How to create a JSON web service on drupal 8 ?

This is a simple example of a web service. For the example, We will make a service to multiply two numbers.

Create JSON WebService module

Create a module.

Here : mywebservice

Create route, the Web Service path.

Example:

mywebservice.multiply:

  path: '/mywebservice/maths/multiply'

  defaults:

    _controller: '\Drupal\mywebservice\Controller\MyWebService::multiply'

    _title: 'MyWebService'

  requirements:

    _permission: 'access content'

Create webservice Controller

Example:

<?php

//

namespace Drupal\mywebservice\Controller;

//

use Drupal\Core\Controller\ControllerBase;

use Symfony\Component\HttpFoundation\JsonResponse;

/**

 * Class MyWebService.

 */

class MyWebService extends ControllerBase {

  /**

   * Multiply.

   */

  public function multiply() {

    $request = \Drupal::request();

    $output['a'] = $request->get('a');

    $output['b'] = $request->get('b');

    $output['result'] = $output['a'] * $output['b'];

    return new JsonResponse($output);

  }

}

Test the web service

Visit : http://yourdomain.loc/mywebservice/maths/multiply

Must return a JSON : {"a":null,"b":null,"result":0}

Visit : http://yourdomain.loc/mywebservice/maths/multiply?a=5&b=2

Must return a JSON : {"a":"5","b":"2","result":10}