class RouteSubscriber

1. 8.x drupal/core/modules/views/lib/Drupal/views/EventSubscriber/RouteSubscriber.php \Drupal\views\EventSubscriber\RouteSubscriber
2. 8.x drupal/core/modules/field_ui/lib/Drupal/field_ui/Routing/RouteSubscriber.php \Drupal\field_ui\Routing\RouteSubscriber
3. 8.x drupal/core/modules/rest/lib/Drupal/rest/EventSubscriber/RouteSubscriber.php \Drupal\rest\EventSubscriber\RouteSubscriber

rest.services.yml in drupal/core/modules/rest/rest.services.yml

drupal/core/modules/rest/rest.services.yml

rest.route_subscriber in drupal/core/modules/rest/rest.services.yml

Drupal\rest\EventSubscriber\RouteSubscriber

class RouteSubscriber implements EventSubscriberInterface {

  /**
   * The plugin manager for REST plugins.
   *
   * @var \Drupal\rest\Plugin\Type\ResourcePluginManager
   */
  protected $manager;

  /**
   * The Drupal configuration factory.
   *
   * @var \Drupal\Core\Config\ConfigFactory
   */
  protected $config;

  /**
   * Constructs a RouteSubscriber object.
   *
   * @param \Drupal\rest\Plugin\Type\ResourcePluginManager $manager
   *   The resource plugin manager.
   * @param \Drupal\Core\Config\ConfigFactory $config
   *   The configuration factory holding resource settings.
   */
  public function __construct(ResourcePluginManager $manager, ConfigFactory $config) {
    $this->manager = $manager;
    $this->config = $config;
  }

  /**
   * Adds routes to enabled REST resources.
   *
   * @param \Drupal\Core\Routing\RouteBuildEvent $event
   *   The route building event.
   */
  public function dynamicRoutes(RouteBuildEvent $event) {
    $collection = $event
      ->getRouteCollection();
    $enabled_resources = $this->config
      ->get('rest.settings')
      ->load()
      ->get('resources');

    // Iterate over all enabled resource plugins.
    foreach ($enabled_resources as $id => $enabled_methods) {
      $plugin = $this->manager
        ->getInstance(array(
        'id' => $id,
      ));
      foreach ($plugin
        ->routes() as $name => $route) {
        $method = $route
          ->getRequirement('_method');

        // Only expose routes where the method is enabled in the configuration.
        if ($method && isset($enabled_methods[$method])) {
          $route
            ->setRequirement('_access_rest_csrf', 'TRUE');

          // If the array of configured format restrictions is empty for a
          // method always add the route.
          if (empty($enabled_methods[$method])) {
            $collection
              ->add("rest.{$name}", $route);
            continue;
          }

          // If there is no format requirement or if it matches the
          // configuration also add the route.
          $format_requirement = $route
            ->getRequirement('_format');
          if (!$format_requirement || isset($enabled_methods[$method][$format_requirement])) {
            $collection
              ->add("rest.{$name}", $route);
          }
        }
      }
    }
  }

  /**
   * Implements EventSubscriberInterface::getSubscribedEvents().
   */
  static function getSubscribedEvents() {
    $events[RoutingEvents::DYNAMIC] = 'dynamicRoutes';
    return $events;
  }

}