RESTFul Services
+++++++++++++++
-> REST stands for 'Representational State Transfer'
-> RESTFul services are used to develop Distributed Applications with
Intereoperability
-> If one application is communicating with another application then those are
called as 'Distributed Apps'
-> Intereoperability means irrespective of the platform and language applications
can communicate
java app <-----------> .Net app
.Net app <----------> Python app
Python app <---------> Java App
-> Distributed applications are used for B 2 B communications
-> B2B means Business to Business Communication
-> Distributed Application will re-use services of one application in another
application
-> RESTful Services are providing 'Intereoperability'
-> Two Actors will be involved in Distributed Applications development
1) Provider
2) Consumer
-> The application which is providing business services is called as Provider
Application
-> The application which is accessing business services is called as Consumer
Application
Note: One provider application can have multiple consumer applications
-> Provider and Consumer will communicate using HTTP as a mediator
-> Provider and Consumer will exchange the data in Text / XML / JSON format
Note: In Industry we will use JSON format to exchange data from one application to
another application
-> To start our journey with RESTFul services development we should be good in
below areas
1) HTTP Protocol (Methods, Status Codes, Req structure & Res Structure)
2) XML and JAX-B Api
3) JSON and Jackson Api
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What is HTTP ?
################
-> HTTP stands for Hyper Text Transfer Protocol
-> It acts as a mediator between client & server ( Consumer & Provider )
-> Consumer application will send HTTP Req to Provider application
-> Provider application will process the request and it will send HTTP response to
Consumer
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HTTP Methods
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-> HTTP methods are used to send request from Consumer application to Provider
application
-> HTTP method will represent what type of operation client / consumer wants to
perform with Provider
a) GET
b) POST
c) PUT
d) DELETE
-> GET request is used to retrieve data from Server / Provider application.
-> GET request will not have body to send data in the request
-> To send any data using GET request then we will use Path Params & Query Params
Ex: https://www.youtube.com/watch?v=VO818de8sdk
Note: Path Params & Query Params data will be displayed in the URL
Note: It is not recommended to send sensitive / secret data using Path Params &
Query Params
-> GET request is Idempotent (means if you send same GET request for multiple times
also nothing will change at server)
-> POST request is used to create a new record at server
-> When consumer wants to send huge data/ sensitive data then Consumer will use
POST request
-> POST request contains request body
-> POST request is Non-Idempotent
Note: In POST request we can send data in URL and in Request Body.
Note: Request Body is the recommended approach to send sensitive data to server
-> PUT request is used to update a record at server
-> When consumer wants to update a record at then consumer will send PUT request to
Provider
-> PUT request contains request body
-> PUT request is Idempotent
Note: In PUT request we can send data in URL and in Request Body.
Note: Request Body is the recommended approach to send sensitive data to server
-> DELETE request is used to delete a record at server
-> DELETE request contains request body
-> DELETE request is Idempotent
Note: In DELETE request we can send data in URL and in Request Body.
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HTTP Request Structure
#######################
1) Intial Request Line ( HTTP method + URL )
2) Request Headers ( key-value )
3) Blank Line to seperate Header & Body
4) Request Body (Request Payload)
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HTTP Response Structure
#######################
1) Initial Response line (Protocl Version + Status Code + Status msg)
2) Response Headers (Key-value)
3) Blank Line to seperate Header & Body
4) Response Body (Response Payload)
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HTTP Status Codes
##################
-> HTTP Status codes will represent how the request process by server / provider
1xx (100 - 199) ---> INFO
2xx (200 - 299) ---> OK (success)
3xx (300 - 399) ---> Redirect
4xx (400 - 499) ---> Client Error
5xx (500 - 599) ---> Server Error
