Maciej Malarz (Codete) - Database? Meh, implementation detail

Database? Meh,
implementation detail
Maciej Malarz (@malarzm)

@malarzm

Entity
/** @ORMEntity */
class Submission
{
/** @ORMOneToOne(targetEntity="User") */
private $acceptedBy;
/** @ORMColumn(type="datetime") */
private $acceptedOn;
/** @ORMColumn(type="string") */
private $applicant;
private $rejectedBy;
private $rejectedOn;
private $title;
}

List action
/**
* @Route("/", name="homepage")
*/
public function listAction()
{
$submissions = $this->getDoctrine()->getManager()
->getRepository(Submission::class)
->findBy(['acceptedOn' => null, 'rejectedOn' => null]);
return [ 'submissions' => $submissions ];
}

View action
/**
* @Route("/{id}", name="submission")
* @Template()
*/
public function viewAction(Request $request)
{
$s = $this->getDoctrine()->getManager()->find(Submission::class, $request->get('id'));
if ($s === null) {
throw $this->createNotFoundException();
}
return [ 'submission' => $s ];
}
/**
* @ParamConverter("submission", class="AppBundleEntitySubmission")
* @Template
*/
public function viewAction(Submission $submission)
{
return [ 'submission' => $submission ];
}

Accept & reject actions
/**
* @Route("/accept/{id}", name="accept")
*/
public function acceptAction(Submission $submission)
{
$submission->setAcceptedBy($this->getUser());
$submission->setAcceptedOn(new DateTime());
$this->getDoctrine()->getManager()->flush();
return $this->redirectToRoute('homepage');
}
/**
* @Route("/accept/{id}", name="reject")
*/
public function rejectAction(Submission $submission)
{
$submission->setRejectedBy($this->getUser());
$submission->setRejectedOn(new DateTime());
}

et voilà!

Forgot the slug
class SubmissionsSlugger
{
public function prePersist(LifecycleEventArgs $event)
{
/** @var Submission $entity */
$entity = $event->getEntity();
if ( ! ($entity instanceof Submission)) {
return;
}
$entity->setSlug($this->slugify($entity->getTitle()));
}
private function slugify($string)
{
return preg_replace('/[^a-z0-9]/', '-', strtolower(trim(strip_tags($string))));
}
}

New features

Oh hey, project was
a success!

1. Value Objects

VO candidate
/** @ORMEntity */
class Submission
{
private $acceptedBy;
private $acceptedOn;
private $applicant;
private $rejectedBy;
private $rejectedOn;
private $title;
}

Introducing VO
/** @ORMEmbeddable */
abstract class AbstractStatus
{
private $by;
private $on;
private $message;
public function __construct(User $by, $message)
{
$this->by = $by;
$this->on = new DateTime();
$this->message = $message;
}
}
class StatusAccepted extends AbstractStatus { }
class StatusCancelled extends AbstractStatus { }
class StatusRejected extends AbstractStatus { }

Mapping
class Submission
{
private $applicant;
private $slug;
/** @ORMEmbedded(class="???") */
private $status;
private $title;
}

Actually you can but with
MongoDB ODM ;)

/** @ORMEmbeddable */
class Status
{
const ACCEPTED = 0;
const CANCELLED = 1;
const REJECTED = 2;
private $by;
private $on;
private $message;
/** @ORMColumn(type="integer") */
private $type;
public function __construct($type, User $by, $message)
{
$this->by = $by;
$this->on = new DateTime();
$this->message = $message;
$this->type = $type;
}
}
Not very good on its own...

A bit better...
/** @ORMEntity */
class Submission
{
/**
* @ORMEmbedded(class="Status")
* @var Status
*/
private $status;
public function getStatus()
{
switch ($this->status->getType()) {
case Status::ACCEPTED:
return new StatusAccepted(/* ... */);
/* ... */
}
}
public function setStatus(Status $status)
{
switch (get_class($status)) {
case StatusAccepted::class:
$this->status = new Status(/* ... */);
break;
/* ... */
}
}

We can do better
Just don't use DB mapped entities as domain entities

Recap: Value Objects
A small simple object, like money or a
date range, whose equality isn't based on
identity.

