com.google.auto.value.AutoValue Maven / Gradle / Ivy

/*
 * Copyright (C) 2012 Google, Inc.
 *
 * Licensed 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 com.google.auto.value;

import java.lang.annotation.Annotation;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

/**
 * Specifies that AutoValue should
 * generate an implementation class for the annotated abstract class, implementing the standard
 * {@link Object} methods like {@link Object#equals equals} to have conventional value semantics. A
 * simple example:  *
 *   @AutoValue
 *   abstract class Person {
 *     static Person create(String name, int id) {
 *       return new AutoValue_Person(name, id);
 *     }
 *
 *     abstract String name();
 *     abstract int id();
 *   }
 *
 * @see AutoValue User's Guide
 *
 * @author Éamonn McManus
 * @author Kevin Bourrillion
 */
@Retention(RetentionPolicy.SOURCE)
@Target(ElementType.TYPE)
public @interface AutoValue {

  /**
   * Specifies that AutoValue should generate an implementation of the annotated class or interface,
   * to serve as a builder for the value-type class it is nested within. As a simple example,
   * here is an alternative way to write the {@code Person} class mentioned in the {@link AutoValue}
   * example:    *
   *   @AutoValue
   *   abstract class Person {
   *     static Builder builder() {
   *       return new AutoValue_Person.Builder();
   *     }
   *
   *     abstract String name();
   *     abstract int id();
   *
   *     @AutoValue.Builder
   *     interface Builder {
   *       Builder name(String x);
   *       Builder id(int x);
   *       Person build();
   *     }
   *   }
   *
   * @author Éamonn McManus
   */
  @Retention(RetentionPolicy.SOURCE)
  @Target(ElementType.TYPE)
  public @interface Builder {}

  /**
   * Specifies that AutoValue should copy any annotations from the annotated element to the
   * generated class. This annotation supports classes and methods.
   *
   * The following annotations are excluded: 1. AutoValue and its nested annotations. 2. Any
   * annotation appearing in the {@link AutoValue.CopyAnnotations#exclude} field. 3. Any class
   * annotation which is itself annotated with the {@link java.lang.annotation.Inherited}
   * meta-annotation.
   *
   * @author Carmi Grushko
   */
  @Retention(RetentionPolicy.SOURCE)
  @Target({ElementType.TYPE, ElementType.METHOD})
  public @interface CopyAnnotations {
    Class[] exclude() default {};
  }
}