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Groovy: A powerful, dynamic language for the JVM
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/*
 *  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 {@code Externalizable} classes.
 * The {@code @ExternalizeMethods} annotation instructs the compiler to execute an
 * AST transformation which adds {@code writeExternal()} and {@code readExternal()} methods
 * to a class and adds {@code Externalizable} to the interfaces which the class implements.
 * The {@code writeExternal()} method writes each property (and optionally field) of the class
 * while the {@code readExternal()} method will read each one back in the same order.
 * Properties or fields marked as {@code transient} are ignored.
 * This annotation is typically used in conjunction with the {@code @ExternalizeMethods} annotation but
 * most usually not directly but rather via {@code @AutoExternalizable} which is a shortcut for both annotations.
 * 
 * Example usage:
 * 
 * import groovy.transform.*
 * {@code @ExternalizeMethods}
 * class Person {
 *   String first, last
 *   List favItems
 *   Date since
 * }
 * 
 * Which will create a class of the following form:
 *  * class Person implements Externalizable {
 *   ...
 *   public void writeExternal(ObjectOutput out) throws IOException {
 *     out.writeObject(first)
 *     out.writeObject(last)
 *     out.writeObject(favItems)
 *     out.writeObject(since)
 *   }
 *
 *   public void readExternal(ObjectInput oin) {
 *     first = (String) oin.readObject()
 *     last = (String) oin.readObject()
 *     favItems = (List) oin.readObject()
 *     since = (Date) oin.readObject()
 *   }
 *   ...
 * }
 * 
 *
 * @author Paul King
 * @since 1.8.0
 */
@java.lang.annotation.Documented
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.TYPE})
@GroovyASTTransformationClass("org.codehaus.groovy.transform.ExternalizeMethodsASTTransformation")
public @interface ExternalizeMethods {
    /**
     * Comma separated list of property names to exclude from externalizing.
     * 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 {};

    /**
     * Include fields as well as properties when externalizing.
     */
    boolean includeFields() default false;
}