Annotation Type TupleConstructor
@Documented
@Retention(SOURCE)
@Target(TYPE)
public @interface TupleConstructor
@ImmutableBase, then the generated
constructor will contain additional code needed for immutable classes.
Should be used with care with other annotations which create constructors - see "Known
Limitations" for more details.
It allows you to write classes in this shortened form:
@groovy.transform.TupleConstructor class Customer {
String first, last
int age
Date since
Collection favItems
}
def c1 = new Customer(first:'Tom', last:'Jones', age:21, since:new Date(), favItems:['Books', 'Games'])
def c2 = new Customer('Tom', 'Jones', 21, new Date(), ['Books', 'Games'])
def c3 = new Customer('Tom', 'Jones')
The @TupleConstructor annotation instructs the compiler to execute an
AST transformation which adds the necessary constructor method to your class.
A tuple constructor is created with a parameter for each property (and optionally field and super properties). The default order is properties, pseudo/JavaBean properties and then fields for parent classes first (if includeSuperXxx annotation attributes are used). A default value is provided (using Java's default values) for all parameters in the constructor. Groovy's normal conventions then allows any number of parameters to be left off the end of the parameter list including all of the parameters - giving a no-arg constructor which can be used with the map-style naming conventions.
The order of parameters is given by the properties of any super classes (if includeSuperProperties is set)
with the most super first followed by the properties of the class followed
by the fields of the class (if includeFields is set). Within each grouping the order
is as attributes appear within the respective class.
More examples:
//--------------------------------------------------------------------------
import groovy.transform.TupleConstructor
@TupleConstructor()
class Person {
String name
List likes
private boolean active = false
}
def person = new Person('mrhaki', ['Groovy', 'Java'])
assert person.name == 'mrhaki'
assert person.likes == ['Groovy', 'Java']
person = new Person('mrhaki')
assert person.name == 'mrhaki'
assert !person.likes
//--------------------------------------------------------------------------
// includeFields in the constructor creation.
import groovy.transform.TupleConstructor
@TupleConstructor(includeFields=true)
class Person {
String name
List likes
private boolean active = false
boolean isActivated() { active }
}
def person = new Person('mrhaki', ['Groovy', 'Java'], true)
assert person.name == 'mrhaki'
assert person.likes == ['Groovy', 'Java']
assert person.activated
//--------------------------------------------------------------------------
// use force attribute to force creation of constructor
// even if we define our own constructors.
import groovy.transform.TupleConstructor
@TupleConstructor(force=true)
class Person {
String name
List likes
private boolean active = false
Person(boolean active) {
this.active = active
}
boolean isActivated() { active }
}
def person = new Person('mrhaki', ['Groovy', 'Java'])
assert person.name == 'mrhaki'
assert person.likes == ['Groovy', 'Java']
assert !person.activated
person = new Person(true)
assert person.activated
//--------------------------------------------------------------------------
// include properties and fields from super class.
import groovy.transform.TupleConstructor
@TupleConstructor(includeFields=true)
class Person {
String name
List likes
private boolean active = false
boolean isActivated() { active }
}
@TupleConstructor(callSuper=true, includeSuperProperties=true, includeSuperFields=true)
class Student extends Person {
List courses
}
def student = new Student('mrhaki', ['Groovy', 'Java'], true, ['IT'])
assert student.name == 'mrhaki'
assert student.likes == ['Groovy', 'Java']
assert student.activated
assert student.courses == ['IT']
Custom visibility:
- The
@TupleConstructorannotation generates a public constructor unless an applicableVisibilityOptionsannotation 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@CompileStaticin conjunction with such an approach since dynamic Groovy currently gives the ability to access even private constructors.) - An optional
visibilityIdattribute can be specified. If present, it must match the optionalidattribute of an applicableVisibilityOptionsannotation. This can be useful if multipleVisibilityOptionsannotations are needed.
Custom property handling:
- The
@TupleConstructorannotation supports customization using@PropertyOptionswhich allows a custom property handler to be defined. This is most typically used behind the scenes by the@Immutablemeta-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).
Named-argument support:
- Groovy supports named-arguments for classes with a no-arg constructor or a constructor
with a Map as the first argument. This is compatible with the default kind of constructor(s)
that
@TupleConstructorproduces. - If the
defaultsannotation attribute is set tofalse, and no other map-based constructor are added then named-argument processing will not be available. - If there is more than one included property (and/or field) and the first property (or field) has type
Object, AbstractMap, Map or HashMap, then a special
LinkedHashMapconstructor will be created in addition to the tuple constructor to support named parameters in the normal way. This won't be created if the class is already annotated with@MapConstructoror if thedefaultsannotation attribute is set tofalse. - If the first property (or field) has type
LinkedHashMapor if there is a single Object, AbstractMap, Map or HashMap property (or field), then no additional constructor will be added and Groovy's normal map-style naming conventions will not be available.
Known limitations/special cases:
- This AST transform might become a no-op if you are defining your own constructors or
combining with other AST transforms which create constructors (e.g.
