org.glassfish.hk2.api.Metadata Maven / Gradle / Ivy
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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();
}