@Documented @Retention(RetentionPolicy.SOURCE) @Target(ElementType.TYPE) @GroovyASTTransformationClass("org.codehaus.groovy.transform.MapConstructorASTTransformation") public @interface MapConstructor
Class annotation used to assist in the creation of map constructors in classes.
If the class is also annotated with @ImmutableBase, then the generated
constructor will contain additional code needed for immutable classes.
It allows you to write classes in this shortened form:
import groovy.transform.*The@TupleConstructorclass Person { String first, last }@CompileStatic// optional@ToString(includeSuperProperties=true)@MapConstructor(pre={ super(args?.first, args?.last); args = args ?: [:] }, post = { first = first?.toUpperCase() }) class Author extends Person { String bookName } assert new Author(first: 'Dierk', last: 'Koenig', bookName: 'ReGinA').toString() == 'Author(ReGinA, DIERK, Koenig)' assert new Author().toString() == 'Author(null, null, null)'
@MapConstructor annotation instructs the compiler to execute an
AST transformation which adds the necessary constructor method to your class.
A map constructor is created which sets properties, and optionally fields and super properties if the property/field name is a key within the map.
For the above example, the generated constructor will be something like:
public Author(java.util.Map args) {
super(args?.first, args?.last)
args = args ? args : [:]
if (args.containsKey('bookName')) {
this.bookName = args['bookName']
}
first = first?.toUpperCase()
}
Custom visibility:
@MapConstructor annotation generates a public constructor unless an applicable
VisibilityOptions annotation is also present. It can be useful to change the visibility
if you want to also create a builder or provide your own static factory method for object creation.
You can make the constructor private and access it from the builder or your factory method. (Note:
you'll probably want to use @CompileStatic in conjunction with such an approach since
dynamic Groovy currently gives the ability to access even private constructors.)visibilityId attribute can be specified. If present, it must match the optional
id attribute of an applicable VisibilityOptions annotation. This can be useful
if multiple VisibilityOptions annotations are needed.Custom property handling:
@MapConstructor annotation supports customization using @PropertyOptions
which allows a custom property handler to be defined. This is most typically used behind the scenes
by the @Immutable meta-annotation but you can also define your own handler. If a custom
handler is present, it will determine the code generated when initializing any property (or field).Known limitations/special cases:
Map unless a single property (or field)
is included and the type of that property (or field) is Object, AbstractMap, Map or HashMap.
In this case, the generated constructor will be of type LinkedHashMap.
This allows the possibility of also adding a tuple constructor without conflict, although
no such constructor is added automatically. You can disable this behavior by setting
the specialNamedArgHandling annotation attribute to false. This means that for the special
case mentioned above, you will not be able to also add a tuple constructor with a single Map
argument but you can supply any kind of map as your argument. We'd also recommend not
having both a map constructor and a tuple constructor with a single Object, AbstractMap or
HashMap since it can cause confusion as to which will be called.
| Type | Name and Description |
|---|---|
boolean |
allNamesWhether to include all fields and/or properties within the constructor, including those with names that are considered internal. |
boolean |
allPropertiesWhether to include all properties (as per the JavaBean spec) in the generated constructor. |
String[] |
excludesList of field and/or property names to exclude from the constructor. |
boolean |
includeFieldsInclude fields in the constructor. |
boolean |
includePropertiesInclude properties in the constructor. |
boolean |
includeStaticWhether to include static properties in the constructor. |
boolean |
includeSuperFieldsInclude fields from super classes in the constructor. |
boolean |
includeSuperPropertiesInclude properties from super classes in the constructor. |
String[] |
includesList of field and/or property names to include within the constructor. |
boolean |
noArgIn addition to the map constructor, provide a no-arg constructor which calls the map constructor with an empty map. |
Class |
postA Closure containing statements which will be appended to the end of the generated constructor. |
Class |
preA Closure containing statements which will be prepended to the generated constructor. |
boolean |
specialNamedArgHandlingIf true, change the type of the map constructor argument from Map to LinkedHashMap only for the case where the class has a single property (or field) with a Map-like type. |
boolean |
useSettersBy default, Groovy properties are set directly using their respective field. |
String |
visibilityIdIf specified, must match the "id" attribute in a VisibilityOptions annotation to enable a custom visibility. |
Whether to include all fields and/or properties within the constructor, including those with names that are considered internal.
Whether to include all properties (as per the JavaBean spec) in the generated constructor. When true, Groovy treats any explicitly created setXxx() methods as property setters as per the JavaBean specification. JavaBean properties come after any Groovy properties but before any fields for a given class (unless 'includes' is used to determine the order).
List of field and/or property names to exclude from the constructor. Must not be used if 'includes' is used. For convenience, a String with comma separated names can be used in addition to an array (using Groovy's literal list notation) of String values.
Include fields in the constructor. Fields come after any properties.
Include properties in the constructor.
Whether to include static properties in the constructor.
Include fields from super classes in the constructor. Groovy properties, JavaBean properties and fields (in that order) from superclasses come before the members from a subclass (unless 'includes' is used to determine the order).
Include properties from super classes in the constructor. Groovy properties, JavaBean properties and fields (in that order) from superclasses come before the members from a subclass (unless 'includes' is used to determine the order).
List of field and/or property names to include within the constructor. Must not be used if 'excludes' is used. For convenience, a String with comma separated names can be used in addition to an array (using Groovy's literal list notation) of String values. The default value is a special marker value indicating that no includes are defined; all fields and/or properties are included if 'includes' remains undefined and 'excludes' is explicitly or implicitly an empty list.
In addition to the map constructor, provide a no-arg constructor which calls the map constructor with an empty map.
A Closure containing statements which will be appended to the end of the generated constructor. Useful for validation steps or tweaking the populated fields/properties.
A Closure containing statements which will be prepended to the generated constructor. The first statement within the Closure may be "super(someArgs)" in which case the no-arg super constructor won't be called.
If true, change the type of the map constructor argument from Map to LinkedHashMap only for the case where the class has a single property (or field) with a Map-like type. This allows both a map and a tuple constructor to be used side-by-side so long as care is taken about the types used when calling.
By default, Groovy properties are set directly using their respective field.
By setting useSetters=true then a writable property will be set using its setter.
If turning on this flag we recommend that setters that might be called are
made null-safe wrt the parameter.
If specified, must match the "id" attribute in a VisibilityOptions annotation to enable a custom visibility.