CDI: How do I ?

CDI : How do I ?

by antonio goncalves@agoncal

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Antonio Goncalves

What is CDI ?

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What is CDI ?

● Dependency injection● Lose coupling, strong typing● Context management● Interceptors and decorators● Event bus● Extensions

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History of CDI

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Implementations

Creating a Web App

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Demos with JBoss Forge

● Java EE scaffolding tool● Shell commands● CRUD application● Gets you start quickly● Takes care of integration● Plugin based

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Demo: Creating a Web App

Dependency Injection

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How Do I ?

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Use @Inject !

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@Inject on Attributes

public class BookBean implements Serializable {

@Inject private NumberGenerator numberGenerator;

@Inject private ItemService itemService;

// ...}

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@Inject on Constructor

private NumberGenerator numberGenerator; private ItemService itemService;

@Inject public BookBean(NumberGenerator numberGenerator, ItemService srv){ this.numberGenerator = numberGenerator; this.itemService = srv; }

// ...}

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@Inject on Setters

@Inject public void setNumberGenerator(NumberGenerator numGen){ this.numberGenerator = numGen; }

@Inject public void setItemService(ItemService itemService) { this.itemService = itemService; } // ...}

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Activate CDI

● In CDI 1.0 beans.xml in archive● Since CDI 1.1 it's activated by default

● All classes having a bean definition annotation● beans.xml to deactivate or activate all

● Archive vs Bean archive

@Inject

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Demo: @Inject One Implementation

Qualifiers

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How Do I ?

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How Do I ?

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How Do I ?

@Default

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Use Qualifiers !

@ThirteenDigits

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Use Qualifiers !

@EightDigits

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A Qualifier

@Qualifier@Retention(RUNTIME)@Target({ METHOD, FIELD, PARAMETER, TYPE })@Documentedpublic @interface ThirteenDigits {}

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Qualifying an Injection Point

@Inject @ThirteenDigits private NumberGenerator numberGenerator;

// ...}

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@Inject @Default private ItemService itemService;

// ...}

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Qualifying a Bean

@ThirteenDigitspublic class IsbnGenerator implements NumberGenerator {

@Override public String generateNumber() { return "13-" + Math.abs(new Random().nextInt()); }}

Qualifiers

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Producers

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How Do I ?

@Inject private EntityManager em;

@Inject private Logger logger;

// ...}

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How Do I ?

// ...}

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How Do I ?

// ...}

Several persistence units@PersistenceContext(unitName = "myPU1")@PersistenceContext(unitName = "myPU2")

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How Do I ?

// ...}

Third party framewok

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Use Producers !

// ...}

public class ResourceProducer {

@Produces @PersistenceContext(unitName = "myPU") private EntityManager entityManager;

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Use Producers !

// ...}

@Produces private Logger produceLogger(InjectionPoint ip) { return Logger.getLogger(ip.getMember().getDeclaringClass().getName());

Producers

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Demo: Producers

Web tier&

Service tier

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How Do I ?

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How Do I ?

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Use Expression Language...

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Use Expression Language and Scopes !

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Service Tier

@Transactionalpublic class BookBean implements Serializable {

public void update() { em.persist(book); }}

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Service Tier + Web Tier

@Named

<h:commandLink value="Create" action='#{bookBean.update}'/>

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@Named("service")

<h:commandLink value="Create" action='#{service.update}'/>

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Several scopes

● @Dependent (default)● @ApplicationScoped, @SessionScoped, @RequestScoped

● @ConversationScoped

● Create your own● @TransactionalScoped

● @ViewScoped

● @ThreadScoped

● @ClusterScoped

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Just choose the right scope

@Named@RequestScoped@Transactionalpublic class BookBean implements Serializable {

public void update() {

public void delete() {

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@Named@SessionScoped@Transactionalpublic class BookBean implements Serializable {

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@Named@ConversationScoped@Transactionalpublic class BookBean implements Serializable {

@Inject private Conversation conversation;

public void update() { conversation.begin(); }

public void delete() { conversation.end(); }}

@Named & scope

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Demo: @Named & Scope

Alternatives

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How Do I ?

public class MockGenerator implements NumberGenerator {

public String generateNumber() { return "mock-" + Math.abs(new Random().nextInt()); }}

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How Do I ?

@Mockpublic class MockGenerator implements NumberGenerator {

@Inject @Mock private NumberGenerator numberGenerator; // ...}

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How Do I ?

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Use an Alternative !

@Alternative@EightDigitspublic class MockGenerator implements NumberGenerator {

@Inject @EightDigits private NumberGenerator numberGenerator; // ...}

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Activate the Alternative

<alternatives> <class>com.foo.MockGenerator</class> </alternatives></beans>

Alternatives

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Demo: Alternatives

Events

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How Do I ?

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How Do I ?

Still too coupled

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Use Events !

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Fire and Observe

@Inject private Event<Book> boughtEvent;

public void update() { boughtEvent.fire(book); }}

public class InventoryService {

private void observeBooks (@Observes Book book) { logger.info("Book recevied " + book.getTitle()); }}

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Fire and Observe with Qualifier

@Inject @Paper private Event<Book> boughtEvent;

private void observeBooks (@Observes @Paper Book book) { logger.info("Book recevied " + book.getTitle()); }}

Events

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Demo: Events

CDI : So Much More

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CDI : So Much More

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CDI Extension ecosystem

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CDI Course on PluralSight

http://www.pluralsight.com/courses/context-dependency-injection-1-1

Thanks

www.antoniogoncalves.organtonio.goncalves@gmail.com

@agoncal@devoxxfr

@lescastcodeurs

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