models and service layers, hemoglobin and hobgoblins

This talk is clocked at 1 slide per 12.8 seconds and features unsafe amounts of code. Presenter is a registered Class 3 Fast Talker (equal to 1 Gilmore Girls episode).

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Surgeon General's Warning

Notice in accordance with the PHP Disarmament Compact of 1992. Void where prohibited.

ZendCon 2014

Models & Service Layers

Hemoglobin & Hobgoblins

Ross Tuck

Freerange CodemonkeyKnow-It-All

Hot-Air Balloon

@rosstuckrosstuck.com

http://twitter.com/rosstuck

http://rosstuck.com/

About Today

Hemoglobin

Anemia.

Objects can too.

class TodoList {

function setName($name);

function getName();

function setStatus($status);

function getStatus();

function addTask($task);

function setTasks($tasks);

function getTasks();

}

Model

array(

'name' => '',

'status' => '',

'tasks' => ''

);

Model

Bad Thing TM

“In essence the problem with anemic domain models is that they incur all of the costs of a

domain model, without yielding any of the benefits.”

-Martin Fowler

Our industry standard is an antipattern.

Important Note

Models

Stuf

Integration over implementation

Our Setup

class TodoList {


function getName();



function addTask($task);



}

Model

class Task {

function setDescription($desc);

function getDescription();

function setPriority($priority);

function getPriority();

}

Model

An ORM that's not Doctrine 2.A framework that's not Symfony2.

I promise.

function addTaskAction($req) {

$task = new Task();

$task->setDescription($req->get('desc'));

$task->setPriority($req->get('priority'));

$list = $this->todoRepo->findById($req->get('id'));

if (!$list) { throw new NotFoundException(); }

$task->setTodoList($list);

$this->repository->save($task);

$this->auditLog->logNewTask($task);

$this->mailer->sendMessage('New thingy!');

return $this->redirect('edit_page');

}

Controller

Anemic ModelHard to Maintain

TestabilitySRP wha?

In Defense Of CRUD.No, seriously.

Low Barrier to Entry.

Easy to follow.If you can keep it in your head.

Sometimes it really is just data entry.(but it usually isn't)(but sometimes it is)

Not entirely a technical issue.

Service Layer

• Service Layer• Service Container• Web Service• Service Oriented Architecture• Domain Service• Stateless Service• Software-as-a-service• Platform-as-a-service• Whatever-as-a-service meme• Delivery Service• Laundry Service

Application Service

Model

Controller

View

Model

Service Layer

Controller

View

1) Multiple User InterfacesWeb + REST API

+ CLI+ Workers

2) “In between” Logic

3) Decouple from frameworks

Model

Service Layer

Controller

View

Just Build The Stupid Thing

ServiceLayer


$task = new Task();

$task->setDescription($req->get('desc'));

$task->setPriority($req->get('priority'));

$list = $this->todoRepo->findById($req->get('id'));







}

Controller

class TodoService {

function addTask(TodoList $list, $desc, $priority) {

$task = new Task();

$task->setDescription($desc);

$task->setPriority($priority);





}

}

Service

class TodoService {

function findById($id) {

return $this->repository->findById($id);

}

}

Service


$list = $this->todoService->findById($req->get('id'));


$this->todoService->addTask(

$list, $req->get('desc'), $req->get('priority')

);


}

Controller






);


Controller

CLI

function addTaskCommand($id, $desc, $priority) {

$list = $this->todoService->findById($id);


$this->todoService->addTask($list, $desc, $priority);






);


Controller





CLI






);


Controller

CLI





class TodoService {



}

}

Service

class TodoService {


$todo = $this->repository->findById($id);

if (!$todo) {

throw new TodoNotFoundException();

}

return $todo;

}

}

Service

not http exception





);


Controller

CLI








);


Controller

CLI

function addTaskCommand($name, $desc, $priority) {

$list = $this->todoService->findByName($name);






);


Controller

CLI

function addTaskCommand($name, $desc, $priority) {

$listId = $this->todoService->findIdByName($name);

$this->todoService->addTask($listId, $desc, $priority);

class TodoService {

public function findLatestLists() {

return $this->repository->findLatestLists();

}

}

Service

class TodoService {


if ($this->cache->has('latest:lists')) {

return $this->cache->get('latest:lists');

}

$results = $this->repository->findLatestLists();

