What is REST API?

Introduction

REST (Representational State Transfer) is an architectural paradigm for establishing web services that define a set of requirements. REST API is a straightforward and flexible approach to accessing online services without going through any processing.

Because REST utilizes less bandwidth, is simple, and is adaptable, it is recommended over the more robust Simple Object Access Protocol (SOAP) technology. It's used to retrieve or send data from a web service. Only HTTP requests are used in all REST API communication.

What is an API?

API stands for Application Programming Interface. It is a set of definitions and protocols for creating and integrating software applications. It's sometimes referred to as a contract between an information supplier and an information user, outlining the content that the consumer (the call) must offer and the producer’s content (the response). For example, the API design for a weather service could require the user to provide a zip code and the producer to respond with a two-part response, the first of which is the high temperature and the second of which is the low temperature.

In other words, if you want to connect with a computer or system to retrieve information or execute a function, an API allows you to convey your request to the system so that it can comprehend and respond.

An API can be considered a middleman between users or customers and the resources or web services they want. It's also a mechanism for a company to exchange resources and information while retaining security, control, and authentication—the ability to govern who has access to what.

REST API (Representational State Transfer Application Programming Interface) is an architectural style for designing networked applications. It uses HTTP requests (GET, POST, PUT, DELETE) to perform operations on resources, typically in a stateless manner. REST APIs are widely used for web services due to their simplicity, scalability, and ease of integration.

How do REST APIs Work?

It's crucial to understand resources to understand how REST APIs work. Any information that can be named, such as a document or image, a collection of other resources, a non-virtual object, and so on, can be considered a resource. On the other hand, REST uses a resource identifier to identify the individual resource engaged in component interaction.

The method refers to the kind of request you make to the server.

The following are the five main resource methods connected with REST APIs:

GET:

To read (or get) a representation of a resource, use the GET method. The safe path produces an XML or JSON representation with an HTTP response code of 200. (OK). It usually produces a 404 (NOT FOUND) or 400 (Issue) code in the event of an error (BAD REQUEST). To obtain hello.htm, the following example uses the GET method:

GET /hello.htm HTTP/1.1

User-Agent: Mozilla/4.0 (compatible; MSIE5.01; Windows NT)

Host: www.tutorialspoint.com

Accept-Language: en-us

Accept-Encoding: gzip, deflate

Connection: Keep-Alive

POST:

To create new resources, the POST verb is frequently used. It's utilized to make subordinate resources in particular. That is, it is subservient to another resource (for example, a parent). Return HTTP status 201 on successful creation, along with a Location header containing a link to the newly created resource with the 201 HTTP status. The following example uses the POST method to deliver form data to the server, which is then processed by the process.cgi and returned as a response:

POST /cgi-bin/process.cgi HTTP/1.1

User-Agent: Mozilla/4.0 (compatible; MSIE5.01; Windows NT)

Host: www.tutorialspoint.com

Content-Type: text/xml; charset=utf-8

Content-Length: 88

Accept-Language: en-us

Accept-Encoding: gzip, deflate

Connection: Keep-Alive

PUT:

It's utilized to keep the capabilities up to date. On the other hand, PUT can be used to create a resource when the client chooses the resource ID rather than the server. In other words, if the PUT is to a URI with the value of a resource ID, that does not exist. Return 200 (or 204 if no content is returned in the body) from a PUT after a successful update. Return HTTP status 201 on successful creation when using PUT. The following example instructs the server to save the specified entity-body in the server's root directory, hello.htm:

PUT /hello.htm HTTP/1.1

User-Agent: Mozilla/4.0 (compatible; MSIE5.01; Windows NT)

Host: www.tutorialspoint.com

Accept-Language: en-us

Connection: Keep-Alive

Content-type: text/html

Content-Length: 182

DELETE:

It's used to get rid of a resource with a URI. Return HTTP status 200 (OK) and a response body upon successful deletion. The following example asks the server to delete the file hello.htm from the server's root directory:

DELETE /hello.htm HTTP/1.1

User-Agent: Mozilla/4.0 (compatible; MSIE5.01; Windows NT)

Host: www.tutorialspoint.com

Accept-Language: en-us

Connection: Keep-Alive

PATCH:

It's used to change the capabilities. The PATCH request simply has to include the resource's changes, not the entire resource. This is similar to PUT, except the body contains a series of instructions indicating how to modify a resource currently on the server to create a new version. This indicates that the PATCH body should be written in a patch language like JSON Patch or XML Patch, rather than merely a modified section of the resource. An example for using the PATCH method is given below:

PATCH /file.txt HTTP/1.1

Host: www.example.com

Content-Type: application/example

If-Match: "e0023aa4e"

Content-Length: 100

Purpose of REST APIs

One of the main advantages of REST is that it offers a great deal of freedom, allowing you to accomplish more with this API. REST APIs can be used for a variety of things, as shown below:

Cloud applications

Because REST API calls are stateless, they are valuable in cloud applications. Stateless components can effortlessly redeploy and scale to suit load changes if something goes wrong.

Cloud services

Because you'd need to manage how the URL is decoded to bind to a service through an API, REST is also helpful in cloud services. Cloud computing and microservices, on the other hand, will surely make RESTful API design the norm in the future.

Web use

These APIs can be accessed from a client-side web project, an iOS app, an IoT device, or a Windows Phone because REST is not bound to client-side technologies. You may develop the infrastructure for your company without having to worry about being bound to a specific client-side stack.

Advantages of REST APIs

For a variety of reasons, REST is preferred over SOAP. REST APIs have the following advantages:

Scalability: The product may easily be grown by development teams due to the separation of client and server.
Flexibility and Portability: It is feasible to migrate from one server to another since REST-style APIs require data from one of the requests to be sent successfully. It is also possible to make updates to the database at any point in time.
Independence: The protocol's separation of client and server makes it easier for different parts of a project to develop separately. REST APIs are also adaptive to the working syntax and platform, allowing for simultaneous testing of many settings while building.

