JsonRenderer.php

<?php

namespace Drupal\common_test\Render\MainContent;

use Drupal\Core\Cache\CacheableJsonResponse;
use Drupal\Core\Cache\CacheableMetadata;
use Drupal\Core\Controller\TitleResolverInterface;
use Drupal\Core\Render\MainContent\MainContentRendererInterface;
use Drupal\Core\Render\RendererInterface;
use Drupal\Core\Routing\RouteMatchInterface;
use Symfony\Component\HttpFoundation\Request;

/**
 * Default main content renderer for JSON requests.
 */
class JsonRenderer implements MainContentRendererInterface {
    
    /**
     * The title resolver.
     *
     * @var \Drupal\Core\Controller\TitleResolverInterface
     */
    protected $titleResolver;
    
    /**
     * The renderer service.
     *
     * @var \Drupal\Core\Render\RendererInterface
     */
    protected $renderer;
    
    /**
     * Constructs a new JsonRenderer.
     *
     * @param \Drupal\Core\Controller\TitleResolverInterface $title_resolver
     *   The title resolver.
     * @param \Drupal\Core\Render\RendererInterface $renderer
     *   The renderer service.
     */
    public function __construct(TitleResolverInterface $title_resolver, RendererInterface $renderer) {
        $this->titleResolver = $title_resolver;
        $this->renderer = $renderer;
    }
    
    /**
     * {@inheritdoc}
     */
    public function renderResponse(array $main_content, Request $request, RouteMatchInterface $route_match) {
        $json = [];
        $json['content'] = (string) $this->renderer
            ->renderRoot($main_content);
        if (!empty($main_content['#title'])) {
            $json['title'] = (string) $main_content['#title'];
        }
        else {
            $json['title'] = (string) $this->titleResolver
                ->getTitle($request, $route_match->getRouteObject());
        }
        $response = new CacheableJsonResponse($json, 200);
        $response->addCacheableDependency(CacheableMetadata::createFromRenderArray($main_content));
        return $response;
    }

}