Transparent Object
Persistence
(within FLOW3)
Karsten Dambekalns <karsten@typo3.org>
Inspiring people to
share
Samstag, 16. Mai 2009

“DDD persistence”
Domain Models encapsulate behavior and data
Concerned about the problem – only
Infrastructure is of no relevance
Unfortunately you need to be aware of the infrastructure at
some point – at least a little
Inspiring people to
share
Samstag, 16. Mai 2009

Entities
Identity is important
Are not defined by their attributes
Examples could be...
• Projects
• Developers
Inspiring people to
share
Samstag, 16. Mai 2009

Value objects
Have no indentity
Their value is of importance
Are interchangeable
Examples could be...
• Colors
• Numbers
• Tags in Forge
Inspiring people to
share
Samstag, 16. Mai 2009

Aggregates
Cluster associated objects
Have a boundary and a root
The root is a specific entity
References from outside point to the root
An example for an aggregate:
• Project
Inspiring people to
share
Samstag, 16. Mai 2009

Repositories
Provide access to entities (and aggregates)
Allow to find a starting point for traversal
Persisted objects can be searched for
Queries can be built in various ways
Handle storage of additions and updates
Inspiring people to
share
Samstag, 16. Mai 2009

A Domain Model
Project
Repository
Project
Developer
SVN twitter
Account Account
Inspiring people to
share
Samstag, 16. Mai 2009

A Domain Model
Project
Repository
it
Project
Repos
Developer
SVN twitter
Account Account
Inspiring people to
share
Samstag, 16. Mai 2009

A Domain Model
Project
Repository
it
Project
Repos
Developer
SVN twitter
Account Account
Inspiring people to
share
Samstag, 16. Mai 2009

A Domain Model
Project
Repository
it
Project
Repos
Developer
SVN twitter
Account Account
Inspiring people to
share
Samstag, 16. Mai 2009

A Domain Model
Project
Repository
it
Project
Repos
Developer
Aggre-
gates SVN twitter
Account Account
Inspiring people to
share
Samstag, 16. Mai 2009

A Domain Model
Developer
SVN twitter
Account Account
Inspiring people to
share
Samstag, 16. Mai 2009

Using FLOW3...
You just implement the model
No need to care about persisting your model
FLOW3 handles this for you – transparently
Even a Repository only needs little work
Define relevant metadata in the source file using annotations
Inspiring people to
share
Samstag, 16. Mai 2009

@nnotations used
Inspiring people to
share
Samstag, 16. Mai 2009

@nnotations used
@entity
Inspiring people to
share
Samstag, 16. Mai 2009

@nnotations used
@entity
@valueobject
Inspiring people to
share
Samstag, 16. Mai 2009

@nnotations used
@entity
@valueobject
@var
Inspiring people to
share
Samstag, 16. Mai 2009

@nnotations used
@entity
@valueobject
@var
@transient
Inspiring people to
share
Samstag, 16. Mai 2009

@nnotations used
@entity
@valueobject
@var
@transient
@uuid
Inspiring people to
share
Samstag, 16. Mai 2009

@nnotations used
@entity
@valueobject
@var
@transient
@uuid
@identity
Inspiring people to
share
Samstag, 16. Mai 2009

@nnotations used
@entity
@valueobject
@var
@transient
@uuid
@identity
@lazy
Inspiring people to
share
Samstag, 16. Mai 2009

Persistence Manager
Mostly invisible to developers
Manages additions of and updates to objects
Concerned only about objects in repositories
Collects objects and hands over to backend
Allows for objects being persisted at any time
Automatically called to persist at end of script run
Inspiring people to
share
Samstag, 16. Mai 2009

Simplified stack
SQLite PgSQL MySQL ...
Inspiring people to
share
Samstag, 16. Mai 2009

Simplified stack
PDO ...
SQLite PgSQL MySQL ...
Inspiring people to
share
Samstag, 16. Mai 2009

