The document discusses dependency injection, providing definitions and examples. It defines dependency as application layers depending on other layers or external components. Dependency injection manages these dependencies by allowing external code to fulfill dependencies at runtime rather than hard-coding fulfillment. The document outlines constructor, setter, and interface injection and describes configuration via annotations, XML, YAML, and PHP code. It provides examples of how dependency injection enables easy unit testing and configurable implementations.

1. Real World Dependency Injection
Stephan Hochdörfer, bitExpert AG
"Dependency Injection is a key element of agile architecture"
Ward Cunningham

2. Agenda
1. About me
2. What is Dependency Injection?
3. Real World examples
4. Pros & Cons
5. Questions

3. About me
 Stephan Hochdörfer, bitExpert AG
 Department Manager Research Labs
 enjoying PHP since 1999
 S.Hochdoerfer@bitExpert.de
 @shochdoerfer

4. What is Dependency Injection?
What is Dependency?

5. What is Dependency Injection?
What is Dependency?
 Application Layer

Data Access layer

Business logic layer

...
 External components

Framework classes

Webservices

...

6. What is Dependency Injection?
Why are Dependencies bad?

7. What is Dependency Injection?
Why are Dependencies bad?
„new“ is evil!

8. What is Dependency Injection?
Why are Dependencies bad?
 Tightly coupled code
 Hard to re-use components
 Hard to test components, no isolation

9. What is Dependency Injection?
Simple Dependency
Main Required
class class

10. What is Dependency Injection?
Complex Dependency
Required
class
Main Required
class class
Required
class

11. What is Dependency Injection?
Very complex Dependency
Database
Required
class
External
Main Required
resource
class class
Required
class
Required Required
Webservice
class class

12. What is Dependency Injection?
Very complex Dependency
Database
Required
class
External
Main Required
resource
class class
Required
class
Required Required
Webservice
class class

13. What is Dependency Injection?
Very complex Dependency
Database
Required
class
External
Main Required
resource
class class
Required
class
Required Required
Webservice
class class

14. What is Dependency Injection?
How to Manage Dependencies?

15. What is Dependency Injection?
How to Manage Dependencies?
You don`t need to. The Framework does it all!

16. What is Dependency Injection?
How to Manage Dependencies?
Simple Container vs. Full stacked Framework

17. What is Dependency Injection?
What is Dependency Injection?

18. What is Dependency Injection?
What is Dependency Injection?
Consumer

19. What is Dependency Injection?
What is Dependency Injection?
Consumer Dependencies

20. What is Dependency Injection?
What is Dependency Injection?
Consumer Dependencies Container

21. What is Dependency Injection?
What is Dependency Injection?
Consumer Dependencies Container

22. What is Dependency Injection?
Types of Dependency Injection
Type 1: Constructor injection
<?php
class MySampleService implements IMySampleService {
/**
* @var ISampleDao
*/
private $oSampleDao;
public function __construct(ISampleDao $poSampleDao) {
$this->oSampleDao = $poSamleDao;
}
}
?>

23. What is Dependency Injection?
Types of Dependency Injection
Type 2: Setter injection
<?php
class MySampleService implements IMySampleService {
/**
* @var ISampleDao
*/
private $oSampleDao;
public function setSampleDao(ISampleDao $poSampleDao) {
$this->oSampleDao = $poSamleDao;
}
}
?>

24. What is Dependency Injection?
Types of Dependency Injection
Type 3: Interface injection
<?php
class MySampleService implements IMySampleService, IApplicationContextAware
{
/**
* @var IApplicationContext
*/
private $oCtx;
public function setApplicationContext(IApplicationContext $poCtx) {
$this->oCtx = $poCtx;
}
}
?>

25. What is Dependency Injection?
Configuration Types
Type 1: Annotations
<?php
class MySampleService implements IMySampleService {
/**
* @var ISampleDao
*/
private $oSampleDao;
/**
* @Inject
*/
public function __construct(ISampleDao $poSampleDao) {
$this->oSampleDao = $poSamleDao;
}
}
?>

26. What is Dependency Injection?
Configuration Types
Type 1: Annotations
<?php
class MySampleService implements IMySampleService {
/**
* @var ISampleDao
*/
private $oSampleDao;
/**
* @Inject
* @Named('TheSampleDao')
*/
public function __construct(ISampleDao $poSampleDao) {
$this->oSampleDao = $poSamleDao;
}
}
?>

27. What is Dependency Injection?
Configuration Types
Type 2: External configuration via XML
<?xml version="1.0" encoding="UTF-8" ?>
<beans xmlns="http://www.bitexpert.de/schema"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.bitexpert.de/schema/
http://www.bitexpert.de/schema/bitFramework-beans.xsd">
<bean id="SampleDao" class="SampleDao">
<constructor-arg value="app_sample" />
<constructor-arg value="iSampleId" />
<constructor-arg value="BoSample" />
</bean>
<bean id="SampleService" class="MySampleService">
<constructor-arg ref="SampleDao" />
</bean>
</beans>

28. What is Dependency Injection?
Configuration Types
Type 2: External configuration via YAML
services:
SampleDao:
class: SampleDao
arguments: ['app_sample', 'iSampleId', 'BoSample']
SampleService:
class: SampleService
arguments: [@SampleDao]

