Post on 12-Feb-2017
a n i n t r o d u c t i o n t o
RESTFUL WEB SERVICESFelipe Dornelas
AGENDA
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▫︎The Internet
▫︎The Web and its Resources
▫︎HTTP
▫︎The Resource-Oriented Architecture
▫︎RESTful Web Services
WHAT IS REST?
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HTTP + Resource-Oriented Architecture
THE INTERNETA network of networks
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THE INTERNET, 2010
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INTERNET ROUTES
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INTERNET ROUTES
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CACHING
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INTERNET LAYERS
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Web, E-mail, BitTorrent, DNS…
TCP, UDP…
Internet Protocol (IP)
WiFi, Ethernet, 3G, LTE…
INTERNET LAYERS
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We will talk about the Web
THE WEBAn application of the Internet
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WHAT IS THE WEB?
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An information system of interlinked hypertext documents and resources
accessed via the Internet
HYPERTEXT DOCUMENTS
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HYPERTEXT MARKUP LANGUAGE
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<!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
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ServerClient
HTTP Requestexample.comMozilla Firefox
HTTP REQUEST
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GET / HTTP/1.1User-Agent: Mozilla FirefoxHost: example.comAccept: */*
HYPERTEXT TRANSFER PROTOCOL
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ServerClient
HTTP Responseexample.comMozilla Firefox
HTTP RESPONSE
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HTTP/1.1 200 OKContent-Type: text/htmlContent-Length: 1270
<!doctype html><html><head> <title>Example Domain</title></head><body> … </body></html>
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INTERNET LAYERS
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HTTP
TCP
Internet Protocol (IP)
WiFi, Ethernet, 3G, LTE…
RESOURCES
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Anything that can be identified, named, addressed or handled on the Web
RESOURCES
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▫︎Can be concrete things:
▫︎Web pages
▫︎Files
▫︎Videos
▫︎Blog posts
▫︎Articles
RESOURCES
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▫︎Can also represent abstract concepts:
▫︎Employees in a enterprise
▫︎Money transfers
▫︎Products in a online store
▫︎Calendar appointments
▫︎User accounts
RESOURCE NAMES
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▫︎URN - Uniform Resource Name
▫︎products/54321
▫︎about-us
▫︎articles/web.html
▫︎posts/2015-04-13
▫︎podcasts/rest.mp3
RESOURCE LOCATORS
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▫︎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
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RESOURCE IDENTIFIERS
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RESOURCE IDENTIFIERS
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A resource only exists on the Web if it has an identifier (URI)
RESOURCES
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HTTP can manipulate not only hypertext documents but any type of resources
READING A TEXT RESOURCE
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http://example.com/hello-world.txt
READING A TEXT RESOURCE
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GET /hello-world.txt HTTP/1.1Host: example.com
HTTP Request
READING A TEXT RESOURCE
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HTTP/1.1 200 OKContent-Type: text/plainContent-Length: 13
Hello, World!
HTTP Response
CREATING A TEXT RESOURCE
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POST / HTTP/1.1Host: example.comContent-Type: text/plain
Hello, Mars!
HTTP Request
CREATING A TEXT RESOURCE
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HTTP/1.1 201 CreatedLocation: /hello-mars.txt
HTTP Response
CREATING A TEXT RESOURCE
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http://example.com/hello-mars.txt
RESOURCE DOES NOT EXIST
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http://example.com/hello-pluto.txt
RESOURCE DOES NOT EXIST
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GET /hello-pluto.txt HTTP/1.1Host: example.com
HTTP Request
RESOURCE DOES NOT EXIST
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HTTP/1.1 404 Not Found
HTTP Response
HTTP CONTENT TYPES
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▫︎Determine the type of the HTTP payload
▫︎text/html - HTML
▫︎text/plain - Plain Text
▫︎audio/mpeg3 - MP3 files
▫︎application/xml - XML
▫︎…
HTTP VERBS
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▫︎GET
▫︎POST
▫︎PUT
▫︎DELETE
▫︎HEAD
▫︎OPTIONS
HTTP STATUS CODES
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▫︎Success (2xx)
▫︎200 OK
▫︎201 Created
▫︎204 No Content
▫︎…
HTTP STATUS CODES
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▫︎Client Error (4xx)
▫︎400 Bad Request
▫︎404 Not Found
▫︎409 Conflict
▫︎…
HTTP STATUS CODES
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▫︎Server Error (5xx)
▫︎500 Internal Server Error
▫︎503 Server Unavailable
▫︎…
THE RESOURCE-ORIENTED ARCHITECTURE
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REST
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Representational State Transfer
REST
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HTTP + Resource-Oriented Architecture
REST
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HTTP + Resource-Oriented Architecture
RESTful
EMPLOYEE RESOURCE
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EMPLOYEE RESOURCE
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▫︎Alice
▫︎Developer
▫︎Female
▫︎…
XML REPRESENTATION
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<employee> <name>Alice</name> <role>Developer</role> <gender>female</gender></employee>
JSON REPRESENTATION
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{ "name": "Alice", "role": "Developer", "gender": "female"}
HTML REPRESENTATION
