package meta
When defining a field, the Scala compiler creates up to four accessors
for it: a getter, a setter, and if the field is annotated with
@BeanProperty, a bean getter and a bean setter.
For instance in the following class definition
class C(@myAnnot @BeanProperty var c: Int)
there are six entities which can carry the annotation @myAnnot: the
constructor parameter, the generated field and the four accessors.
By default, annotations on (val-, var- or plain) constructor parameters
end up on the parameter, not on any other entity. Annotations on fields
by default only end up on the field.
The meta-annotations in package scala.annotation.meta are used
to control where annotations on fields and class parameters are copied.
This is done by annotating either the annotation type or the annotation
class with one or several of the meta-annotations in this package.
Annotating the annotation type
The target meta-annotations can be put on the annotation type when
instantiating the annotation. In the following example, the annotation
@Id will be added only to the bean getter getX.
import javax.persistence.Id class A { @(Id @beanGetter) @BeanProperty val x = 0 }
In order to annotate the field as well, the meta-annotation @field
would need to be added.
The syntax can be improved using a type alias:
object ScalaJPA { type Id = javax.persistence.Id @beanGetter } import ScalaJPA.Id class A { @Id @BeanProperty val x = 0 }
Annotating the annotation class
For annotations defined in Scala, a default target can be specified in the annotation class itself, for example
@getter class myAnnotation extends Annotation
This only changes the default target for the annotation myAnnotation.
When instantiating the annotation, the target can still be specified
as described in the last section.
- Source
- package.scala
Type Members
-
final
class
beanGetter extends Annotation with StaticAnnotation
Consult the documentation in package scala.annotation.meta.
-
final
class
beanSetter extends Annotation with StaticAnnotation
Consult the documentation in package scala.annotation.meta.
-
final
class
companionClass extends Annotation with StaticAnnotation
When defining an implicit class, the Scala compiler creates an implicit conversion method for it.
When defining an implicit class, the Scala compiler creates an implicit conversion method for it. Annotations
@companionClassand@companionMethodcontrol where an annotation on the implicit class will go. By default, annotations on an implicit class end up only on the class. -
final
class
companionMethod extends Annotation with StaticAnnotation
When defining an implicit class, the Scala compiler creates an implicit conversion method for it.
When defining an implicit class, the Scala compiler creates an implicit conversion method for it. Annotations
@companionClassand@companionMethodcontrol where an annotation on the implicit class will go. By default, annotations on an implicit class end up only on the class. -
final
class
companionObject extends Annotation with StaticAnnotation
Currently unused; intended as an annotation target for classes such as case classes that automatically generate a companion object
-
final
class
field extends Annotation with StaticAnnotation
Consult the documentation in package scala.annotation.meta.
-
final
class
getter extends Annotation with StaticAnnotation
Consult the documentation in package scala.annotation.meta.
-
final
class
languageFeature extends Annotation with StaticAnnotation
An annotation giving particulars for a language feature in object
scala.language. -
final
class
param extends Annotation with StaticAnnotation
Consult the documentation in package scala.annotation.meta.
-
final
class
setter extends Annotation with StaticAnnotation
Consult the documentation in package scala.annotation.meta.
This is the documentation for the Scala standard library.
Package structure
The scala package contains core types like
Int,Float,ArrayorOptionwhich are accessible in all Scala compilation units without explicit qualification or imports.Notable packages include:
scala.collectionand its sub-packages contain Scala's collections frameworkscala.collection.immutable- Immutable, sequential data-structures such asVector,List,Range,HashMaporHashSetscala.collection.mutable- Mutable, sequential data-structures such asArrayBuffer,StringBuilder,HashMaporHashSetscala.collection.concurrent- Mutable, concurrent data-structures such asTrieMapscala.collection.parallel.immutable- Immutable, parallel data-structures such asParVector,ParRange,ParHashMaporParHashSetscala.collection.parallel.mutable- Mutable, parallel data-structures such asParArray,ParHashMap,ParTrieMaporParHashSetscala.concurrent- Primitives for concurrent programming such asFuturesandPromisesscala.io- Input and output operationsscala.math- Basic math functions and additional numeric types likeBigIntandBigDecimalscala.sys- Interaction with other processes and the operating systemscala.util.matching- Regular expressionsOther packages exist. See the complete list on the right.
Additional parts of the standard library are shipped as separate libraries. These include:
scala.reflect- Scala's reflection API (scala-reflect.jar)scala.xml- XML parsing, manipulation, and serialization (scala-xml.jar)scala.swing- A convenient wrapper around Java's GUI framework called Swing (scala-swing.jar)scala.util.parsing- Parser combinators (scala-parser-combinators.jar)Automatic imports
Identifiers in the scala package and the
scala.Predefobject are always in scope by default.Some of these identifiers are type aliases provided as shortcuts to commonly used classes. For example,
Listis an alias forscala.collection.immutable.List.Other aliases refer to classes provided by the underlying platform. For example, on the JVM,
Stringis an alias forjava.lang.String.