DrupalKernel.php in Zircon Profile 8

Contains \Drupal\Core\DrupalKernel.

Namespace

Drupal\Core

File

core/lib/Drupal/Core/DrupalKernel.php

<?php

/**
 * @file
 * Contains \Drupal\Core\DrupalKernel.
 */
namespace Drupal\Core;

use Drupal\Component\FileCache\FileCacheFactory;
use Drupal\Component\Utility\Crypt;
use Drupal\Component\Utility\Unicode;
use Drupal\Component\Utility\UrlHelper;
use Drupal\Core\Config\BootstrapConfigStorageFactory;
use Drupal\Core\Config\NullStorage;
use Drupal\Core\Database\Database;
use Drupal\Core\DependencyInjection\ContainerBuilder;
use Drupal\Core\DependencyInjection\ServiceModifierInterface;
use Drupal\Core\DependencyInjection\ServiceProviderInterface;
use Drupal\Core\DependencyInjection\YamlFileLoader;
use Drupal\Core\Extension\ExtensionDiscovery;
use Drupal\Core\File\MimeType\MimeTypeGuesser;
use Drupal\Core\Http\TrustedHostsRequestFactory;
use Drupal\Core\Language\Language;
use Drupal\Core\Site\Settings;
use Symfony\Cmf\Component\Routing\RouteObjectInterface;
use Symfony\Component\DependencyInjection\ContainerInterface;
use Symfony\Component\DependencyInjection\ParameterBag\ParameterBag;
use Symfony\Component\HttpFoundation\RedirectResponse;
use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\HttpFoundation\Response;
use Symfony\Component\HttpKernel\Exception\BadRequestHttpException;
use Symfony\Component\HttpKernel\Exception\HttpExceptionInterface;
use Symfony\Component\HttpKernel\TerminableInterface;
use Symfony\Component\Routing\Route;

/**
 * The DrupalKernel class is the core of Drupal itself.
 *
 * This class is responsible for building the Dependency Injection Container and
 * also deals with the registration of service providers. It allows registered
 * service providers to add their services to the container. Core provides the
 * CoreServiceProvider, which, in addition to registering any core services that
 * cannot be registered in the core.services.yaml file, adds any compiler passes
 * needed by core, e.g. for processing tagged services. Each module can add its
 * own service provider, i.e. a class implementing
 * Drupal\Core\DependencyInjection\ServiceProvider, to register services to the
 * container, or modify existing services.
 */
class DrupalKernel implements DrupalKernelInterface, TerminableInterface {

  /**
   * Holds the class used for dumping the container to a PHP array.
   *
   * In combination with swapping the container class this is useful to e.g.
   * dump to the human-readable PHP array format to debug the container
   * definition in an easier way.
   *
   * @var string
   */
  protected $phpArrayDumperClass = '\\Drupal\\Component\\DependencyInjection\\Dumper\\OptimizedPhpArrayDumper';

  /**
   * Holds the default bootstrap container definition.
   *
   * @var array
   */
  protected $defaultBootstrapContainerDefinition = [
    'parameters' => [],
    'services' => [
      'database' => [
        'class' => 'Drupal\\Core\\Database\\Connection',
        'factory' => 'Drupal\\Core\\Database\\Database::getConnection',
        'arguments' => [
          'default',
        ],
      ],
      'cache.container' => [
        'class' => 'Drupal\\Core\\Cache\\DatabaseBackend',
        'arguments' => [
          '@database',
          '@cache_tags_provider.container',
          'container',
        ],
      ],
      'cache_tags_provider.container' => [
        'class' => 'Drupal\\Core\\Cache\\DatabaseCacheTagsChecksum',
        'arguments' => [
          '@database',
        ],
      ],
    ],
  ];

  /**
   * Holds the class used for instantiating the bootstrap container.
   *
   * @var string
   */
  protected $bootstrapContainerClass = '\\Drupal\\Component\\DependencyInjection\\PhpArrayContainer';

  /**
   * Holds the bootstrap container.
   *
   * @var \Symfony\Component\DependencyInjection\ContainerInterface
   */
  protected $bootstrapContainer;

  /**
   * Holds the container instance.
   *
   * @var \Symfony\Component\DependencyInjection\ContainerInterface
   */
  protected $container;

  /**
   * The environment, e.g. 'testing', 'install'.
   *
   * @var string
   */
  protected $environment;

  /**
   * Whether the kernel has been booted.
   *
   * @var bool
   */
  protected $booted = FALSE;

  /**
   * Whether essential services have been set up properly by preHandle().
   *
   * @var bool
   */
  protected $prepared = FALSE;

  /**
   * Holds the list of enabled modules.
   *
   * @var array
   *   An associative array whose keys are module names and whose values are
   *   ignored.
   */
  protected $moduleList;

  /**
   * List of available modules and installation profiles.
   *
   * @var \Drupal\Core\Extension\Extension[]
   */
  protected $moduleData = array();

  /**
   * The class loader object.
   *
   * @var \Composer\Autoload\ClassLoader
   */
  protected $classLoader;

  /**
   * Config storage object used for reading enabled modules configuration.
   *
   * @var \Drupal\Core\Config\StorageInterface
   */
  protected $configStorage;

  /**
   * Whether the container can be dumped.
   *
   * @var bool
   */
  protected $allowDumping;

  /**
   * Whether the container needs to be rebuilt the next time it is initialized.
   *
   * @var bool
   */
  protected $containerNeedsRebuild = FALSE;

  /**
   * Whether the container needs to be dumped once booting is complete.
   *
   * @var bool
   */
  protected $containerNeedsDumping;

  /**
   * List of discovered services.yml pathnames.
   *
   * This is a nested array whose top-level keys are 'app' and 'site', denoting
   * the origin of a service provider. Site-specific providers have to be
   * collected separately, because they need to be processed last, so as to be
   * able to override services from application service providers.
   *
   * @var array
   */
  protected $serviceYamls;

