CODEWITHSUNDEEP
javajakarta-eecdi
Abc
Abc

Reputation: 1382

Context Dependency Inhections in Java EE

I'm new to Context Dependency Injections in Java EE (I'm on EE 6), and I would like to please ask about something I ran into:

Let's say you declare this annotation:

@Target({ElementType.TYPE, ElementType.METHOD, ElementType.PARAMETER, ElementType.FIELD })
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Qualifier
public @interface MaxPassengers {}

In a different class I say that the getMaxPassengers method produces the value to be injected when the @MaxPassengers annotation is used:

public class AirplaneInformation implements Serializable {
    @Produces @MaxPassengers Integer getMaxPassengers() {
        return 250;
    }
}

In yet a third class, I inject the @MaxPassengers into a variable:

@MaxPassengers
@Inject
private Integer maxPassengers;

All this work great, but here's the twist:

What if I want change the signature of @Produces @MaxPassengers Integer getMaxPassengers() to @Produces @MaxPassengers Integer getMaxPassengers(String planeType)

And return the a dynamic value of maxPassengers based on the planeType.

I'm wondering if this can be done, and if so, how do I change the following annotation

@MaxPassengers
@Inject
private Integer maxPassengers;

to also supply the planeType argument.

Thank you for your help, -Daniel

Upvotes: 0

Views: 68

Answers (1)

John Ament
John Ament

Reputation: 11723

The way this is done is to add the planeType to the qualifier as @NonBinding. You would then pass in an InjectionPoint object to your method and look up the MaxPassengers this way: injectionPoint.getAnnotated().getAnnotation(MaxPassengers.class);

If you want to pull this up at runtime, you would use an Instance object an an AnnotationLiteral of your MaxPassengers, something like this:

@Inject @Any
private Instance<Integer> integerInstance;


...

integerInstance.select(new MaxPassengersLiteral("foo")).get();

Upvotes: 1

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