Still on Drupal 7? Security support for Drupal 7 ended on 5 January 2025. Please visit our Drupal 7 End of Life resources page to review all of your options.Responses overview
What?
HTTP is all about requests and responses. Drupal represents the responses it sends as Response objects. Drupal’s responses are Symfony Response objects. Symfony’s documentation also applies to Drupal.
Drupal core’s additions
Symfony's Response objects are fully supported, but are insufficient to fully support the rich Drupal ecosystem: we need more structured metadata than the very simple Symfony Response objects can provide.
Unfortunately, Symfony Response objects do not have an interface: every specialized Response "type" needs to extend from Symfony's Response base class.
Drupal’s additional response interfaces
Drupal core defines two response interfaces that any response can implement to indicate it supports these particular Drupal capabilities.
CacheableResponseInterface- An interface for responses that can expose cacheability metadata. (Cache contexts, tags and max-age.)
- Note: can easily be implemented by using the corresponding
CacheableResponseTrait. - See CacheableResponseInterface for more about this!
AttachmentsInterface- An interface for responses that can expose
#attachedmetadata. (Asset libraries,<head>elements, placeholders …) - Note: can easily be implemented by using the corresponding
AttachmentsTrait.
Drupal’s additional response classes
Finally, to make discovery easier, here are the most important specialized Response subclasses that are available to developers.
CacheableResponse- A response that contains and can expose cacheability metadata. Supports Drupal's caching concepts: cache tags for invalidation and cache contexts for variations.
- This is simply
class CacheableResponse extends Response implements CacheableResponseInterface {}. HtmlResponse- This is what a controller returning a render array will result in after going through the Render API and its render pipeline.
- This is simply
class HtmlResponse extends Response implements CacheableResponseInterface, AttachmentsInterface {}. CacheableJsonResponse- A
JsonResponsethat contains and can expose cacheability metadata. - This is simply
class CacheableJsonResponse extends JsonResponse implements CacheableResponseInterface {}— i.e. it extends Symfony'sJsonResponse. CacheableRedirectResponse- A
RedirectResponsethat contains and can expose cacheability metadata. - This is simply
class CacheableRedirectResponse extends RedirectResponse implements CacheableResponseInterface {}— i.e. it extends Symfony'sRedirectResponse. LocalRedirectResponse- A redirect response which cannot redirect to an external URL. (Extends
CacheableRedirectResponse.) TrustedRedirectResponse- A redirect response which should only redirect to a trusted (potentially external) URL. (Also extends
CacheableRedirectResponse.)
Response caching
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