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Groovy: A powerful, dynamic language for the JVM
/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
package groovy.transform;
import org.codehaus.groovy.transform.GroovyASTTransformationClass;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
/**
* Class annotation used to assist in the creation of tuple constructors in classes.
* If the class is also annotated with {@code @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:
*
* {@code @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 {@code @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 {@code includeSuperProperties} is set)
* with the most super first followed by the properties of the class followed
* by the fields of the class (if {@code 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 {@code @TupleConstructor} annotation generates a public constructor unless an applicable
* {@link 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 {@code @CompileStatic} in conjunction with such an approach since
* dynamic Groovy currently gives the ability to access even private constructors.)
* - An optional {@code visibilityId} attribute can be specified. If present, it must match the optional
* {@code id} attribute of an applicable {@code VisibilityOptions} annotation. This can be useful
* if multiple {@code VisibilityOptions} annotations are needed.
*
*
* Custom property handling:
*
* - The {@code @TupleConstructor} annotation supports customization using {@code @PropertyOptions}
* which allows a custom property handler to be defined. This is most typically used behind the scenes
* by the {@code @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 {@code @TupleConstructor} produces.
* - If the {@code defaults} annotation attribute is set to {@code 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 {@code 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 {@code @MapConstructor} or if the {@code defaults}
* annotation attribute is set to {@code false}.
* - If the first property (or field) has type {@code 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. {@code @InheritConstructors});
* the order in which the particular transforms are processed becomes important in that case.
* See the {@code 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. {@code @InheritConstructors});
* the order in which the particular transforms are processed becomes important in that case.
* See the {@code defaults} attribute for further details about customizing this behavior.
*
*
* @see PropertyOptions
* @see VisibilityOptions
* @since 1.8.0
*/
@java.lang.annotation.Documented
@Retention(RetentionPolicy.SOURCE)
@Target({ElementType.TYPE})
@GroovyASTTransformationClass("org.codehaus.groovy.transform.TupleConstructorASTTransformation")
public @interface TupleConstructor {
/**
* 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.
*/
String[] excludes() default {};
/**
* 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.
*/
String[] includes() default {Undefined.STRING};
/**
* Include properties in the constructor.
*/
boolean includeProperties() default true;
/**
* Include fields in the constructor. Fields come after any properties.
*/
boolean includeFields() default false;
/**
* 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).
*/
boolean includeSuperProperties() default false;
/**
* 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).
*/
boolean includeSuperFields() default false;
/**
* Should super properties be called within a call to the parent constructor
* rather than set as properties. Typically used in combination with {@code includeSuperProperties}.
* Can't be true if using {@code pre} with a {@code super} first statement.
*/
boolean callSuper() default false;
/**
* By default, this annotation becomes a no-op if you provide your own constructor.
* By setting {@code 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.
*/
boolean force() default false;
/**
* 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
*/
boolean defaults() default true;
/**
* By default, properties are set directly using their respective field.
* By setting {@code 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
*/
boolean useSetters() default false;
/**
* Whether to include all fields and/or properties within the constructor, including those with names that are
* considered internal.
*
* @since 2.5.0
*/
boolean allNames() default false;
/**
* 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
*/
boolean allProperties() default false;
/**
* If specified, must match the "id" attribute in a VisibilityOptions annotation to enable a custom visibility.
*
* @since 2.5.0
*/
String visibilityId() default Undefined.STRING;
/**
* A Closure containing statements which will be prepended to the generated constructor. The first statement
* within the Closure may be {@code super(someArgs)} in which case the no-arg super constructor won't be called.
*
* @since 2.5.0
*/
Class pre() default Undefined.CLASS.class;
/**
* 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
*/
Class post() default Undefined.CLASS.class;
}