REST - A Super Quick Intro
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This document introduces REST (Representational State Transfer) as a method for applying web principles to application-to-application integration problems, using HTTP as the primary application protocol. It outlines key concepts such as standard HTTP verbs (GET, POST, etc.), status codes, and the importance of self-describing messages and hypermedia links in driving client-server interactions. Additionally, it emphasizes the client-driven process, the significance of resource identification, and the constraints that make REST scalable and efficient.
REST - A Super Quick Intro
- 3. Say What???
- 4. Apply ‘Web’ Principles to A2A Integration Problems
- 5. Remember the OSI Stack?http://en.wikipedia.org/wiki/Osi_stack
- 6. So what?
- 7. REST uses HTTP as the Application Protocol!Not (just) as the transport
- 8. How does that work?
- 9. Standard VerbsThe HTTP Spec give you the verbs to use:GETPUTPOSTDELETEHEADOPTIONSPATCHTRACEhttp://en.wikipedia.org/wiki/HTTP#Request_methods
- 10. SOAP Doesn’t…getAccountCustomerByInternalIdsearchCustomerByBasicDataupdateSalesProspectStatusByPartnerSalesRepresentativeBasicData_syncEverything works via HTTP POST(i.e. uses HTTP as the dumb transport)
- 11. Status CodesThe HTTP Spec give you the verbs to use:200 OK302 Moved Permanently404 Not Found406 Method Not Allowed418 I’m a Teapot…http://en.wikipedia.org/wiki/List_of_HTTP_status_codes
- 12. SOAP Doesn’t…<SOAP-ENV:Faultxmlns:sqlsoapfaultcode="http://schemas.microsoft.com/sqlserver/2004/SOAP/SqlSoapFaultCode"> <faultcode>SOAP-ENV:Client</faultcode> <faultstring>There was an error in the incoming SOAP request packet: Client, InvalidXml</faultstring> <faultactor>http://schemas.microsoft.com/sqlserver/2004/SOAP</faultactor> <detail xmlns:SOAP-1_2-ENV="http://www.w3.org/2003/05/soap-envelope"> <SOAP-1_2-ENV:Code> <SOAP-1_2-ENV:Value>SOAP-1_2-ENV:Sender</SOAP-1_2-ENV:Value> <SOAP-1_2-ENV:Subcode> <SOAP-1_2-ENV:Value>sqlsoapfaultcode:InvalidXml</SOAP-1_2-ENV:Value> </SOAP-1_2-ENV:Subcode> </SOAP-1_2-ENV:Code> <SOAP-1_2-ENV:Reason> <SOAP-1_2-ENV:Text xml:lang="en-US">There was an error in the incoming SOAP request packet: Sender, InvalidXml</SOAP-1_2-ENV:Text> </SOAP-1_2-ENV:Reason> <SOAP-1_2-ENV:Node>http://MyServer:80/sql</SOAP-1_2-ENV:Node> <SOAP-1_2-ENV:Role>http://schemas.microsoft.com/sqlserver/2004/SOAP</SOAP-1_2-ENV:Role> <SOAP-1_2-ENV:Detail> <sqlresultstream:SqlMessagexsi:type="sqlmessage:SqlMessage"> <sqlmessage:Class>16</sqlmessage:Class> <sqlmessage:LineNumber>0</sqlmessage:LineNumber> <sqlmessage:Message>XML parsing: line 3, character 0, incorrect document syntax</sqlmessage:Message> <sqlmessage:Number>9422</sqlmessage:Number> <sqlmessage:Source>Microsoft-SQL/9.0</sqlmessage:Source> <sqlmessage:State>1</sqlmessage:State> </sqlresultstream:SqlMessage> </SOAP-1_2-ENV:Detail> </detail></SOAP-ENV:Fault>
- 13. So What’s Wrong with that?
- 14. So What’s Wrong with that?Suboptimal
- 15. ScalabilityHTTP GET is the most optimised piece of code on the planet!Easily cached to support millions of clientsDefined semanticsHTTP = Application ProtocolEveryone knows how to do a GETEveryone knows how to behave
- 17. Representations?The server can store its data/objects in whatever way it likesThe clients can store the same stuff differentlyWe serialise that into Representations
- 18. Less Abstract…A Website is a Representation of the server’s database, code, etc.Clients don’t care how the server stores it, as long as it understands the Representation
- 19. State Transfer?
- 20. State is Transferred between Server and ClientNot just kept at the Server!
- 21. Client requests Shopping CartServer sends HTML page with items and linksClient’s moveClient clicks “Check Out”Server sends HTML page with Total AmountClient’s moveClient clicks “Pay”Server sends HTML page with “Thank You”and we’re done!
- 23. The Client Drives the InteractionResponsible for moving forwardOr not!The server guides the client forward(with ‘Check Out’, ‘Pay’ links)The client is responsible for completing the processIf the client stops, the server doesn’t care!
- 24. And…
- 25. Everything has a URL
- 26. So it’s like the Web!…Just for Machines
- 27. Restbucksworks with whisky too ;-)http://www.infoq.com/articles/webber-rest-workflow
- 28. So, the Formal Principles:
- 29. REST PrinciplesIdentify Resources (URLs)Manipulate Resources through RepresentationsSelf-Descriptive MessagesHATEOAShttp://www.infoq.com/articles/rest-introduction
- 31. In other words:Linking Things TogetherDriving the Process via LinksLike the ‘Check Out’ link!
- 32. …and some Constraints:Client-ServerStatelessCacheableLayered SystemUniform InterfaceDuh!= scalable= scalableload balancers, proxiesHTTP verbs & codes
- 35. More Resources:http://en.wikipedia.org/wiki/RESThttp://www.infoq.com/resthttp://www.infoq.com/articles/webber-rest-workflowhttp://www.infoq.com/minibooks/emag-03-2010-rest (Excellent FREE eBook)CD108 from 2010 TechEdhttps://www.ibm.com/developerworks/webservices/library/ws-restful/