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Diffstat (limited to 'www/wiki/includes/services/ServiceContainer.php')
| -rw-r--r-- | www/wiki/includes/services/ServiceContainer.php | 378 |
1 files changed, 378 insertions, 0 deletions
diff --git a/www/wiki/includes/services/ServiceContainer.php b/www/wiki/includes/services/ServiceContainer.php new file mode 100644 index 00000000..9f09e22f --- /dev/null +++ b/www/wiki/includes/services/ServiceContainer.php @@ -0,0 +1,378 @@ +<?php +namespace MediaWiki\Services; + +use InvalidArgumentException; +use RuntimeException; +use Wikimedia\Assert\Assert; + +/** + * Generic service container. + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License along + * with this program; if not, write to the Free Software Foundation, Inc., + * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. + * http://www.gnu.org/copyleft/gpl.html + * + * @file + * + * @since 1.27 + */ + +/** + * ServiceContainer provides a generic service to manage named services using + * lazy instantiation based on instantiator callback functions. + * + * Services managed by an instance of ServiceContainer may or may not implement + * a common interface. + * + * @note When using ServiceContainer to manage a set of services, consider + * creating a wrapper or a subclass that provides access to the services via + * getter methods with more meaningful names and more specific return type + * declarations. + * + * @see docs/injection.txt for an overview of using dependency injection in the + * MediaWiki code base. + */ +class ServiceContainer implements DestructibleService { + + /** + * @var object[] + */ + private $services = []; + + /** + * @var callable[] + */ + private $serviceInstantiators = []; + + /** + * @var bool[] disabled status, per service name + */ + private $disabled = []; + + /** + * @var array + */ + private $extraInstantiationParams; + + /** + * @var bool + */ + private $destroyed = false; + + /** + * @param array $extraInstantiationParams Any additional parameters to be passed to the + * instantiator function when creating a service. This is typically used to provide + * access to additional ServiceContainers or Config objects. + */ + public function __construct( array $extraInstantiationParams = [] ) { + $this->extraInstantiationParams = $extraInstantiationParams; + } + + /** + * Destroys all contained service instances that implement the DestructibleService + * interface. This will render all services obtained from this MediaWikiServices + * instance unusable. In particular, this will disable access to the storage backend + * via any of these services. Any future call to getService() will throw an exception. + * + * @see resetGlobalInstance() + */ + public function destroy() { + foreach ( $this->getServiceNames() as $name ) { + $service = $this->peekService( $name ); + if ( $service !== null && $service instanceof DestructibleService ) { + $service->destroy(); + } + } + + $this->destroyed = true; + } + + /** + * @param array $wiringFiles A list of PHP files to load wiring information from. + * Each file is loaded using PHP's include mechanism. Each file is expected to + * return an associative array that maps service names to instantiator functions. + */ + public function loadWiringFiles( array $wiringFiles ) { + foreach ( $wiringFiles as $file ) { + // the wiring file is required to return an array of instantiators. + $wiring = require $file; + + Assert::postcondition( + is_array( $wiring ), + "Wiring file $file is expected to return an array!" + ); + + $this->applyWiring( $wiring ); + } + } + + /** + * Registers multiple services (aka a "wiring"). + * + * @param array $serviceInstantiators An associative array mapping service names to + * instantiator functions. + */ + public function applyWiring( array $serviceInstantiators ) { + Assert::parameterElementType( 'callable', $serviceInstantiators, '$serviceInstantiators' ); + + foreach ( $serviceInstantiators as $name => $instantiator ) { + $this->defineService( $name, $instantiator ); + } + } + + /** + * Imports all wiring defined in $container. Wiring defined in $container + * will override any wiring already defined locally. However, already + * existing service instances will be preserved. + * + * @since 1.28 + * + * @param ServiceContainer $container + * @param string[] $skip A list of service names to skip during import + */ + public function importWiring( ServiceContainer $container, $skip = [] ) { + $newInstantiators = array_diff_key( + $container->serviceInstantiators, + array_flip( $skip ) + ); + + $this->serviceInstantiators = array_merge( + $this->serviceInstantiators, + $newInstantiators + ); + } + + /** + * Returns true if a service is defined for $name, that is, if a call to getService( $name ) + * would return a service instance. + * + * @param string $name + * + * @return bool + */ + public function hasService( $name ) { + return isset( $this->serviceInstantiators[$name] ); + } + + /** + * Returns the service instance for $name only if that service has already been instantiated. + * This is intended for situations where services get destroyed/cleaned up, so we can + * avoid creating a service just to destroy it again. + * + * @note This is intended for internal use and for test fixtures. + * Application logic should use getService() instead. + * + * @see getService(). + * + * @param string $name + * + * @return object|null The service instance, or null if the service has not yet been instantiated. + * @throws RuntimeException if $name does not refer to a known service. + */ + public function peekService( $name ) { + if ( !