29. What is Dependency Injection?
Configuration Types
Type 3: PHP Configuration
<?php
class BeanCache extends bF_Beanfactory_Container_PHP_ACache {
protected function createSampleDao() {
$oBean = new SampleDao('app_sample', 'iSampleId', 'BoSample');
return array("oBean" => $oBean, "bSingleton" => "1");
}
protected function createMySampleService() {
$oBean = new MySampleService($this->getBean('SampleDao'));
return array("oBean" => $oBean, "bSingleton" => "1");
}
?>

30. What is Dependency Injection?
Cache, Cache, Cache!
180
160
140
120
100
80
60
40
20
0
XML no Caching XML with Caching PHP PHP compiled
Requests per Second meassured via Apache HTTP server benchmarking tool

31. Real world examples
"High-level modules should not depend on low-level modules.
Both should depend on abstractions."
Robert C. Martin

32. Real World examples
Unittesting made easy
<?php
require_once 'PHPUnit/Framework.php';
class ServiceTest extends PHPUnit_Framework_TestCase {
public function testSampleService() {
$oSampleDao = $this->getMock('ISampleDao');
// run test case
$oService = new MySampleService($oSampleDao);
$bReturn = $oService->doWork();
// check assertions
$this->assertTrue($bReturn);
}
}
?>

33. Real World examples
One class, multiple configurations
Implementation
Live Working
<?xml version="1.0" encoding="UTF-8" ?>
<beans xmlns="http://www.bitexpert.de/schema"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.bitexpert.de/schema/
http://www.bitexpert.de/schema/bitFramework-beans.xsd">
<bean id="ExportLive" class="MyApp_Service_ExportManager">
<constructor-arg ref="DAOPageLive" />
</bean>
<bean id="ExportWorking" class="MyApp_Service_ExportManager">
<constructor-arg ref="DAOPageWorking" />
</bean>
</beans>

34. Real World examples
One class, multiple configurations II
<?php
class Promio_Action_Account_Auth extends bF_Mvc_Action_AFormAction {
private $oAccountManager;
private $iType;
public function __construct(Promio_Service_IAccountManager $poAccountManager) {
$this->oAccountManager = $poAccountManager;
}
public function setType($piType) {
$this->iType = (int) $piType;
}
protected function processFormSubmission(bF_Bo_ABo $poBOFormBackingObject) {
$oMaV = new bF_Mvc_ModelAndView($this->getSuccessView(), true);
try {
$poBOFormBackingObject->setType($this->iType);
$this->oAccountManager->save($poBOFormBackingObject);
}
catch(bF_Service_ServiceException $oException) {
$oMaV = new bF_Mvc_ModelAndView($this->getFailureView(), true);
}
return $oMaV;
}
}
?>

35. Real World examples
Mocking external services
Consumer Connector Webservice
IConnector interface
<?xml version="1.0" encoding="UTF-8" ?>
<beans xmlns="http://www.bitexpert.de/schema"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.bitexpert.de/schema/
http://www.bitexpert.de/schema/bitFramework-beans.xsd">
<bean id="Consumer" class="MyApp_Service_Consumer">
<constructor-arg ref="Connector" />
</bean>
</beans>

36. Real World examples
Mocking external services
alternative Local
Consumer
Connector filesystem
IConnector interface
<?xml version="1.0" encoding="UTF-8" ?>
<beans xmlns="http://www.bitexpert.de/schema"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.bitexpert.de/schema/
http://www.bitexpert.de/schema/bitFramework-beans.xsd">
<bean id="Consumer" class="MyApp_Service_Consumer">
<constructor-arg ref="AltConnector" />
</bean>
</beans>

37. Real World examples
Clean, readable code
<?php
class Promio_Action_News_Delete extends bF_Mvc_Action_AAction {
/**
* @var Promio_Service_INewsManager
*/
private $oNewsManager;
public function __construct(Promio_Service_INewsManager $poNewsManager) {
$this->oNewsManager = $poNewsManager;
}
protected function execute(bF_Mvc_Request $poRequest) {
try {
$this->oNewsManager->delete((int) $poRequest->getVar('iNewsId'));
}
catch(bF_Service_ServiceException $oException) {
}
$oMaV = new bF_Mvc_ModelAndView($this->getSuccessView(), true);
return $oMaV;
}
}
?>

38. Real World examples
No framework dependency
<?php
class MySampleService implements IMySampleService {
/**
* @var ISampleDao
*/
private $oSampleDao;
public function __construct(ISampleDao $poSampleDao) {
$this->oSampleDao = $poSamleDao;
}
public function getSample($piSampleId) {
try {
return $this->oSampleDao->readByPrimaryKey((int) $piSampleId);
}
catch(DaoException $oException) {
}
}
}
?>

39. Pros & Cons
Benefits
 Good for agile development

Reducing amount of code

Helpful for Unit testing
 Loose coupling

Least intrusive mechanism

Switching implementations by changing configuration

Separation of glue code from business logic
 Clean view on the code

Separate configuration from code

Getting rid of boilerpate configuration code

40. Pros & Cons
Cons
 To many different implementations, no standard today!

Bucket, Crafty, FLOW3, Imind_Context, PicoContainer,
Pimple, Phemto, Stubbles, Symfony 2.0, Sphicy, Solar,
Substrate, XJConf, Yadif, Zend_Di (Proposal), Lion
Framework, Spiral Framework, Xyster Framework, …

No JSR 330 for PHP
 Simple Containers vs. fully-stacked Framework

No dependency from application to Container!
 Developers need to be aware of configuration ↔ runtime

41. http://joind.in/1553