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<h1>Alice</h1><dl><dt>Role:</dt> <dd>Developer</dd><dt>Gender:</dt> <dd>Female</dd></dl>
EMPLOYEE RESOURCE
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/employees
EMPLOYEE RESOURCE
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/employees/alice
/employees/bob
/employees/eve
RESOURCE OPERATIONS
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▫︎Create
▫︎Read
▫︎Update
▫︎Delete
▫︎List
LIST EMPLOYEE RESOURCES
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GET /employees HTTP/1.1Host: example.comAccept: application/xml
HTTP Request
LIST EMPLOYEE RESOURCES
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HTTP/1.1 200 OKContent-Type: application/xml
<employees> <employee href="/employees/alice"/> <employee href="/employees/bob"/> <employee href="/employees/eve"/></employee>
HTTP Response
READ EMPLOYEE RESOURCE
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GET /employees/alice HTTP/1.1Host: example.comAccept: application/xml
HTTP Request
READ EMPLOYEE RESOURCE
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HTTP/1.1 200 OKContent-Type: application/xml
<employee> <name>Alice</name> <role>Developer</role> <gender>female</gender></employee>
HTTP Response
CREATE EMPLOYEE RESOURCE
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POST /employees HTTP/1.1Host: example.comContent-Type: application/xml
<employee><name>John</name><role>QA</role><gender>male</gender>
</employee>
HTTP Request
CREATE EMPLOYEE RESOURCE
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HTTP/1.1 201 CreatedLocation: /employees/john
HTTP Response
UPDATE EMPLOYEE RESOURCE
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PUT /employees/alice HTTP/1.1Host: example.comContent-Type: application/xml
<employee><name>Alice</name><role>Manager</role><gender>female</gender>
</employee>
HTTP Request
UPDATE EMPLOYEE RESOURCE
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HTTP/1.1 200 OK
HTTP Response
DELETE EMPLOYEE RESOURCE
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DELETE /employees/alice HTTP/1.1Host: example.com
HTTP Request
DELETE EMPLOYEE RESOURCE
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HTTP/1.1 204 No Content
HTTP Response
RESOURCE-ORIENTED ARCHITECTURE
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1. Addressability
2. Statelessness
3. Connectedness
4. Uniform Interface
ADDRESSABILITY
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Every interesting piece of information the server can provide should be exposed as a resource,
and given its own URI
ADDRESSABILITY
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http://example.com/employees/alice
STATELESSNESS
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Every HTTP request should happen in complete isolation
STATELESSNESS
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http://google.com/search?q=jellyfish
STATELESSNESS
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STATELESSNESS
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STATELESSNESS
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http://google.com/search?q=jellyfish&start=10
STATELESSNESS
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Application State vs. Resource State
CONNECTEDNESS
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Documents should contain not just data, but links to other resources
CONNECTEDNESS
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CONNECTEDNESS
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CONNECTEDNESS
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CONNECTEDNESS
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{ "employees": [ "/employees/alice", "/employees/bob", "/employees/eve", ... ]
"next_page": "/employees?start=10", "create_employee": "/employees"}
HATEOAS
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Hypermedia As The Engine of Application State
UNIFORM INTERFACE
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▫︎Create: POST /employees
▫︎Read: GET /employees/alice
▫︎Update: PUT /employees/alice
▫︎Delete: DELETE /employees/alice
▫︎List: GET /employees
UNIFORM INTERFACE
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▫︎Create: POST /resource
▫︎Read: GET /resource/{name}
▫︎Update: PUT /resource/{name}
▫︎Delete: DELETE /resource/{name}
▫︎List: GET /resource
SAFETY
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GET and HEAD never change the resource state
INDEMPOTENCE
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PUT and DELETE are indempotent
RESTFUL WEB SERVICES
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WEB SERVICES
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client server
Web
BIG WEB SERVICES
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▫︎Heavy
▫︎Don’t scale
▫︎Hard to understand
▫︎Tight coupling
▫︎SOAP, WSDL, etc…
TIGHT COUPLING
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BROKEN TIGHT COUPLING
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RESTFUL WEB SERVICES
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▫︎Lightweight
▫︎Cacheable
▫︎Scalable
▫︎Discoverable
▫︎Loose coupling
RESOURCE-ORIENTED ARCHITECTURE
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1. Addressability
2. Statelessness
3. Connectedness
4. Uniform Interface
CACHEABILITY
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GET http://example.com/employees/alice
CACHEABILITY
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GET http://example.com/employees/alice
SCALABILITY
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GET http://example.com/employees/alice
clientserver
SCALABILITY
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GET http://example.com/employees/alice
client
server cluster
DISCOVERABILITY
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DISCOVERABILITY
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{ "employees": [ "/employees/alice", "/employees/bob", "/employees/eve", ... ]
"next_page": "/employees?start=10", "create_employee": "/employees"}
PUBLIC RESTFUL APIS
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▫︎Twitter
▫︎GitHub
▫︎Amazon S3
REFERENCE
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RESTful Web Services Leonard Richardson Sam Ruby