Simplified stack
TYPO3 Content Repository
PDO ...
SQLite PgSQL MySQL ...
Inspiring people to
share
Samstag, 16. Mai 2009

Simplified stack
FLOW3 Persistence
TYPO3 Content Repository
PDO ...
SQLite PgSQL MySQL ...
Inspiring people to
share
Samstag, 16. Mai 2009

Simplified stack
Application Application
FLOW3 Persistence
TYPO3 Content Repository
PDO ...
SQLite PgSQL MySQL ...
Inspiring people to
share
Samstag, 16. Mai 2009

Simplified stack
FLOW3 Persistence
Persistence
TYPO3 CR
Backend
Inspiring people to
share
Samstag, 16. Mai 2009

TYPO3 CR
FLOW3
Inspiring people to
share
Samstag, 16. Mai 2009

Transparent persistence
Explicit support for Domain-Driven Design
Class Schemata are defined by the Domain Model class
• No need to write an XML or YAML schema definition
• No need to define the database model and object model
multiple times at different places
Automatic persistence in the JSR-283 based Content Repository
Legacy data sources can be mounted
Inspiring people to
share
Samstag, 16. Mai 2009

Query Factory
Creates a query for you
Decouples persistence layer from backend
Must be implemented by backend
API with one method:
• public function create($className);
Inspiring people to
share
Samstag, 16. Mai 2009

Query objects
Represent a query for an object type
Allow criteria to be attached
Must be implemented by backend
Simple API
• execute()
• matching()
• equals(), lessThan(), ...
• ...
Inspiring people to
share
Samstag, 16. Mai 2009

Object reconstitution
When fetching objects the content repository looks for
matching nodes
The nodes are mapped to objects by a data mapper
Reconstitution
• does not call __construct()
• restores all non-transient properties
• reinjects dependencies (skips constructor arguments)
Inspiring people to
share
Samstag, 16. Mai 2009

Object reconstitution
public function map(\\F3\\PHPCR\\NodeIteratorInterface $nodes) {
$objects = array();
foreach ($nodes as $node) {
$object = $this->mapSingleNode($node);
$this->persistenceManager->getSession()->registerReconstitutedObject($object);
$objects[] = $object;
}
return $objects;
}
\\F3\\TYPO3CR\\FLOW3\\Persistence\\DataMapper
Inspiring people to
share
Samstag, 16. Mai 2009

Object reconstitution
$explodedNodeTypeName = explode(':', $node->getPrimaryNodeType()->getName(), 2);
$className = str_replace('_', '\\\\', $explodedNodeTypeName[1]);
$classSchema = $this->persistenceManager->getClassSchema($className);
$objectConfiguration = $this->objectManager->getObjectConfiguration($className);
$object = $this->objectBuilder->createEmptyObject($className,
$objectConfiguration);
$this->identityMap->registerObject($object, $node->getIdentifier());
$this->objectBuilder->reinjectDependencies($object, $objectConfiguration);
$this->thawProperties($object, $node, $classSchema);
$object->FLOW3_Persistence_memorizeCleanState();
\\F3\\TYPO3CR\\FLOW3\\Persistence\\DataMapper
Inspiring people to
share
Samstag, 16. Mai 2009

Object reconstitution
public function createEmptyObject($objectName, \\F3\\FLOW3\\Object\\Configuration
$objectConfiguration) {
$className = $objectConfiguration->getClassName();
if (!in_array('F3\\FLOW3\\AOP\\ProxyInterface', class_implements($className))) {
throw new \\F3\\FLOW3\\Object\\Exception\\CannotReconstituteObject('Cannot create
empty instance of the class \"' . $className . '\" because it does not implement
the AOP Proxy Interface.', 1234386924);
}
$object = unserialize('O:' . strlen($className) . ':\"' . $className . '\":0:{};');
$object->FLOW3_AOP_Proxy_setProperty('objectFactory', $this->objectFactory);
$object->FLOW3_AOP_Proxy_setProperty('objectManager', $this->objectManager);
$object->FLOW3_AOP_Proxy_declareMethodsAndAdvices();
return $object;
}
\\F3\\FLOW3\\Object\\Builder
Inspiring people to
share
Samstag, 16. Mai 2009

