OData in SAP Part 1

Source : SCN Post

How internet works:
- Your request a URL using web browser.
- Web browser sends your request to the web server using HTTP. ( HTTP defines the semantics of what the browser and web server can communicate to each other ).
- Web server then sends back HTTP response to your browser. (HTTP is stateless because, every single request received by the server is forgotten after a response has been sent across. web servers do not process HTTP requests by remembering the previous request).
- Browser parsed that HTTP response and prepare a DOM tree. DOM stands for document object   model and it is a language independent convention for representing objects in HTML.

URI vs URL:


GET and POST Methods :
- When you type a string in google search page and press enter, it actually generates a HTTP request with GET method in background. (Retrieve information from server)
- When you login to some web page using username and password and press enter, it actually generates a HTTP request with POST method in background. (send data to server)

HTTP Response:
- HTTP response comes with data and a status code.

- HTTP codes are 3 digit integers.

Code and Description

1xx: Informational It means the request has been received and the process is continuing.

2xx: Success It means the action was successfully received, understood, and accepted.

3xx: Redirection It means further action must be taken in order to complete the request.

4xx: Client Error It means the request contains incorrect syntax or cannot be fulfilled.

5xx: Server Error It means the server failed to fulfill an apparently valid request.

For example, status code 400 means Bad Request. It means that the server did not understand the request.