  /**
   * List of discovered service provider class names or objects.
   *
   * This is a nested array whose top-level keys are 'app' and 'site', denoting
   * the origin of a service provider. Site-specific providers have to be
   * collected separately, because they need to be processed last, so as to be
   * able to override services from application service providers.
   *
   * Allowing objects is for example used to allow
   * \Drupal\KernelTests\KernelTestBase to register itself as service provider.
   *
   * @var array
   */
  protected $serviceProviderClasses;

  /**
   * List of instantiated service provider classes.
   *
   * @see \Drupal\Core\DrupalKernel::$serviceProviderClasses
   *
   * @var array
   */
  protected $serviceProviders;

  /**
   * Whether the PHP environment has been initialized.
   *
   * This legacy phase can only be booted once because it sets session INI
   * settings. If a session has already been started, re-generating these
   * settings would break the session.
   *
   * @var bool
   */
  protected static $isEnvironmentInitialized = FALSE;

  /**
   * The site directory.
   *
   * @var string
   */
  protected $sitePath;

  /**
   * The app root.
   *
   * @var string
   */
  protected $root;

  /**
   * Create a DrupalKernel object from a request.
   *
   * @param \Symfony\Component\HttpFoundation\Request $request
   *   The request.
   * @param $class_loader
   *   The class loader. Normally Composer's ClassLoader, as included by the
   *   front controller, but may also be decorated; e.g.,
   *   \Symfony\Component\ClassLoader\ApcClassLoader.
   * @param string $environment
   *   String indicating the environment, e.g. 'prod' or 'dev'.
   * @param bool $allow_dumping
   *   (optional) FALSE to stop the container from being written to or read
   *   from disk. Defaults to TRUE.
   *
   * @return static
   *
   * @throws \Symfony\Component\HttpKernel\Exception\BadRequestHttpException
   *   In case the host name in the request is not trusted.
   */
  public static function createFromRequest(Request $request, $class_loader, $environment, $allow_dumping = TRUE) {
    $kernel = new static($environment, $class_loader, $allow_dumping);
    static::bootEnvironment();
    $kernel
      ->initializeSettings($request);
    return $kernel;
  }

  /**
   * Constructs a DrupalKernel object.
   *
   * @param string $environment
   *   String indicating the environment, e.g. 'prod' or 'dev'.
   * @param $class_loader
   *   The class loader. Normally \Composer\Autoload\ClassLoader, as included by
   *   the front controller, but may also be decorated; e.g.,
   *   \Symfony\Component\ClassLoader\ApcClassLoader.
   * @param bool $allow_dumping
   *   (optional) FALSE to stop the container from being written to or read
   *   from disk. Defaults to TRUE.
   */
  public function __construct($environment, $class_loader, $allow_dumping = TRUE) {
    $this->environment = $environment;
    $this->classLoader = $class_loader;
    $this->allowDumping = $allow_dumping;
    $this->root = dirname(dirname(substr(__DIR__, 0, -strlen(__NAMESPACE__))));
  }

  /**
   * Returns the appropriate site directory for a request.
   *
   * Once the kernel has been created DrupalKernelInterface::getSitePath() is
   * preferred since it gets the statically cached result of this method.
   *
   * Site directories contain all site specific code. This includes settings.php
   * for bootstrap level configuration, file configuration stores, public file
   * storage and site specific modules and themes.
   *
   * Finds a matching site directory file by stripping the website's hostname
   * from left to right and pathname from right to left. By default, the
   * directory must contain a 'settings.php' file for it to match. If the
   * parameter $require_settings is set to FALSE, then a directory without a
   * 'settings.php' file will match as well. The first configuration file found
   * will be used and the remaining ones will be ignored. If no configuration
   * file is found, returns a default value 'sites/default'. See
   * default.settings.php for examples on how the URL is converted to a
   * directory.
   *
   * If a file named sites.php is present in the sites directory, it will be
   * loaded prior to scanning for directories. That file can define aliases in
   * an associative array named $sites. The array is written in the format
   * '<port>.<domain>.<path>' => 'directory'. As an example, to create a
   * directory alias for https://www.drupal.org:8080/mysite/test whose
   * configuration file is in sites/example.com, the array should be defined as:
   * @code
   * $sites = array(
   *   '8080.www.drupal.org.mysite.test' => 'example.com',
   * );
   * @endcode
   *
   * @param \Symfony\Component\HttpFoundation\Request $request
   *   The current request.
   * @param bool $require_settings
   *   Only directories with an existing settings.php file will be recognized.
   *   Defaults to TRUE. During initial installation, this is set to FALSE so
   *   that Drupal can detect a matching directory, then create a new
   *   settings.php file in it.
   *
   * @return string
   *   The path of the matching directory.
   *
   * @throws \Symfony\Component\HttpKernel\Exception\BadRequestHttpException
   *   In case the host name in the request is invalid.
   *
   * @see \Drupal\Core\DrupalKernelInterface::getSitePath()
   * @see \Drupal\Core\DrupalKernelInterface::setSitePath()
   * @see default.settings.php
   * @see example.sites.php
   */
  public static function findSitePath(Request $request, $require_settings = TRUE) {
    if (static::validateHostname($request) === FALSE) {
      throw new BadRequestHttpException();
    }

    // Check for a simpletest override.
    if ($test_prefix = drupal_valid_test_ua()) {
      return 'sites/simpletest/' . substr($test_prefix, 10);
    }

    // Determine whether multi-site functionality is enabled.
    if (!file_exists(DRUPAL_ROOT . '/sites/sites.php')) {
      return 'sites/default';
    }

