API and Web Service

API

API - Application Programming Interface

Letter

Word

Meaning

A

Application

Software that does a task

P

Programming

Program (P) that does the task in the Application (A)

I

Interface

Place (I) to tell the program (P) to run

API Definition: You tell (I) a program (P) to run in an application (A)

Level od Difficulty

Example

I (Interface)

P (Program)

A (Application)

Simple

Messenger message using smartphone

smartphone

message

Messenger

Simple

Google search using computer

computer

search

Google

Moderate/Complex

Create orders in Amazon (in system)

Amazon

create orders

Amazon

How API works

  1. Request

  2. Program

  3. Response

  1. We type any search to www.google.com like "wikipedia"

  2. Press Enter > Request is send to google Server

  3. A program "/search" is run

  4. Send by response our results of searching

www.google.com/search?q=wikipedia

/search -> folder on www.google.com server ?q=wikipedia -> our search parameter

Web Service

Web -> internet Service -> API Web Service -> API that uses the internet

Web Service

API

All web services are APIs.

All APIs are not web services.

It supports XML.

Responses are formatted using Web API's MediaTypeFormatter into XML, JSON, or any other given format.

You need a SOAP protocol to send or receive and data over the network. Therefore it does not have light-weight architecture.

API has a light-weight architecture.

It can be used by any client who understands XML.

It can be used by a client who understands JSON or XML.

Web service uses three styles: REST, SOAP, and XML-RPC for communication.

API can be used for any style of communication.

It provides supports only for the HTTP protocol.

It provides support for the HTTP/s protocol: URL Request/Response Headers, etc.

the difference i just copy from

HTTP

HTTP - Hypertext Transfer Protocol http(s)://www.google.com

Parts of HTTP

HTTP

Request

Response

Start line

Version HTTP/1.1, Method (GET/POST...),API program location, parameters...

Version HTTP/1.1, Status Code (200 OK)

HEADERS

  • Host: www.google.com

  • Token: xxxxxx (API token)

  • Cookie: xxx

  • Cookie: xyz...

  • HTML

Blank line

(just separator of HEAD and BODY)

(just separator of HEAD and BODY)

BODY

When use POST by registration Username and Password

HTML

Start line

Request

Response

Name

Start line, Request line

Start line, Response line

HTTP Version

HTTP/1.1

HTTP/1.1

Method

GET, POST, PUT, DELETE, ...

No

API Program Folder Location

Yes (example: /search)

No

Parameters

Yes (example: ?q=wikipedia)

No

Status Code

No

Yes (example: 200 OK)

Format

Method (space) API Program Folder Location+Parameters (space) HTTP Version

HTTP Version + Status Code

Example

GET /search?q=wikipedia(optional) HTTP/1.1

HTTP/1.1 200 OK

Headers

Blank line

There is where head end and body beginning.

Body

HTTP Methods

The most popular are GET, POST, PUT, DELETE like in database CRUD (Create, Read, Update, Delete)

HTTP methods

Description

GET

Read (get data from server)

POST

Create (post data into server)

PUT

Update (put file into server)

DELETE

Delete (delete the object at the location)

HEAD

TRACE

OPTIONS

CONNECT

PATCH

HTTP Status Codes

The groups of HTTP status codes:

1xx Informational response

2xx Success

200 OK 201 Created

3xx Redirection

4xx Client errors

400 Bad Request 404 Not Found

5xx Server errors

500 Internal Server Error 502 Bad Gateway

JSON

Nowadays is more populary than XML

JSON -> JavaScripts Object Notation

HTTP Header Line: Content-Type: application/json HTTP Body: JSON JSON uses "Key" : "Value" (e.g. "Fruit" : "Apple")

To show how JSON works i used online editor:

Mozilla Firefox could open .JSON file without any extension

XML

XML -> eXtensible Markup Language

HTTP Header Line: Content-Type: application/xml HTTP Body: XML XML uses tags <> (e.g. <button>Click Me!</button>)

REST

Nowadays is more populary than SOAP

REST -> Representational State Transfer

REST is used to complete a Web Service (API) using HTTP

4 HTTP Request Parts Start line All Methods (GET, POST, PUT, DELETE, ...) Header Line All Blank Line Body Any (JSON, XML, html, images, ...)

SOAP

SOAP -> Simple Object Access Protocol

SOAP uses a WSDL (Web Service Description Language)

4 HTTP Request Parts Start line POST WSDL HTTP Version Header Line Content-Type: text/xml Blank Line Body XML envelope formed using WSDL

Browser DevTools

GoogleChrome F12 MozillaFirefox F12 Opera Ctrl+Shift+C

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