98 lines
4.4 KiB
Java
98 lines
4.4 KiB
Java
/*
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* Copyright (c) 1996, 2004, 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.io.ObjectOutput;
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import java.io.ObjectInput;
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/**
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* Only the identity of the class of an Externalizable instance is
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* written in the serialization stream and it is the responsibility
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* of the class to save and restore the contents of its instances.
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*
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* The writeExternal and readExternal methods of the Externalizable
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* interface are implemented by a class to give the class complete
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* control over the format and contents of the stream for an object
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* and its supertypes. These methods must explicitly
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* coordinate with the supertype to save its state. These methods supersede
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* customized implementations of writeObject and readObject methods.<br>
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*
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* Object Serialization uses the Serializable and Externalizable
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* interfaces. Object persistence mechanisms can use them as well. Each
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* object to be stored is tested for the Externalizable interface. If
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* the object supports Externalizable, the writeExternal method is called. If the
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* object does not support Externalizable and does implement
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* Serializable, the object is saved using
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* ObjectOutputStream. <br> When an Externalizable object is
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* reconstructed, an instance is created using the public no-arg
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* constructor, then the readExternal method called. Serializable
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* objects are restored by reading them from an ObjectInputStream.<br>
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*
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* An Externalizable instance can designate a substitution object via
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* the writeReplace and readResolve methods documented in the Serializable
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* interface.<br>
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*
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* @author unascribed
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* @see java.io.ObjectOutputStream
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* @see java.io.ObjectInputStream
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* @see java.io.ObjectOutput
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* @see java.io.ObjectInput
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* @see java.io.Serializable
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* @since 1.1
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*/
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public interface Externalizable extends java.io.Serializable {
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/**
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* The object implements the writeExternal method to save its contents
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* by calling the methods of DataOutput for its primitive values or
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* calling the writeObject method of ObjectOutput for objects, strings,
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* and arrays.
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*
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* @serialData Overriding methods should use this tag to describe
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* the data layout of this Externalizable object.
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* List the sequence of element types and, if possible,
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* relate the element to a public/protected field and/or
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* method of this Externalizable class.
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*
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* @param out the stream to write the object to
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* @exception IOException Includes any I/O exceptions that may occur
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*/
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void writeExternal(ObjectOutput out) throws IOException;
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/**
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* The object implements the readExternal method to restore its
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* contents by calling the methods of DataInput for primitive
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* types and readObject for objects, strings and arrays. The
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* readExternal method must read the values in the same sequence
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* and with the same types as were written by writeExternal.
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*
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* @param in the stream to read data from in order to restore the object
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* @exception IOException if I/O errors occur
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* @exception ClassNotFoundException If the class for an object being
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* restored cannot be found.
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*/
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void readExternal(ObjectInput in) throws IOException, ClassNotFoundException;
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}
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