$this->cache->set('latest:lists', $results);

return $results;

}

}

Service

Indirect Advantages

Readability

Interface Protection

Discoverability

class TodoService {

function findById($id);

function addTask($todo, $desc, $priority);

function prance();

}

Service

Mission Accomplished

class TodoList {


function getName();





}

Model

Dumb as a box of rocks.

class TodoList {


function getName();





}

Model

Where's mah logic?

class TodoListService {


$task = new Task();







}

}

Service

“Organizes business logic by procedures where each procedure handles a single

request from the presentation.”-Fowler

Transaction Scripts

Simple

More flexibleThan CRUD, at least

Don't scale quite as well

What does belong in a service layer?



$task = new Task();







}

}

Service

Orchestration

TransactionsSecurity

NotificationsBulk operations

Facade

Fat Model, Skinny Controller

Fat Model, Skinny Service Layer

(re)Thinking

addTask()

findById()

findLatestLists()

Service

writereadread

Remodeling our Reading

by

Refactoring our Repository

Redux

class TodoService {



if (!$todo) {


}

return $todo;

}

}

Service

interface TodoRepository {

public function findById($id);

public function findLatestLists();

}

Repository

class TodoDbRepository implements TodoRepository {

public function findById($id) {

$todo = $this->db->select(...);

if (!$todo) {


}

return $todo;

}

}

Repository



$todo = $this->db->select(...);

if (!$todo) {


}

return $todo;

}

}

Repository

raw db connection



$todo = $this->repository->find($id);

if (!$todo) {


}

return $todo;

}

}

Repository

FIXED




}

Repository

interface EntityRepository {

public function createQueryBuilder($alias);

public function createResultSetMappingBuilder($alias);

public function createNamedQuery($queryName);

public function createNativeNamedQuery($queryName);

public function clear();

public function find($id, $lockMode, $lockVersion);

public function findAll();

public function findBy($criteria, $orderBy, $limit, $offset);

public function findOneBy($criteria, $orderBy);

public function __call($method, $arguments);

public function getClassName();

public function matching(Criteria $criteria);

}

Repository




}

Repository

class TodoService {



if (!$todo) {


}

return $todo;

}

}

Service

class TodoService {



}

}

Service

class TodoService {




}

$results = $this->repository->findLatestLists();


return $results;

}

}

Service





}

$results = $this->repository->query(...);


return $results;

}

}

Repository

class CachingTodoRepository implements TodoRepository {




}

$results = $this->innerRepository->findLatestLists();


return $results;

}

}

Repository Decorator Decorator object

TodoDbRepository

new TodoService(

new CachingTodoRepository(

new TodoDbRepository(

$entityManager->getRepository('TodoList')

)

)

)

DI Layer

The Inverse Biggie Law

Mo' classesMo' decoupling and reduced overall design issues

Too many finder methods?

$this->todoService->matching(array(

new ListIsClosedCriteria(),

new HighPriorityCriteria()

));

Controller

Doctrine\Criteria

Interlude: Services here...

...services there...

...services everywhere!

Task

TaskService

TodoList

TodoListService

Tag

TagService

TaskRepository TodoListRepository TagRepository

Task

TodoList

TodoService

Tag

Task

TodoList

TodoService

Tag

User

UserService


public function findByUser(User $user) {

return $this->repository->findByUser($user);

}

}

Service


public function findByUser(UserId $userId) {

return $this->repository->findByUser($userId);

}

}

Service

Task

TodoList

TodoService

Tag

User

UserService

Interfaces!

Services aren't only for entities

Scale can differ wildly

PrintingService

Quality of Implementation

(re)Modeling our Writing



$task = new Task();







}

}

Service

class TodoList {

function addTask(Task $task) {

$this->tasks[] = $task;

}

}

Model

class TodoList {

function addTask($desc, $priority) {

$task = new Task();




}

}

Model

class TodoList {


$task = new Task($desc, $priority);


}

}

Model

class TodoList {


$task = new Task($desc, $priority, $this);


}

}

Model

ORM allowance

class TodoList {




}

}

Model



$list->addTask($desc, $priority);

$this->repository->save($list);



}

}

Service

class TodoList {




}

}

Model

Model

class TodoList {




if (count($this->tasks) > 10) {

$this->status = static::UNREALISTIC;

}

}

}

Meaningful Tests

Working Together







}

}

Service

Model

class TodoList {






}

}

}







}

}

Service








$this->auditLog->logTooAmbitious($task);

$this->mailer->sendMessage('Too unrealistic');

}

}

}

Service

PrintingService

TodoService

Something new...