    // Otherwise, use find the site path using the request.
    $script_name = $request->server
      ->get('SCRIPT_NAME');
    if (!$script_name) {
      $script_name = $request->server
        ->get('SCRIPT_FILENAME');
    }
    $http_host = $request
      ->getHttpHost();
    $sites = array();
    include DRUPAL_ROOT . '/sites/sites.php';
    $uri = explode('/', $script_name);
    $server = explode('.', implode('.', array_reverse(explode(':', rtrim($http_host, '.')))));
    for ($i = count($uri) - 1; $i > 0; $i--) {
      for ($j = count($server); $j > 0; $j--) {
        $dir = implode('.', array_slice($server, -$j)) . implode('.', array_slice($uri, 0, $i));
        if (isset($sites[$dir]) && file_exists(DRUPAL_ROOT . '/sites/' . $sites[$dir])) {
          $dir = $sites[$dir];
        }
        if (file_exists(DRUPAL_ROOT . '/sites/' . $dir . '/settings.php') || !$require_settings && file_exists(DRUPAL_ROOT . '/sites/' . $dir)) {
          return "sites/{$dir}";
        }
      }
    }
    return 'sites/default';
  }

  /**
   * {@inheritdoc}
   */
  public function setSitePath($path) {
    if ($this->booted) {
      throw new \LogicException('Site path cannot be changed after calling boot()');
    }
    $this->sitePath = $path;
  }

  /**
   * {@inheritdoc}
   */
  public function getSitePath() {
    return $this->sitePath;
  }

  /**
   * {@inheritdoc}
   */
  public function getAppRoot() {
    return $this->root;
  }

  /**
   * {@inheritdoc}
   */
  public function boot() {
    if ($this->booted) {
      return $this;
    }

    // Ensure that findSitePath is set.
    if (!$this->sitePath) {
      throw new \Exception('Kernel does not have site path set before calling boot()');
    }

    // Initialize the FileCacheFactory component. We have to do it here instead
    // of in \Drupal\Component\FileCache\FileCacheFactory because we can not use
    // the Settings object in a component.
    $configuration = Settings::get('file_cache');

    // Provide a default configuration, if not set.
    if (!isset($configuration['default'])) {
      $configuration['default'] = [
        'class' => '\\Drupal\\Component\\FileCache\\FileCache',
        'cache_backend_class' => NULL,
        'cache_backend_configuration' => [],
      ];

      // @todo Use extension_loaded('apcu') for non-testbot
      //  https://www.drupal.org/node/2447753.
      if (function_exists('apc_fetch')) {
        $configuration['default']['cache_backend_class'] = '\\Drupal\\Component\\FileCache\\ApcuFileCacheBackend';
      }
    }
    FileCacheFactory::setConfiguration($configuration);
    FileCacheFactory::setPrefix(Settings::getApcuPrefix('file_cache', $this->root));
    $this->bootstrapContainer = new $this->bootstrapContainerClass(Settings::get('bootstrap_container_definition', $this->defaultBootstrapContainerDefinition));

    // Initialize the container.
    $this
      ->initializeContainer();

    // Ensure mt_rand() is reseeded to prevent random values from one page load
    // being exploited to predict random values in subsequent page loads.
    $seed = unpack("L", Crypt::randomBytes(4));
    mt_srand($seed[1]);
    $this->booted = TRUE;
    return $this;
  }

  /**
   * {@inheritdoc}
   */
  public function shutdown() {
    if (FALSE === $this->booted) {
      return;
    }
    $this->container
      ->get('stream_wrapper_manager')
      ->unregister();
    $this->booted = FALSE;
    $this->container = NULL;
    $this->moduleList = NULL;
    $this->moduleData = array();
  }

  /**
   * {@inheritdoc}
   */
  public function getContainer() {
    return $this->container;
  }

  /**
   * {@inheritdoc}
   */
  public function setContainer(ContainerInterface $container = NULL) {
    if (isset($this->container)) {
      throw new \Exception('The container should not override an existing container.');
    }
    if ($this->booted) {
      throw new \Exception('The container cannot be set after a booted kernel.');
    }
    $this->container = $container;
    return $this;
  }

  /**
   * {@inheritdoc}
   */
  public function getCachedContainerDefinition() {
    $cache = $this->bootstrapContainer
      ->get('cache.container')
      ->get($this
      ->getContainerCacheKey());
    if ($cache) {
      return $cache->data;
    }
    return NULL;
  }

  /**
   * {@inheritdoc}
   */
  public function loadLegacyIncludes() {
    require_once $this->root . '/core/includes/common.inc';
    require_once $this->root . '/core/includes/database.inc';
    require_once $this->root . '/core/includes/module.inc';
    require_once $this->root . '/core/includes/theme.inc';
    require_once $this->root . '/core/includes/pager.inc';
    require_once $this->root . '/core/includes/menu.inc';
    require_once $this->root . '/core/includes/tablesort.inc';
    require_once $this->root . '/core/includes/file.inc';
    require_once $this->root . '/core/includes/unicode.inc';
    require_once $this->root . '/core/includes/form.inc';
    require_once $this->root . '/core/includes/errors.inc';
    require_once $this->root . '/core/includes/schema.inc';
    require_once $this->root . '/core/includes/entity.inc';
  }

  /**
   * {@inheritdoc}
   */
  public function preHandle(Request $request) {
    $this
      ->loadLegacyIncludes();

    // Load all enabled modules.
    $this->container
      ->get('module_handler')
      ->loadAll();

    // Register stream wrappers.
    $this->container
      ->get('stream_wrapper_manager')
      ->register();

    // Initialize legacy request globals.
    $this
      ->initializeRequestGlobals($request);

    // Put the request on the stack.
    $this->container
      ->get('request_stack')
      ->push($request);

    // Set the allowed protocols.
    UrlHelper::setAllowedProtocols($this->container
      ->getParameter('filter_protocols'));

    // Override of Symfony's mime type guesser singleton.
    MimeTypeGuesser::registerWithSymfonyGuesser($this->container);
    $this->prepared = TRUE;
  }

  /**
   * {@inheritdoc}
   */
  public function discoverServiceProviders() {
    $this->serviceYamls = array(
      'app' => array(),
      'site' => array(),
    );
    $this->serviceProviderClasses = array(
      'app' => array(),
      'site' => array(),
    );
    $this->serviceYamls['app']['core'] = 'core/core.services.yml';
    $this->serviceProviderClasses['app']['core'] = 'Drupal\\Core\\CoreServiceProvider';

