Interface Instance<T>
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- Type Parameters:
T
- the required bean type
- All Superinterfaces:
java.lang.Iterable<T>
,Provider<T>
- All Known Implementing Classes:
CDI
public interface Instance<T> extends java.lang.Iterable<T>, Provider<T>
Allows the application to dynamically obtain instances of beans with a specified combination of required type and qualifiers.
In certain situations, injection is not the most convenient way to obtain a contextual reference. For example, it may not be used when:
- the bean type or qualifiers vary dynamically at runtime, or
- depending upon the deployment, there may be no bean which satisfies the type and qualifiers, or
- we would like to iterate over all beans of a certain type.
In these situations, an instance of the Instance may be injected:
@Inject Instance<PaymentProcessor> paymentProcessor;
Any combination of qualifiers may be specified at the injection point:
@Inject @PayBy(CHEQUE) Instance<PaymentProcessor> chequePaymentProcessor;
Or, the
@Any
qualifier may be used, allowing the application to specify qualifiers dynamically:@Inject @Any Instance<PaymentProcessor> anyPaymentProcessor;
Finally, the
@New
qualifier may be used, allowing the application to obtain a@New
qualified bean:@Inject @New(ChequePaymentProcessor.class) Instance<PaymentProcessor> chequePaymentProcessor;
For an injected Instance:
- the required type is the type parameter specified at the injection point, and
- the required qualifiers are the qualifiers specified at the injection point.
The inherited
Provider.get()
method returns a contextual references for the unique bean that matches the required type and required qualifiers and is eligible for injection into the class into which the parent Instance was injected, or throws anUnsatisfiedResolutionException
orAmbiguousResolutionException
.PaymentProcessor pp = chequePaymentProcessor.get();
The inherited
Iterable.iterator()
method returns an iterator over contextual references for beans that match the required type and required qualifiers and are eligible for injection into the class into which the parent Instance was injected.for (PaymentProcessor pp : anyPaymentProcessor) pp.test();
- See Also:
Provider.get()
,Iterable.iterator()
,AnnotationLiteral
,TypeLiteral
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Method Summary
All Methods Instance Methods Abstract Methods Modifier and Type Method Description void
destroy(T instance)
Ondestroy(Object)
being called, the container destroys the instance if the active context object for the scope type of the bean supports destroying bean instances.boolean
isAmbiguous()
Determines if there is more than one bean that matches the required type and qualifiers and is eligible for injection into the class into which the parent Instance was injected.boolean
isUnsatisfied()
Determines if there is no bean that matches the required type and qualifiers and is eligible for injection into the class into which the parent Instance was injected.Instance<T>
select(java.lang.annotation.Annotation... qualifiers)
Obtains a child Instance for the given additional required qualifiers.<U extends T>
Instance<U>select(java.lang.Class<U> subtype, java.lang.annotation.Annotation... qualifiers)
Obtains a child Instance for the given required type and additional required qualifiers.<U extends T>
Instance<U>select(TypeLiteral<U> subtype, java.lang.annotation.Annotation... qualifiers)
Obtains a child Instance for the given required type and additional required qualifiers.
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Method Detail
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select
Instance<T> select(java.lang.annotation.Annotation... qualifiers)
Obtains a child Instance for the given additional required qualifiers.
- Parameters:
qualifiers
- the additional required qualifiers- Returns:
- the child Instance
- Throws:
java.lang.IllegalArgumentException
- if passed two instances of the same qualifier type, or an instance of an annotation that is not a qualifier type
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select
<U extends T> Instance<U> select(java.lang.Class<U> subtype, java.lang.annotation.Annotation... qualifiers)
Obtains a child Instance for the given required type and additional required qualifiers.
- Type Parameters:
U
- the required type- Parameters:
subtype
- aClass
representing the required typequalifiers
- the additional required qualifiers- Returns:
- the child Instance
- Throws:
java.lang.IllegalArgumentException
- if passed two instances of the same qualifier type, or an instance of an annotation that is not a qualifier type
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select
<U extends T> Instance<U> select(TypeLiteral<U> subtype, java.lang.annotation.Annotation... qualifiers)
Obtains a child Instance for the given required type and additional required qualifiers.
- Type Parameters:
U
- the required type- Parameters:
subtype
- aTypeLiteral
representing the required typequalifiers
- the additional required qualifiers- Returns:
- the child Instance
- Throws:
java.lang.IllegalArgumentException
- if passed two instances of the same qualifier type, or an instance of an annotation that is not a qualifier type
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isUnsatisfied
boolean isUnsatisfied()
Determines if there is no bean that matches the required type and qualifiers and is eligible for injection into the class into which the parent Instance was injected.
- Returns:
- true if there is no bean that matches the required type and qualifiers and is eligible for injection into the class into which the parent Instance was injected, or false otherwise.
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isAmbiguous
boolean isAmbiguous()
Determines if there is more than one bean that matches the required type and qualifiers and is eligible for injection into the class into which the parent Instance was injected.
- Returns:
- true if there is more than one bean that matches the required type and qualifiers and is eligible for injection into the class into which the parent Instance was injected, or false otherwise.
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destroy
void destroy(T instance)
On
destroy(Object)
being called, the container destroys the instance if the active context object for the scope type of the bean supports destroying bean instances. All normal scoped built-in contexts support destroying bean instances.The instance passed should either be a dependent scoped bean instance, or the client proxy for a normal scoped bean instance.
- Parameters:
instance
- the instance to destroy- Throws:
java.lang.UnsupportedOperationException
- if the active context object for the scope type of the bean does not support destroying bean instances- Since:
- 1.1
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