Creating your own Entity/Object Manager

Most of us are used to working with an Entity or Object manager. In ORMs like Doctrine, they are the central point to talk to to keep track of our objects (and safely load/store them into a DB or document store). We can use this approach to not only manage objects in our database, but to manage third party sources, like webservices, etc... This talk will explain the place of the Entity Manager in our projects and how to write your own version of it.

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1. CREATING YOUR OWN ENTITY/OBJECT MANAGER Jachim Coudenys / jachim.be @coudenysj
2. ABOUT ME Jachim Coudenys ( ) (Ab)Using PHP since 2002 (4.1.0) @coudenysj
3. KING FOO Developer at King Foo ( ) http://king-foo.be SYMFONY2 TRAINING SensioLabs partner SF4PHPBNL http://training.king-foo.be
4. PHP-WVL Co-Organizer of PHP-WVL ( ) http://php-wvl.be
5. $user = new User(); $user->setName('Jachim Coudenys'); $user->setEmail('jachim@king-foo.be'); $em->persist($user); $em->flush(); $user = $em->find('User', 123); $user->setEmail('jachimcoudenys@gmail.com'); $em->flush(); Who recognizes this? Who is using this? Who loves using this?
6. WHAT?
7. define EntityManager The EntityManager API is used to access a database in a particular unit of work. It is used to create and remove persistent entity instances, to find entities by their primary key identity, and to query over all entities. ( ) http://docs.jboss.org/hibernate/entitymanager/3.5/reference/en/html/architecture.html
8. WHY?
9. TIME FOR SOME HISTORY Small extraction of my presentation. The Database Access rEvolution (with @miljar)
10. FILES Textbook example: guestbook
11. <DATABASE>-FUNCTIONS cubrid_* dbplus_* dbase_* filepro_* ibase_* fbsql_* db2_* ifx_* ingres_* maxdb_* msql_* mssql_* mysql_ oci_* ovrimos_* px_* pg_* sqlite_* sqlsrv_* sybase_*
12. PDO The PHP Data Objects (PDO) extension defines a lightweight, consistent interface for accessing databases in PHP ( ) PHP.net manual
13. ORM FRAMEWORK Object-relational mapping in computer software is a programming technique for converting data between incompatible type systems in relational databases and object- oriented programming languages ( ) Wikipedia
14. ORM FRAMEWORK: ACTIVE RECORD An object that wraps a row in a database table or view, encapsulates the database access, and adds domain logic on that data. ( ) PoEAA: Active Record Doctrine 1.x
15. ORM FRAMEWORK: GATEWAYS An object that encapsulates access to an external system or resource ( ) PoEAA: Gateway Zend_Db_Table Zend_Db_Table_Row
16. ORM FRAMEWORK: DATA MAPPER A layer of Mappers that moves data between objects and a database while keeping them independent of each other and the mapper itself. ( ) PoEAA: Data Mapper Doctrine 2
17. ORM FRAMEWORK: DATA MAPPER This is where an entity/object manager enters the stage.
18. NO REALLY, WHY? Use code that most people recognize Separation of responsibilities Better overview Because you can
19. VARIANTS We will write our own variant, but many exist already ORM ODM Object Document Mapper OGM Object Graph Mapper Etc... Object Relational Mapper Mongo CouchDB PHPCR Neo4j-PHP-OGM
20. HOW?
21. LET'S GET STARTED We want to talk to a SOAP server We want to use entities to send data back and forth We will only implement what we need
22. EXTENDING THE ENTITY MANAGER Let's open the Doctrine\ORM\EntityManager class The class DocBlock says: You should never attempt to inherit from the EntityManager: Inheritance is not a valid extension point for the EntityManager. Instead you should take a look at the {@see \Doctrine\ ORM\ Decorator\ EntityManagerDecorator} and wrap your entity manager in a decorator.
