As discussed so far in the earlier chapter that RESTful web service makes use of HTTP for determining the action to be conceded out on the particular resources. For comprehending the REST structural design, it is exceedingly vital that to understand the HTTP evidently as there is excessive use of the HTTP protocols for building a REST API.

HTTP is everywhere on the internet. Each time you look for some information or resource on the internet, you make use of a URL in your browser where an HTTP request is launched from the client to the web server, and in response, you obtain the HTML content. It is important to note that, while websites are typically for human utilization, the RESTful API deals with application consumption.

More About the HTTP Methods

So, to request data from any target website that data has to be in a browser readable form, this is in HTML, whereas for the REST API, the response will be something related to XML/JSON or in any other compatible type. As REST gets its motivation from HTTP, therefore, it can be said as the stamina and structural pillar of the REST. As you might know that HTTP is a TCP/IP based connection protocol; it is implemented for delivering data across the World Wide Web. REST does not get connected to the web and also does not respond when tried to access using a web browser, even though it is based on HTTP.

Basic HTTP Features for REST

As you know that the HTTP is a protocol that permits us to send and receive files over the internet, using client-server architecture and is easier to monitor. The essential features of HTTP are:

  • HTTP is a connectionless protocol.
  • HTTP is stateless because both the server and the client keep track of the last request.
  • Any data can be transmitted and received via the HTTP protocol, hence type-independent.

For identifying any resources implemented using REST or in general, as well as establishing any connection, HTTP makes use of the Uniform Resource Identifier (URI). HTTP's request and response consist of the following four items:

  • A starting line
  • One or more headers
  • A blank line that indicates the finish of the header field(s)
  • And finally an optional message body

CRUD Operations in the HTTP method

Here you will get to know how to use the HTTP methods in REST for performing the basic CRUD operations.

Let suppose you wish to GET or DELETE any data from the student having student ID as 10. The resource URI of such operation will be http://localhost/appName/student/10. Now the catch is how a server can identify which request is associated with GET operation and which one is associated with DELETE for the same URI. It is by checking the HTTP method parameter that will be 'GET', and for the second case, it should be 'DELETE'.

The standard HTTP methods are:
  • GET
  • PUT
  • POST

Other methods which are hardly ever used are HEAD and OPTIONS.

Example, to fetch the Student related Information:

HTTP Method URI Operation
GET http://localhost/appName/students/ For fetching information for all students.
GET http://localhost/appName/students/10 For fetching the student having roll number 10.

To delete any record:

HTTP Method URI Operation
DELETE http://localhost/appName/student/10 For removing the student record having ID number 10
DELETE http://localhost/appName/courses/4 To remove the course having course-id 4.

To update student or course information:

HTTP Method URI Operation
PUT http://localhost/appName/student/10 For update the student record having ID number 10
PUT http://localhost/appName/courses/4 For upgrading the course having course-id 4.

To insert and create a new entry for the student:

HTTP Method URI Operation
POST http://localhost/appName/student To create a new entry.

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