API (Application Programming Interface)

General

Letter	Word	Meaning
A	Application	Software that does a task
P	Programming	Program that does the task in the Application
I	Interface	Place to the program to run

Advantages

• Just use the program, don’t write it
• Platform independent
• Upgrade safe </a>

API Mashup: An API that is calling other APIs.

Web Service

API that uses the internet. All web services are APIs, but not all APIs are web services.

Web services use:

• XML or JSON to format data over the internet
• REST, SOAP, or XML/RPC to transfer that data </a>

HTTP (HyperText Transfer Protocol)

http	REQUEST	RESPONSE
startline	Version (1.1), Method, Folders, Parameters	Version (1.1), Status
headers	Host (www.google.com), Token	Cookies, Html
blank line
body	Username, Password	Html

Startline

	REQUEST	RESPONSE
Name	Start Line, Request Line	Start Line, Response Line, Status Line
HTTP Version	HTTP/1.1	HTTP/1.1
Method	GET, POST, PUT, DELETE	-
API Program Folder Location	/search	-
Parameters	?q=tuna	-
Status	-	200 OK
Format	Method(space)API Program Folder+Parameters(space)HTTP Version	HTTP Version(space)Status code
Example	GET /search?q=tuna HTTP/1.1	HTTP/1.1 200 OK

Methods

C.reate R.ead U.pdate D.elete

Method	Function	Itempodent (safe to repeat)
GET	Get information	yes
POST	Create information	no
PUT	Change Information	yes
DELETE	Delete Information	yes

Status Codes

Code	Description
1xx	Still running, wait
2xx	Success
3xx	Redirection
4xx	Error from origin
5xx	Error from destination

XML (eXtensible Markup Language)

W3 Schools

test.xml

<?xml version="1.0"?>
<Pizza>
  <Size>Small</Size>
  <Toppings>
    <Topping>Onions</Topping>
    <Topping>Mushrooms</Topping>
  </Toppings>
</Pizza>

JSON (JavaScript Object Notation)

W3 Schools

test.json

{ "Pizza" : [
  {"Size" : "Small",
    "Toppings" : ["Onions","Mushrooms"],
  },
  {"Size" : "Large",
    "Toppings" : ["Ham","Egg"],
  }
  ]
}

SOAP (Simple Object Access Protocol)

W3 Schools

Soap uses a WSDL (Web Services Description Language) that describes the web service. SOAP uses POST method.

Item	Content
Start Line	POST WSL HTTP Version
Header Line	Content-Type: text/xml
Blank Line	-
Body	XML envelope formed using WSDL

<?xml version="1.0"?>

<soap:Envelope
xmlns:soap="http://www.w3.org/2003/05/soap-envelope/"
soap:encodingStyle="http://www.w3.org/2003/05/soap-encoding">

<soap:Header>
...
</soap:Header>

<soap:Body>
...
  <soap:Fault>
  ...
  </soap:Fault>
</soap:Body>

</soap:Envelope>

REST (Representational State Transfer)

W3c

Item	Content
Start Line	GET, POST, PUT, DELETE, etc
Header Line	All
Blank Line	-
Body	JSON, XML, Image, Html, …

Start Line

PUT

Header Line

Authorization:Bearer ...
Accept:application/json
Content-Type:application/json
Content-Language:en-US

Body

{
  "availability": {
    "shipToLocationAbailability": {
      "quantity": 50
    }
  },
  "condition": "NEW",
  "product": {
    "title": "An Item"
  }
}

Demo

Twitter API

import tweepy

client_secret = '1eQr5yqKHnzXKJHCCsZ-fwo4YZ1OvXdd6k-5ub68aANVskxr8N'

ak = 'xxx'
aks = 'xxx'

at = 'xxx'
ats = 'xxx'

def OAuth():
    try:
        auth = tweepy.OAuthHandler(ak,aks)
        auth.set_access_token(at,ats)
        return auth
    except Exception as e:
        return None

oauth = OAuth()
apicall = tweepy.API(oauth)

apicall.update_status('Here is a sample tweet from the API call program.')

print('Tweet created')

API Access

Authorization and Authentication

• Authentication: Prove Identity
• Authorization: Limited Access

Name	Authentication	Authorization	Examples
No Auth	N	N	Google search page
Basic Auth	Y	N	Email
Bearer Token	N	Y	Not many
OAuth	Y	Y	Wayz
Two Factor	Y	N	Git

OAuth (Open Authorization)

An application is authorized to acces certain ressources.

Postman

API Directories

• Rapid API
• API List

Postman

• Basic Auth
• Digest Auth
• Bearer Auth
• OAuth

Python

import requests

url = "https://httpbin.org/bearer"

payload = {}
headers = {
  'Authorization': 'Bearer sdfgsdfg'
}

response = requests.request("GET", url, headers=headers, data=payload)

print(response.text)

Webhooks (Reverse API)

A hook is an event that calls a webservice.

1. Event/Trigger
2. Configuration (Endpoints)
3. HTTP request
4. HTTP response </a>

Microservice

A microservice is a ‘small’ API.

Monolith Architecture	Microservice
One API	Many APIs
API calls many programs	Specific API for each program
	+ scalable, language independent, specialised teams
	- inconsistent