Information about an annotation.
The API of Annotation
instances.
An extractor class to create and pattern match with syntax Annotation(tpe, scalaArgs, javaArgs)
.
An array argument to a Java annotation as in @Target(value={TYPE,FIELD,METHOD,PARAMETER})
API of ArrayArgument
instances.
An extractor class to create and pattern match with syntax ArrayArgument(args)
where args
is the argument array.
A Java annotation argument
Has no special methods.
A literal argument to a Java annotation as "Use X instead"
in @Deprecated("Use X instead")
The API of LiteralArgument
instances.
An extractor class to create and pattern match with syntax LiteralArgument(value)
where value
is the constant argument.
A nested annotation argument to a Java annotation as @Nested
in @Outer(@Nested)
.
API of NestedArgument
instances.
An extractor class to create and pattern match with syntax NestedArgument(annotation)
where annotation
is the nested annotation.
The constructor/extractor for Annotation
instances.
The constructor/extractor for ArrayArgument
instances.
The constructor/extractor for ArrayArgument
instances.
(Since version 2.11.0) Use Annotation.tree
to inspect annotation arguments
The constructor/extractor for LiteralArgument
instances.
The constructor/extractor for LiteralArgument
instances.
(Since version 2.11.0) Use Annotation.tree
to inspect annotation arguments
The constructor/extractor for NestedArgument
instances.
The constructor/extractor for NestedArgument
instances.
(Since version 2.11.0) Use Annotation.tree
to inspect annotation arguments
The methods available for each reflection entity, without the implementation. Since the reflection entities are later overridden by runtime reflection and macros, their API counterparts guarantee a minimum set of methods that are implemented.
Extractors provide the machinery necessary to allow pattern matching and construction of reflection entities that is similar to case classes, although the entities are only abstract types that are later overridden.
EXPERIMENTAL
This trait provides annotation support for the reflection API.
In Scala, annotations belong to one of the two categories:
When a Scala annotation that inherits from scala.annotation.StaticAnnotation or scala.annotation.ClassfileAnnotation is compiled, it is stored as special attributes in the corresponding classfile, and not as a Java annotation. Note that subclassing just scala.annotation.Annotation is not enough to have the corresponding metadata persisted for runtime reflection.
Both Java and Scala annotations are represented as typed trees carrying constructor invocations corresponding to the annotation. For instance, the annotation in
@ann(1, 2) class C
is represented asq"@new ann(1, 2)"
.Unlike Java reflection, Scala reflection does not support evaluation of constructor invocations stored in annotations into underlying objects. For instance it's impossible to go from
@ann(1, 2) class C
toann(1, 2)
, so one has to analyze trees representing annotation arguments to manually extract corresponding values. Towards that end, arguments of an annotation can be obtained viaannotation.tree.children.tail
.For more information about
Annotation
s, see the Reflection Guide: Annotations, Names, Scopes, and More