Something better...

Domain Events

Common Pattern

Observer

New usage

Model




$this->raise(

new TaskAddedEvent($this->id, $desc, $priority)

);



}

}

Event

class TaskAddedEvent {

protected $description;

protected $priority;

function __construct($desc, $priority) {

$this->description = $desc;

$this->priority = $priority;

}

}

Model




$this->raise(


);



}

}

Model

class TodoList {

protected $pendingEvents = array();

protected function raise($event) {

$this->pendingEvents[] = $event;

}

public function releaseEvents() {

$events = $this->pendingEvents;

$this->pendingEvents = array();

return $events;

}

}

Excellent Trait

No dispatcher







}

}

Service





$events = $list->releaseEvents();

$this->eventDispatcher->dispatch($events);

}

}

Service

Event Listeners

class EmailListener {

function onTaskAdded($event) {

$taskDesc = $event->getDescription();

$this->mailer->sendMessage('New thingy: '.$taskDesc);

}

function onUserRegistered($event) {

$this->mailer->sendMessage('welcome sucka!');

}

}

Model




$this->raise(


);



}

}

Model




$this->raise(


);



$this->raise(new WasTooAmbitiousEvent($this->id));

}

}

Nice things:

Model




$this->raise(


);



$this->raise(new WasTooAmbitiousEvent($this->id));

}

}

Logic is here!


protected $dependency1;






}

Service

Big ball of mud

in the making

Event Listeners

class EmailListener {

function onTaskAdded($event) {

$taskName = $event->task->getName();

$this->mailer->sendMessage('New thingy: '.$taskName);

}

function onUserRegistered($event) {

$this->mailer->sendMessage('welcome sucka!');

}

} Thin. Easy to test

PrintingService

TodoService

Serialize & Send,

Sucka!

Model




$this->raise(


);



}

}

Less nice things.

Humans hate debugging events.

Dev Logging.Debug comma

nds.

Model

Service Layer

Controller

View

Consuming Application Services





);


}

Controller



$list->addTask($req->get('desc'), $req->get('priority'));


}

Controller




$list->rename('blah');


}

Controller




$list->rename('blah');

$this->todoService->addTask(...);


}

Controller

Model

Service Layer

Controller

View

View Models

PHP version, not MVVM.

class TodoService {


$todoList = $this->repository->findById($id);

return $todoList;

}

}

Service

class TodoService {


$todoList = $this->repository->findById($id);

return new TodoDTO($todoList);

}

}

Service

class TodoDTO {

public function getName();

public function getStatus();

public function getMostRecentTask();

}

TodoDTO

class TodoService {

function generateReport() {

$data = $this->repository->performSomeCrazyQuery();

return new AnnualGoalReport($data);

}

}

Service

Ain't rocket science.

Reverse it: DTOs not for output...

...but for input.

Going Commando

Command

class AddTaskCommand {

public $description;

public $priority;

public $todoListId;

}


$command = new AddTaskCommand();

$command->description = $req->get('description');

$command->priority = $req->get('priority');

$command->todoListId = $req->get('todo_id');

$this->todoService->execute($command);


}

}

Controller

ServiceController Handler Bar

Handler Baz

Handler Foo

ServiceController

Handler Baz


}

Service


function execute($command) {

}

}

Service



get_class($command);

}

}

Service



$command->getName();

}

}

Service



$command->execute();

}

}

Service



}

}

Service

What goes in a handler?

class TodoListHandler {

function handleAddTask($cmd) {

$list = $this->repository->findById($cmd->todoListId);

$list->addTask($cmd->description, $cmd->priority);

}

function handleCompleteTask($command)

function handleRemoveTask($command)

}

Handler



}

}

Service

class CommandBus {


}

}

Service

class MyCommandBus implements CommandBus {


}

}

Service

class ValidatingCommandBus implements CommandBus {


if (!$this->validator->isValid($command)) {

throw new InvalidCommandException();

}

$this->innerCommandBus->execute($command);

}

}

Service

Command



public $priority;

public $todoListId;

}

Command

use Symfony\Component\Validator\Constraints as Assert;


/** @Assert\Length(max="50") */


public $priority;

public $todoListId;

}

LoggingTransactions

Event Dispatching

Fewer Dependencies per class.Simple layers.Easy to test.

