An Introduction to REST with Examples – Part 1


REST stands for Representational State Transfer. If you have just transitioned from a desktop application development environment to the world of web development, then you have probably heard about REST APIs.

To understand REST API, let’s take an example. Suppose you search “Avengers: Endgame” in the search bar of YouTube. As a result, you can check a seemingly endless list of videos on the result pages; this is exactly how a REST API is supposed to work—providing you results for anything that you want to find.

Broadly speaking, an API is just a number of fixed functionalities that help programs in communicating with each other. The API is created by the developer on the server—to which the client communicates. REST is a software architectural style that determines the working of the API. Developers use it to design their APIs. Among REST rules, one is to ensure that the user gets any specific data—also referred to as a resource—if a specific URL is linked. In this context, URL is known as a request and the data that is received by the user is known as a response.

What Makes Up a Request?

Usually, there are four components make up a request.

  1. The endpoint
  2. The method
  3. The headers
  4. The data

The Endpoint

The URL that is requested by a user is known as an endpoint. It comprises of the following structure.

root-endpoint/?

Here, the “root-endpoint” signifies an API’s starting point from which a user requests data. For instance, Twitter’s root-endpoint API is https://apitwitter.com.

The path indicates the requested resource. Just think of it as a simple automated menu: you get what you click on. Paths can be accessed the same way as a website’s sections. For instance, if there is a website https://techtalkwithbhatt.com on which you want to check all the tagged posts on Java, then you can go to https://techtalkwithbhatt.com/tag/java. Here, as you can guess, https://techtalkwithbhatt.com is the root-endpoint while the path is the /tag/java.

In order to check the available paths, you must go through the documentation of that specific API. For instance, suppose you have to check repositories of a user via the Github’s API; you can simply go to this link and learn the path.

/users/:username/repos

In place of the colons in the above path, you have to alter and add any username of your choice. For instance, if there is a user named sarveshbhatt, then you should write the following:

https://api.github.com/users/sarveshbhatt/repos

Lastly, we also have the query parameters in the endpoint. Strictly speaking, they do not come under the REST architecture but they are extensively used in the APIs. Query parameters offer the functionality to change your request by adding key-value pairs. These pairs start off with a question mark and all parameter pairs are separated by adding a “&” character. The format is listed below.

?queryone=valueone&querytwo=valuetwo

Using Curl

These requests can be sent with different languages. For example, Python developers use Python Requests; JavaScript developers use the jQuery’s Ajax method and the Fetch API.

However, for this post, we are going to use a user-friendly utility that is already installed in your computer, cURL. Since API documentation typically resembles cURL, therefore if you can get the hang of it then you can understand any API documentation—allowing you to create requests easily.

But first, let’s check whether or not cURL is installed on your PC. Depending on your OS, open the Terminal and enter the following.

curl –version.

In response, you can get a result which looks similar to the following screen.

 

Those who do not have CURL can see a “command not found” error. To install curl, you can check this link. In order to work with cURL, you can enter “curl” with any endpoint. For instance, to check the Github root endpoint, you can use the following line.

curl https://api.github.com

The resulting response can seem like the following.

Similarly, you can check the repositories of a user by adding a path to the endpoint—we discussed how to do this above. Just add “curl” and write the following command.

curl https://api.github.com/users/Sarveshbhatt/repos

However, keep in mind that while using query parameters in the command line, you have to add a backslash (“\”) prior to the question mark (“q”) and “=” characters. The reason behind this is that both the “=” and “?” are recognized by the command line as the special characters. Therefore you have to add “\” so they are interpreted by the command line as a part of the command.

JSON

JSON stands for JavaScript Object Notation; a popular format used to send and request data with a REST API. If you send a request to Github, then it can send you back a response that bears the JSON format. As the name suggests, a JSON object is essentially an object in JavaScript. JSON’s property-value pairs are encompassed with a double quotation mark.

The Method

Going back to the request, now let’s come to the second component: the method. The method is simply a request type which is sent to the server. The method types are: GET, POST, PUT, PATCH and DELETE.

The function of these methods is to give meaning to the request. CRUD (Create, Read, Update, and Delete) operations are performed by these methods.

  • GET

 

 

The GET request is used when a server resource is needed. When it is used, the server searches for your requested data and sends it to you. It is the default request method.

  • POST

The POST request generates a new resource on the server. When you use this request, the server generates a new record in the DB and responds to you about its success.

  • PUT and PATCH

These requests provide an update on a server’s resource. When these requests are used, a database entry is updated by the server and you get a message about its success.

  • DELETE

The DELETE request effectively eliminates a server resource. When you use this request, it performs a deletion in the database entry and informs you about its success.

 

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