    // Retrieve enabled modules and register their namespaces.
    if (!isset($this->moduleList)) {
      $extensions = $this
        ->getConfigStorage()
        ->read('core.extension');
      $this->moduleList = isset($extensions['module']) ? $extensions['module'] : array();
    }
    $module_filenames = $this
      ->getModuleFileNames();
    $this
      ->classLoaderAddMultiplePsr4($this
      ->getModuleNamespacesPsr4($module_filenames));

    // Load each module's serviceProvider class.
    foreach ($module_filenames as $module => $filename) {
      $camelized = ContainerBuilder::camelize($module);
      $name = "{$camelized}ServiceProvider";
      $class = "Drupal\\{$module}\\{$name}";
      if (class_exists($class)) {
        $this->serviceProviderClasses['app'][$module] = $class;
      }
      $filename = dirname($filename) . "/{$module}.services.yml";
      if (file_exists($filename)) {
        $this->serviceYamls['app'][$module] = $filename;
      }
    }

    // Add site-specific service providers.
    if (!empty($GLOBALS['conf']['container_service_providers'])) {
      foreach ($GLOBALS['conf']['container_service_providers'] as $class) {
        if (is_string($class) && class_exists($class) || is_object($class) && ($class instanceof ServiceProviderInterface || $class instanceof ServiceModifierInterface)) {
          $this->serviceProviderClasses['site'][] = $class;
        }
      }
    }
    $this
      ->addServiceFiles(Settings::get('container_yamls', []));
  }

  /**
   * {@inheritdoc}
   */
  public function getServiceProviders($origin) {
    return $this->serviceProviders[$origin];
  }

  /**
   * {@inheritdoc}
   */
  public function terminate(Request $request, Response $response) {

    // Only run terminate() when essential services have been set up properly
    // by preHandle() before.
    if (FALSE === $this->prepared) {
      return;
    }
    if ($this
      ->getHttpKernel() instanceof TerminableInterface) {
      $this
        ->getHttpKernel()
        ->terminate($request, $response);
    }
  }

  /**
   * {@inheritdoc}
   */
  public function handle(Request $request, $type = self::MASTER_REQUEST, $catch = TRUE) {

    // Ensure sane PHP environment variables.
    static::bootEnvironment();
    try {
      $this
        ->initializeSettings($request);

      // Redirect the user to the installation script if Drupal has not been
      // installed yet (i.e., if no $databases array has been defined in the
      // settings.php file) and we are not already installing.
      if (!Database::getConnectionInfo() && !drupal_installation_attempted() && PHP_SAPI !== 'cli') {
        $response = new RedirectResponse($request
          ->getBasePath() . '/core/install.php');
      }
      else {
        $this
          ->boot();
        $response = $this
          ->getHttpKernel()
          ->handle($request, $type, $catch);
      }
    } catch (\Exception $e) {
      if ($catch === FALSE) {
        throw $e;
      }
      $response = $this
        ->handleException($e, $request, $type);
    }

    // Adapt response headers to the current request.
    $response
      ->prepare($request);
    return $response;
  }

  /**
   * Converts an exception into a response.
   *
   * @param \Exception $e
   *   An exception
   * @param Request $request
   *   A Request instance
   * @param int $type
   *   The type of the request (one of HttpKernelInterface::MASTER_REQUEST or
   *   HttpKernelInterface::SUB_REQUEST)
   *
   * @return Response
   *   A Response instance
   *
   * @throws \Exception
   *   If the passed in exception cannot be turned into a response.
   */
  protected function handleException(\Exception $e, $request, $type) {
    if ($e instanceof HttpExceptionInterface) {
      $response = new Response($e
        ->getMessage(), $e
        ->getStatusCode());
      $response->headers
        ->add($e
        ->getHeaders());
      return $response;
    }
    else {
      throw $e;
    }
  }

  /**
   * {@inheritdoc}
   */
  public function prepareLegacyRequest(Request $request) {
    $this
      ->boot();
    $this
      ->preHandle($request);

    // Setup services which are normally initialized from within stack
    // middleware or during the request kernel event.
    if (PHP_SAPI !== 'cli') {
      $request
        ->setSession($this->container
        ->get('session'));
    }
    $request->attributes
      ->set(RouteObjectInterface::ROUTE_OBJECT, new Route('<none>'));
    $request->attributes
      ->set(RouteObjectInterface::ROUTE_NAME, '<none>');
    $this->container
      ->get('request_stack')
      ->push($request);
    $this->container
      ->get('router.request_context')
      ->fromRequest($request);
    return $this;
  }

  /**
   * Returns module data on the filesystem.
   *
   * @param $module
   *   The name of the module.
   *
   * @return \Drupal\Core\Extension\Extension|bool
   *   Returns an Extension object if the module is found, FALSE otherwise.
   */
  protected function moduleData($module) {
    if (!$this->moduleData) {

      // First, find profiles.
      $listing = new ExtensionDiscovery($this->root);
      $listing
        ->setProfileDirectories(array());
      $all_profiles = $listing
        ->scan('profile');
      $profiles = array_intersect_key($all_profiles, $this->moduleList);

      // If a module is within a profile directory but specifies another
      // profile for testing, it needs to be found in the parent profile.
      $settings = $this
        ->getConfigStorage()
        ->read('simpletest.settings');
      $parent_profile = !empty($settings['parent_profile']) ? $settings['parent_profile'] : NULL;
      if ($parent_profile && !isset($profiles[$parent_profile])) {

        // In case both profile directories contain the same extension, the
        // actual profile always has precedence.
        $profiles = array(
          $parent_profile => $all_profiles[$parent_profile],
        ) + $profiles;
      }
      $profile_directories = array_map(function ($profile) {
        return $profile
          ->getPath();
      }, $profiles);
      $listing
        ->setProfileDirectories($profile_directories);

      // Now find modules.
      $this->moduleData = $profiles + $listing
        ->scan('module');
    }
    return isset($this->moduleData[$module]) ? $this->moduleData[$module] : FALSE;
  }

