REST & RESTful Web Service

REST &
RESTful WEB SERVICE
Power Lunch by Vu Tran

REST & RESTful WEB SERVICE
● REST
● REST Characteristics
● RESTful Web Service

REST
Communication
Server Server

REST
● REST stands for Representational State Transfer
● It is an architectural pattern for developing web
services as opposed to a specification
● REST web services communicate over the HTTP
specification, using HTTP vocabulary
– Methods (GET, POST, etc.)
– HTTP URI syntax (paths, parameters, etc.)
– HTTP Response codes.
– Media types (xml, json, html, plain text, etc)

HTTP-REST Request Basics
The HTTP request is sent from the client.
– Identifies the location of a resource (URL)
– Specifies the verb, or HTTP method (GET, POST, etc).
– Supplies optional request headers (GET - e.g. name-value
pairs)
– Supplies an optional request body (POST - e.g. form
parameters, attachments, etc.)

HTTP-REST Request Basics
API Server
http://customer.info/customers/12345
Client
● URL : http://customer.info/getCustomersInfo
● Verb or HTTP method : GET
● Request headers : ?id=12345
● Request body : NA

HTTP-REST Response Basics
The HTTP response is sent from the server.
– Gives the status of the processed request. (HTTP code)
– Supplies response headers (name-value pairs) that
provide additional information about the response.
– Supplies an optional response body that identifies
additional data to be downloaded to the client (html, xml,
binary data, etc.)

HTTP-REST Response Basics
API Server
Client
● HTTP status : 200 OK
● Response headers
Content-Type: text/html
Content-Length: 1024
● Response body
<html>
<!-- some HTML content →
</html>
Response

REST Characteristics
Resources
● URI: Every resource is uniquely addressable using URIs.
Constraints
● Client-Server
● Stateless
● Cacheable
● Layered
● Code on demand (optional)
● Uniform Interface
o Method : Use only HTTP methods (GET, POST, PUT,
DELETE)
o Representation : json, xml, etc

Client-Server
1. Separation of concerns.
2. Client and server are independent from each other.
3. Client doesn’t know anything about the resource which
is kept in the server.
4. Server responds as long as the right requests come in.
➔ Goal: Platform independency and to improve scalability.

Stateless
1. Each request is independent from other requests.
2. No client session data or any context stored on the
server.
3. Every request from client stores the required
information, so that the server can respond.
4. If there are needs for session-specific data, it should be
held and maintained by the client and transferred to the
server with each request as needed.
5. A service layer which doesn’t have to maintain client
sessions is much easier to scale.

Cacheable
1. HTTP responses must be cacheable by the clients.
2. Important for performance.
3. If a new request for the resources comes within a while,
then the cached response will be returned.

Layered System
1. There can be many intermediaries between you and the server you
are connecting to.
2. Actually, a client does not know if it is connected to the last server
or an intermediary server.
3. Intermediaries may improve performance by caching and message
passing.
4. Intermediary servers can increase scalability by load-balancing and
can force clients to form some sort of security policies.
5. This structure can be used when encapsulation is needed.

Code on Demand (optional)
1. Servers can send some kind of executable scripts to the client-
side in order to increase or change the functionality on the client
side.
2. This may cause low visibility, so it is the only optional constraint.
EXAMPLE :
...
<head>
<script src="utility.js" type="text/javascript">
</script>
</head
..

Uniform Interface
1. All resources share a uniform interface for the transfer of state
between client and resource, consisting of
o HTTP Method
o HTTP Status Code

HTTP Methods
OPERATION HTTP METHOD Characteristic
Create POST
Read GET safe, idempotent, cacheable
Update PUT (or POST) idempotent
Delete DELETE idempotent
➔ Idempotent : meaning that the operation will produce the same result no matter how many times
it is repeated

HTTP Status Code
HTTP Status Code Group Comment
1xx Informational (100,101)
2xx Success (200,201)
3xx Redirect (301, 304)
4xx Client error (401, 404, 405)
5xx Server error (500, 503)

RESTful WEB SERVICE
Constraints
● Client-Server
● Stateless
● Cacheable
● Layered
● Code on demand (optional)
● Uniform Interface
➔ If a service does not include all constraints out of «Code on
Demand», it is not a RESTful web service.

RESTful Examplehttp://customer.info/customers/ http://customer.info/customers/12345
GET List the URIs and perhaps other
details of the collection's
customers.
Retrieve a representation of the
addressed customer of the
collection.
PUT Not generally used. Replace the addressed customer of
the collection, or if it does not exist,
create it.
POST Create a new customer’s entry in
the collection.
Not generally used.
DELETE Delete the entire collection. Delete the addressed customer of
the collection.

REST & RESTful Web Service

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