Lazy Loading
Loading a full object tree makes sense – or not
It does most of the time
If your domain model has small aggregates eager loading
makes sense
If you have expensive to create objects or a lot of smaller ones
you don’t always need, lazy loading helps
Example: displaying a list of projects doesn’t need the projects
details, just the names
Inspiring people to
share
Samstag, 16. Mai 2009

Lazy Loading
Ideally you would not think about lazy loading beyond the
addition of the @lazy annotation
In practice you need to be aware of some technical issues
In place of the real object you get a proxy, so
• you can’t use it at type hinted places
• pass it around without some thinking
Using it otherwise works as expected
After first use the proxy will be completely gone
Inspiring people to
share
Samstag, 16. Mai 2009

The LazyLoadingProxy
public function _loadRealInstance() {
$realInstance = $this
->F3_FLOW3_Persistence_LazyLoadingProxy_population
->__invoke();
$this
->F3_FLOW3_Persistence_LazyLoadingProxy_parent
->FLOW3_AOP_Proxy_setProperty(
$this->F3_FLOW3_Persistence_LazyLoadingProxy_propertyName,
$realInstance
);
return $realInstance;
}
\\F3\\FLOW3\\Persistence\\LazyLoadingProxy
Inspiring people to
share
Samstag, 16. Mai 2009

$dataMapper = $this; // make available to closure...
$objectStorage = new \\F3\\FLOW3\\Persistence\\LazyLoadingProxy(
$parent,
$propertyName,
function() use ($proxyNode, $dataMapper) {
$objectStorage = new \\SplObjectStorage();
$itemNodes = $proxyNode->getNodes();
foreach ($itemNodes as $itemNode) {
$objectNode = $itemNode->getNode('flow3:object');
if ($objectNode->getPrimaryNodeType()->getName() ===
\\F3\\TYPO3CR\\FLOW3\\Persistence\\Backend::NODETYPE_OBJECTPROXY) {
$object = $dataMapper->mapObjectProxyNode($objectNode);
} else {
$object = $dataMapper->mapSingleNode($objectNode);
}
$objectStorage->attach($object);
}
return $objectStorage;
}
);
\\F3\\TYPO3CR\\FLOW3\\Persistence\\DataMapper
Inspiring people to
share
Samstag, 16. Mai 2009

Node structure
PHP has more data structures than a content repository, e.g.
• JSR-283 defines multi-valued properties without keys and
without stable ordering
• Arrays in PHP have keys and order that are stable and might
be important for your code
Thus we do some more mapping to node structures
Inspiring people to
share
Samstag, 16. Mai 2009

Inspiring people to
share
Samstag, 16. Mai 2009

Inspiring people to
share
Samstag, 16. Mai 2009

Inspiring people to
share
Samstag, 16. Mai 2009

Inspiring people to
share
Samstag, 16. Mai 2009

Inspiring people to
share
Samstag, 16. Mai 2009

Questions!
Inspiring people to
share
Samstag, 16. Mai 2009

Inspiring people to
share
Samstag, 16. Mai 2009

Links
FLOW3
http://flow3.typo3.org/
TYPO3CR
http://forge.typo3.org/projects/show/package-typo3cr
JSR-283
http://jcp.org/en/jsr/detail?id=283
Inspiring people to
share
Samstag, 16. Mai 2009

Samstag, 16. Mai 2009

Flickr photo credits:
megapixel13 (barcode), rmrayner (ring), Ducatirider (grapes), Here’s Kate (book shelf)
Pumpkin pictures:
http://ptnoticias.com/pumpkinway/
Inspiring people to
share
Samstag, 16. Mai 2009