1. Web Resources
A Web Resource is any data that can be obtained via internet.
A resource can be
- HTML document
- CSS document
- JSON Data or Plain text
- Image, Video, etc.
2. Uniform Resource Locator (URL)
URL is a text string that specifies where a resource can be found on the internet.
We can access web resources using the URL.
Syntax:
In the URL
- httpis a Protocol
- www.flipkart.comis a Domain Name
- /watchesis a Path
- type=digital&rating=4is the Query Parameters
2.1 Protocol
A protocol is a standard set of rules that allow electronic devices to communicate with each other.
There are different types of protocols.
- Hypertext Transfer Protocol (HTTP)
- Hypertext Transfer Protocol Secure (HTTPS)
- Web Sockets, etc.
2.1.1 HTTP
The Hypertext Transfer Protocol (HTTP), is a protocol used to transfer resources over the web.
Examples: Internet forums, Educational sites, etc.
HTTP Request: Message sent by the client
HTTP Response: Message sent by the server
2.1.2 HTTPS
In Hypertext Transfer Protocol Secure (HTTPS), information is transferred in an encrypted format and provides secure communication.
Examples: Banking Websites, Payment gateway, Login Pages, Emails and Corporate Sector Websites, etc.
2.2 Domain Name
It indicates which Web server is being requested.
2.3 Path
The path is to identify the resources on the server.
Examples:
- /watches in http://www.flipkart.com/watches
- /electronics/laptops/gaming in http://www.flipkart.com/electronics/laptops/gaming
2.4 Query Parameters
Query parameters add some criteria to the request for the resource.
Multiple query parameters can be added by using an
For example,
3. HTTP
3.1 HTTP Requests
HTTP requests are messages sent by the client to initiate an action on the server.
HTTP request includes
- Start Line
- Headers
- Body
3.1.1 Start Line
A Start Line specifies a
- URL
- HTTP Method
- HTTP Version
HTTP Methods
The HTTP Request methods indicate the desired action to be performed for a given resource.
| Methods | Description |
|---|---|
| GET (Read) | Request for a resource(s) from the server |
| POST (Create) | Submit data to the server |
| PUT (Update) | The data within the request must be stored at the URL supplied, replacing any existing data |
| DELETE (Delete) | Delete a resource(s) |
HTTP Version
| Year | Version |
|---|---|
| 1991 | HTTP/0.9 |
| 1994 | HTTPS |
| 1996 | HTTP/1.0 |
| 1997 | HTTP/1.1 |
| 2015 | HTTP/2 |
| 2019 | HTTP/3 |
3.1.2 Headers
HTTP Headers let the client and the server to pass additional information with an HTTP request or response.
3.1.3 Body
We place the data in the Request body when we want to send data to the server.
For example, form details filled by the user.
HTTP Requests
- Start Line
- URL
- Protocol
- HTTP
- HTTPS
- Domain Name
- Path
- Query Parameters
- Protocol
- HTTP Method
- GET (Read)
- POST (Create)
- PUT (Update)
- DELETE (Delete)
- HTTP Version
- URL
- Headers
- Body
3.2 HTTP Responses
HTTP responses are messages sent by the server as an answer to the clients request.
HTTP Response includes
- Status Line
- Headers
- Body
3.2.1 Status Line
A Status line specifies a
- HTTP version
- Status code
- Status text
Status code
Status codes Indicate whether an HTTP request has been successfully completed or not.
| Status Code Series | Indicates |
|---|---|
| 1XX | Information |
| 2XX | Success |
| 3XX | Redirection |
| 4XX | Client Error |
| 5XX | Server Error |
200 ( Success ) - Indicates that the request has succeeded
201 ( Created ) - The request has succeeded and a new resource has been created as a result
Status text
| Status Code | Status Text |
|---|---|
| 200 | OK |
| 204 | No Response |
| 301 | Moved Permanently |
| 401 | Unauthorized |
| 403 | Forbidden |
| 404 | Not Found |
3.2.2 Body
Response Body contains the resource data that was requested by the client.
HTTP Responses
- Status Line
- HTTP version
- Status code
- 1XX
- 2XX
- 3XX
- 4XX
- 5XX
- Status text
- Headers
- Body