HTTP

What is The Hypertext Transfer Protocol (HTTP)

It is an application protocol for distributed, collaborative, hypermedia information systems.

• responsible for communication between web servers and clients

HTTP request methods

HTTP defines a set of request methods (HTTP verbs) to indicate the desired action to be performed for a given resource.

Each of them implements a different semantic, but some common features are shared by a group of them: e.g. a request method can be safe, idempotent, or cacheable.

• GET
  • retrieves data from the server
  • The GET method requests a representation of the specified resource. Requests using GET should only retrieve data.
• POST
  • submits data to the server
  • The POST method submits an entity to the specified resource, often causing a change in state or side effects on the server.
• PUT
  • update data already on the server
  • The PUT method replaces all current representations of the target resource with the request payload.
• DELETE
  • delete data from the server
  • The DELETE method deletes the specified resource.
• CONNECT The CONNECT method establishes a tunnel to the server identified by the target resource.
• OPTIONS The OPTIONS method describes the communication options for the target resource.
• TRACE The TRACE method performs a message loop-back test along the path to the target resource.
• PATCH The PATCH method applies partial modifications to a resource.
• HEAD The HEAD method asks for a response identical to a GET request, but without the response body.

HTTP header fields

General Header Fields:

• Cache-Control
• Connection
• Date
• Pragma
• Trailer
• Transfer-Encoding
• Upgrade
• Via

Response-Specific Header Fields:

• Accept-Ranges
• Age
• Content-Encoding
• Content-Language
• Content-Length
• Content-Location
• Content-Type
• Expires
• Last-Modified
• Server
• Set-Cookie

Request-Specific Header Fields:

• Accept
• Accept-Encoding
• Accept-Language
• Authorization
• Content-Length
• Content-Type
• Cookie
• Host
• Referer
• User-Agent

HTTP status code

General

• 1xx: informational
• 2xx: success
• 3xx: redirect
• 4xx: client error
• 5xx: server error

Most popular

• 200: ok
• 201: ok created
• 301: moved to new url
• 304: not modified (cached version)
• 400: bad request
• 401: unauthorized
• 404: not found
• 500: internal server error

RESTful APIs Routes

• Index Route: GET /books
  • return all the items of a database table
• Show Route: GET /books:id
  • returns a single item
• Create Route: POST /books
  • returns the newly created item
• Edit/Update Route: PUT /books:id or PATCH /books:id
  • returns the updated item
• Delete Route: DELETE /books:id
  • returns the deleted item

Why REST is useful

For providing a predictable, industry standard, well-organized way to structure API endpoints.

Notes

• every request is independent
• http is stateless
• each request consist of a header and a body