  /**
   * Implements Drupal\Core\DrupalKernelInterface::updateModules().
   *
   * @todo Remove obsolete $module_list parameter. Only $module_filenames is
   *   needed.
   */
  public function updateModules(array $module_list, array $module_filenames = array()) {
    $this->moduleList = $module_list;
    foreach ($module_filenames as $name => $extension) {
      $this->moduleData[$name] = $extension;
    }

    // If we haven't yet booted, we don't need to do anything: the new module
    // list will take effect when boot() is called. However we set a
    // flag that the container needs a rebuild, so that a potentially cached
    // container is not used. If we have already booted, then rebuild the
    // container in order to refresh the serviceProvider list and container.
    $this->containerNeedsRebuild = TRUE;
    if ($this->booted) {
      $this
        ->initializeContainer();
    }
  }

  /**
   * Returns the container cache key based on the environment.
   *
   * @return string
   *   The cache key used for the service container.
   */
  protected function getContainerCacheKey() {
    $parts = array(
      'service_container',
      $this->environment,
      \Drupal::VERSION,
      Settings::get('deployment_identifier'),
    );
    return implode(':', $parts);
  }

  /**
   * Returns the kernel parameters.
   *
   * @return array An array of kernel parameters
   */
  protected function getKernelParameters() {
    return array(
      'kernel.environment' => $this->environment,
    );
  }

  /**
   * Initializes the service container.
   *
   * @return \Symfony\Component\DependencyInjection\ContainerInterface
   */
  protected function initializeContainer() {
    $this->containerNeedsDumping = FALSE;
    $session_started = FALSE;
    if (isset($this->container)) {

      // Save the id of the currently logged in user.
      if ($this->container
        ->initialized('current_user')) {
        $current_user_id = $this->container
          ->get('current_user')
          ->id();
      }

      // If there is a session, close and save it.
      if ($this->container
        ->initialized('session')) {
        $session = $this->container
          ->get('session');
        if ($session
          ->isStarted()) {
          $session_started = TRUE;
          $session
            ->save();
        }
        unset($session);
      }
    }

    // If we haven't booted yet but there is a container, then we're asked to
    // boot the container injected via setContainer().
    // @see \Drupal\KernelTests\KernelTestBase::setUp()
    if (isset($this->container) && !$this->booted) {
      $container = $this->container;
    }

    // If the module list hasn't already been set in updateModules and we are
    // not forcing a rebuild, then try and load the container from the cache.
    if (empty($this->moduleList) && !$this->containerNeedsRebuild) {
      $container_definition = $this
        ->getCachedContainerDefinition();
    }

    // If there is no container and no cached container definition, build a new
    // one from scratch.
    if (!isset($container) && !isset($container_definition)) {
      $container = $this
        ->compileContainer();

      // Only dump the container if dumping is allowed. This is useful for
      // KernelTestBase, which never wants to use the real container, but always
      // the container builder.
      if ($this->allowDumping) {
        $dumper = new $this->phpArrayDumperClass($container);
        $container_definition = $dumper
          ->getArray();
      }
    }

    // The container was rebuilt successfully.
    $this->containerNeedsRebuild = FALSE;

    // Only create a new class if we have a container definition.
    if (isset($container_definition)) {
      $class = Settings::get('container_base_class', '\\Drupal\\Core\\DependencyInjection\\Container');
      $container = new $class($container_definition);
    }
    $this
      ->attachSynthetic($container);
    $this->container = $container;
    if ($session_started) {
      $this->container
        ->get('session')
        ->start();
    }

    // The request stack is preserved across container rebuilds. Reinject the
    // new session into the master request if one was present before.
    if ($request_stack = $this->container
      ->get('request_stack', ContainerInterface::NULL_ON_INVALID_REFERENCE)) {
      if ($request = $request_stack
        ->getMasterRequest()) {
        if ($request
          ->hasSession()) {
          $request
            ->setSession($this->container
            ->get('session'));
        }
      }
    }
    if (!empty($current_user_id)) {
      $this->container
        ->get('current_user')
        ->setInitialAccountId($current_user_id);
    }
    \Drupal::setContainer($this->container);

    // If needs dumping flag was set, dump the container.
    if ($this->containerNeedsDumping && !$this
      ->cacheDrupalContainer($container_definition)) {
      $this->container
        ->get('logger.factory')
        ->get('DrupalKernel')
        ->notice('Container cannot be saved to cache.');
    }
    return $this->container;
  }

  /**
   * Setup a consistent PHP environment.
   *
   * This method sets PHP environment options we want to be sure are set
   * correctly for security or just saneness.
   */
  public static function bootEnvironment() {
    if (static::$isEnvironmentInitialized) {
      return;
    }

    // Include our bootstrap file.
    $core_root = dirname(dirname(dirname(__DIR__)));
    require_once $core_root . '/includes/bootstrap.inc';

    // Enforce E_STRICT, but allow users to set levels not part of E_STRICT.
    error_reporting(E_STRICT | E_ALL);

    // Override PHP settings required for Drupal to work properly.
    // sites/default/default.settings.php contains more runtime settings.
    // The .htaccess file contains settings that cannot be changed at runtime.
    // Use session cookies, not transparent sessions that puts the session id in
    // the query string.
    ini_set('session.use_cookies', '1');
    ini_set('session.use_only_cookies', '1');
    ini_set('session.use_trans_sid', '0');

    // Don't send HTTP headers using PHP's session handler.
    // Send an empty string to disable the cache limiter.
    ini_set('session.cache_limiter', '');

    // Use httponly session cookies.
    ini_set('session.cookie_httponly', '1');

    // Set sane locale settings, to ensure consistent string, dates, times and
    // numbers handling.
    setlocale(LC_ALL, 'C');

    // Detect string handling method.
    Unicode::check();

    // Indicate that code is operating in a test child site.
    if (!defined('DRUPAL_TEST_IN_CHILD_SITE')) {
      if ($test_prefix = drupal_valid_test_ua()) {

