This document provides an overview of REST APIs, including: 1. What is an API and how it connects different platforms and applications. 2. What is a REST API and the key architectural constraints it follows including being stateless, cacheable, having a uniform interface, and using a layered system. 3. An overview of HTTP as the most popular protocol for REST APIs and how it uses verbs like GET, POST, PUT, and DELETE to make requests.

1. REST API

2. Content
1. What is an API
2. What is a REST API
3. REST Architectural Style
i. Architectures
ii. Overview of HTTP
iii. Message Formats
4. How to use REST APIs

3. What is an API
API - Application Programming Interface
API is a contract. A promise to perform described services when
asked in specific ways.
App

4. Its a set of functions, classes or objects that software module
exposes for other programs to use by passing arguments (inputs).
Usually API’s are used
to connect the two
different platforms
What is an API

5. Without APIs
Web app
Mobile apps
Web Server
Database
User

6. With APIs
Web app
Mobile app
REST API
Database
User

7. What is a REST API
REST - Representational State Transfer
REST is simply an architectural style achieved by combining a number of
different well-known architectures.
It be used to modify or view resources on the server without
performing any server-side operations.

8. Client-Server
Client
Server
Response
Request

9. Stateless
Client
Start Session
Client
ServerEnd Session
Stateless
The state is
managed by
the clientSession use to keep
track of client data

10. Cacheable
Server
Response
Request
Labeled
Data
Data Labeled
Data
intermediary servers or components Cache
App
Response
No
Yes
If it
cacheable
data

11. Uniform Interface
Client 1 Client 2 Client 3
API A
JAVA EE
MySQL
API B
.NET
SQL Server
API C
Node JS
Mongo DB
Abstraction

12. Layered System
Solution
SharedLayer Layer 2
Layer 3
Layer 1

13. Layered System
Solution
CommonUtilityLayer Business Logic Layer
Presentation Layer
Data Access Layer

14. Overview of HTTP
The most popular protocol used for RESTful implementations is HTTP.
REST architecture use HTML Verbs to make requests.
HTML Verbs - uniquely address data using a uniform and minimal set of
commands.
• GET - Read data or resources.
• POST - Create data or resource.
• PUT - Update data or resources.
• DELETE - Delete data or resources.

15. Message Formats
REST is not tied to a specific
message format.
• XML - Extensible Markup
Language
• JSON - JavaScript Object
Notation
<?xml version="1.0" encoding="UTF-8"?>
<Person>
<Name>Matt</Name>
<Surname>Van Der Westhuizen</Surname>
<Hobbies>
<Hobby>Boardgames</Hobby>
<Hobby>GameDev</Hobby>
<Hobby>Reading</Hobby>
</Hobbies>
<PhoneNumbers>
<PhoneNumber>
<Type>home</Type>
<Number>1234567890</Number>
</PhoneNumber>
<PhoneNumber>
<Type>cell</Type>
<Number>0821234567</Number>
</PhoneNumber>
</PhoneNumbers>
</Person>
{
"name": "Matt",
"surname": "Van Der Westhuizen",
"hobbies": [
"Boardgames",
"GameDev",
"Reading"
],
"phoneNumbers": [
{"type": "home", "number": "1234567890"},
{"type": "cell", "number": "0821234567"}
]
}

16. How to use REST APIs
Here is some examples in Google Map API
https://maps.googleapis.com/maps/api/geocode/json?&address=pitakotte
Extrogene Software Pvt Ltd. Place ID = ChIJS2KQ2d5b4joR4vOh1RaicjQ
https://maps.googleapis.com/maps/api/place/details/json?placeid=ChIJS2
KQ2d5b4joR4vOh1RaicjQ&key=AIzaSyBXMUhoE8lu0wjm7SCO9RacyKE-
ef8J0Gw

17. Kanushka Gayan
SE intern @ Extrogene Software (Pvt) Ltd
kanushkanet@gmail.com
Thank You!