RESTful Web Services

a n i n t r o d u c
t i o n t o RESTFUL WEB SERVICES Felipe Dornelas

AGENDA 2 ▫︎The Internet ▫︎The Web and its Resources ▫︎HTTP
▫︎The Resource-Oriented Architecture ▫︎RESTful Web Services

WHAT IS REST? 3 HTTP + Resource-Oriented Architecture

THE INTERNET A network of networks 4

THE INTERNET, 2010 7

INTERNET ROUTES 8

INTERNET ROUTES 9

CACHING 10

INTERNET LAYERS 11 Web, E-mail, BitTorrent, DNS… TCP, UDP… Internet
Protocol (IP) WiFi, Ethernet, 3G, LTE…

INTERNET LAYERS 12 We will talk about the Web

THE WEB An application of the Internet 13

WHAT IS THE WEB? 14 An information system of interlinked
hypertext documents and resources accessed via the Internet

HYPERTEXT DOCUMENTS 15

HYPERTEXT MARKUP LANGUAGE 16 <!doctype html> <html> <head> <title>Example Hypertext
Document</title> </head> <body> <div> <h1>Example Hypertext Document</h1> <p>This is an example hypertext document to be used for illustrative purposes.</p> <p><a href=“http://example.org”> Example Hyperlink</a></p> </div> </body> </html>

HYPERTEXT TRANSFER PROTOCOL 17 Server Client example.com Mozilla Firefox

HYPERTEXT TRANSFER PROTOCOL 18 Server Client HTTP Request example.com Mozilla
Firefox

HTTP REQUEST 19 GET / HTTP/1.1 User-Agent: Mozilla Firefox Host:
example.com Accept: */*

HYPERTEXT TRANSFER PROTOCOL 20 Server Client HTTP Response example.com Mozilla
Firefox

HTTP RESPONSE 21 HTTP/1.1 200 OK Content-Type: text/html Content-Length: 1270
<!doctype html> <html> <head> <title>Example Domain</title> </head> <body> … </body> </html>

INTERNET LAYERS 23 HTTP TCP Internet Protocol (IP) WiFi, Ethernet,
3G, LTE…

RESOURCES 24 Anything that can be identiﬁed, named, addressed or
handled on the Web

RESOURCES 25 ▫︎Can be concrete things: ▫︎Web pages ▫︎Files ▫︎Videos
▫︎Blog posts ▫︎Articles

RESOURCES 26 ▫︎Can also represent abstract concepts: ▫︎Employees in a
enterprise ▫︎Money transfers ▫︎Products in a online store ▫︎Calendar appointments ▫︎User accounts

RESOURCE NAMES 27 ▫︎URN - Uniform Resource Name ▫︎products/54321 ▫︎about-us
▫︎articles/web.html ▫︎posts/2015-04-13 ▫︎podcasts/rest.mp3

RESOURCE LOCATORS 28 ▫︎URL - Uniform Resource Locator ▫︎http://example.com/products/54321 ▫︎http://example.com/about-us
▫︎http://example.com/articles/web.html ▫︎http://example.com/posts/2015-04-13 ▫︎http://example.com/podcasts/rest.mp3

ANATOMY OF AN URL 29

RESOURCE IDENTIFIERS 30

RESOURCE IDENTIFIERS 31 A resource only exists on the Web
if it has an identiﬁer (URI)

RESOURCES 32 HTTP can manipulate not only hypertext documents but
any type of resources

Imaginary HTTP server: example.com 33

READING A TEXT RESOURCE 34 http://example.com/hello-world.txt

READING A TEXT RESOURCE 35 GET /hello-world.txt HTTP/1.1 Host: example.com
HTTP Request

READING A TEXT RESOURCE 36 HTTP/1.1 200 OK Content-Type: text/plain
Content-Length: 13 Hello, World! HTTP Response

CREATING A TEXT RESOURCE 37 POST / HTTP/1.1 Host: example.com
Content-Type: text/plain Hello, Mars! HTTP Request

CREATING A TEXT RESOURCE 38 HTTP/1.1 201 Created Location: /hello-mars.txt
HTTP Response

CREATING A TEXT RESOURCE 39 http://example.com/hello-mars.txt

RESOURCE DOES NOT EXIST 40 http://example.com/hello-pluto.txt

RESOURCE DOES NOT EXIST 41 GET /hello-pluto.txt HTTP/1.1 Host: example.com
HTTP Request

RESOURCE DOES NOT EXIST 42 HTTP/1.1 404 Not Found HTTP
Response

HTTP CONTENT TYPES 43 ▫︎Determine the type of the HTTP
payload ▫︎text/html - HTML ▫︎text/plain - Plain Text ▫︎audio/mpeg3 - MP3 ﬁles ▫︎application/xml - XML ▫︎…

HTTP VERBS 44 ▫︎GET ▫︎POST ▫︎PUT ▫︎DELETE ▫︎HEAD ▫︎OPTIONS

HTTP STATUS CODES 45 ▫︎Success (2xx) ▫︎200 OK ▫︎201 Created
▫︎204 No Content ▫︎…

HTTP STATUS CODES 46 ▫︎Client Error (4xx) ▫︎400 Bad Request
▫︎404 Not Found ▫︎409 Conflict ▫︎…

HTTP STATUS CODES 47 ▫︎Server Error (5xx) ▫︎500 Internal Server
Error ▫︎503 Server Unavailable ▫︎…

