Context and Dependency Injection API

• Basics @Inject @LoggedIn User user user = what, LoggedIn = which one (not string based!)
• Can coexist with @Resource and @PostConstruct
• Can inject fields, methods or constructors
  • Constructor (My prefered type) Example:

    public class CheckoutHandler {
      @Inject
      CheckoutHandler(@LoggedIn User user, 
          PaymentProcessor processor, 
          @Default Card cart) {
        // ...
      }
    }
    
    // Multiple qualifer example
    public class CheckoutHandler {
      @Inject
      CheckoutHandler(@LoggedIn User user, 
          @Reliable
          @PayBy(CREDIT_CARS)
          PaymentProcessor processor, 
          @Default Card cart) {
        // ...
      }
    }

• Easy to write your own qualifiers. Just create an annotation and annotate it with @Qualifier:

  @Qualifer
  @Retention(RUNTIME)
  @Target({FIELD, TYPE})
  public @interface Red{}

• ManagedBean
  • Anything injected is a bean. Examples include:
    • EJB Session beans
    • Plain classes with @ManagedBean
    • Any class CDI can discover in a module
    • Example:

      @Reliable
      @PayBy(CREDIT_CARD)
      @ManagedBean
      public class ReliableCreditCardPaymentProcessor implements PaymentProcessor {
      
        void pay(Amount amount) throws PaymentException {
          ...
        }
      }

    • Same example as an EJB:

      @Reliable
      @PayBy(CREDIT_CARD)
      //@ManagedBean
      @Stateless
      public class ReliableCreditCardPaymentProcessor implements PaymentProcessor {
      
        void pay(Amount amount) throws PaymentException {
          ...
        }
      }

    • Same example as a Request-scoped Bean:

      @Reliable
      @PayBy(CREDIT_CARD)
      @RequestScoped
      @ManagedBean
      public class ReliableCreditCardPaymentProcessor implements PaymentProcessor {
      
        void pay(Amount amount) throws PaymentException {
          ...
        }
      }

      • Scopes allowed everywhere: @ApplicationScoped, @RequestScoped
      • Also allowed in web apps: @SessionScoped
• Named beans. (Built in support for Unified EL)
  • You can name a bean with @Named("cart"). The refer to it in a JSP page using the EL:

    <h.commandButton value="Checkout" action="#{cart.checkout}">

• Events with annotation-based event model
  • A bean @Observes an event:

    void onLogin(@Observes LoginEvent event) { ...}

    Another bean fires an event using the Event.fire(T event) method