Using hook_jsonapi_resource_response_alter()for Drupal 8 , 9 , 10 , and 11

Introduction

As we continue exploring advanced customization techniques in headless Drupal setups, this lesson focuses on leveraging hook_jsonapi_resource_response_alter() to tailor API outputs. This powerful Drupal hook allows developers to modify JSON:API responses, enabling precise control over the API data presented to clients.

What is hook_jsonapi_resource_response_alter()?

The hook_jsonapi_resource_response_alter() is a PHP hook provided by the JSON:API module. It is designed to give developers an opportunity to modify the resource response object before it is sent to the client. This level of control allows for the injection or removal of data, including metadata adjustments or structure modifications.

Why Use hook_jsonapi_resource_response_alter()?

Using this hook provides several benefits:

• Flexibility: Customize API responses to meet client-specific requirements such as adding computed fields.
• Data Consistency: Ensure consistent data presentation by modifying or validating response content.
• Integration: Seamlessly integrate additional information or dependencies, enriching the API response.

Implementing hook_jsonapi_resource_response_alter()

Step 1: Create a Custom Module

If you haven't already, create a custom module to implement hooks:

• Create a directory named custom_module in modules/custom.
• Create a custom_module.info.yml file to define the module:

name: 'Custom JSON:API Alter'
type: module
description: 'Custom module to alter JSON:API responses.'
core_version_requirement: ^8 || ^9
dependencies:
  - drupal:jsonapi

Step 2: Implement the Hook in Your Module

In your custom module directory, create a file named custom_module.module and implement the hook:

/**
 * Implements hook_jsonapi_resource_response_alter().
 */
function custom_module_jsonapi_resource_response_alter(array &$response, \Drupal\Core\Cache\CacheableMetadata $cacheable_metadata, array $context) {
  if ($context['resource_type']->getTypeName() == 'node--article') {
    foreach ($response['data'] as &$resource) {
      // Example: Add a calculated thumbnail URL.
      $thumbnail = \Drupal::service('file_url_generator')->generateAbsoluteString('public://thumbnails/' . $resource['id'] . '.jpg');
      $resource['attributes']['thumbnail_url'] = $thumbnail;
    }
  }
}

In this example, for each article resource, a computed field thumbnail_url is added, enhancing the API response.

Practical Use Cases

Example 1: Add Computed Field

By adding calculated fields, extra contextual data can be provided directly within API responses without altering the base entity data model.

Example 2: Modify Metadata

Alter response headers or integrate caching information to optimize responses through metadata adjustments.

Best Practices

• Minimal Impact: Ensure alterations to responses are optimized and minimally impact performance.
• Maintainability: Document modifications clearly, especially when computing fields or altering structures, to maintain code clarity.
• Testing: Thoroughly test altered responses to ensure expected outcomes, using tools like Postman for simulating API calls.

Testing the Customizations

To test the customizations effectively:

• Send API requests using various tools (e.g., Postman) to verify changes.
• Check for the presence of new attributes or modifications within the API response JSON.

Conclusion

Utilizing hook_jsonapi_resource_response_alter() provides rich opportunities to tailor JSON:API outputs to match specific client requirements, enhancing the functionality and usability of your headless Drupal applications through flexible and dynamic API responses.

In future lessons, we'll delve into the topic of "Enhancing API security with custom access control in JSON:API" to further refine our control over Drupal's headless interfaces. Stay engaged and continue fortifying your Drupal mastery!