet is a lightweight open source framework for framework implemen'ng REST concepts in Java Restlet web services are created by conﬁguring the web.xml Web services and implemen'ng abstract classes A router delegates to resources in the same way that a Delega/on Struts controller delegates to ac'ons The router maps external requests to resources based on a URI Universal Resource Indicator (URI) A guard is also associated to a router and provides a Guard mechanism for client authen'ca'on.

Restlet Components Guard Resource «delegate» Router Resource URI – Resource Resource Mappings

Facili'es Management Demo UML Sequence Diagram: Update Building The demo web applica'ons, along with the source code and tests, Demo Download can be downloaded from hPp://ﬁles.me.com/jtdeane/0udh04 The web services expose transac'ons for managing facili'es. For Web Services example, web services exist for crea'ng, retrieving, upda'ng, and dele'ng buildings.

Addi'onal Resources RESTful Web RESTful Web Services vs. WS-‐* RESTful Web Services Services Cookbook REST An'-‐Pa@erns Web Services by Tilkov By Richardson By Allamaraju By Zimmermann Introduc'on to Resource-‐Oriented Hypermedia in Resource-‐Oriented Architecture: RESTful applica'ons Compu'ng Resource Metadata By Baker by 1060 Research by Brian Sle@en

Ques'ons & Feedback Jeremy Deane Director of Research & Architecture My Contact Plymouth Rock Assurance informa/on: jeremy.deane@gmail.com h@p://www.jeremydeane.net/ The source code along with instructions for building, installing and running the demo can be downloaded from http://files.me.com/jtdeane/0udh04