Building a Custom REST ResourceBase Plugin in Drupal 9 for Node Operations: GET, POST, DELETE, UPDATE with Sample Responses

// Step 1: Define the custom REST ResourceBase Plugin.

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

namespace Drupal\custom_rest\Plugin\rest\resource;

use Drupal\rest\Plugin\ResourceBase;
use Drupal\rest\ResourceResponse;

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

  // Step 2: Implement the GET method.

  /**
   * Responds to GET requests.
   *
   * @param int $nid
   *   The node ID.
   *
   * @return \Drupal\rest\ResourceResponse
   *   The response containing node details.
   */
  public function get($nid) {
    // Fetch node details.
    $node = \Drupal::entityTypeManager()->getStorage('node')->load($nid);

    // Return the response.
    return new ResourceResponse($node->toArray());
  }

  // Step 3: Implement the POST method.

  /**
   * Responds to POST requests.
   *
   * @param array $data
   *   The data to create a node.
   *
   * @return \Drupal\rest\ResourceResponse
   *   The response containing the created node details.
   */
  public function post(array $data) {
    // Create a new node.
    $node = \Drupal\node\Entity\Node::create($data);
    $node->save();

    // Return the response.
    return new ResourceResponse($node->toArray(), 201);
  }

  // Step 4: Implement the DELETE method.

  /**
   * Responds to DELETE requests.
   *
   * @param int $nid
   *   The node ID to delete.
   */
  public function delete($nid) {
    // Load and delete the node.
    $node = \Drupal::entityTypeManager()->getStorage('node')->load($nid);
    $node->delete();

    // Return a success message.
    return new ResourceResponse(['message' => 'Node deleted successfully.']);
  }

  // Step 5: Implement the PATCH method for updating.

  /**
   * Responds to PATCH requests.
   *
   * @param int $nid
   *   The node ID to update.
   * @param array $data
   *   The data to update the node.
   *
   * @return \Drupal\rest\ResourceResponse
   *   The response containing the updated node details.
   */
  public function patch($nid, array $data) {
    // Load and update the node.
    $node = \Drupal::entityTypeManager()->getStorage('node')->load($nid);
    $node->set($data);
    $node->save();

    // Return the response.
    return new ResourceResponse($node->toArray());
  }

}

Explanation:

1. CustomRestResource Class: Defines the custom REST resource using the ResourceBase class.
2. GET Method (Retrieve): Implements the get method to respond to GET requests, fetching node details by ID.
3. POST Method (Create): Implements the post method for creating a new node based on the provided data.
4. DELETE Method (Delete): Implements the delete method for deleting a node by ID.
5. PATCH Method (Update): Implements the patch method for updating a node by ID with provided data.
6. ResourceResponse: Utilizes ResourceResponse to format and return responses with appropriate HTTP status codes.