Java:JSR330

JSR330定义了Java依赖注入的标准。主要提供了一系列的定义（javax.inject.*）：

• Provider<T> Provides instances of T.
• Inject Identifies injectable constructors, methods, and fields.
• Named String-based qualifier.
• Qualifier Identifies qualifier annotations.
• Scope Identifies scope annotations.
• Singleton Identifies a type that the injector only instantiates once.

@Inject

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public interface Payment {
    void pay(BigDecimal amount);
}

public class CashPaymentImpl implements Payment {

    private static final Logger LOGGER = Logger.getLogger(CashPaymentImpl.class.toString());

    @Override
    public void pay(BigDecimal amount) {
        LOGGER.log(Level.INFO, "payed {0} cash", amount.toString());
    }
}

@Inject private Payment payment;

@Named

@Named("cash")
public class CashPaymentImpl implements Payment {

    private static final Logger LOGGER = Logger.getLogger(CashPaymentImpl.class.toString());

    @Override
    public void pay(BigDecimal amount) {
        LOGGER.log(Level.INFO, "payed {0} cash", amount.toString());
    }
}
@Named("visa")
public class VisaPaymentImpl implements Payment {

    private static final Logger LOGGER = Logger.getLogger(VisaPaymentImpl.class.toString());

    @Override
    public void pay(BigDecimal amount) {
        LOGGER.log(Level.INFO, "payed {0} with visa", amount.toString());
    }
}
@Inject private @Named("visa") Payment payment;