THE RESOURCE-ORIENTED ARCHITECTURE 48

REST 49 Representational State Transfer

REST 50 HTTP + Resource-Oriented Architecture

REST 51 HTTP + Resource-Oriented Architecture RESTful

EMPLOYEE RESOURCE 52

EMPLOYEE RESOURCE 53 ▫︎Alice ▫︎Developer ▫︎Female ▫︎…

XML REPRESENTATION 54 <employee> <name>Alice</name> <role>Developer</role> <gender>female</gender> </employee>

JSON REPRESENTATION 55 { "name": "Alice", "role": "Developer", "gender": "female"
}

HTML REPRESENTATION 56 <h1>Alice</h1> <dl> <dt>Role:</dt> <dd>Developer</dd> <dt>Gender:</dt> <dd>Female</dd> </dl>

EMPLOYEE RESOURCE 57 /employees

EMPLOYEE RESOURCE 58 /employees/alice /employees/bob /employees/eve

RESOURCE OPERATIONS 59 ▫︎Create ▫︎Read ▫︎Update ▫︎Delete ▫︎List

LIST EMPLOYEE RESOURCES 60 GET /employees HTTP/1.1 Host: example.com Accept:
application/xml HTTP Request

LIST EMPLOYEE RESOURCES 61 HTTP/1.1 200 OK Content-Type: application/xml <employees>
<employee href="/employees/alice"/> <employee href="/employees/bob"/> <employee href="/employees/eve"/> </employee> HTTP Response

READ EMPLOYEE RESOURCE 62 GET /employees/alice HTTP/1.1 Host: example.com Accept:
application/xml HTTP Request

READ EMPLOYEE RESOURCE 63 HTTP/1.1 200 OK Content-Type: application/xml <employee>
<name>Alice</name> <role>Developer</role> <gender>female</gender> </employee> HTTP Response

CREATE EMPLOYEE RESOURCE 64 POST /employees HTTP/1.1 Host: example.com Content-Type:
application/xml <employee> <name>John</name> <role>QA</role> <gender>male</gender> </employee> HTTP Request

CREATE EMPLOYEE RESOURCE 65 HTTP/1.1 201 Created Location: /employees/john HTTP
Response

UPDATE EMPLOYEE RESOURCE 66 PUT /employees/alice HTTP/1.1 Host: example.com Content-Type:
application/xml <employee> <name>Alice</name> <role>Manager</role> <gender>female</gender> </employee> HTTP Request

UPDATE EMPLOYEE RESOURCE 67 HTTP/1.1 200 OK HTTP Response

DELETE EMPLOYEE RESOURCE 68 DELETE /employees/alice HTTP/1.1 Host: example.com HTTP
Request

DELETE EMPLOYEE RESOURCE 69 HTTP/1.1 204 No Content HTTP Response

RESOURCE-ORIENTED ARCHITECTURE 70 1. Addressability 2. Statelessness 3. Connectedness 4.
Uniform Interface

ADDRESSABILITY 71 Every interesting piece of information the server can
provide should be exposed as a resource, and given its own URI

ADDRESSABILITY 72 http://example.com/employees/alice

STATELESSNESS 73 Every HTTP request should happen in complete isolation

STATELESSNESS 74 http://google.com/search?q=jellyfish

STATELESSNESS 75

STATELESSNESS 76

STATELESSNESS 77 http://google.com/search? q=jellyfish&start=10

STATELESSNESS 78 Application State vs. Resource State

CONNECTEDNESS 79 Documents should contain not just data, but links
to other resources

CONNECTEDNESS 80

CONNECTEDNESS 81

CONNECTEDNESS 82

CONNECTEDNESS 83 { "employees": [ "/employees/alice", "/employees/bob", "/employees/eve", ... ]
"next_page": "/employees?start=10", "create_employee": "/employees" }

HATEOAS 84 Hypermedia As The Engine of Application State

UNIFORM INTERFACE 85 ▫︎Create: POST /employees ▫︎Read: GET /employees/alice ▫︎Update:
PUT /employees/alice ▫︎Delete: DELETE /employees/alice ▫︎List: GET /employees

UNIFORM INTERFACE 86 ▫︎Create: POST /resource ▫︎Read: GET /resource/{name} ▫︎Update:
PUT /resource/{name} ▫︎Delete: DELETE /resource/{name} ▫︎List: GET /resource

SAFETY 87 GET and HEAD never change the resource state

INDEMPOTENCE 88 PUT and DELETE are indempotent

RESTFUL WEB SERVICES 89

WEB SERVICES 90 client server Web

BIG WEB SERVICES 91 ▫︎Heavy ▫︎Don’t scale ▫︎Hard to understand
▫︎Tight coupling ▫︎SOAP, WSDL, etc…

TIGHT COUPLING 92

BROKEN TIGHT COUPLING 93

RESTFUL WEB SERVICES 94 ▫︎Lightweight ▫︎Cacheable ▫︎Scalable ▫︎Discoverable ▫︎Loose coupling

RESOURCE-ORIENTED ARCHITECTURE 95 1. Addressability 2. Statelessness 3. Connectedness 4.
Uniform Interface

CACHEABILITY 96 GET http://example.com/employees/alice

CACHEABILITY 97 GET http://example.com/employees/alice

SCALABILITY 98 GET http://example.com/employees/alice client server

SCALABILITY 99 GET http://example.com/employees/alice client server cluster

DISCOVERABILITY 100

DISCOVERABILITY 101 { "employees": [ "/employees/alice", "/employees/bob", "/employees/eve", ... ]
"next_page": "/employees?start=10", "create_employee": "/employees" }

PUBLIC RESTFUL APIS 102 ▫︎Twitter ▫︎GitHub ▫︎Amazon S3

REFERENCE 103 RESTful Web Services Leonard Richardson Sam Ruby

Felipe Dornelas [email protected] THANK YOU

RESTful Web Services

RESTful Web Services

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