2. Object Managers

Remember these ones?
/**
* @Route("{id}", name="submission")
*/
{
$s = $this->getDoctrine()->getManager()->find(Submission::class, $request->get('id'));
if ($s === null) {
}
}
/**
* @Route("/accept/{id}", name="reject")
*/
public function rejectAction(Submission $submission)
{
$submission->setRejectedBy($this->getUser());
$submission->setRejectedOn(new DateTime());
}

Your very own manager!
class SubmissionManager
{
/** @var ObjectManager */
private $objectManager;
public function __construct(ObjectManager $objectManager)
{
$this->objectManager = $objectManager;
}
public function find($id)
{
return $this->objectManager->find(Submission::class, $id);
}
public function save(Submission $submission)
{
$this->objectManager->persist($submission);
$this->objectManager->flush($submission);
}
}

Look ma! Using only my own stuff
/**
* @Template
*/
{
$s = $this->get('submission_manager')->find($request->get('id'));
if ($s === null) {
}
}
/**
* @Route("/accept/{id}", name="accept")
*/
public function acceptAction(Submission $submission)
{
$submission->setAcceptedBy($this->getUser());
$submission->setAcceptedOn(new DateTime());
$this->get('submission_manager')->save($submission);
}

Own events
{
/** @var ObjectManager */
private $objectManager;
/** @var EventDispatcherInterface */
private $eventDispatcher;
public function __construct(ObjectManager $objectManager, EventDispatcherInterface $eventDispatcher)
{
$this->objectManager = $objectManager;
$this->eventDispatcher = $eventDispatcher;
}
{
if ($this->objectManager->contains($submission)) {
$this->eventDispatcher->dispatch('submission.update', new SubmissionEvent($submission));
} else {
$this->objectManager->persist($submission);
$this->eventDispatcher->dispatch('submission.create', new SubmissionEvent($submission));
}
$this->objectManager->flush($submission);
}
}

Recap: Object Managers
Manages lifecycle and instances of entities.

3. Repositories

We had this action:
{
}

Custom repositories
class SubmissionRepository extends EntityRepository
{
public function findPending()
{
return $this->findBy(['acceptedOn' => null, 'rejectedOn' => null]);
}
}
{
public function getRepository()
{
return $this->objectManager->getRepository(Submission::class);
}
}
{
$submissions = $this->get('submission_repository')->findPending();
}

Moar customization
{
/** @var SubmissionContext */
private $context;
public function __construct(EntityManager $em, ClassMetadata $class, SubmissionContext $context)
{
parent::__construct($em, $class);
$this->context = $context;
}
public function findAccepted()
{
$qb = $this->createQueryBuilder('s');
$accepted = $qb->where($qb->expr()->isNotNull('s.accepted'))
->getQuery()->getArrayResult();
return $this->finalizeCollection($accepted);
}
{
return $this->finalizeCollection($this->findBy(['acceptedOn' => null, 'rejectedOn' => null]));
}
private function finalizeCollection($submissions)
{
return array_filter($submissions, array($this->context, 'applyRules'));
}
}

Verbs matter
class SubmissionRepository
{
{
return $this->objectManager->find(Submission::class, $id);
}
public function get($id)
{
$s = $this->find($id);
if ($s === null) {
throw new NoResultException();
}
return $s;
}
}

Separate queries
class DoctrineSubmissionQuery
{
private $context;
/** @var SubmissionRepository */
private $repository;
public function __construct(SubmissionRepository $repository, SubmissionContext $context)
{
$this->repository = $repository;
}
public function __invoke()
{
// ...
}
}

Wanna cache? No problem!
class CacheSubmissionQuery
{
/** @var Cache */
private $cache;
private $context;
public function __construct(Cache $cache, SubmissionContext $context)
{
$this->cache = $cache;
}
public function __invoke()
{
// Get data from check based on some context hash
}
}

Recap: Repositories
Repositories contains business-specific
methods for locating entities.

4. Entities

Stay valid after __construct
$payment = new Payment();
$payment->setCurrency('USD');
$payment->setAmount(-69);

class Payment
{
private $amount;
private $currency;
public function __construct($amount, $currency)
{
if ((int) $amount <= 0) {
throw new InvalidArgumentException('Payment amount must be greater than 0');
}
if ( ! in_array($currency, ['USD', 'PLN'])) {
throw new InvalidArgumentException($currency . ' currency is not allowed');
}
$this->amount = $amount;
$this->currency = $currency;
}
}

You may need DTO
class PaymentDTO
{
/**
* @AssertGreaterThan(0)
*/
public $amount;
public $currency;
public function toPayment()
{
return new Payment($this->amount, $this->currency);
}
}

Recap: Entities
A thing with unique and independent
existence. Since it does exist it shall be
always valid.

