The document discusses domain-driven design principles and patterns for building an employee management application using Symfony and Doctrine ORM. It starts with an anemic domain model and shows how to refactor it to be more domain-focused using value objects, entities and repositories. It also covers using commands and queries to separate concerns and allow importing employee data without direct database access. The document emphasizes applying DDD and CQRS patterns to structure the application and avoid potential issues around legacy code and direct ORM usage.

1. CODEMEAHR!CODEMEAHR!

2. HI,IAMHI,IAMARNAUD!ARNAUD!

4. ANEMICMODELANEMICMODELVERSUSVERSUSMODELRICHMODELRICH

5. PLAYGROUNDPLAYGROUND
Business: Human resources management
Technical: Symfony / Doctrine ORM

6. WHATDOWEUSUALLYDO?WHATDOWEUSUALLYDO?CRUD!CRUD!
Create Read Update Delete

7. WESTARTWITHCREATINGWESTARTWITHCREATINGANEMICMODELANEMICMODEL

8. namespace AlDomain;
final class Employee
{
/** @var Uuid */
private $id;
/** @var string */
private $name;
/** @var string */
private $position;
/** @var DateTimeInterface */
private $createdAt;
/** @var DateTimeInterface */
private $deletedAt;
// Getter and Setter
}

9. THENATHENAFORMFORMANDAANDACONTROLLERCONTROLLER

10. namespace AlInfrastructureUserInterfaceWebForm;
final class EmployeeType extends AbstractType
{
public function buildForm(FormBuilderInterface $builder, array $options)
{
$builder->add('name');
$builder->add('position');
}
public function configureOptions(OptionsResolver $resolver)
{
$resolver->setDefaults(array(
'data_class' => Employee::class,
));
}
}

11. namespace AlInfrastructureUserInterfaceWebController;
class EmployeeController extends Controller
{
public function indexAction(Request $request): Response
{
}
public function showAction(Request $request): Response
{
}
public function createAction(Request $request): Response
{
}
public function updateAction(Request $request): Response
{
}
public function deleteAction(Request $request): Response
{
}
}

12. namespace AlInfrastructureUserInterfaceWebController;
class EmployeeController extends Controller
{
public function createAction(Request $request): Response
{
$form = $this->createForm(EmployeeType::class, new Employee());
$form->handleRequest($request);
// First, data are mapped to the model then it is validated.
if ($form->isSubmitted() && $form->isValid()) {
$em = $this->get('doctrine.orm.entity_manager');
$em->persist($form->getData());
$em->flush();
return $this->redirectToRoute('employee_list');
}
return $this->render('employee/hire.html.twig', [
'form' => $form->createView()
]);
}
}

14. LET'SREFACTOROURLET'SREFACTOROURANEMICMODELANEMICMODEL

15. HOWDOESESTELLETALKABOUTHERHOWDOESESTELLETALKABOUTHER
WORK?WORK?

17. namespace AlDomain;
final class Employee
{
public function hire(Uuid $identifier, string $name, string $forPosition)
{
}
public function promote(string $toNewPosition)
{
}
public function fire()
{
}
public function retire()
{
}
}

18. namespace AlDomain;
final class Employee
{
/** @var Uuid */
private $id;
/** @var string */
private $name;
/** @var string */
private $position;
/** @var DateTimeInterface */
private $hiredAt;
/** @var DateTimeInterface */
private $firedAt = null;
/** @var DateTimeInterface */
private $retiredAt = null;
}

19. namespace AlDomain;
final class Employee
{
private function __construct(Uuid $identifier, string $name, string $position)
{
$this->id = $identifier;
$this->name = $name;
$this->position = $position;
$this->hireAt = new DateTime();
}
public static function hire(Uuid $identifier, string $name, string $forPosition)
{
return new self($identifier, $name, $forPosition, $hiredAt);
}
public function promote(string $toNewPosition)
{
$this->position = $toNewPosition;
}
public function fire()
{
$this->firedAt = new DateTime();
}
public function retire()
{
$this->retiredAt = new DateTime();
}
}

