Package org.linkki.util

Class MetaAnnotation<META extends Annotation>

java.lang.Object

org.linkki.util.MetaAnnotation<META>

Type Parameters:

META - the meta-annotation

public class MetaAnnotation<META extends Annotation>
extends Object

Helper class for handling meta-annotations (Annotations with Target ElementType.ANNOTATION_TYPE).

Method Summary

Modifier and Type	Method	Description
Stream<META>	findAllOn(Annotation annotation)	Returns all meta-annotations present on the given Annotation.
Stream<Annotation>	findAnnotatedAnnotationsOn(AnnotatedElement annotatedElement)	Finds all Annotations on the given AnnotatedElement that are annotated with the meta-annotation.
Optional<META>	findOn(Annotation annotation)	Returns the meta-annotation if it is present on the given Annotation.
boolean	isPresentOn(Annotation annotation)	Returns true if the meta-annotation is present on the given Annotation, otherwise false;
boolean	isPresentOnAnyAnnotationOn(AnnotatedElement annotatedElement)	Returns true if the meta-annotation is present on any Annotation on the given AnnotatedElement, otherwise false;
boolean	isRepeatable()	Returns true if the meta-annotation is @Repeatable.
Supplier<? extends IllegalArgumentException>	missingAnnotation(Annotation annotation, AnnotatedElement annotatedElement, String checkerMethod)	Creates a Supplier for an IllegalArgumentException that names the given Annotation on the AnnotatedElement as not having the meta-annotation and suggests using the checkerMethod to safeguard against this exception.
static <META extends Annotation> MetaAnnotation<META>	of(Class<META> metaAnnotationClass)	Creates a new MetaAnnotation<META> from the given Annotation class.
<A extends Annotation> BinaryOperator<A>	onlyOneOn(AnnotatedElement annotatedElement)	Creates a BinaryOperator usable for a Stream.reduce(BinaryOperator) operation on a stream of annotations as returned by findAnnotatedAnnotationsOn(AnnotatedElement) that throws an IllegalArgumentException if there is more than one annotation in the stream.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

of

public static <META extends Annotation> MetaAnnotation<META> of(Class<META> metaAnnotationClass)

Creates a new MetaAnnotation<META> from the given Annotation class.

Type Parameters:

META - the meta-annotation class

Parameters:

metaAnnotationClass - the meta-annotation class

Returns:

a MetaAnnotation for the metaAnnotationClass

Throws:

IllegalArgumentException - if the given Annotation class is not a meta-annotation

isRepeatable

public boolean isRepeatable()

Returns true if the meta-annotation is @Repeatable.

Returns:

whether the meta-annotation is @Repeatable

isPresentOnAnyAnnotationOn

public boolean isPresentOnAnyAnnotationOn(AnnotatedElement annotatedElement)

Returns true if the meta-annotation is present on any Annotation on the given AnnotatedElement, otherwise false;

Parameters:

annotatedElement - an AnnotatedElement to be checked for meta-annotations on its annotations

Returns:

whether the meta-annotation is present on any Annotation on the given AnnotatedElement

isPresentOn

public boolean isPresentOn(@CheckForNull
                           Annotation annotation)

Returns true if the meta-annotation is present on the given Annotation, otherwise false;

Parameters:

annotation - an Annotation to be checked for the meta-annotation

Returns:

whether the meta-annotation is present on the given Annotation

findOn

public Optional<META> findOn(Annotation annotation)

Returns the meta-annotation if it is present on the given Annotation.

If this meta-annotation is repeatable, this method returns an Optional with the single meta-annotation if it was not repeated but throws an IllegalArgumentException if it was.

Parameters:

annotation - an Annotation

Returns:

the meta-annotation instance, if the annotation is annotated with it

Throws:

IllegalArgumentException - if the meta-annotation is repeatable and present multiple times.

See Also:

findAllOn(Annotation) for repeatable annotations

findAllOn

public Stream<META> findAllOn(Annotation annotation)

Returns all meta-annotations present on the given Annotation.

Parameters:

annotation - an Annotation

Returns:

the meta-annotation instance, if the annotation is annotated with it

findAnnotatedAnnotationsOn

public Stream<Annotation> findAnnotatedAnnotationsOn(AnnotatedElement annotatedElement)

Finds all Annotations on the given AnnotatedElement that are annotated with the meta-annotation.

Parameters:

annotatedElement - an AnnotatedElement

Returns:

a Stream of the Annotations annotated with the meta-annotation

See Also:

use if you expect there to be no more than one such annotation.

onlyOneOn

public <A extends Annotation> BinaryOperator<A> onlyOneOn(AnnotatedElement annotatedElement)

Creates a BinaryOperator usable for a Stream.reduce(BinaryOperator) operation on a stream of annotations as returned by findAnnotatedAnnotationsOn(AnnotatedElement) that throws an IllegalArgumentException if there is more than one annotation in the stream.

Parameters:

annotatedElement - the AnnotatedElement that was passed to findAnnotatedAnnotationsOn(AnnotatedElement); will be included in the exception message

Returns:

a BinaryOperator usable for a Stream.reduce(BinaryOperator) operation on a stream of annotations as returned by findAnnotatedAnnotationsOn(AnnotatedElement)

missingAnnotation

public Supplier<? extends IllegalArgumentException> missingAnnotation(Annotation annotation,
                                                                      AnnotatedElement annotatedElement,
                                                                      String checkerMethod)

Creates a Supplier for an IllegalArgumentException that names the given Annotation on the AnnotatedElement as not having the meta-annotation and suggests using the checkerMethod to safeguard against this exception.

Parameters:

annotation - an Annotation on the AnnotatedElement

annotatedElement - an AnnotatedElement

checkerMethod - description of a method to be called before the method that throws this exception to safeguard against it

Returns:

a Supplier for an IllegalArgumentException