Building a Custom REST Resource in Drupal 9 for Node Operations with Sample Responses

/**
 * @file
 * Contains \Drupal\custom_rest_resource\Plugin\rest\resource\CustomRestResource.
 */

namespace Drupal\custom_rest_resource\Plugin\rest\resource;

use Drupal\Core\Entity\EntityTypeManagerInterface;
use Drupal\rest\Plugin\ResourceBase;
use Drupal\rest\ResourceResponse;
use Symfony\Component\DependencyInjection\ContainerInterface;
use Psr\Log\LoggerInterface;

/**
 * Provides a resource to get, create, update, and delete nodes.
 *
 * @RestResource(
 *   id = "custom_rest_resource",
 *   label = @Translation("Custom REST Resource"),
 *   uri_paths = {
 *     "canonical" = "/custom-rest-resource/{nid}",
 *     "https://www.drupal.org/link-relations/create" = "/custom-rest-resource"
 *   }
 * )
 */
class CustomRestResource extends ResourceBase {

  /**
   * A curent user instance.
   *
   * @var \Drupal\Core\Entity\EntityTypeManagerInterface
   */
  protected $entityTypeManager;

  /**
   * Constructs a Drupal\rest\Plugin\ResourceBase object.
   *
   * @param array $configuration
   *   A configuration array containing information about the plugin instance.
   * @param string $plugin_id
   *   The plugin_id for the plugin instance.
   * @param mixed $plugin_definition
   *   The plugin implementation definition.
   * @param array $serializer_formats
   *   The available serialization formats.
   * @param \Psr\Log\LoggerInterface $logger
   *   A logger instance.
   * @param \Drupal\Core\Entity\EntityTypeManagerInterface $entity_type_manager
   *   The entity type manager.
   */
  public function __construct(
    array $configuration,
    $plugin_id,
    $plugin_definition,
    array $serializer_formats,
    LoggerInterface $logger,
    EntityTypeManagerInterface $entity_type_manager
  ) {
    parent::__construct($configuration, $plugin_id, $plugin_definition, $serializer_formats, $logger);

    $this->entityTypeManager = $entity_type_manager;
  }

  /**
   * {@inheritdoc}
   */
  public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition) {
    return new static(
      $configuration,
      $plugin_id,
      $plugin_definition,
      $container->getParameter('serializer.formats'),
      $container->get('logger.factory')->get('custom_rest_resource'),
      $container->get('entity_type.manager')
    );
  }

  /**
   * Responds to GET requests.
   *
   * Returns a node for a given NID.
   *
   * @param int $nid
   *   The node ID.
   *
   * @return \Drupal\rest\ResourceResponse
   *   The response containing the node data.
   */
  public function get($nid) {
    // Implementation for GET request.
    // Load the node using $nid.
    // Build the response array.
    $response = [
      'nid' => $nid,
      'title' => 'Sample Node Title',
      // Add more fields as needed.
    ];
    return new ResourceResponse($response);
  }

  /**
   * Responds to POST requests.
   *
   * Creates a new node.
   *
   * @param array $data
   *   The data to create the node.
   *
   * @return \Drupal\rest\ResourceResponse
   *   The response containing the newly created node data.
   */
  public function post(array $data) {
    // Implementation for POST request.
    // Create a new node using $data.
    // Build the response array.
    $response = [
      'nid' => 123, // ID of the newly created node.
      'message' => 'Node created successfully.',
    ];
    return new ResourceResponse($response);
  }

  /**
   * Responds to DELETE requests.
   *
   * Deletes a node for a given NID.
   *
   * @param int $nid
   *   The node ID to delete.
   *
   * @return \Drupal\rest\ResourceResponse
   *   The response indicating the success of the deletion.
   */
  public function delete($nid) {
    // Implementation for DELETE request.
    // Delete the node using $nid.
    // Build the response array.
    $response = [
      'message' => 'Node deleted successfully.',
    ];
    return new ResourceResponse($response);
  }

  /**
   * Responds to PATCH requests.
   *
   * Updates a node for a given NID.
   *
   * @param int $nid
   *   The node ID to update.
   * @param array $data
   *   The data to update the node.
   *
   * @return \Drupal\rest\ResourceResponse
   *   The response containing the updated node data.
   */
  public function patch($nid, array $data) {
    // Implementation for PATCH request.
    // Update the node using $nid and $data.
    // Build the response array.
    $response = [
      'nid' => $nid,
      'message' => 'Node updated successfully.',
      // Include updated fields as needed.
    ];
    return new ResourceResponse($response);
  }

}

This code defines a custom REST resource in Drupal 9 for performing CRUD operations on nodes. It includes methods for GET, POST, DELETE, and PATCH requests with sample response data.