REST A brief introduction

Transcription

1 REST A brief introduction Juergen Brendel

2 What is it good for? Something with networks: APIs Interactions Distributed systems? All contents Copyright 2010, Mulesoft Inc. 2

3 Getting more popular All contents Copyright 2010, Mulesoft Inc. 3

4 Confusion So, like XML-RPC, RMI, CORBA? Not really... Many REST APIs are not REST ( HTTP!= REST) All contents Copyright 2010, Mulesoft Inc. 4

5 The origins of REST All contents Copyright 2010, Mulesoft Inc. 5

6 The origins of REST Roy Fielding All contents Copyright 2010, Mulesoft Inc. 6

7 The origins of REST Roy Fielding 1999: RFC 2616: HTTP/ : PhD thesis Architectural Styles and the Design of Network-based Software Architectures Defined REST REpresentational State Transfer All contents Copyright 2010, Mulesoft Inc. 7

8 REST: What is it NOT? Protocol API Framework Product Technique 1:1 replacement for RPC All contents Copyright 2010, Mulesoft Inc. 8

9 What is REST? Architectural style Constraints and principles All contents Copyright 2010, Mulesoft Inc. 9

10 Goals Work WITH the web, not against it Trade scalability for latency Intermediaries as active participants Caches Proxies Load balancers Generic servers All contents Copyright 2010, Mulesoft Inc. 10

11 (interlude: the HTTP header) You enter this: All contents Copyright 2010, Mulesoft Inc. 11

12 (interlude: the HTTP header) You enter this: Browser connects and sends: GET /xyz/bar?name=smith HTTP/1.1 Host: User agent: Mozilla/5.0,... Accept: */*... All contents Copyright 2010, Mulesoft Inc. 12

13 (interlude: the HTTP header) You enter this: Verb : HTTP method (what are we doing) Browser connects and sends: GET /xyz/bar?name=smith HTTP/1.1 Host: User agent: Mozilla/5.0,... Accept: */*... All contents Copyright 2010, Mulesoft Inc. 13

14 (interlude: the HTTP header) You enter this: Browser connects and sends: Noun : Path of URL (what are we operating on) GET /xyz/bar?name=smith HTTP/1.1 Host: User agent: Mozilla/5.0,... Accept: */*... All contents Copyright 2010, Mulesoft Inc. 14

15 REST principles, part 1 Well known actions ('verbs') Resources ('nouns') HTTP? All contents Copyright 2010, Mulesoft Inc. 15

16 Names and standard methods SOAP: RPC via HTTP, uses HTTP as tunnel All contents Copyright 2010, Mulesoft Inc. 16

17 Names and standard methods SOAP: RPC via HTTP, uses HTTP as tunnel POST /myservice HTTP/1.1 Host: <?xml version="1.0"?> <soap:envelope xmlns:soap=" envelope" soap:encodingstyle=" encoding"> <soap:body xmlns:m=" <m:getcustomer> <m:customername>smith</m:customername> </m:getcustomer> </soap:body> </soap:envelope> All contents Copyright 2010, Mulesoft Inc. 17

18 Names and standard methods SOAP: RPC via HTTP, uses HTTP as tunnel POST /myservice HTTP/1.1 Host: Not descriptive: Same for each request <?xml version="1.0"?> <soap:envelope xmlns:soap=" envelope" soap:encodingstyle=" encoding"> <soap:body xmlns:m=" <m:getcustomer> <m:customername>smith</m:customername> </m:getcustomer> </soap:body> </soap:envelope> Why is that a problem? All contents Copyright 2010, Mulesoft Inc. 18

19 Names and standard methods Better, but still only uses HTTP as tunnel All contents Copyright 2010, Mulesoft Inc. 19

20 Names and standard methods Better, but still only uses HTTP as tunnel cache? All contents Copyright 2010, Mulesoft Inc. 20

21 Names and standard methods Better, but still only uses HTTP as tunnel cache? name=smith& first=john reload? All contents Copyright 2010, Mulesoft Inc. 21

22 Names and standard methods RESTful (retrieving record) GET /customer/smith HTTP/1.1 Host: foo.com Accept: application/json All contents Copyright 2010, Mulesoft Inc. 22