Challenges of Using REST APIs

Lack of Standardization – REST APIs do not follow a strict standard, leading to inconsistencies in implementation across different platforms.
Security Concerns – APIs are vulnerable to attacks like SQL injection, cross-site scripting (XSS), and DDoS attacks, requiring strong authentication and encryption.
Handling Versioning – Updating APIs without breaking existing integrations is challenging, requiring proper version control strategies.
Performance Bottlenecks – Frequent API calls can increase latency and overload servers, affecting application performance.
Error Handling Complexity – Proper error messages and handling mechanisms are necessary for better debugging and troubleshooting.
Limited Support for Real-Time Communication – REST is stateless, making it inefficient for real-time data updates compared to WebSockets.
Data Overfetching or Underfetching – Clients may receive too much or too little data, impacting performance and increasing bandwidth usage.

To overcome these challenges, developers must follow best practices like authentication, caching, proper API documentation, and efficient request handling.

Architectural Constraints of REST API

The following are six architectural constraints that each web service must adhere to:

Uniform Interface
Stateless
Cacheable
Client-Server
Layered System
Code on Demand

Uniform Interface

Multiple architectural constraints are necessary to control the behavior of components to achieve a unified interface. Furthermore, resources should be distinct so that a single URL can identify them.

Stateless

The information needed for the server to interpret and process the request from the client must be included in the request. The server is unable to store any information about the client's current state.

Cacheable

Cacheable and non-cacheable data must be identified in response to a request.

Client-Server

The consistent interface distinguishes between user and data storage concerns. The client's domain is concerned with user interface and request collection, whereas the server's domain is concerned with data access, workload management, and security. Because the client and server are separated, each may be created and improved independently of the other.

Layered System

REST enables the creation of a hierarchical architecture. As a result, each component is unable to see beyond the layer with which it is communicating.

Code on Demand

There is greater client functionality with REST APIs because they download and execute code in applets or scripts. A server will frequently return a static representation of resources, such as XML or JSON. When necessary, servers can also communicate executable codes to the client.

Applications of REST APIs

Web and Mobile Applications – REST APIs enable communication between front-end and back-end services, making them essential for dynamic websites and mobile apps.
Cloud Services Integration – REST APIs allow seamless interaction with cloud platforms like AWS, Google Cloud, and Azure for storage, computing, and analytics.
IoT (Internet of Things) – IoT devices use REST APIs to send and receive data over the internet, enabling smart home automation, healthcare monitoring, and industrial automation.
Social Media Integration – Platforms like Facebook, Twitter, and Instagram provide REST APIs for developers to integrate social sharing, authentication, and user engagement.
E-commerce and Payment Processing – REST APIs are used for secure transactions, connecting online stores with payment gateways like PayPal, Stripe, and Razorpay.
Microservices Architecture – REST APIs allow independent microservices to communicate efficiently, enhancing scalability, flexibility, and maintainability.
Data Analytics and AI Integration – APIs help fetch real-time data for business intelligence, AI models, and machine learning applications.

Difference between REST APIs and SOAPs?

SOAP and REST APIs are not comparable in any way. However, there are a few items to consider below that will help you pick between these two web services. Here are several examples:

REST stands for REpresentational State Transfer, and SOAP is for Simple Object Access Protocol.
Because SOAP is a protocol, it adheres to tight guidelines to allow communication between the client and the server. In contrast, REST is an architectural style that does not comply with any set of guidelines but does adhere to six limitations outlined by Roy Fielding in 2000. The limitations include Uniform Interface, Client-Server, Stateless, Cacheable, Layered System, and Code on Demand.
SOAP is limited to XML for transmitting information in its message format, whereas REST is not. It is up to the implementer to decide which media type to use, such as XML, JSON, or plain text. Furthermore, REST can use the SOAP protocol, but SOAP cannot make use of REST.
SOAP employs @WebService for service interfaces to business logic, whereas REST uses URIs like @Path instead of interfaces.
SOAP is complex to implement and consumes more bandwidth, but REST is simple to implement and consumes less bandwidth, making it ideal for mobile devices.
SOAP provides several advantages over REST, one of which is that SOAP transactions are ACID-compliant. Some applications demand transactional capability, which SOAP provides but REST does not.
SOAP uses SSL (Secure Socket Layer) and WS-security for security, whereas REST uses SSL and HTTPS. SOAP is favored over REST for dealing with bank account passwords, credit card numbers, and other sensitive information. The security issue is that it depends entirely on your application's requirements; you must implement security on your own. It all comes down to the protocol you choose.

Frequently Asked Questions

What are the 5 basic principles of REST API?

The five basic principles of REST API are: Statelessness, Client-Server Architecture, Cacheability, Uniform Interface, and Layered System, ensuring scalability, flexibility, and efficient data communication.

What does REST stand for?

REST stands for Representational State Transfer, an architectural style used for designing networked applications that follow stateless communication and use standard HTTP methods.

Is Postman a REST API?

No, Postman is not a REST API. It is a tool used for testing and interacting with REST APIs, making requests, and evaluating responses.

Is REST API Frontend or Backend?

A REST API is typically part of the backend. It handles client-server communication, allowing front-end applications to interact with server-side resources.

When to Use REST API?

Use a REST API when you need a stateless, scalable, and flexible way to perform CRUD operations on resources over HTTP, particularly in web applications.

Conclusion

In this blog, we learned about REST APIs and how they work with different requests, such as GET, POST, PUT, and PATCH. We also learned about REST API's advantages and how they compare with SOAP API.

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