20. namespace AlDomain;
final class Employee
{
private function __construct(Uuid $identifier, string $name, string $position)
{
if (empty($name)) {
throw new Exception('The name of the employee must not be empty');
}
if (empty($position)) {
throw new Exception('The position of the employee must not be empty');
}
$this->id = $identifier;
$this->name = $name;
$this->position = $position;
$this->hireAt = new DateTime();
}
public function retire()
{
if (null !== $this->fired) {
throw new Exception(
sprint('%s employee has been fired!', $this->name)
);
}
$this->retiredAt = new DateTime();
}
}

21. namespace AlDomain;
final class Name
{
private $name;
private function __construct(string $name)
{
if (empty($name)) {
throw new Exception('The name of the employee must not be empty');
}
$this->name = $name
}
public function __toString(): string
{
return $this->name;
}
}

22. namespace AlDomain;
final class Employee
{
private function __construct(
EmployeeIdentifier $identifier,
Name $name,
Position $position
) {
$this->id = $identifier;
$this->name = $name;
$this->position = $position;
$this->hireAt = new DateTime();
}
}

23. HOWCANWEUSEITINOURAPPLICATION?HOWCANWEUSEITINOURAPPLICATION?

24. FIRSTPROBLEM:FIRSTPROBLEM:HOWDOWEUSEHOWDOWEUSE
DOCTRINE?DOCTRINE?
We use them as query repositories
interface EmployeeRepository
{
public function findByNameAndPositionWithoutFiredPeople(
string $name,
string $position
): mixed;
}

25. WHATISAWHATISAREPOSITORYREPOSITORY??
«A repository behaves like a collection of unique entities
without taking care about the storage»

26. WHATDOESITLOOKLIKE?WHATDOESITLOOKLIKE?

27. namespace AlInfrastructure;
final class EmployeeRepository implements EmployeeRepositoryInterface
{
public function get(Uuid $identifier): Employee
{
}
public function add(Employee $employee): void
{
}
public function remove(Employee $employee): void
{
}
}

28. namespace AlInfrastructure;
final class EmployeeRepository implements EmployeeRepositoryInterface
{
/** @var EntityManagerInterface */
private $entityManager;
public function __construct(EntityManagerInterface $entityManager)
{
$this->entityManager = $entityManager;
}
}

29. namespace AlInfrastructure;
final class EmployeeRepository implements EmployeeRepositoryInterface
{
public function get(Uuid $identifier): Employee
{
$employee = $this->entityManager->find(
Employee::class,
$identifier->toString()
);
if (null === $employee) {
throw new NonExistingEmployee($identifier->toString());
}
return $employee;
}
public function add(Employee $employee): void
{
$this->entityManager->persist($employee);
$this->entityManager->flush($employee);
}
public function remove(Employee $employee): void
{
$this->entityManager->remove($employee);
$this->entityManager->flush($employee);
}
}

30. ISITMANDATORYTOUSESETTER?ISITMANDATORYTOUSESETTER?NO!NO!
Doctrine uses the re ection to map data
Doctrine does not instantiate objects (Ocramius/Instantiator)

31. SECONDPROBLEM:SECONDPROBLEM:FORMCOMPONENTFORMCOMPONENT
PropertyAccessor is used to map data, it needs public properties or setter.

32. COMMANDCOMMANDTOTHERESCUE!TOTHERESCUE!
« A Command is an object that represents all the information
needed to call a method.»

33. LET’SCREATEACOMMANDLET’SCREATEACOMMAND

34. namespace AlApplication;
final class HireEmployeeCommand
{
/** @var string */
public $name = '';
/** @var string */
public $position = '';
}

35. LET’SUPDATEOURCONTROLLERLET’SUPDATEOURCONTROLLER

36. namespace AlInfrastructureUserInterfaceWebController;
class EmployeeController extends Controller
{
public function hireAction(Request $request): Response
{
$form = $this->createForm(EmployeeType::class, new HireEmployeeCommand());
$form->handleRequest($request);
// Superficial validation
if ($form->isSubmitted() && $form->isValid()) {
$employeeCommand = $form->getData();
// Domain validation
$employee = Employee::hire(
Uuid::uuid4(),
$employeeCommand->getName(),
$employeeCommand->getPosition()
);
$this->get('employee.repository')->add($employee);
return $this->redirectToRoute('employee_list');
}
return $this->render('employee/hire.html.twig', [
'form' => $form->createView()
]);
}
}

38. NOW,ESTELLEWANTSTOIMPORTNOW,ESTELLEWANTSTOIMPORT
EMPLOYEES!EMPLOYEES!

39. COMMANDBUSCOMMANDBUSTOTHERESCUETOTHERESCUE
«A Command Bus accepts a Command object and delegates it
to a Command Handler.»

