What language is REST API written in?

REST (Representational State Transfer) APIs have become the standard for building web services and web APIs. As REST has gained popularity, developers have implemented REST APIs in a variety of programming languages. However, some languages are better suited for building REST APIs than others.

What is a REST API?

First, let’s define what exactly a REST API is. REST stands for Representational State Transfer and is an architectural style for building web services. A REST API allows clients to access and manipulate resources hosted on a server using a predefined set of stateless operations.

REST APIs use HTTP requests like GET, POST, PUT, and DELETE to perform create, read, update, and delete operations. Resources in a REST API are identified using URIs (Uniform Resource Identifiers). REST APIs return data in easy to parse formats like JSON and XML.

Some key principles of REST APIs include:

• Stateless – No client session data is stored on the server
• Cacheable – API responses can be cached to improve performance
• Client-Server separation – Client and server can evolve independently
• Uniform interface – All resources can be accessed in the same manner

By following REST principles, APIs can be flexible, lightweight, and fast. This has helped fuel the popularity of REST as an API design style.

Evaluating Languages for Building REST APIs

When choosing a language for implementing a REST API, there are several factors to consider:

• Popularity – Languages with strong community support make development easier.
• Performance – Speed and ability to handle concurrent requests.
• Scalability – Can easily add resources to handle more load.
• Simplicity – Clean and consistent syntax for readable code.
• Libraries – Availability of web frameworks and helper libraries.
• Hosting – Platforms and cloud services that support the language.

Based on these criteria, let’s look at some of the most popular languages for building REST APIs and their key advantages.

JavaScript

JavaScript is one of the most popular languages for REST API development. Here are some reasons why:

• JavaScript has a huge community and is the language of the web.
• The Node.js runtime allows building fast, scalable REST APIs.
• npm package manager provides access to hundreds of useful libraries.
• Express.js and Fastify are excellent JavaScript web frameworks.
• Easy to find JavaScript developers and Node.js hosting options.

With Node.js, APIs can handle tens of thousands of concurrent requests easily. The non-blocking I/O model makes Node ideal for I/O bound REST APIs. Template systems like EJS make rendering views easy.

Example REST API in JavaScript

// Import Express 
const express = require('express')

// Create Express app 
const app = express()

// Respond to GET requests to /api/users
app.get('/api/users', (req, res) => {
  // Get users from database or file
  
  // Return JSON response
  res.json(users) 
})

// Listen on port 5000
app.listen(5000, () => {
  console.log('REST API listening on port 5000')
})

This simple example responds to GET requests to /api/users and returns JSON user data. Building a production-ready REST API will require more code but Express.js handles the routing and JSON serialization under the hood.

Python

Python is another very popular server-side language well suited for REST APIs:

• Simple and readable syntax makes Python easy to learn.
• Many libraries and frameworks specifically for REST APIs.
• Flask is a powerful Python web framework for REST APIs.
• Django REST Framework adds REST capabilities to Django.
• Fast performance for high-load REST API applications.

Python code tends to be more concise compared to other languages like Java or C#. This improves developer productivity. The Python standard library includes packages like http.server for building simple REST APIs.

Example REST API in Python

from flask import Flask

app = Flask(__name__)

@app.route('/api/users')
def get_users():
  users = # get list of users
  return jsonify(users)

if __name__ == '__main__':
  app.run(debug=True) 

This Flask app creates the /api/users route that returns JSON user data. Flask provides built-in JSON support through the jsonify function. For more complex APIs, Flask extensions like Flask-RESTful add additional features.

Java

Java is a robust, mature language that is a popular choice for REST API development:

• Statically typed nature of Java catches bugs during compilation.
• The JVM allows Java to run fast and efficiently at scale.
• Spring Boot simplifies API development with automatic configuration.
• Spring MVC provides a model-view-controller framework for REST APIs.
• Hibernate ORM enables mapping Java objects to database tables.

Java EE application servers like WildFly also provide tools for building REST web services. The strong typing in Java prevents bugs but can mean more code compared to dynamic languages.

Example REST API in Java

@RestController
@RequestMapping("/api/users")
public class UserController {

  @GetMapping
  public List getUsers() {
    
    // Get users from DAO 
    
    return users;
  }

}

This Spring RestController exposes a /api/users endpoint that returns a list of users. The @RestController and @RequestMapping annotations handle the routing. For a production API, Spring Bean Validation can be used to validate data.

PHP

PHP is a popular server-side scripting language capable of building REST APIs:

• PHP runs on most web servers like Apache and Nginx.
• Built-in libraries for tasks like handling HTTP requests.
• Large community of PHP developers to draw on.
• Frameworks like Laravel and Slim PHP enable quick REST API creation.
• Good support for databases like MySQL and PostgreSQL.

Since PHP wasn’t designed specifically for APIs, it can be less ideal compared to Node or Python. But if your team has more experience in PHP, it can still be a good choice.

Example REST API in PHP

get('/api/users', function ($req, $res, $args) {
  // Fetch list of users
  
  return $res->withJson($users); 
});

$app->run();

This simple Slim application implements a /api/users route that responds with JSON user data. The Slim framework provides a router, middleware, and error handling out of the box.

Ruby

Ruby is another scripting language well suited for REST APIs:

• Ruby on Rails web framework streamlines REST API creation.
• Rails Active Record ORM for simple database access.
• Large library of Gems for added functionality.
• Fast performance with support for threading and caching.
• Code readability from Ruby’s clean syntax.

Ruby may not be as fast as other compiled languages. But Rails makes it simple to scaffold a REST API with just a few commands. Rails has seen wide adoption, especially by startups.

Example REST API in Ruby

# config/routes.rb

Rails.application.routes.draw do
  namespace :api do
    resources :users
  end
end

# Returns JSON list of users
GET /api/users 

Here Rails automatically creates a route for /api/users that responds with JSON from the User model. Rails routing removes the boilerplate code needed to build API endpoints.

Other Languages

There are many other languages that can also be used for implementing REST APIs:

• C# – ASP.NET Core provides an efficient REST API framework.
• Go – Go’s goroutines enable scalable concurrent REST APIs.
• Rust – Rust focuses on speed, safety, and concurrency.
• Scala – Combines object-oriented and functional programming.
• Kotlin – JetBrains created this new JVM language.

These languages have great performance, safety, and concurrency features. But may not have as much library support or hosting options compared to more mainstream languages.

Conclusion

In summary, REST APIs can be implemented in virtually any programming language. However, JavaScript, Python, Java, PHP, and Ruby tend to be the most popular choices.

JavaScript with Node.js provides outstanding performance and scalability. Python offers simplicity and great libraries like Flask. Java is robust and good for larger organizations. PHP runs on most web servers. And Ruby on Rails streamlines development.

The best language ultimately depends on your team’s skills and project requirements. All of these languages can successfully power production REST APIs with proper planning.