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Groovy: A powerful multi-faceted 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 java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
/**
* The AnnotationCollector can be used to define aliases for groups of
* annotations. The Alias needs to be a class or annotation annotated with
* AnnotationCollector, otherwise nothing is required. The alias will be
* replaced on the AST level and will never appear in later. Any members of the
* class or annotation will be ignored, but could be used by a custom processor.
* Annotation arguments are mapped to the aliased annotations
* if existing. Should the default processor not be able to map one of the
* arguments and error will be given. Is this not wished or if you want a
* different mapping a custom processor has to be used. There are two ways of
* using the alias. The first way is by providing the annotations as list/array:
*
* import groovy.transform.*
* @AnnotationCollector([ToString, EqualsAndHashCode, Immutable])
* @interface Alias {}
* @Alias(excludes=["a"])
* class Foo {
* Integer a, b
* }
* assert Foo.class.annotations.size() == 3
* assert new Foo(a: 1, b: 2).toString() == "Foo(2)"
*
* In the example above we have Alias as the alias annotation and an argument
* excludes which will be mapped to ToString and EqualsAndHashCode. Immutable
* doesn't have excludes, thus nothing will be done there.
* The other way is to add annotations to the alias:
*
* import groovy.transform.*
* @ToString(excludes=["a"])
* @EqualsAndHashCode
* @Immutable
* @AnnotationCollector
* @interface Alias {}
*
* @Alias
* class Foo {
* Integer a, b
* }
* assert Foo.class.annotations.size() == 3
* assert new Foo(a: 1, b: 2).toString() == "Foo(2)"
*
* In the example above we have again Alias as the alias annotation, but
* this time the argument is part of the alias. Instead of mapping excludes to
* ToString as well as EqualsAndHashCode, only ToString will have the excludes.
* Again the alias can have an argument excludes, which would overwrite the
* excludes given in from the definition and be mapped to ToString as well as
* EqualsAndHashCode.
* If both ways are combined, then the list overwrites annotation usage.
* NOTE: The aliasing does not support aliasing of aliased annotations.
* More examples:
*
* //--------------------------------------------------------------------------
* import groovy.transform.*
* @AnnotationCollector([EqualsAndHashCode, ToString])
* @interface Simple {}
*
*
* @Simple
* class User {
* String username
* int age
* }
*
* def user = new User(username: 'mrhaki', age: 39)
* assert user.toString() == 'User(mrhaki, 39)'
*
* // We still have 2 annotations:
* assert User.class.annotations.size() == 2
*
*
* // We can use the attributes from the
* // grouped annotations.
* @Simple(excludes = 'street')
* class Address {
* String street, town
* }
*
* def address = new Address(street: 'Evergreen Terrace', town: 'Springfield')
* assert address.toString() == 'Address(Springfield)'
*
*
* //--------------------------------------------------------------------------
* // Use a custom processor to handle attributes.
* import org.codehaus.groovy.transform.*
* import org.codehaus.groovy.ast.*
* import org.codehaus.groovy.control.*
*
* class SimpleProcessor extends AnnotationCollectorTransform {
*
* public List<AnnotationNode> visit(AnnotationNode collector,
* AnnotationNode aliasAnnotationUsage,
* AnnotatedNode aliasAnnotated,
* SourceUnit source) {
*
* // Get attributes and attribute value for dontUse.
* def attributes = aliasAnnotationUsage.getMembers()
* def dontUse = attributes.get('dontUse')
* attributes.remove('dontUse')
*
* if (dontUse) {
* // Assign value of dontUse to excludes attributes.
* aliasAnnotationUsage.addMember("excludes", dontUse)
* }
*
* super.visit(collector, aliasAnnotationUsage, aliasAnnotated, source)
* }
*
* }
*
* new GroovyShell(this.class.classLoader).evaluate '''
* import groovy.transform.*
*
* @AnnotationCollector(value = [EqualsAndHashCode, ToString], processor = 'SimpleProcessor')
* @interface Simple {}
*
*
* @Simple(dontUse = 'age')
* class User {
* String username
* int age
* }
*
* def user = new User(username: 'mrhaki', age: 39)
* assert user.toString() == 'User(mrhaki)'
* '''
*
*
* //--------------------------------------------------------------------------
* // Use AnnotationCollector as last annotation to group the
* // previous annotations.
* import groovy.transform.*
* @EqualsAndHashCode
* @ToString
* @AnnotationCollector
* @interface Simple {}
*
*
* @Simple
* class User {
* String username
* }
*
* def user = new User(username: 'mrhaki')
* assert user.toString() == 'User(mrhaki)'
*
*
* @see org.codehaus.groovy.transform.AnnotationCollectorTransform
* @since 2.1.0
*/
@java.lang.annotation.Documented
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.ANNOTATION_TYPE, ElementType.TYPE})
public @interface AnnotationCollector {
/**
* Processor used for computing custom logic or the list of annotations, or
* both. The default is org.codehaus.groovy.transform.AnnotationCollectorTransform.
* Custom processors need to extend that class.
*/
String processor() default "org.codehaus.groovy.transform.AnnotationCollectorTransform";
/**
* When the collector annotation is replaced, whether to check for duplicates between
* the replacement annotations and existing explicit annotations.
* If you use a custom processor, it is up to that processor whether it honors or ignores
* this parameter. The default processor honors the parameter.
*/
AnnotationCollectorMode mode() default AnnotationCollectorMode.DUPLICATE;
/**
* List of aliased annotations.
*/
Class[] value() default {};
/**
* Used internally - the default value is a marker value indicating that the attribute hasn't been set.
* Normally set automatically during annotation processing to an automatically created
* nested helper class which holds serialization information used in pre-compiled scenarios.
* If set to the collector annotation, re-purposes the annotation itself to become the helper
* class (legacy approach used in Groovy 2.5 up to 2.5.2).
*/
Class serializeClass() default Undefined.CLASS.class;
}