40. LET’SUPDATEOURCONTROLLERLET’SUPDATEOURCONTROLLER
Here, we are going to use simple-bus/message-bus

41. namespace AlInfrastructureUserInterfaceWebController;
class EmployeeController extends Controller
{
public function hireAction(Request $request): Response
{
$form = $this->createForm(EmployeeType::class, new HireEmployeeCommand());
$form->handleRequest($request);
if ($form->isSubmitted() && $form->isValid()) {
$employeeCommand = $form->getData();
try {
$this->get('command_bus')->handle($employeeCommand);
} catch (Exception $e) {
$this->addFlash('error', 'An error occurs!');
}code
return $this->redirectToRoute('employee_list');
}
return $this->render('employee/hire.html.twig', [
'form' => $form->createView()
]);
}
}

42. LET’SCREATEACOMMANDHANDLERLET’SCREATEACOMMANDHANDLER

43. namespace AlApplicationHandler;
final class HireEmployeeHandler
{
/** @var EmployeeRepositoryInterface */
private $employeeRepository;
public function __construct(EmployeeRepositoryInterface $employeeRepository)
{
$this->employeeRepository = $employeeRepository;
}
public function handle(HireEmployee $command): void
{
$employee = Employee::hire(
Uuid::uuid4(),
$command->getName(),
$command->getPosition()
);
$this->employeeRepository->add($employee);
}
}

45. ESTELLEWON'TUSEESTELLEWON'TUSEPHPMYADMINPHPMYADMINTOREADTOREAD
DATA!DATA!

46. DOOURMODELSNEEDGETTER?DOOURMODELSNEEDGETTER?NOTNOT
NECESSARILY!NECESSARILY!

47. DTO(DATATRANSFEROBJECT)DTO(DATATRANSFEROBJECT)TOTHETOTHE
RESCUE!RESCUE!
«A Data Transfer Object is an object that is used to
encapsulate data, and to send it from one subsystem of an
application to another.»

48. DOCTRINE(>=2.4):DOCTRINE(>=2.4):OPERATORNEWOPERATORNEW

49. namespace AlDomainReadModel;
final class Employee
{
/** string */
private $id;
/** string */
private $name;
/** string */
private $position;
public function __construct(string $id, string $name, string $position)
{
$this->id = $id;
$this->name = $name;
$this->position = $position;
}
// Define an accessor for each property
}

50. namespace AlInfrastructure;
final class ListEmployeeQuery implement SearchEmployeeQueryInterface
{
private $entityManager;
public function __construct(EntityManagerInterface $entityManager)
{
$this->entityManager = $entityManager;
}
public function search(): array
{
$queryBuilder = $this->entityManager->createQueryBuilder()
->from(Employee::class, 'e')
->select(
sprintf('NEW %s(e.id, e.name, e.position)', Employee::class)
);
// NEW AlDomainReadModelEmployee(e.id, e.name, e.position)
return $queryBuilder->getQuery()->getResult();
}
}

51. WECANSEARCHANDDISPLAYEMPLOYEEWECANSEARCHANDDISPLAYEMPLOYEE
DATA!DATA!

53. LEGACYBLINDNESSLEGACYBLINDNESS//DDDDDD//CQRSCQRS
Domain Driven Design
Command Query Responsibility Segregation

54. WHATISTHEBESTSOLUTION?WHATISTHEBESTSOLUTION?
It depends on what you want!

55. THAT'STHEEND!THAT'STHEEND!

56. THANKYOU!QUESTIONS?THANKYOU!QUESTIONS?
aRn0D _aRn0D