103 lines
4.3 KiB
Java
103 lines
4.3 KiB
Java
/*
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* Copyright (c) 2018, 2020, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package java.io;
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import java.lang.annotation.*;
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/**
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* Indicates that an annotated field or method is part of the {@linkplain
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* Serializable serialization mechanism} defined by the
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* <cite>Java Object Serialization Specification</cite>. This
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* annotation type is intended to allow compile-time checking of
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* serialization-related declarations, analogous to the checking
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* enabled by the {@link java.lang.Override} annotation type to
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* validate method overriding. {@code Serializable} classes are encouraged to
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* use {@code @Serial} annotations to help a compiler catch
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* mis-declared serialization-related fields and methods,
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* mis-declarations that may otherwise be difficult to detect.
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*
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* <p>Specifically, annotations of this type should be
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* applied to serialization-related methods and fields in classes
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* declared to be {@code Serializable}. The five serialization-related
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* methods are:
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*
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* <ul>
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* <li>{@code private void writeObject(java.io.ObjectOutputStream stream) throws IOException}
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* <li>{@code private void readObject(java.io.ObjectInputStream stream) throws IOException, ClassNotFoundException}
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* <li>{@code private void readObjectNoData() throws ObjectStreamException}
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* <li><i>ANY-ACCESS-MODIFIER</i> {@code Object writeReplace() throws ObjectStreamException}
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* <li><i>ANY-ACCESS-MODIFIER</i> {@code Object readResolve() throws ObjectStreamException}
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* </ul>
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*
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* The two serialization-related fields are:
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*
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* <ul>
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* <li>{@code private static final ObjectStreamField[] serialPersistentFields}
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* <li>{@code private static final long serialVersionUID}
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* </ul>
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*
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* Compilers are encouraged to validate that a method or field marked with a
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* {@code @Serial} annotation is one of the defined serialization-related
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* methods or fields declared in a meaningful context and issue a warning
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* if that is not the case.
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*
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* <p>It is a semantic error to apply this annotation to other fields or methods, including:
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* <ul>
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* <li>fields or methods in a class that is not {@code Serializable}
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*
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* <li>fields or methods of the proper structural declaration, but in
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* a type where they are ineffectual. For example, {@code enum} types
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* are defined to have a {@code serialVersionUID} of {@code 0L} so a
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* {@code serialVersionUID} field declared in an {@code enum} type is
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* ignored. The five serialization-related methods identified above
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* are likewise ignored for an {@code enum} type.
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*
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* <li>in a class that is {@code Externalizable}:
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* <ul>
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* <li> method declarations of {@code writeObject}, {@code
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* readObject}, and {@code readObjectNoData}
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*
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* <li>a field declaration for {@code serialPersistentFields}
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* </ul>
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*
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* While the {@code Externalizable} interface extends {@code
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* Serializable}, the three methods and one field above are
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* <em>not</em> used for externalizable classes.
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*
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* </ul>
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*
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* Note that serialization mechanism accesses its designated fields
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* and methods reflectively and those fields and methods may appear
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* otherwise unused in a {@code Serializable} class.
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*
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* @see Serializable
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* @see Externalizable
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* @since 14
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*/
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@Target({ElementType.METHOD, ElementType.FIELD})
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@Retention(RetentionPolicy.SOURCE)
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public @interface Serial {}
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