AcceptHeaderMiddleware.php

<?php

declare (strict_types=1);
namespace Drupal\accept_header_routing_test;

use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\HttpFoundation\Response;
use Symfony\Component\HttpKernel\HttpKernelInterface;

/**
 * Example implementation of "accept header"-based content negotiation.
 */
class AcceptHeaderMiddleware implements HttpKernelInterface {
  
  /**
   * The app kernel.
   */
  protected HttpKernelInterface $httpKernel;
  
  /**
   * Constructs a new AcceptHeaderMiddleware instance.
   *
   * @param \Symfony\Component\HttpKernel\HttpKernelInterface $http_kernel
   *   The app.
   */
  public function __construct(HttpKernelInterface $http_kernel) {
    $this->httpKernel = $http_kernel;
  }
  
  /**
   * {@inheritdoc}
   */
  public function handle(Request $request, $type = self::MAIN_REQUEST, $catch = TRUE) : Response {
    $mapping = [
      'application/json' => 'json',
      'application/xml' => 'xml',
      'text/html' => 'html',
    ];
    $accept = $request->headers
      ->get('Accept') ?: [
      'text/html',
    ];
    if (isset($mapping[$accept[0]])) {
      $request->setRequestFormat($mapping[$accept[0]]);
    }
    return $this->httpKernel
      ->handle($request, $type, $catch);
  }

}