Package groovy.transform

Annotation Type TupleConstructor

@Documented
@Retention(SOURCE)
@Target(TYPE)
public @interface TupleConstructor
Class annotation used to assist in the creation of tuple constructors in classes. If the class is also annotated with @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 @TupleConstructor 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.)
  • An optional 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:

  • The @TupleConstructor 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).

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 @TupleConstructor produces.
  • If the defaults annotation attribute is set to false, 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 LinkedHashMap constructor 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 @MapConstructor or if the defaults annotation attribute is set to false.
  • If the first property (or field) has type LinkedHashMap or 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 the force attribute 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 the defaults attribute 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
    boolean allNames
    Whether to include all fields and/or properties within the constructor, including those with names that are considered internal.
    boolean allProperties
    Whether to include all properties (as per the JavaBean spec) in the generated constructor.
    boolean callSuper
    Should super properties be called within a call to the parent constructor rather than set as properties.
    boolean defaults
    Used to set whether default value processing is enabled (the default) or disabled.
    String[] excludes
    List of field and/or property names to exclude from the constructor.
    boolean force
    By default, this annotation becomes a no-op if you provide your own constructor.
    boolean includeFields
    Include fields in the constructor.
    boolean includeProperties
    Include properties in the constructor.
    String[] includes
    List of field and/or property names to include within the constructor.
    boolean includeSuperFields
    Include visible fields from super classes in the constructor.
    boolean includeSuperProperties
    Include properties from super classes in the constructor.
    Class post
    A Closure containing statements which will be appended to the end of the generated constructor.
    Class pre
    A Closure containing statements which will be prepended to the generated constructor.
    boolean useSetters
    By default, properties are set directly using their respective field.
    String visibilityId
    If specified, must match the "id" attribute in a VisibilityOptions annotation to enable a custom visibility.

  • Element Details

    • excludes

      String[] excludes
      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.
      Default:
      {}

    • includes

      String[] includes
      List 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 includeProperties
      Include properties in the constructor.
      Default:
      true

    • includeFields

      boolean includeFields
      Include fields in the constructor. Fields come after any properties.
      Default:
      false

    • includeSuperProperties

      boolean includeSuperProperties
      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).
      Default:
      false

    • includeSuperFields

      boolean includeSuperFields
      Include 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 callSuper
      Should super properties be called within a call to the parent constructor rather than set as properties. Typically used in combination with includeSuperProperties. Can't be true if using pre with a super first statement.
      Default:
      false

    • force

      boolean force
      By default, this annotation becomes a no-op if you provide your own constructor. By setting force=true then 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 defaults
      Used 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 useSetters
      By default, 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.
      Since:
      2.5.0
      Default:
      false

    • allNames

      boolean allNames
      Whether 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 allProperties
      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).
      Since:
      2.5.0
      Default:
      false

    • visibilityId

      String visibilityId
      If specified, must match the "id" attribute in a VisibilityOptions annotation to enable a custom visibility.
      Since:
      2.5.0
      Default:
      "<DummyUndefinedMarkerString-DoNotUse>"

    • pre

      Class pre
      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.
      Since:
      2.5.0
      Default:
      groovy.transform.Undefined.CLASS.class

    • post

      Class post
      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.
      Since:
      2.5.0
      Default:
      groovy.transform.Undefined.CLASS.class