$this->hasService( $name ) ) { + throw new NoSuchServiceException( $name ); + } + + return isset( $this->services[$name] ) ? $this->services[$name] : null; + } + + /** + * @return string[] + */ + public function getServiceNames() { + return array_keys( $this->serviceInstantiators ); + } + + /** + * Define a new service. The service must not be known already. + * + * @see getService(). + * @see replaceService(). + * + * @param string $name The name of the service to register, for use with getService(). + * @param callable $instantiator Callback that returns a service instance. + * Will be called with this MediaWikiServices instance as the only parameter. + * Any extra instantiation parameters provided to the constructor will be + * passed as subsequent parameters when invoking the instantiator. + * + * @throws RuntimeException if there is already a service registered as $name. + */ + public function defineService( $name, callable $instantiator ) { + Assert::parameterType( 'string', $name, '$name' ); + + if ( $this->hasService( $name ) ) { + throw new ServiceAlreadyDefinedException( $name ); + } + + $this->serviceInstantiators[$name] = $instantiator; + } + + /** + * Replace an already defined service. + * + * @see defineService(). + * + * @note This causes any previously instantiated instance of the service to be discarded. + * + * @param string $name The name of the service to register. + * @param callable $instantiator Callback function that returns a service instance. + * Will be called with this MediaWikiServices instance as the only parameter. + * The instantiator must return a service compatible with the originally defined service. + * Any extra instantiation parameters provided to the constructor will be + * passed as subsequent parameters when invoking the instantiator. + * + * @throws RuntimeException if $name is not a known service. + */ + public function redefineService( $name, callable $instantiator ) { + Assert::parameterType( 'string', $name, '$name' ); + + if ( !$this->hasService( $name ) ) { + throw new NoSuchServiceException( $name ); + } + + if ( isset( $this->services[$name] ) ) { + throw new CannotReplaceActiveServiceException( $name ); + } + + $this->serviceInstantiators[$name] = $instantiator; + unset( $this->disabled[$name] ); + } + + /** + * Disables a service. + * + * @note Attempts to call getService() for a disabled service will result + * in a DisabledServiceException. Calling peekService for a disabled service will + * return null. Disabled services are listed by getServiceNames(). A disabled service + * can be enabled again using redefineService(). + * + * @note If the service was already active (that is, instantiated) when getting disabled, + * and the service instance implements DestructibleService, destroy() is called on the + * service instance. + * + * @see redefineService() + * @see resetService() + * + * @param string $name The name of the service to disable. + * + * @throws RuntimeException if $name is not a known service. + */ + public function disableService( $name ) { + $this->resetService( $name ); + + $this->disabled[$name] = true; + } + + /** + * Resets a service by dropping the service instance. + * If the service instances implements DestructibleService, destroy() + * is called on the service instance. + * + * @warning This is generally unsafe! Other services may still retain references + * to the stale service instance, leading to failures and inconsistencies. Subclasses + * may use this method to reset specific services under specific instances, but + * it should not be exposed to application logic. + * + * @note This is declared final so subclasses can not interfere with the expectations + * disableService() has when calling resetService(). + * + * @see redefineService() + * @see disableService(). + * + * @param string $name The name of the service to reset. + * @param bool $destroy Whether the service instance should be destroyed if it exists. + * When set to false, any existing service instance will effectively be detached + * from the container. + * + * @throws RuntimeException if $name is not a known service. + */ + final protected function resetService( $name, $destroy = true ) { + Assert::parameterType( 'string', $name, '$name' ); + + $instance = $this->peekService( $name ); + + if ( $destroy && $instance instanceof DestructibleService ) { + $instance->destroy(); + } + + unset( $this->services[$name] ); + unset( $this->disabled[$name] ); + } + + /** + * Returns a service object of the kind associated with $name. + * Services instances are instantiated lazily, on demand. + * This method may or may not return the same service instance + * when called multiple times with the same $name. + * + * @note Rather than calling this method directly, it is recommended to provide + * getters with more meaningful names and more specific return types, using + * a subclass or wrapper. + * + * @see redefineService(). + * + * @param string $name The service name + * + * @throws NoSuchServiceException if $name is not a known service. + * @throws ContainerDisabledException if this container has already been destroyed. + * @throws ServiceDisabledException if the requested service has been disabled. + * + * @return object The service instance + */ + public function getService( $name ) { + if ( $this->destroyed ) { + throw new ContainerDisabledException(); + } + + if ( isset( $this->disabled[$name] ) ) { + throw new ServiceDisabledException( $name ); + } + + if ( !isset( $this->services[$name] ) ) { + $this->services[$name] = $this->createService( $name ); + } + + return $this->services[$name]; + } + + /** + * @param string $name + * + * @throws InvalidArgumentException if $name is not a known service. + * @return object + */ + private function createService( $name ) { + if ( isset( $this->serviceInstantiators[$name] ) ) { + $service = call_user_func_array( + $this->serviceInstantiators[$name], + array_merge( [ $this ], $this->extraInstantiationParams ) + ); + // NOTE: when adding more wiring logic here, make sure copyWiring() is kept in sync! + } else { + throw new NoSuchServiceException( $name ); + } + + return $service; + } + + /** + * @param string $name + * @return bool Whether the service is disabled + * @since 1.28 + */ + public function isServiceDisabled( $name ) { + return isset( $this->disabled[$name] ); + } +} |