What is a RESTful API?

REST APIs and why they are important in Backend Development.

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If you’ve worked on any significant web project or mobile project, you’ve probably encountered REST APIs.

REST stands for Representational State Transfer. This means that when a client requests a resource using a REST API, the server transfers back the current state of the resource in a standardized representation.

Representational State Transfer (REST) is a software architecture that imposes conditions on how an API should work. REST was initially created as a guideline to manage communication on a complex network like the internet. You can use REST-based architecture to support high-performing and reliable communication at scale. You can easily implement and modify it, bringing visibility and cross-platform portability to any API system.

API developers can design APIs using several different architectures. APIs that follow the REST architectural style are called REST APIs. Web services that implement REST architecture are called RESTful web services. The term RESTful API generally refers to RESTful web APIs. However, you can use the terms REST API and RESTful API interchangeably.

The Six Rules of REST APIs

To fully benefit from REST functionality, APIs must meet five required and one optional requirement, laying the groundwork for a fast and versatile API.

Uniform interface

The uniform interface is fundamental to the design of any RESTful web service. It indicates that the server transfers information in a standard format. In REST, we call the formatted resource a representation. This format can differ from how the server application internally represents the resource. For example, the server can store data as text but send it in an HTML representation format.

Uniform interface imposes four architectural constraints:

1. Requests should identify resources. They do so by using a uniform resource identifier.
2. Clients have enough information in the resource representation. They can use it to modify or delete the resource if they want to. The server meets this condition by sending metadata that describes the resource further.
3. Clients receive information about how to process the representation further. The server achieves this by sending self-descriptive messages. The messages contain metadata about how the client can best use them.
4. Clients receive information about all other resources they need to complete a task. The server achieves this by sending hyperlinks in the representation. Clients can use these hyperlinks to dynamically discover more resources.

Statelessness

In REST architecture, statelessness refers to a communication method. In this method, the server completes every client request independently of all previous requests. Clients can request resources in any order. Every request is stateless or isolated from other requests. This REST API design constraint implies that the server can completely understand and fulfill the request every time.

Layered system

In a layered system architecture, the client can connect to other authorized intermediaries between the client and server, and it will still receive responses from the server. Servers can also pass on requests to other servers. You can design your RESTful web service to run on several servers. These servers could have multiple layers, such as security, application, and business logic. These layers work together to fulfill client requests. These layers remain invisible to the client.

Cacheability

RESTful web services support caching. This process stores some responses on the client or on an intermediary. This improves server response time. For example, suppose that you visit a website that has common header and footer images on every page. Every time you visit a new website page, the server must resend the same images. To avoid this, the client caches or stores these images after the first response. Then, the client uses the images directly from the cache. RESTful web services control caching using API responses. The responses define themselves as cacheable or noncacheable.

Code on demand

In REST architectural style, servers can temporarily extend or customize client functionality. They do this by transferring software programming code to the client. For example, when you fill out a registration form on any website, your browser immediately highlights any mistakes you make. For instance, it will flag incorrect phone numbers. It can do this because of the code sent by the server.

Why Use REST APIs?

REST APIs are widely used by popular companies like Facebook, YouTube, Twitter, and Google. The REST framework, developed in 2000 by computer scientist Roy Fielding, is an essential component of how we view, modify, and transfer content online.

REST APIs offer several benefits that make them an excellent system for web applications. These APIs are flexible and can handle various requests, sending data in many formats.

REST APIs are scalable, designed to communicate between two pieces of software, regardless of their size or capability. As web applications grow and add more resources, their REST APIs can easily handle the increasing amount and variety of requests.

REST APIs incorporate existing web technologies, making them relatively easy to build and use. To request a resource via a REST API, all you need to do is provide its URL.

How do RESTful APIs work?

The basic function of a RESTful API is the same as browsing the internet. The client contacts the server by using the API when it requires a resource. API developers explain how the client should use the REST API in the server application’s API documentation. These are the general steps for any REST API call:

1. The client sends a request to the server. The client follows the API documentation to format the request in a way that the server understands.
2. The server authenticates the client. It confirms that the client can make that request.
3. The server receives the request and processes it internally.
4. The server returns a response to the client. The response contains information that tells the client whether the request was successful. The response also includes any information that the client requested.

The details of the REST API request and response vary slightly. This depends on how the API developers design the API.

What does the RESTful API client request contain?

RESTful APIs require requests to contain the following main components:

Unique resource identifier

The server identifies each resource with unique resource identifiers. For REST services, the server typically uses a Uniform Resource Locator (URL) to identify resources. The URL specifies the path to the resource. A URL is similar to the website address that you enter into your browser to visit any webpage. The URL is also called the request endpoint. It clearly specifies to the server what the client requires.

Method

Developers often implement RESTful APIs using the Hypertext Transfer Protocol (HTTP). An HTTP method tells the server what it needs to do to the resource. The following are four common HTTP methods:

GET

Clients use GET to access resources that are located at the specified URL on the server. They can cache GET requests. They send parameters in the RESTful API request to instruct the server to filter data before sending.

POST

Clients use POST to send data to the server. They include the data representation with the request. Sending multiple POST requests creates duplicate resources.

PUT

Clients use PUT to update existing resources on the server. Unlike POST, making multiple PUT requests to a RESTful web service yields the same result.

DELETE

Clients use the DELETE request to remove the resource. A DELETE request can change the server state. However, if the user does not have appropriate authentication, the request fails.

HTTP headers

Request headers are the metadata exchanged between the client and server. For instance, the request header indicates the format of the request and response. It provides information about request status, and so on.

Data

REST API requests might include data for the POST, PUT, and other HTTP methods to work successfully.

Parameters

RESTful API requests can include parameters. These give the server more details about what needs to be done. The following are some different types of parameters:

• Path parameters that specify URL details.
• Query parameters that request more information about the resource.
• Cookie parameters that authenticate clients quickly.

What are RESTful API authentication methods?

A RESTful web service must authenticate requests before it can send a response. Authentication is the process of verifying an identity. For example, you can prove your identity by showing an ID card or driver’s license. Similarly, RESTful service clients must prove their identity to the server to establish trust.

RESTful API has four common authentication methods:

HTTP authentication

HTTP defines some authentication schemes. You can use them directly when implementing REST API. The following are two of these schemes:

Basic authentication

In basic authentication, the client includes a username and password in the request header. It encodes them with base64. Base64 is an encoding technique that converts the pair into a set of 64 characters for safe transmission.

Bearer authentication

The term bearer authentication refers to the process of giving access control to the token bearer. The bearer token is an encrypted string of characters that the server generates in response to a login request. The client sends the token in the request headers to access resources.

API keys

API keys are another option for REST API authentication. In this approach, the server assigns a unique generated value to a first-time client. Whenever the client tries to access resources, it uses the unique API key to verify itself. API keys are less secure. The client has to transmit the key, making it vulnerable to network theft.

OAuth

OAuth combines passwords and tokens for highly secure login access to any system. The server first requests a password. Then, it asks for an additional token to complete the authorization process. It can check the token at any time and also over time with a specific scope and longevity.

In summary, RESTful APIs are a crucial element in modern web development, allowing for efficient and reliable communication between different systems and applications. By understanding the key principles and best practices of RESTful API design, developers can create highly functional and scalable APIs that can help power the next generation of web and mobile applications.

So, if you are a developer looking to create APIs that are easy to use, maintain and scale, make sure to keep these principles in mind. And if you found this article helpful, don’t forget to like, share and comment below to let me know what you think.