jakarta.enterprise.inject.Instance Maven / Gradle / Ivy
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* JBoss, Home of Professional Open Source
* Copyright 2010, Red Hat, Inc., and individual contributors
* by the @authors tag. See the copyright.txt in the distribution for a
* full listing of individual contributors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
* http://www.apache.org/licenses/LICENSE-2.0
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package jakarta.enterprise.inject;
import java.lang.annotation.Annotation;
import java.util.stream.Stream;
import java.util.stream.StreamSupport;
import jakarta.enterprise.inject.spi.Bean;
import jakarta.enterprise.util.AnnotationLiteral;
import jakarta.enterprise.util.TypeLiteral;
import jakarta.inject.Provider;
/**
*
* 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 {@link Any @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 {@link jakarta.inject.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 {@link UnsatisfiedResolutionException} or
* {@link AmbiguousResolutionException}.
*
*
*
* PaymentProcessor pp = chequePaymentProcessor.get();
*
*
*
* The inherited {@link java.lang.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 jakarta.inject.Provider#get()
* @see java.lang.Iterable#iterator()
* @see AnnotationLiteral
* @see TypeLiteral
*
* @author Gavin King
* @author John Ament
* @author Martin Kouba
*
* @param the required bean type
*/
public interface Instance extends Iterable, Provider {
/**
*
* Obtains a child Instance for the given additional required qualifiers.
*
*
* @param qualifiers the additional required qualifiers
* @return 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
* @throws IllegalStateException if the container is already shutdown
*/
Instance select(Annotation... qualifiers);
/**
*
* Obtains a child Instance for the given required type and additional required qualifiers.
*
*
* @param the required type
* @param subtype a {@link java.lang.Class} representing the required type
* @param qualifiers the additional required qualifiers
* @return 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
* @throws IllegalStateException if the container is already shutdown
*/
Instance select(Class subtype, Annotation... qualifiers);
/**
*
* Obtains a child Instance for the given required type and additional required qualifiers.
*
*
* @param the required type
* @param subtype a {@link TypeLiteral} representing the required type
* @param qualifiers the additional required qualifiers
* @return 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
* @throws IllegalStateException if the container is already shutdown
*/
Instance select(TypeLiteral subtype, Annotation... qualifiers);
/**
*
* When called, provides back a Stream of the beans available in this Instance. If no beans are found, it returns an empty
* stream.
*
*
* @since 2.0
* @return a Stream representing the beans associated with this {@link Instance} object
*/
default Stream stream() {
return StreamSupport.stream(this.spliterator(), false);
}
/**
*
* 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.
*
*
* @return 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.
*/
boolean isUnsatisfied();
/**
*
* 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.
*
*
* @return 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.
*/
boolean isAmbiguous();
/**
*
* 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.
*
*
* @since 2.0
* @return 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.
*/
default boolean isResolvable() {
return !isUnsatisfied() && !isAmbiguous();
}
/**
*
* 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 {@link Instance} object, or
* the client proxy for a normal scoped bean instance.
*
*
*
* @since 1.1
* @param 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
*/
void destroy(T instance);
/**
* 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.
*
*
* @return a new {@link Handle} instnace
* @throws UnsatisfiedResolutionException if there is no bean with given type and qualifiers
* @throws AmbiguousResolutionException if there is more than one bean given type and qualifiers
*/
Handle getHandle();
/**
* 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 {@link Iterable} is stateless. Therefore, each {@link Iterable#iterator()} produces a new set of handles.
*
*
* @return a new iterable
*/
Iterable> handles();
/**
* Returns stream of {@link Handle} objects.
*
* @return a new stream of contextual reference handles
*/
default Stream> handlesStream() {
return StreamSupport.stream(handles().spliterator(), false);
}
/**
* This interface represents a contextual reference handle.
*
* Allows to inspect the metadata of the relevant bean before resolving its contextual reference and also to destroy
* the underlying contextual instance.
*
*
* @author Matej Novotny
* @param the required bean type
*/
interface Handle extends AutoCloseable {
/**
* The contextual reference is obtained lazily, i.e. when first needed.
*
* @return the contextual reference
* @see Instance#get()
* @throws IllegalStateException If the producing {@link Instance} does not exist
* @throws IllegalStateException If invoked on {@link Handle} that previously successfully destroyed its
* underlying contextual reference
*/
T get();
/**
*
* @return the bean metadata
*/
Bean getBean();
/**
* Destroy the contextual instance.
*
* It's a no-op if:
*
* - called multiple times
* - if the producing {@link Instance} does not exist
* - if the handle does not hold a contextual reference, i.e. {@link #get()} was never called
*
*
* @see Instance#destroy(Object)
*/
void destroy();
/**
* Delegates to {@link #destroy()}.
*/
@Override
void close();
}
}