23. ENTITYMANAGER DECORATOR namespace Doctrine\ORM\Decorator; use Doctrine\DBAL\LockMode; use Doctrine\ORM\Query\ResultSetMapping; use Doctrine\ORM\EntityManagerInterface; use Doctrine\Common\Persistence\ObjectManagerDecorator; abstract class EntityManagerDecorator extends ObjectManagerDecorator implements EntityManagerInterface { /** * @var EntityManagerInterface */ protected $wrapped; /** * @param EntityManagerInterface $wrapped */ public function __construct(EntityManagerInterface $wrapped) { $this->wrapped = $wrapped; } /** Allows you to override specific methods Still ORM oriented A lot of stuff we won't actually use
24. OBJECTMANAGER namespace Doctrine\Common\Persistence; interface ObjectManager { /** * Finds an object by its identifier. * * This is just a convenient shortcut for getRepository($className)->find($ * * @param string $className The class name of the object to find. * @param mixed $id The identity of the object to find. * * @return object The found object. */ public function find($className, $id); /** * Tells the ObjectManager to make an instance managed and persistent. * * The object will be entered into the database as a result of the flush op * * NOTE: The persist operation always considers objects that are not yet kn * this ObjectManager as NEW. Do not pass detached objects to the persist o * * @param object $object The instance to make managed and persistent. * Base for all (or most) variants More than enough for now Start with throw exception at first and implement what you need
25. SETUP "Inject" a connection and config namespace My\Project; use Doctrine\Common\Persistence\ObjectManager; use My\Project\Service\SoapClient; class EntityManager implements ObjectManager { /** * @param SoapClient $conn * @param mixed $config */ protected function __construct(SoapClient $conn, $config) { $this->conn = $conn; $this->config = $config; } }
26. find /** * Finds an object by its identifier. * * This is just a convenient shortcut for * getRepository($className)->find($id). * * @param string $className The class name of the object to find. * @param mixed $id The identity of the object to find. * * @return object The found object. */ public function find($className, $id);
27. getRepository /** * Gets the repository for a class. * * @param string $className * * @return \Doctrine\Common\Persistence\ObjectRepository */ public function getRepository($className);
28. REPOSITORY Mediates between the domain and data mapping layers using a collection-like interface for accessing domain objects. http://www.martinfowler.com/eaaCatalog/repository.html
29. getRepository public function getRepository($className) { if (!array_key_exists($className, $this->repositories)) { $repositoryName = str_replace( 'Entity', 'Repository', $className ); $repositoryName .= 'Repository'; $repository = new $repositoryName($this); $this->repositories[$className] = $repository; } return $this->repositories[$className]; } My\Project\Entity\User My\Project\Repository\UserRepository
30. CUSTOM REPOSITORY namespace Doctrine\Common\Persistence; interface ObjectRepository { /** * Finds an object by its primary key / identifier. * * @param mixed $id The identifier. * * @return object The object. */ public function find($id); /** * Finds all objects in the repository. * * @return array The objects. */ public function findAll(); /** * Finds objects by a set of criteria.
