Package jakarta.enterprise.inject

Interface Instance<T>

Type Parameters:
T - the required bean type
All Superinterfaces:
Iterable<T>, jakarta.inject.Provider<T>
All Known Subinterfaces:
SeContainer
All Known Implementing Classes:
CDI
public interface Instance<T> extends Iterable<T>, jakarta.inject.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;

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 an UnsatisfiedResolutionException or AmbiguousResolutionException. 

 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();
Author:
Gavin King, John Ament, Martin Kouba
See Also:

  • Nested Class Summary

    Nested Classes
    Modifier and Type
    Interface
    Description
    static interface 
    Instance.Handle<T>
    This interface represents a contextual reference handle.

  • Method Summary

    Modifier and Type
    Method
    Description
    void
    destroy(T instance)
    When called, the container destroys the instance if the active context object for the scope type of the bean supports destroying bean instances.
    Instance.Handle<T>
    getHandle()
    Obtains an initialized contextual reference handle for a bean that has the required type and qualifiers and is eligible for injection.
    Iterable<? extends Instance.Handle<T>>
    handles()
    Allows iterating over contextual reference handles for all beans that have the required type and required qualifiers and are eligible for injection.
    default Stream<? extends Instance.Handle<T>>
    handlesStream()
    Returns stream of Instance.Handle objects.
    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.
    default boolean
    isResolvable()
    Determines if there is exactly 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.
    <U extends T>
    Instance<U>
    select(TypeLiteral<U> subtype, Annotation... qualifiers)
    Obtains a child Instance for the given required type and additional required qualifiers.
    Instance<T>
    select(Annotation... qualifiers)
    Obtains a child Instance for the given additional required qualifiers.
    <U extends T>
    Instance<U>
    select(Class<U> subtype, Annotation... qualifiers)
    Obtains a child Instance for the given required type and additional required qualifiers.
    default Stream<T>
    stream()
    When called, provides back a Stream of the beans available in this Instance.

    Methods inherited from interface java.lang.Iterable

    forEach, iterator, spliterator

    Methods inherited from interface jakarta.inject.Provider

    get

  • Method Details

    • select

      Instance<T> select(Annotation... qualifiers)

      Obtains a child Instance for the given additional required qualifiers.

      Parameters:
      qualifiers - the additional required qualifiers
      Returns:
      the child Instance
      Throws:
      IllegalArgumentException - if passed two instances of the same non repeating qualifier type, or an instance of an annotation that is not a qualifier type
      IllegalStateException - if the container is already shutdown

    • select

      <U extends T> Instance<U> select(Class<U> subtype, Annotation... qualifiers)

      Obtains a child Instance for the given required type and additional required qualifiers.

      Type Parameters:
      U - the required type
      Parameters:
      subtype - a Class representing the required type
      qualifiers - the additional required qualifiers
      Returns:
      the child Instance
      Throws:
      IllegalArgumentException - if passed two instances of the same non repeating qualifier type, or an instance of an annotation that is not a qualifier type
      IllegalStateException - if the container is already shutdown

    • select

      <U extends T> Instance<U> select(TypeLiteral<U> subtype, Annotation... qualifiers)

      Obtains a child Instance for the given required type and additional required qualifiers.

      Type Parameters:
      U - the required type
      Parameters:
      subtype - a TypeLiteral representing the required type
      qualifiers - the additional required qualifiers
      Returns:
      the child Instance
      Throws:
      IllegalArgumentException - if passed two instances of the same non repeating qualifier type, or an instance of an annotation that is not a qualifier type
      IllegalStateException - if the container is already shutdown

    • stream

      default Stream<T> stream()

      When called, provides back a Stream of the beans available in this Instance. If no beans are found, it returns an empty stream.

      Returns:
      a Stream representing the beans associated with this Instance object
      Since:
      2.0

    • 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.

    • 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.

    • isResolvable

      default boolean isResolvable()

      Determines if there is exactly 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 exactly 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.
      Since:
      2.0

    • destroy

      void destroy(T instance)

      When 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 obtained from the same Instance object, or the client proxy for a normal scoped bean instance.

      Parameters:
      instance - the instance to destroy
      Throws:
      UnsupportedOperationException - if the active context object for the scope type of the bean does not support destroying bean instances
      Since:
      1.1

    • getHandle

      Instance.Handle<T> getHandle()
      Obtains an initialized contextual reference handle for a bean that has the required type and qualifiers and is eligible for injection. Throws exceptions if there is no such bean or more than one.

      The contextual reference is obtained lazily, i.e. when first needed.

      Returns:
      a new Instance.Handle instnace
      Throws:
      UnsatisfiedResolutionException - if there is no bean with given type and qualifiers
      AmbiguousResolutionException - if there is more than one bean given type and qualifiers

    • handles

      Iterable<? extends Instance.Handle<T>> handles()
      Allows iterating over contextual reference handles for all beans that have the required type and required qualifiers and are eligible for injection.

      Note that the returned Iterable is stateless. Therefore, each Iterable.iterator() produces a new set of handles.

      Returns:
      a new iterable

    • handlesStream

      default Stream<? extends Instance.Handle<T>> handlesStream()
      Returns stream of Instance.Handle objects.
      Returns:
      a new stream of contextual reference handles