@InheritConstructors); the order in which the particular transforms are processed becomes important in that case. See theforceattribute for further details about customizing this behavior. - This AST transform normally uses default parameter values which creates multiple constructors under
the covers. You should use with care if you are defining your own constructors or
combining with other AST transforms which create constructors (e.g.
@InheritConstructors); the order in which the particular transforms are processed becomes important in that case. See thedefaultsattribute for further details about customizing this behavior.
- Since:
- 1.8.0
- See Also:
PropertyOptions,VisibilityOptions
-
Optional Element Summary
Optional Elements Modifier and Type Optional Element Description booleanallNamesWhether to include all fields and/or properties within the constructor, including those with names that are considered internal.booleanallPropertiesWhether to include all properties (as per the JavaBean spec) in the generated constructor.booleancallSuperShould super properties be called within a call to the parent constructor rather than set as properties.booleandefaultsUsed to set whether default value processing is enabled (the default) or disabled.java.lang.String[]excludesList of field and/or property names to exclude from the constructor.booleanforceBy default, this annotation becomes a no-op if you provide your own constructor.booleanincludeFieldsInclude fields in the constructor.booleanincludePropertiesInclude properties in the constructor.java.lang.String[]includesList of field and/or property names to include within the constructor.booleanincludeSuperFieldsInclude visible fields from super classes in the constructor.booleanincludeSuperPropertiesInclude properties from super classes in the constructor.java.lang.ClasspostA Closure containing statements which will be appended to the end of the generated constructor.java.lang.ClasspreA Closure containing statements which will be prepended to the generated constructor.booleanuseSettersBy default, properties are set directly using their respective field.java.lang.StringvisibilityIdIf specified, must match the "id" attribute in a VisibilityOptions annotation to enable a custom visibility.
-
Element Details
-
excludes
java.lang.String[] excludesList 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.- Default:
- {}
-
includes
java.lang.String[] includesList of field and/or property names to include within the constructor. The order of inclusion is determined by the order in which the names are specified. 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 are included if includes remains undefined and excludes is explicitly or implicitly an empty list.- Default:
- {"<DummyUndefinedMarkerString-DoNotUse>"}
-
includeProperties
boolean includePropertiesInclude properties in the constructor.- Default:
- true
-
includeFields
boolean includeFieldsInclude fields in the constructor. Fields come after any properties.- Default:
- false
-
includeSuperProperties
boolean includeSuperPropertiesInclude 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).- Default:
- false
-
includeSuperFields
boolean includeSuperFieldsInclude visible 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).- Default:
- false
-
callSuper
boolean callSuperShould super properties be called within a call to the parent constructor rather than set as properties. Typically used in combination withincludeSuperProperties. Can't be true if usingprewith asuperfirst statement.- Default:
- false
-
force
boolean forceBy default, this annotation becomes a no-op if you provide your own constructor. By settingforce=truethen the tuple constructor(s) will be added regardless of whether existing constructors exist. It is up to you to avoid creating duplicate constructors.- Default:
- false
-
defaults
boolean defaultsUsed to set whether default value processing is enabled (the default) or disabled. By default, every constructor parameter is given a default value. This value will be Java's default for primitive types (zero or false) and null for Objects, unless an initial value is given when declaring the property or field. A consequence of this design is that you can leave off parameters from the right if the default value will suffice. As far as Java interoperability is concerned, Groovy will create additional constructors under the covers representing the constructors with parameters left off, all the way from the constructor with all arguments to the no-arg constructor. However, when set to false, default values are not allowed for properties and fields. Only the constructor containing all arguments will be provided. In particular, a no-arg constructor won't be provided and since this is currently used by Groovy when using named-arguments, the named-argument style won't be available.- Since:
- 2.5.0
- Default:
- true
-
useSetters
boolean useSettersBy default, properties are set directly using their respective field. By settinguseSetters=truethen 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.- Since:
- 2.5.0
- Default:
- false
-
allNames
boolean allNamesWhether to include all fields and/or properties within the constructor, including those with names that are considered internal.- Since:
- 2.5.0
- Default:
- false
-
allProperties
boolean allPropertiesWhether 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).- Since:
- 2.5.0
- Default:
- false
-
visibilityId
java.lang.String visibilityIdIf specified, must match the "id" attribute in a VisibilityOptions annotation to enable a custom visibility.- Since:
- 2.5.0
- Default:
- "<DummyUndefinedMarkerString-DoNotUse>"
-
pre
java.lang.Class preA Closure containing statements which will be prepended to the generated constructor. The first statement within the Closure may besuper(someArgs)in which case the no-arg super constructor won't be called.- Since:
- 2.5.0
- Default:
- groovy.transform.Undefined.CLASS.class
-
post
java.lang.Class postA Closure containing statements which will be appended to the end of the generated constructor. Useful for validation steps or tweaking the populated fields/properties.- Since:
- 2.5.0
- Default:
- groovy.transform.Undefined.CLASS.class
-