Recap: All ze stuff
Value Objects
Object Managers
Repositories Entities

5. Holy Grails

5.1 Tests

Not very testable
/**
* @Route("/", name="homepage")
*/
{
}

Better but...
{
// public function __construct(EntityManager $em, ClassMetadata $class)
// {
// parent::__construct($em, $class);
// }
{
}
}

Pull out an interface
interface SubmissionRepository
{
public function findPending();
}
class DoctrineSubmissionRepository extends EntityRepository implements SubmissionRepository
{
{
}
}
class InMemorySubmissionRepository implements SubmissionRepository
{
private $data = array();
{
return array_filter($this->data, function(Submission $s) {
return $s->getAcceptedOn() === null && $s->getRejectedOn() === null;
});
}
}

Need stub?
class InMemorySubmissionRepository implements SubmissionRepository
{
private $data = array();
public function __construct(array $data = array())
{
$this->data = $data;
}
{
return array_filter($this->data, function(Submission $s) {
return $s->getAcceptedOn() === null && $s->getRejectedOn() === null;
});
}
}

Or full flow?
interface SubmissionManager
{
public function find($id);
public function save(Submission $submission);
}
class InMemorySubmissionManager implements SubmissionManager
{
/** @var InMemorySubmissionRepository */
private $repository;
public function __construct(InMemorySubmissionRepository $repository)
{
$this->repository = $repository;
}
{
return $this->repository->find($id);
}
{
$this->repository->store($submission);
}
}

Applies everywhere!
interface TaxCalculator
{
public function calculate(Income $income);
}
class Some3rdPartTaxCalculator implements TaxCalculator
{
public function calculate(Income $income)
{
// Some expensive API call
}
}
class StubbedTaxCalculator implements TaxCalculator
{
public function calculate(Income $income)
{
return $income->getMoney() * 0.19;
}
}

5.2 One-off storages

Hey, let's integrate with UniSubmission8.0
class UniSubmissionManager implements SubmissionManager
{
/** @var UniSubmissionApi */
private $api;
public function __construct(UniSubmissionApi $api)
{
$this->api = $api;
}
{
$this->api->find($id);
}
{
$this->api->push($submission);
}
}
class UniSubmissionRepository implements SubmissionRepository
{
// ...
}

5.3 Changing ORM

Doctrine not cool anymore
class SuperDuperORMSubmissionManager implements SubmissionManager
{
/** @var SuperDuperORM */
private $orm;
/** @var EventDispatcherInterface */
private $eventDispatcher;
public function __construct(SuperDuperORM $orm, EventDispatcherInterface $eventDispatcher)
{
$this->orm = $orm;
$this->eventDispatcher = $eventDispatcher;
}
{
$this->orm->gimme(Submission::class, $id);
}
{
if ($this->orm->haz($submission)) {
$this->eventDispatcher->dispatch('submission.update', new SubmissionEvent($submission));
} else {
$this->orm->register($submission);
$this->eventDispatcher->dispatch('submission.create', new SubmissionEvent($submission));
}
$this->orm->push($submission);
}
}

But for this you
should really have
own persistence
interface and write
adapters

5.4 Integrity

Saw (actually written, I regret) this
class Menu
{
private $tree;
private $flattened;
public function getFlattened()
{
if ($this->flattened !== null) {
return $this->flattened;
}
return $this->flattened = $this->doFlattenTree();
}
public function removeNode(Node $node)
{
$this->tree->remove($node);
// "Meh, after removing node the page is refreshing, no need to refresh flattened structure"
}
}

6. Thank you!

7. Questions?

8. Thank you!
www.slideshare.net/MaciejMalarz/database-meh-implementation-detail

Maciej Malarz (Codete) - Database? Meh, implementation detail

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Viewers also liked

Viewers also liked (16)

Similar to Maciej Malarz (Codete) - Database? Meh, implementation detail

Similar to Maciej Malarz (Codete) - Database? Meh, implementation detail (20)

More from Business Link Krakow

More from Business Link Krakow (20)

Recently uploaded

Recently uploaded (20)

Maciej Malarz (Codete) - Database? Meh, implementation detail