31. MAPPING Holds details of object-relational mapping in metadata. http://www.martinfowler.com/eaaCatalog/metadataMapping.html
32. getMetadataFactory /** * Gets the metadata factory used to gather the metadata of classes. * * @return \Doctrine\Common\Persistence\Mapping\ClassMetadataFactory */ public function getMetadataFactory();
33. getClassMetadata /** * Returns the ClassMetadata descriptor for a class. * * The class name must be the fully-qualified class name without a * leading backslash (as it is returned by get_class($obj)). * * @param string $className * * @return \Doctrine\Common\Persistence\Mapping\ClassMetadata */ public function getClassMetadata($className);
34. Doctrine\Common\Persistenc e\Mapping\ClassMetadata namespace Doctrine\Common\Persistence\Mapping; interface ClassMetadata { /** * Gets the fully-qualified class name of this persistent class. * * @return string */ public function getName(); /** * Gets the mapped identifier field name. * * The returned structure is an array of the identifier field names. * * @return array */ public function getIdentifier();
35. getRepository public function getRepository($className) { if (!array_key_exists($className, $this->repositories)) { $classMetadata = $this->getClassMetadata($className); // Doctrine ORM approach $repositoryName = $classMetadata->customRepositoryClassName; $repository = new $repositoryName($this, $classMetadata); $this->repositories[$className] = $repository; } return $this->repositories[$className]; }
36. FIND VIA REPOSITORY namespace My\Project\Repository; use Doctrine\Common\Persistence\ObjectRepository; class UserRepository implements ObjectRepository { public function find($id) { $response = $this->getEntityManager() ->getConnection()->call('UserGet', ['userId' => $id]); // ... // return User entity? } }
37. HYDRATION Hydration is the act of populating an object from a set of data. http://framework.zend.com/manual/current/en/modules/zend.stdlib.hydrator.html
38. DATA HYDRATORS http://doctrine.readthedocs.org/en/latest/en/manual/data-hydrators.html Query::HYDRATE_OBJECT Query::HYDRATE_ARRAY Query::HYDRATE_SCALAR Query::HYDRATE_SINGLE_SCALAR
39. RETURN AN ENTITY IN FIND // UserRepository public function find($id) { // ... $user = new User(); $hydrator = new \Zend\Stdlib\Hydrator\ClassMethods(); $hydrator->hydrate($response, $user); return $user; } Improvements: $this->em->getHydrator($classname); Work with the mapping
40. ENTITIES Now we have a list of objects with an identifier We can (or need to) keep track of these in the OM
41. IDENTITY MAP Ensures that each object gets loaded only once by keeping every loaded object in a map. Looks up objects using the map when referring to them. http://www.martinfowler.com/eaaCatalog/identityMap.html
42. IDENTITY MAP namespace My\Project; use Doctrine\Common\Persistence\ObjectManager; class EntityManager implements ObjectManager { /** * Collection of identities: * array( * 'User' => [1 => object, 5 => object], * // ... * ) */ private $identityMap = array(); public function find($className, $id) { // check map first // store in map } // ...
43. OBJECT STATES EXISTING OBJECTS $user = $em->find('User', 123); $user->setEmail('jachimcoudenys@gmail.com'); $em->flush(): NEW OBJECTS $user = new User(); $user->setName('Jachim Coudenys'); $user->setEmail('jachim@king-foo.be'); $em->persist($user); $em->flush();
44. OBJECT STATES STATE_MANAGED STATE_NEW STATE_DETACHED STATE_REMOVED
45. UNIT OF WORK Maintains a list of objects affected by a business transaction and coordinates the writing out of changes and the resolution of concurrency problems. http://www.martinfowler.com/eaaCatalog/unitOfWork.html
46. UNIT OF WORK Can be an object in the OM (Doctrine) Can be a construction in the OM
47. persist /** * Tells the ObjectManager to make an instance managed and * persistent. The object will be entered into the database as * a result of the flush operation. * * NOTE: The persist operation always considers objects that * are not yet known to this ObjectManager as NEW. Do not pass * detached objects to the persist operation. * * @param object $object The instance to make managed and persistent * * @return void */ public function persist($object);
48. persist IMPLEMENTED class EntityManager implements ObjectManager { private $entities = array(); public function persist($object) { $this->entities[spl_object_hash($object)] = $object; } }
49. remove /** * Removes an object instance. * * A removed object will be removed from the database as a * result of the flush operation. * * @param object $object The object instance to remove. * * @return void */ public function remove($object);
50. remove IMPLEMENTED class EntityManager implements ObjectManager { private $entitiesToRemove = array(); public function remove($object) { $this->entitiesToRemove[spl_object_hash($object)] = $object; } }
