/*

 * Copyright (c) 2018, 2020, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package java.io;

import java.lang.annotation.*;

/**

 * Indicates that an annotated field or method is part of the {@linkplain

 * Serializable serialization mechanism} defined by the

 * <cite>Java Object Serialization Specification</cite>. This

 * annotation type is intended to allow compile-time checking of

 * serialization-related declarations, analogous to the checking

 * enabled by the {@link java.lang.Override} annotation type to

 * validate method overriding. {@code Serializable} classes are encouraged to

 * use {@code @Serial} annotations to help a compiler catch

 * mis-declared serialization-related fields and methods,

 * mis-declarations that may otherwise be difficult to detect.

 *

 * <p>Specifically, annotations of this type should be

 * applied to serialization-related methods and fields in classes

 * declared to be {@code Serializable}. The five serialization-related

 * methods are:

 *

 * <ul>

 * <li>{@code private void writeObject(java.io.ObjectOutputStream stream) throws IOException}

 * <li>{@code private void readObject(java.io.ObjectInputStream stream) throws IOException, ClassNotFoundException}

 * <li>{@code private void readObjectNoData() throws ObjectStreamException}

 * <li><i>ANY-ACCESS-MODIFIER</i> {@code Object writeReplace() throws ObjectStreamException}

 * <li><i>ANY-ACCESS-MODIFIER</i> {@code Object readResolve() throws ObjectStreamException}

 * </ul>

 *

 * The two serialization-related fields are:

 *

 * <ul>

 * <li>{@code private static final ObjectStreamField[] serialPersistentFields}

 * <li>{@code private static final long serialVersionUID}

 * </ul>

 *

 * Compilers are encouraged to validate that a method or field marked with a

 * {@code @Serial} annotation is one of the defined serialization-related

 * methods or fields declared in a meaningful context and issue a warning

 * if that is not the case.

 *

 * <p>It is a semantic error to apply this annotation to other fields or methods, including:

 * <ul>

 * <li>fields or methods in a class that is not {@code Serializable}

 *

 * <li>fields or methods of the proper structural declaration, but in

 * a type where they are ineffectual. For example, {@code enum} types

 * are defined to have a {@code serialVersionUID} of {@code 0L} so a

 * {@code serialVersionUID} field declared in an {@code enum} type is

 * ignored. The five serialization-related methods identified above

 * are likewise ignored for an {@code enum} type.

 *

 * <li>in a class that is {@code Externalizable}:

 * <ul>

 *   <li> method declarations of {@code writeObject}, {@code

 *   readObject}, and {@code readObjectNoData}

 *

 *  <li>a field declaration for {@code serialPersistentFields}

 * </ul>

 *

 * While the {@code Externalizable} interface extends {@code

 * Serializable}, the three methods and one field above are

 * <em>not</em> used for externalizable classes.

 *

 * </ul>

 *

 * Note that serialization mechanism accesses its designated fields

 * and methods reflectively and those fields and methods may appear

 * otherwise unused in a {@code Serializable} class.

 *

 * @see Serializable

 * @see Externalizable

 * @since 14

 */

@Target({ElementType.METHOD, ElementType.FIELD})

@Retention(RetentionPolicy.SOURCE)

public @interface Serial {}