        // Only code that interfaces directly with tests should rely on this
        // constant; e.g., the error/exception handler conditionally adds further
        // error information into HTTP response headers that are consumed by
        // Simpletest's internal browser.
        define('DRUPAL_TEST_IN_CHILD_SITE', TRUE);

        // Web tests are to be conducted with runtime assertions active.
        assert_options(ASSERT_ACTIVE, TRUE);

        // Now synchronize PHP 5 and 7's handling of assertions as much as
        // possible.
        \Drupal\Component\Assertion\Handle::register();

        // Log fatal errors to the test site directory.
        ini_set('log_errors', 1);
        ini_set('error_log', DRUPAL_ROOT . '/sites/simpletest/' . substr($test_prefix, 10) . '/error.log');
      }
      else {

        // Ensure that no other code defines this.
        define('DRUPAL_TEST_IN_CHILD_SITE', FALSE);
      }
    }

    // Set the Drupal custom error handler.
    set_error_handler('_drupal_error_handler');
    set_exception_handler('_drupal_exception_handler');
    static::$isEnvironmentInitialized = TRUE;
  }

  /**
   * Locate site path and initialize settings singleton.
   *
   * @param \Symfony\Component\HttpFoundation\Request $request
   *   The current request.
   *
   * @throws \Symfony\Component\HttpKernel\Exception\BadRequestHttpException
   *   In case the host name in the request is not trusted.
   */
  protected function initializeSettings(Request $request) {
    $site_path = static::findSitePath($request);
    $this
      ->setSitePath($site_path);
    $class_loader_class = get_class($this->classLoader);
    Settings::initialize($this->root, $site_path, $this->classLoader);

    // Initialize our list of trusted HTTP Host headers to protect against
    // header attacks.
    $host_patterns = Settings::get('trusted_host_patterns', array());
    if (PHP_SAPI !== 'cli' && !empty($host_patterns)) {
      if (static::setupTrustedHosts($request, $host_patterns) === FALSE) {
        throw new BadRequestHttpException('The provided host name is not valid for this server.');
      }
    }

    // If the class loader is still the same, possibly upgrade to the APC class
    // loader.
    if ($class_loader_class == get_class($this->classLoader) && Settings::get('class_loader_auto_detect', TRUE) && function_exists('apc_fetch')) {
      $prefix = Settings::getApcuPrefix('class_loader', $this->root);
      $apc_loader = new \Symfony\Component\ClassLoader\ApcClassLoader($prefix, $this->classLoader);
      $this->classLoader
        ->unregister();
      $apc_loader
        ->register();
      $this->classLoader = $apc_loader;
    }
  }

  /**
   * Bootstraps the legacy global request variables.
   *
   * @param \Symfony\Component\HttpFoundation\Request $request
   *   The current request.
   *
   * @todo D8: Eliminate this entirely in favor of Request object.
   */
  protected function initializeRequestGlobals(Request $request) {
    global $base_url;

    // Set and derived from $base_url by this function.
    global $base_path, $base_root;
    global $base_secure_url, $base_insecure_url;

    // Create base URL.
    $base_root = $request
      ->getSchemeAndHttpHost();
    $base_url = $base_root;

    // For a request URI of '/index.php/foo', $_SERVER['SCRIPT_NAME'] is
    // '/index.php', whereas $_SERVER['PHP_SELF'] is '/index.php/foo'.
    if ($dir = rtrim(dirname($request->server
      ->get('SCRIPT_NAME')), '\\/')) {

      // Remove "core" directory if present, allowing install.php,
      // authorize.php, and others to auto-detect a base path.
      $core_position = strrpos($dir, '/core');
      if ($core_position !== FALSE && strlen($dir) - 5 == $core_position) {
        $base_path = substr($dir, 0, $core_position);
      }
      else {
        $base_path = $dir;
      }
      $base_url .= $base_path;
      $base_path .= '/';
    }
    else {
      $base_path = '/';
    }
    $base_secure_url = str_replace('http://', 'https://', $base_url);
    $base_insecure_url = str_replace('https://', 'http://', $base_url);
  }

  /**
   * Returns service instances to persist from an old container to a new one.
   */
  protected function getServicesToPersist(ContainerInterface $container) {
    $persist = array();
    foreach ($container
      ->getParameter('persist_ids') as $id) {

      // It's pointless to persist services not yet initialized.
      if ($container
        ->initialized($id)) {
        $persist[$id] = $container
          ->get($id);
      }
    }
    return $persist;
  }

  /**
   * Moves persistent service instances into a new container.
   */
  protected function persistServices(ContainerInterface $container, array $persist) {
    foreach ($persist as $id => $object) {

      // Do not override services already set() on the new container, for
      // example 'service_container'.
      if (!$container
        ->initialized($id)) {
        $container
          ->set($id, $object);
      }
    }
  }

  /**
   * {@inheritdoc}
   */
  public function rebuildContainer() {

    // Empty module properties and for them to be reloaded from scratch.
    $this->moduleList = NULL;
    $this->moduleData = array();
    $this->containerNeedsRebuild = TRUE;
    return $this
      ->initializeContainer();
  }

  /**
   * {@inheritdoc}
   */
  public function invalidateContainer() {

    // An invalidated container needs a rebuild.
    $this->containerNeedsRebuild = TRUE;

    // If we have not yet booted, settings or bootstrap services might not yet
    // be available. In that case the container will not be loaded from cache
    // due to the above setting when the Kernel is booted.
    if (!$this->booted) {
      return;
    }

    // Also remove the container definition from the cache backend.
    $this->bootstrapContainer
      ->get('cache.container')
      ->deleteAll();
  }

  /**
   * Attach synthetic values on to kernel.
   *
   * @param ContainerInterface $container
   *   Container object
   *
   * @return ContainerInterface
   */
  protected function attachSynthetic(ContainerInterface $container) {
    $persist = array();
    if (isset($this->container)) {
      $persist = $this
        ->getServicesToPersist($this->container);
    }
    $this
      ->persistServices($container, $persist);