51. contains /** * Checks if the object is part of the current UnitOfWork * and therefore managed. * * @param object $object * * @return bool */ public function contains($object);
52. merge /** * Merges the state of a detached object into the persistence * context of this ObjectManager and returns the managed copy * of the object. The object passed to merge will not become * associated/managed with this ObjectManager. * * @param object $object * * @return object */ public function merge($object);
53. refresh /** * Refreshes the persistent state of an object from the database, * overriding any local changes that have not yet been persisted. * * @param object $object The object to refresh. * * @return void */ public function refresh($object);
54. detach /** * Detaches an object from the ObjectManager, causing a managed * object to become detached. Unflushed changes made to the * object if any (including removal of the object), will not be * synchronized to the database. Objects which previously referenced * the detached object will continue to reference it. * * @param object $object The object to detach. * * @return void */ public function detach($object);
55. clear /** * Clears the ObjectManager. All objects that are currently managed * by this ObjectManager become detached. * * @param string|null $objectName if given, only objects of * this type will get detached. * * @return void */ public function clear($objectName = null);
56. flush /** * Flushes all changes to objects that have been queued up to now * to the database. This effectively synchronizes the in-memory * state of managed objects with the database. * * @return void */ public function flush();
57. flush IMPLEMENTED class EntityManager implements ObjectManager { public function flush() { // - loop over $this->entities and save them // - optionally set the identifier of the entity // - update the states of the entities // - loop over $this->entitiesToRemove and delete them // - reset $this->entitiesToRemove } }
58. flush IMPROVED class EntityManager implements ObjectManager { private $entities; private $originalEntities; public function flush() { // actually use a "Unit of Work" object to calculate // changed values between // $this->originalEntities and $this->entities // ... } }
59. flush HACKED EXAMPLE class EntityManager implements ObjectManager { private $entities; private $originalEntities; public function flush() { foreach ($this->entities as $entity) { // keep some SOAP logic together $this->getRepository(get_class($entity)) ->flush($entity); } } }
60. flush HACKED EXAMPLE class UserRepository extends ObjectRepository { public function flush(User $user) { $changedValues = // calculate diffs // different SOAP calls if (array_key_exists('password', $changedValues)) { $this->getEntityManager() ->getConnection()->call( 'UpdatePassword', ['userId' => $user->getId(), 'password' => $changedValues['password']] ); } // etc ... } }
61. initializeObject /** * Helper method to initialize a lazy loading proxy * or persistent collection. * * This method is a no-op for other objects. * * @param object $obj * * @return void */ public function initializeObject($obj);
62. LAZY LOADING An object that doesn't contain all of the data you need but knows how to get it. http://www.martinfowler.com/eaaCatalog/lazyLoad.html
63. THE PROXY PATTERN IN PHP http://ocramius.github.io/presentations/proxy-pattern-in- php/
64. OBJECTMANAGER interface ObjectManager { public function find($className, $id); public function persist($object); public function remove($object); public function merge($object); public function clear($objectName = null); public function detach($object); public function refresh($object); public function flush(); public function getRepository($className); public function getClassMetadata($className); public function getMetadataFactory(); public function initializeObject($obj); public function contains($object); }
65. WELCOME, OBJECT MANAGER
66. EXTRA BITS
67. CACHING 3 types of Metadata Cache Query Cache Result Cache Your turn on repositories Other Doctrine caching ObjectCache
68. QUERY OBJECT An object that represents a database query. http://www.martinfowler.com/eaaCatalog/queryObject.html
69. OTHER VARIANTS Elasticsearch Suggestions?
70. CONCLUSION A lot of variants exist already Not that hard (only take what you need) Check if you can start by extending the ORM (if you are working relational) Use the ObjectManager interface for the rest
71. RESOURCES http://doctrine- orm.readthedocs.org/en/latest/reference/unitofwork.html http://www.martinfowler.com/books/eaa.html
72. THANK YOU https://joind.in/13180 @coudenysj king-foo.be php-wvl.be QUESTIONS?