View Models + Commands

Model

Service Layer

Controller

View

ViewModelsCommands

CRUD for the framework.Domain Model for the chewy center.

formstemplatesvalidators

tough logicsemanticstesting

Diverge Further

On the surface, it looks the same.


$command = new AddTaskCommand();

$command->description = $req->get('description');

$command->priority = $req->get('priority');

$command->todoListId = $req->get('todo_id');

$this->commandBus->execute($command);


}

}

Controller

Commands = Change DataQueries = Read Data

Model

class TodoList {

function rename($name);

function addTask($desc, $priority);

function getName();


}

Two Models

Write Model

class TodoListModel {



}

class TodoListView {

function getName();


}

Read Model

Model

class TodoList {



function getName();


function getParticipatingUsers();

}

Write Model




}


function getName();



}

Read Model

Write Model




}


function getName();



}

Read Model

ORM entity1 Model

SQL queryN Models

Read and Write are two different systems.

User and Shopping Cart?

Same kind of split.

Surrounding classes?

A lot of it looks the same.





}

}

Handler




}

}

Service




}

}

Service





}

}

Handler

$todoList = new TodoList();

$this->repository->save($todoList);

$todoList->getId();

Controller

$command = new CreateTodoCommand(UUID::create());

$commandBus->execute($command);

$command->uuid;

Controller

Zoom Out

Martin Fowler waz here

Domain events

DB Views

BigHonkingQueue

github.com/beberlei/litecqrs-php/github.com/qandidate-labs/broadway

github.com/gregoryyoung/m-r

Pros & Cons

Big mental leap.Usually more LOC.

Not for every domain.Can be mixed.

Easy to Scale.Bears Complexity.Async Operations.

Event Sourcing.

Event Sourcing?

CQRS+

Event Sourcing

Instead of storing the current state in the db...

...store the domain events?

SnapshotsDebuggingAudit Log

Business IntelligenceOnline/Offline users

Retroactively Fix Bugs

Google it.Or ask me afterwards.

Epilogue

"A foolish consistency is the hobgoblin of little minds."

- Ralph Waldo Emerson

Strong opinions, weakly held.

Strong techniques, weakly held.

PHP 4 -5

PHP 5.3+

Might seem crazy.

Bang for the buck.

People ARE doing this.

It IS working for them.

You can too.

Questions?

Further Reading• codebetter.com/gregyoung• martinfowler.com/tags/domain driven design.html• shawnmc.cool/domain-driven-design• whitewashing.de• verraes.net

Thanks To:

• Warnar Boekkooi @boekkooi

• Daan van Renterghem @DRvanR• Matthijs van den Bos @matthijsvandenb

Image Credits• http://www.flickr.com/photos/calgaryreviews/6427412605/sizes/l/

• http://msnbcmedia.msn.com/j/MSNBC/Components/Slideshows/_production/twisp_090511_/twisp_090511_02.ss_full.jpg

• http://shotthroughawindow.wordpress.com/2011/07/22/hp7b/

• http://www.sxc.hu/photo/605471

• http://martinfowler.com/bliki/images/cqrs/cqrs.png

• http://www.flickr.com/photos/83346641@N00/5578975430/in/photolist-9uZH2y-8rTZL1-dixjR-ffBPiv-8SbK8K-ffS4md-6UeEGP

• http://www.flickr.com/photos/lac-bac/7195938394/sizes/o/

• http://tdzdaily.org/wp-content/uploads/2013/03/Dumb-and-Dumber.png

• http://upload.wikimedia.org/wikipedia/commons/1/17/Charlton_Heston_in_The_Ten_Commandments_film_trailer.jpg

• http://commons.wikimedia.org/wiki/File:Trench_construction_diagram_1914.png

• http://www.flickr.com/photos/jeffreyww/4747314852/sizes/l/

• http://www.flickr.com/photos/jdhancock/3540861791/sizes/l/

• http://www.flickr.com/photos/superfantastic/50088733/sizes/l

joind.in/12101

@rosstuck

Ross Tuckrosstuck.com

models and service layers, hemoglobin and hobgoblins

Technology