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package org.glassfish.hk2.api;

import java.lang.annotation.Documented;
import java.lang.annotation.Retention;
import java.lang.annotation.Target;

import static java.lang.annotation.ElementType.METHOD;
import static java.lang.annotation.RetentionPolicy.RUNTIME;

/**
 * This annotation marks a method of an annotation as providing a value that
 * should be placed into the metadata of a {@link Descriptor}.
 * 

* One downside of using Qualifiers (or values in the Scope annotation) is that * in order to get these values the underlying classes must be reified. In order * to relieve the system from having to reify classes to get the data in the * scope and qualifier annotations this annotation can be placed on the methods * of an annotation to indicate that the values found in the annotation should be * placed into the metadata of the descriptor. Since the metadata of a descriptor * can be accessed without classloading the underlying class the descriptor is * describing this data can then be accessed without needing to reify the class. *

* This qualifier will be honored whenever the system does automatic analysis of * a class (for example, when analyzing a pre-reified class file or object). It * will also be used by the automatic inhabitant generator when analyzing class files * marked @Service. However, if the programmatic API is being used to build up * a descriptor file this annotation is not taken into account, and it is hence the * responsibility of the user of the programmatic API to fill in the metadata values * itself. *

* This annotation can be placed on any method of an annotation marked with * {@link javax.inject.Scope} or {@link javax.inject.Qualifier}. The "toString" of the object returned * from that method will be placed in the metadata of the descriptor that is * created (unless the object returned is a Class, in which case the name of * the Class is used) *

* @see Descriptor ActiveDescriptor * * @author jwells * */ @Documented @Retention(RUNTIME) @Target({METHOD}) public @interface Metadata { /** * This is the key that will be used in the metadata field of the descriptor. * Values returned from the methods annotated with this annotation will have * their toString called and the result will be added to the metadata key with * this value (unless the return type is Class, in which case the name of * the class will be used) * * @return The key of the metadata field that will be added to */ public String value(); }





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