Dependency Injection with CDI in 15 minutes
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Injection in CDI in 15 minutes by antonio goncalves @agoncal
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This 15 minutes talk focuses on Dependency Injection with CDI
Transcript of Dependency Injection with CDI in 15 minutes
Injection in CDI in 15 minutes
by antonio goncalves@agoncal
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Antonio Goncalves
History of CDI
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History of CDI
@Inject
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Dependency Injection
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Attributes
@Path("/items")public class ItemRestService {
@Inject private IsbnGenerator numberGenerator;
@Inject private ItemEJB itemEJB;
// ...}
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Constructor
@Path("/items")public class ItemRestService {
private IsbnGenerator numberGenerator; private ItemEJB itemEJB;
@Inject public ItemRestService(IsbnGenerator numberGenerator, ItemEJB itemEJB) { this.numberGenerator = numberGenerator; this.itemEJB = itemEJB; }
// ...}
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Setter
@Path("/items")public class ItemRestService {
private IsbnGenerator numberGenerator; private ItemEJB itemEJB;
@Inject public void setNumberGenerator(IsbnGenerator gen) { this.numberGenerator = gen; }
@Inject public void setItemEJB(ItemEJB itemEJB) { this.itemEJB = itemEJB; } // ...}
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Ambiguous Dependency Injection
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Ambiguous Dependency Injection
Qualifiers
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Type Safe Dependency Injection
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Qualifier
@Path("/items")public class ItemRestService {
@Inject @ThirteenDigits private NumberGenerator numberGenerator;
@Inject private ItemEJB itemEJB;
// ...}
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Qualifier and Bean
@Qualifier@Retention(RUNTIME)@Target({FIELD, TYPE, METHOD, PARAMETER})public @interface ThirteenDigits { }
@ThirteenDigitspublic class IsbnGenerator implements NumberGenerator {
@Override public String generateNumber() { return "13-" + Math.abs(new Random().nextInt()); }}
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Qualifier with Attributes
@Path("/items")public class ItemRestService {
@Inject @NumberDigits(Digits.Thirteen, true) private NumberGenerator numberGenerator;
@Inject private ItemEJB itemEJB;
// ...}
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Multiple Qualifiers
@Path("/items")public class ItemRestService {
@Inject @ThirteenDigits @Odd private NumberGenerator numberGenerator;
@Inject private ItemEJB itemEJB;
// ...}
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Qualifier and Bean
@Qualifier@Retention(RUNTIME)@Target({FIELD, TYPE, METHOD, PARAMETER})public @interface Odd { }
@ThirteenDigits @Oddpublic class IsbnGenerator implements NumberGenerator {
@Override public String generateNumber() { return "13-" + Math.abs(new Random().nextInt()); }}
@Default@Any@Named
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Programmatic Lookup
@Path("/items")public class ItemRestService {
@Inject @ThirteenDigits private Instance<NumberGenerator> numberGenerator;
@Inject private ItemEJB itemEJB;
public String getISBN() { return numberGenerator.get().generateNumber(); }
// ...}
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Programmatic Lookup
@Path("/items")public class ItemRestService {
@Inject @Any private Instance<NumberGenerator> numberGenerators;
@Inject private ItemEJB itemEJB;
public void generateNumbers() { for(NumberGenerator generator: numberGenerators) { display(generator.generateNumber()); } }
// ...}
Producers
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Injectable ?
@Path("/items")public class ItemRestService {
@PersistenceContext(unitName = "myPU") private EntityManager em;
// ...}
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Injectable ?
@Path("/items")public class ItemRestService {
@Inject(unitName = "myPU") private EntityManager em;
// ...}
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Injectable ?
@Path("/items")public class ItemRestService {
@Inject(unitName = "myPU") private EntityManager em;
// ...}
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Inject with Qualifier
@Path("/items")public class ItemRestService {
@Inject @Item private EntityManager em;
// ...}
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Produce it
@Path("/items")public class ItemRestService {
@Inject @Item private EntityManager em;
// ...}
public class DatabaseProducer {
@Produces @PersistenceContext(unitName = "myPU") @Item private EntityManager em;}
Strong TypingLoose coupling
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CDI is Much More !
Q & A
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Creative Commons
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