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HTTP

HTML - "Hyper Text Markup Language" HTTP - "Hyper Text Transfer Protocol"

So what exactly is this "Hyper Text"?

https://www.w3.org/WhatIs.html https://www.merriam-webster.com/dictionary/hypertext - see etymology

Request & Response Framework

http://slides.com/dhrumilmehta/how-to-tell-a-story-with-data-tools-of-the-trade#/6/4

http://slides.com/dhrumilmehta/how-to-tell-a-story-with-data-tools-of-the-trade#/6/5

Which layer is it?

  • HTTP is on the "application layer" of the OSI stack
  • It assumes a reliable transport layer protocol (like TCP/IP)
  • But maybe these acronyms are all TMI...point being - HTTP is an abstraction at the application layer

HTTP Verbs

http://www.w3schools.com/tags/ref_httpmethods.asp

  • GET - when you navigate to a website like www.google.com you're issuing a get request to google's servers. Their server then sends you back the google homepage.

  • POST - when you fill out the google search for and hit "Search", you're issuing a "POST" request. POST requests contain a payload in the body that is not visible in the URL. That is why it is most often used to send form data to a website.

  • HEAD, PUT, DELETE ... and some others

GET vs POST

GET POST
Requests data from a specific resource Submits data to be processed by a specific resource.
Data is submitted as part of the URL Data is submitted in the request body
Less secure but faster More secure but slower
Can be cached by browser Not Cached by Browser
Length Limited by URL size MaxLength determined by server

Representational State Transfer (REST)

So what is being "got" when you GET?... A Resource!

You'll read a little more about REST-ful webpages in your homework tonight. For now, I want to just show you an example of a REST-ful web app. Regardless of what is going on behind the scenes, a layer of REST-ful abstraction can help things make sense to an outside consumer of your content.

  • Demo of the polls database.
    • Note how the URL (Universal Resource Locator) refers to a "resource".
    • I can GET a resource or list of resources, or I can POST to an endpoint which can trigger the creation of a resource.
    • Any kind of request can be programmed to do any kind of thing (for example POST requests can also trigger scraping in the polls database), but a well formed REST-ful web applicaiton will stick to conventions.

A Simple CRUD Application

A source once said to me:

The government is just as series of CRUD applications that interact with each other.

"CRUD apps" have four functions: Create Read Update Delete resoures. Understanding the concept of a CRUD app can help you understand REST and HTTP verbs a little better.

❇️ Example

Let's spin up a simple CRUD APP!

  1. Create an Ubuntu EC2 instance on Amazon Web Services (AWS) and SSH into it
  2. Host the "back end"
  3. open the INSOMNIA app to make an http GET request to the "back end"
  4. in the INSOMNIA app to make a http POST request to the "back end"
  5. spin up the "front end" locally and point to the new "back end"