    // All namespaces must be registered before we attempt to use any service
    // from the container.
    $this
      ->classLoaderAddMultiplePsr4($container
      ->getParameter('container.namespaces'));
    $container
      ->set('kernel', $this);

    // Set the class loader which was registered as a synthetic service.
    $container
      ->set('class_loader', $this->classLoader);
    return $container;
  }

  /**
   * Compiles a new service container.
   *
   * @return ContainerBuilder The compiled service container
   */
  protected function compileContainer() {

    // We are forcing a container build so it is reasonable to assume that the
    // calling method knows something about the system has changed requiring the
    // container to be dumped to the filesystem.
    if ($this->allowDumping) {
      $this->containerNeedsDumping = TRUE;
    }
    $this
      ->initializeServiceProviders();
    $container = $this
      ->getContainerBuilder();
    $container
      ->set('kernel', $this);
    $container
      ->setParameter('container.modules', $this
      ->getModulesParameter());

    // Get a list of namespaces and put it onto the container.
    $namespaces = $this
      ->getModuleNamespacesPsr4($this
      ->getModuleFileNames());

    // Add all components in \Drupal\Core and \Drupal\Component that have one of
    // the following directories:
    // - Element
    // - Entity
    // - Plugin
    foreach (array(
      'Core',
      'Component',
    ) as $parent_directory) {
      $path = 'core/lib/Drupal/' . $parent_directory;
      $parent_namespace = 'Drupal\\' . $parent_directory;
      foreach (new \DirectoryIterator($this->root . '/' . $path) as $component) {

        /** @var $component \DirectoryIterator */
        $pathname = $component
          ->getPathname();
        if (!$component
          ->isDot() && $component
          ->isDir() && (is_dir($pathname . '/Plugin') || is_dir($pathname . '/Entity') || is_dir($pathname . '/Element'))) {
          $namespaces[$parent_namespace . '\\' . $component
            ->getFilename()] = $path . '/' . $component
            ->getFilename();
        }
      }
    }
    $container
      ->setParameter('container.namespaces', $namespaces);

    // Store the default language values on the container. This is so that the
    // default language can be configured using the configuration factory. This
    // avoids the circular dependencies that would created by
    // \Drupal\language\LanguageServiceProvider::alter() and allows the default
    // language to not be English in the installer.
    $default_language_values = Language::$defaultValues;
    if ($system = $this
      ->getConfigStorage()
      ->read('system.site')) {
      if ($default_language_values['id'] != $system['langcode']) {
        $default_language_values = array(
          'id' => $system['langcode'],
        );
      }
    }
    $container
      ->setParameter('language.default_values', $default_language_values);

    // Register synthetic services.
    $container
      ->register('class_loader')
      ->setSynthetic(TRUE);
    $container
      ->register('kernel', 'Symfony\\Component\\HttpKernel\\KernelInterface')
      ->setSynthetic(TRUE);
    $container
      ->register('service_container', 'Symfony\\Component\\DependencyInjection\\ContainerInterface')
      ->setSynthetic(TRUE);

    // Register application services.
    $yaml_loader = new YamlFileLoader($container);
    foreach ($this->serviceYamls['app'] as $filename) {
      $yaml_loader
        ->load($filename);
    }
    foreach ($this->serviceProviders['app'] as $provider) {
      if ($provider instanceof ServiceProviderInterface) {
        $provider
          ->register($container);
      }
    }

    // Register site-specific service overrides.
    foreach ($this->serviceYamls['site'] as $filename) {
      $yaml_loader
        ->load($filename);
    }
    foreach ($this->serviceProviders['site'] as $provider) {
      if ($provider instanceof ServiceProviderInterface) {
        $provider
          ->register($container);
      }
    }

    // Identify all services whose instances should be persisted when rebuilding
    // the container during the lifetime of the kernel (e.g., during a kernel
    // reboot). Include synthetic services, because by definition, they cannot
    // be automatically reinstantiated. Also include services tagged to persist.
    $persist_ids = array();
    foreach ($container
      ->getDefinitions() as $id => $definition) {
      if ($definition
        ->isSynthetic() || $definition
        ->getTag('persist')) {
        $persist_ids[] = $id;
      }
    }
    $container
      ->setParameter('persist_ids', $persist_ids);
    $container
      ->compile();
    return $container;
  }

  /**
   * Registers all service providers to the kernel.
   *
   * @throws \LogicException
   */
  protected function initializeServiceProviders() {
    $this
      ->discoverServiceProviders();
    $this->serviceProviders = array(
      'app' => array(),
      'site' => array(),
    );
    foreach ($this->serviceProviderClasses as $origin => $classes) {
      foreach ($classes as $name => $class) {
        if (!is_object($class)) {
          $this->serviceProviders[$origin][$name] = new $class();
        }
        else {
          $this->serviceProviders[$origin][$name] = $class;
        }
      }
    }
  }

  /**
   * Gets a new ContainerBuilder instance used to build the service container.
   *
   * @return ContainerBuilder
   */
  protected function getContainerBuilder() {
    return new ContainerBuilder(new ParameterBag($this
      ->getKernelParameters()));
  }

  /**
   * Stores the container definition in a cache.
   *
   * @param array $container_definition
   *   The container definition to cache.
   *
   * @return bool
   *   TRUE if the container was successfully cached.
   */
  protected function cacheDrupalContainer(array $container_definition) {
    $saved = TRUE;
    try {
      $this->bootstrapContainer
        ->get('cache.container')
        ->set($this
        ->getContainerCacheKey(), $container_definition);
    } catch (\Exception $e) {

      // There is no way to get from the Cache API if the cache set was
      // successful or not, hence an Exception is caught and the caller informed
      // about the error condition.
      $saved = FALSE;
    }
    return $saved;
  }

  /**
   * Gets a http kernel from the container
   *
   * @return \Symfony\Component\HttpKernel\HttpKernelInterface
   */
  protected function getHttpKernel() {
    return $this->container
      ->get('http_kernel');
  }

  /**
   * Returns the active configuration storage to use during building the container.
   *
   * @return \Drupal\Core\Config\StorageInterface
   */
  protected function getConfigStorage() {
    if (!isset($this->configStorage)) {

