class HeadersCacheContext in Drupal 8

Defines the HeadersCacheContext service, for "per header" caching.

Cache context ID: 'headers' (to vary by all headers). Calculated cache context ID: 'headers:%name', e.g. 'headers:X-Something' (to vary by the 'X-Something' header).

Hierarchy

• class \Drupal\Core\Cache\Context\RequestStackCacheContextBase
  • class \Drupal\Core\Cache\Context\HeadersCacheContext implements CalculatedCacheContextInterface

1 file declares its use of HeadersCacheContext

HeadersCacheContextTest.php in core/tests/Drupal/Tests/Core/Cache/Context/HeadersCacheContextTest.php

1 string reference to 'HeadersCacheContext'

core.services.yml in core/core.services.yml

core/core.services.yml

1 service uses HeadersCacheContext

cache_context.headers in core/core.services.yml

Drupal\Core\Cache\Context\HeadersCacheContext

File

core/lib/Drupal/Core/Cache/Context/HeadersCacheContext.php, line 14

Namespace

Drupal\Core\Cache\Context

class HeadersCacheContext extends RequestStackCacheContextBase implements CalculatedCacheContextInterface {

  /**
   * {@inheritdoc}
   */
  public static function getLabel() {
    return t('HTTP headers');
  }

  /**
   * {@inheritdoc}
   */
  public function getContext($header = NULL) {
    if ($header === NULL) {
      $headers = $this->requestStack
        ->getCurrentRequest()->headers
        ->all();

      // Order headers by name to have less cache variations.
      ksort($headers);
      $result = '';
      foreach ($headers as $name => $value) {
        if ($result) {
          $result .= '&';
        }

        // Sort values to minimize cache variations.
        sort($value);
        $result .= $name . '=' . implode(',', $value);
      }
      return $result;
    }
    elseif ($this->requestStack
      ->getCurrentRequest()->headers
      ->has($header)) {
      $value = $this->requestStack
        ->getCurrentRequest()->headers
        ->get($header);
      if ($value !== '') {
        return $value;
      }
      return '?valueless?';
    }
    return '';
  }

  /**
   * {@inheritdoc}
   */
  public function getCacheableMetadata($header = NULL) {
    return new CacheableMetadata();
  }

}

Members

Name	Modifiers	Type	Description	Overrides
HeadersCacheContext::getCacheableMetadata	public	function	Gets the cacheability metadata for the context based on the parameter value. Overrides CalculatedCacheContextInterface::getCacheableMetadata
HeadersCacheContext::getContext	public	function	Returns the string representation of the cache context. Overrides CalculatedCacheContextInterface::getContext
HeadersCacheContext::getLabel	public static	function	Returns the label of the cache context. Overrides CalculatedCacheContextInterface::getLabel
RequestStackCacheContextBase::$requestStack	protected	property	The request stack.
RequestStackCacheContextBase::__construct	public	function	Constructs a new RequestStackCacheContextBase class.