23 Names and standard methods RESTful (retrieving record) GET /customer/smith HTTP/1.1 Host: foo.com Accept: application/json A collection All contents Copyright 2010, Mulesoft Inc. 23

24 Names and standard methods RESTful (retrieving record) GET /customer/smith HTTP/1.1 Host: foo.com Accept: application/json ID of item in collection All contents Copyright 2010, Mulesoft Inc. 24

25 Names and standard methods RESTful (retrieving record) GET /customer/smith HTTP/1.1 Host: foo.com Accept: application/json { } name first : Smith, : Frank All contents Copyright 2010, Mulesoft Inc. 25

26 Names and standard methods RESTful (updating record) PUT /customer/smith HTTP/1.1 Host: foo.com Content type: application/json { } name first : Smith, : Frank All contents Copyright 2010, Mulesoft Inc. 26

27 Names and standard methods RESTful (deleting record) DELETE /customer/smith HTTP/1.1 Host: foo.com All contents Copyright 2010, Mulesoft Inc. 27

28 Names and standard methods RESTful (creating record) POST /customer HTTP/1.1 Host: foo.com Content type: application/json { } name : Smith, first : John All contents Copyright 2010, Mulesoft Inc. 28

29 Names and standard methods RESTful (get collection) GET /customer HTTP/1.1 Host: foo.com Content type: application/json { } Smith : { link : /customer/smith, method : GET }, Jones : { link : /customer/jones, method : GET } All contents Copyright 2010, Mulesoft Inc. 29

30 REST principles, part 2 Resources not Actions Proper use of HTTP methods All contents Copyright 2010, Mulesoft Inc. 30

31 REST principles, part 2 Resources not Actions Proper use of HTTP methods Stateless Representations / media types Links (HATEOAS) All contents Copyright 2010, Mulesoft Inc. 31

32 Representations GET /customer/smith HTTP/1.1 Accept: application/xml GET /customer/smith HTTP/1.1 Accept: application/json <person> <name>smith</name> <first>john</first> </person> { } name : Smith, first : John All contents Copyright 2010, Mulesoft Inc. 32

33 Media types Preferred: IANA registered MIME types Think about intermediaries If necessary: Custom type All contents Copyright 2010, Mulesoft Inc. 33

34 HATEOAS Hypermedia as the Engine of Application State Or: There are links in the representation All contents Copyright 2010, Mulesoft Inc. 34

35 HATEOAS Resources carry links Describe how state of resource can be changed Dynamic Example: Web pages All contents Copyright 2010, Mulesoft Inc. 35

36 Example: Collection { } entries : { Smith : { link : /customers/smith, method : GET }, Jones : { link : /customers/jones, method : GET } }, links : [ { link : /customers, rel : add, method : POST }, { link : /customers, rel : list, method : GET } ] All contents Copyright 2010, Mulesoft Inc. 36

37 Example: Order record { } id : 6227, customer : { link : /customer/smith, method : GET }, item : { link : /items/4552, method : GET }, quantity : 4, amount : , links : [ { link : /orders/6227, rel : edit, method : PUT }, { link : /orders/6227/status, rel : status, method : GET } ] All contents Copyright 2010, Mulesoft Inc. 37

38 Example: Order record { } id : 6227, customer : { link : /customer/smith, method : GET }, item : { link : /items/4552, method : GET }, quantity : 4, amount : , links : [ { link : /orders/6227, rel : edit, method : PUT }, { link : /orders/6227/status, rel : status, method : GET } ] Could disappear, if order is finalized All contents Copyright 2010, Mulesoft Inc. 38

39 Benefit: Scalability Performance: Caches / load-balancers Stateless Agility Adoption: Bookmarkable links Any HTTP enabled client All contents Copyright 2010, Mulesoft Inc. 39

40 Benefit: Simplicity / reuse Development: Open source app frameworks / tools Testing: Click it! Operation: Scheduling? cron + curl Caching? squid, varnish Security? ssl, HTTP-auth, apache, nginx, etc. All contents Copyright 2010, Mulesoft Inc. 40

41 REST challenges Focus on resource not action No 1:1 mapping to OO Requires rethinking A lot of investment into methods and RPC Scalability, not latency Frameworks Often low-level All contents Copyright 2010, Mulesoft Inc. 41

42 The All contents Copyright 2010, Mulesoft Inc. 42