What is RESTful API?
Since the invention of the internet, we have been using different applications and web pages to get data for various resources. However, have you ever thought, where does this data come from? Well, it’s the servers from where we get the data. So in this article on What is REST API, let us look into how a client communicates with the servers to extract the required information.
What is REST API?
So, over here, you have an object and you are sending the state of an object. This is why REST is known as Representational State Transfer.
The architectural style of REST helps in leveraging the lesser use of bandwidth to make an application more suitable for the internet. It is often regarded as the “language of the internet” and is completely based on the resources.
Now that you know what it is, let us move on and understand the need for REST API.
Why use REST API?
Consider a scenario where you are using the Book My Show app. Now, obviously, this application needs a lot of Input data, as the data present in the application is never static. Either it is movies getting released on a frequent basis, or various cities showing different languages movies at various times of the day. It’s never static which implies the fact that data is always changing in these applications.
Now, where do you think we get this data from?
Well, this data is received from the Server or most commonly known as a Web-server. So, the client requests the server for the required information, via an API, and then, the server sends a response to the client.
Over here, the response sent to the client is in the form of an HTML Web Page. But, do you think this is an apt response that you would expect when you send a request?
Well, I am assuming the fact that you would say NO. Since, you would prefer the data to be returned in the form of a structured format, rather than the complete Web page.
So, for such reasons, the data returned by the server, in response to the request of the client is either in the format of JSON or XML. Both JSON and XML formats have a proper hierarchical structure of data.
Now, this sounds quite simple, right?
But, the only issue which is present in this framework until now is that you have to use a lot of methods to get the required information. To the fact, using these methods to retrieve information, becomes quite cumbersome when you require complex data.
So, this is where REST API comes into the picture. The REST API creates an object, and thereafter sends the values of an object in response to the client. It breaks down a transaction in order to create small modules. Now, each of these modules is used to address a specific part of the transaction. This approach provides more flexibility but requires a lot of effort to be built from the very scratch.
Moving ahead, let us take a look at the Principles of REST API.
Principles of REST API
Well, there are six ground principles laid down by Dr. Fielding who was the one to define the REST API design in 2000. Below are the six guiding principles of REST:
Stateless
The requests sent from a client to a server will contain all the required information to make the server understand the requests sent from the client. This can be either a part of URL, query-string parameters, body, or even headers. The URL is used to uniquely identify the resource and the body holds the state of the requesting resource. Once the server processes the request, a response is sent to the client through body, status or headers
Client-Server
The client-server architecture enables a uniform interface and separates clients from the servers. This enhances the portability across multiple platforms as well as the scalability of the server components.
Uniform Interface
To obtain the uniformity throughout the application, REST has the following four interface constraints:
- Resource identification
- Resource Manipulation using representations
- Self-descriptive messages
- Hypermedia as the engine of application state
Cacheable
In order to provide a better performance, the applications are often made cacheable. This is done by labeling the response from the server as cacheable or non-cacheable either implicitly or explicitly. If the response is defined as cacheable, then the client cache can reuse the response data for equivalent responses in the future.
Layered system
The layered system architecture allows an application to be more stable by limiting component behavior. This type of architecture helps in enhancing the application’s security as components in each layer cannot interact beyond the next immediate layer they are in. Also, it enables load balancing and provides shared caches for promoting scalability.
Code on demand
This is an optional constraint and is used the least. It permits a clients code or applets to be downloaded and to be used within the application. In essence, it simplifies the clients by creating a smart application which doesn’t rely on its own code structure.
Now, that you know the principles behind REST API, next let’s look into the Methods of REST API.
Methods of REST API
All of us working with the technology of the web, do CRUD operations. When I say CRUD operations, I mean that we create a resource, read a resource, update a resource and delete a resource. Now, to do these actions, you can actually use the HTTP methods, which are nothing but the REST API Methods. Refer below.
Now that you know what is a REST API and what all you need to mind in order to deliver an efficient application, let’s dive deeper and see the process of building REST API.