javax.enterprise.inject.Instance Maven / Gradle / Ivy
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* 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 javax.enterprise.inject;
import java.lang.annotation.Annotation;
import javax.enterprise.util.TypeLiteral;
import javax.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 javax.enterprise.inject.Any @Any} qualifier may
* be used, allowing the application to specify qualifiers dynamically:
*
*
* @Inject @Any Instance<PaymentProcessor> anyPaymentProcessor;
*
*
* Finally, the {@link javax.enterprise.inject.New @New} qualifier
* may be used, allowing the application to obtain a
* {@link javax.enterprise.inject.New @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 {@link javax.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 javax.enterprise.inject.UnsatisfiedResolutionException} or
* {@link javax.enterprise.inject.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 javax.inject.Provider#get()
* @see java.lang.Iterable#iterator()
* @see javax.enterprise.util.AnnotationLiteral
* @see javax.enterprise.util.TypeLiteral
*
* @author Gavin King
*
* @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 qualifier type, or an instance of an annotation that is not
* a qualifier type
*/
public 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 qualifier type, or an instance of an annotation that is not
* a qualifier type
*/
public 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 javax.enterprise.util.TypeLiteral} representing the required type
* @param qualifiers the additional required qualifiers
* @return the child Instance
* @throws IllegalArgumentException if passed two instances of the
* same qualifier type, or an instance of an annotation that is not
* a qualifier type
*/
public Instance select(TypeLiteral subtype, Annotation... qualifiers);
/**
* 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.
*/
public 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.
*/
public boolean isAmbiguous();
}