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/Scala 2.13 Reflection

Trait scala.reflect.api.Annotations

trait Annotations extends AnyRef

EXPERIMENTAL

This trait provides annotation support for the reflection API.

In Scala, annotations belong to one of the two categories:

  • Java annotations: annotations on definitions produced by the Java compiler, i.e., subtypes of java.lang.annotation.Annotation attached to program definitions.
  • Scala annotations: annotations on definitions or types produced by the Scala compiler.

When a Scala annotation that inherits from scala.annotation.StaticAnnotation 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 as q"@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 to ann(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 via annotation.tree.children.tail.

For more information about Annotations, see the Reflection Guide: Annotations, Names, Scopes, and More

Self Type
Universe
Source
Annotations.scala
Linear Supertypes
AnyRef, Any
Known Subclasses
JavaUniverse, Universe, Universe

Type Members

abstract type Annotation >: Null <: Universe.AnnotationApi

trait AnnotationApi extends AnyRef

The API of Annotation instances. The main source of information about annotations is the scala.reflect.api.Annotations page.

abstract class AnnotationExtractor extends AnyRef

An extractor class to create and pattern match with syntax Annotation(tpe, scalaArgs, javaArgs). Here, tpe is the annotation type, scalaArgs the payload of Scala annotations, and javaArgs the payload of Java annotations.

Abstract Value Members

abstract val Annotation: Universe.AnnotationExtractor

abstract def annotationToTree(ann: Universe.Annotation): Universe.Tree

Attributes
protected[scala]

abstract def treeToAnnotation(tree: Universe.Tree): Universe.Annotation

Attributes
protected[scala]

Concrete Value Members

final def !=(arg0: Any): Boolean

Definition Classes
AnyRef → Any

final def ##(): Int

Definition Classes
AnyRef → Any

def +(other: String): String

Implicit
This member is added by an implicit conversion from Annotations toany2stringadd[Annotations] performed by method any2stringadd in scala.Predef.
Definition Classes
any2stringadd

def ->[B](y: B): (Annotations, B)

Implicit
This member is added by an implicit conversion from Annotations toArrowAssoc[Annotations] performed by method ArrowAssoc in scala.Predef.
Definition Classes
ArrowAssoc
Annotations
@inline()

final def ==(arg0: Any): Boolean

Definition Classes
AnyRef → Any

final def asInstanceOf[T0]: T0

Definition Classes
Any

def clone(): AnyRef

Attributes
protected[java.lang]
Definition Classes
AnyRef
Annotations
@throws(classOf[java.lang.CloneNotSupportedException]) @native()

def ensuring(cond: (Annotations) => Boolean, msg: => Any): Annotations

Implicit
This member is added by an implicit conversion from Annotations toEnsuring[Annotations] performed by method Ensuring in scala.Predef.
Definition Classes
Ensuring

def ensuring(cond: (Annotations) => Boolean): Annotations

Implicit
This member is added by an implicit conversion from Annotations toEnsuring[Annotations] performed by method Ensuring in scala.Predef.
Definition Classes
Ensuring

def ensuring(cond: Boolean, msg: => Any): Annotations

Implicit
This member is added by an implicit conversion from Annotations toEnsuring[Annotations] performed by method Ensuring in scala.Predef.
Definition Classes
Ensuring

def ensuring(cond: Boolean): Annotations

Implicit
This member is added by an implicit conversion from Annotations toEnsuring[Annotations] performed by method Ensuring in scala.Predef.
Definition Classes
Ensuring

final def eq(arg0: AnyRef): Boolean

Definition Classes
AnyRef

def equals(arg0: AnyRef): Boolean

Definition Classes
AnyRef → Any

def finalize(): Unit

Attributes
protected[java.lang]
Definition Classes
AnyRef
Annotations
@throws(classOf[java.lang.Throwable])

def formatted(fmtstr: String): String

Implicit
This member is added by an implicit conversion from Annotations toStringFormat[Annotations] performed by method StringFormat in scala.Predef.
Definition Classes
StringFormat
Annotations
@inline()

final def getClass(): Class[_ <: AnyRef]

Definition Classes
AnyRef → Any
Annotations
@native()

def hashCode(): Int

Definition Classes
AnyRef → Any
Annotations
@native()

final def isInstanceOf[T0]: Boolean

Definition Classes
Any

final def ne(arg0: AnyRef): Boolean

Definition Classes
AnyRef

final def notify(): Unit

Definition Classes
AnyRef
Annotations
@native()

final def notifyAll(): Unit

Definition Classes
AnyRef
Annotations
@native()

final def synchronized[T0](arg0: => T0): T0

Definition Classes
AnyRef

def toString(): String

Definition Classes
AnyRef → Any

final def wait(): Unit

Definition Classes
AnyRef
Annotations
@throws(classOf[java.lang.InterruptedException])

final def wait(arg0: Long, arg1: Int): Unit

Definition Classes
AnyRef
Annotations
@throws(classOf[java.lang.InterruptedException])

final def wait(arg0: Long): Unit

Definition Classes
AnyRef
Annotations
@throws(classOf[java.lang.InterruptedException]) @native()

© 2002-2019 EPFL, with contributions from Lightbend.
Licensed under the Apache License, Version 2.0.
https://www.scala-lang.org/api/2.13.0/scala-reflect/scala/reflect/api/Annotations.html