      // The active configuration storage may not exist yet; e.g., in the early
      // installer. Catch the exception thrown by config_get_config_directory().
      try {
        $this->configStorage = BootstrapConfigStorageFactory::get($this->classLoader);
      } catch (\Exception $e) {
        $this->configStorage = new NullStorage();
      }
    }
    return $this->configStorage;
  }

  /**
   * Returns an array of Extension class parameters for all enabled modules.
   *
   * @return array
   */
  protected function getModulesParameter() {
    $extensions = array();
    foreach ($this->moduleList as $name => $weight) {
      if ($data = $this
        ->moduleData($name)) {
        $extensions[$name] = array(
          'type' => $data
            ->getType(),
          'pathname' => $data
            ->getPathname(),
          'filename' => $data
            ->getExtensionFilename(),
        );
      }
    }
    return $extensions;
  }

  /**
   * Gets the file name for each enabled module.
   *
   * @return array
   *   Array where each key is a module name, and each value is a path to the
   *   respective *.module or *.profile file.
   */
  protected function getModuleFileNames() {
    $filenames = array();
    foreach ($this->moduleList as $module => $weight) {
      if ($data = $this
        ->moduleData($module)) {
        $filenames[$module] = $data
          ->getPathname();
      }
    }
    return $filenames;
  }

  /**
   * Gets the PSR-4 base directories for module namespaces.
   *
   * @param string[] $module_file_names
   *   Array where each key is a module name, and each value is a path to the
   *   respective *.module or *.profile file.
   *
   * @return string[]
   *   Array where each key is a module namespace like 'Drupal\system', and each
   *   value is the PSR-4 base directory associated with the module namespace.
   */
  protected function getModuleNamespacesPsr4($module_file_names) {
    $namespaces = array();
    foreach ($module_file_names as $module => $filename) {
      $namespaces["Drupal\\{$module}"] = dirname($filename) . '/src';
    }
    return $namespaces;
  }

  /**
   * Registers a list of namespaces with PSR-4 directories for class loading.
   *
   * @param array $namespaces
   *   Array where each key is a namespace like 'Drupal\system', and each value
   *   is either a PSR-4 base directory, or an array of PSR-4 base directories
   *   associated with this namespace.
   */
  protected function classLoaderAddMultiplePsr4(array $namespaces = array()) {
    foreach ($namespaces as $prefix => $paths) {
      if (is_array($paths)) {
        foreach ($paths as $key => $value) {
          $paths[$key] = $this->root . '/' . $value;
        }
      }
      elseif (is_string($paths)) {
        $paths = $this->root . '/' . $paths;
      }
      $this->classLoader
        ->addPsr4($prefix . '\\', $paths);
    }
  }

  /**
   * Validates a hostname length.
   *
   * @param string $host
   *   A hostname.
   *
   * @return bool
   *   TRUE if the length is appropriate, or FALSE otherwise.
   */
  protected static function validateHostnameLength($host) {

    // Limit the length of the host name to 1000 bytes to prevent DoS attacks
    // with long host names.
    return strlen($host) <= 1000 && substr_count($host, '.') <= 100 && substr_count($host, ':') <= 100;
  }

  /**
   * Validates the hostname supplied from the HTTP request.
   *
   * @param \Symfony\Component\HttpFoundation\Request $request
   *   The request object
   *
   * @return bool
   *   TRUE if the hostname is valid, or FALSE otherwise.
   */
  public static function validateHostname(Request $request) {

    // $request->getHost() can throw an UnexpectedValueException if it
    // detects a bad hostname, but it does not validate the length.
    try {
      $http_host = $request
        ->getHost();
    } catch (\UnexpectedValueException $e) {
      return FALSE;
    }
    if (static::validateHostnameLength($http_host) === FALSE) {
      return FALSE;
    }
    return TRUE;
  }

  /**
   * Sets up the lists of trusted HTTP Host headers.
   *
   * Since the HTTP Host header can be set by the user making the request, it
   * is possible to create an attack vectors against a site by overriding this.
   * Symfony provides a mechanism for creating a list of trusted Host values.
   *
   * Host patterns (as regular expressions) can be configured through
   * settings.php for multisite installations, sites using ServerAlias without
   * canonical redirection, or configurations where the site responds to default
   * requests. For example,
   *
   * @code
   * $settings['trusted_host_patterns'] = array(
   *   '^example\.com$',
   *   '^*.example\.com$',
   * );
   * @endcode
   *
   * @param \Symfony\Component\HttpFoundation\Request $request
   *   The request object.
   * @param array $host_patterns
   *   The array of trusted host patterns.
   *
   * @return bool
   *   TRUE if the Host header is trusted, FALSE otherwise.
   *
   * @see https://www.drupal.org/node/1992030
   * @see \Drupal\Core\Http\TrustedHostsRequestFactory
   */
  protected static function setupTrustedHosts(Request $request, $host_patterns) {
    $request
      ->setTrustedHosts($host_patterns);

    // Get the host, which will validate the current request.
    try {
      $host = $request
        ->getHost();

      // Fake requests created through Request::create() without passing in the
      // server variables from the main request have a default host of
      // 'localhost'. If 'localhost' does not match any of the trusted host
      // patterns these fake requests would fail the host verification. Instead,
      // TrustedHostsRequestFactory makes sure to pass in the server variables
      // from the main request.
      $request_factory = new TrustedHostsRequestFactory($host);
      Request::setFactory([
        $request_factory,
        'createRequest',
      ]);
    } catch (\UnexpectedValueException $e) {
      return FALSE;
    }
    return TRUE;
  }

  /**
   * Add service files.
   *
   * @param string[] $service_yamls
   *   A list of service files.
   */
  protected function addServiceFiles(array $service_yamls) {
    $this->serviceYamls['site'] = array_filter($service_yamls, 'file_exists');
  }

}

Classes

Name	Description
DrupalKernel	The DrupalKernel class is the core of Drupal itself.