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| 1 | /* | ||
| 2 | * Copyright (c) 1996, 2004, Oracle and/or its affiliates. All rights reserved. | ||
| 3 | * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. | ||
| 4 | * | ||
| 5 | * This code is free software; you can redistribute it and/or modify it | ||
| 6 | * under the terms of the GNU General Public License version 2 only, as | ||
| 7 | * published by the Free Software Foundation. Oracle designates this | ||
| 8 | * particular file as subject to the "Classpath" exception as provided | ||
| 9 | * by Oracle in the LICENSE file that accompanied this code. | ||
| 10 | * | ||
| 11 | * This code is distributed in the hope that it will be useful, but WITHOUT | ||
| 12 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | ||
| 13 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | ||
| 14 | * version 2 for more details (a copy is included in the LICENSE file that | ||
| 15 | * accompanied this code). | ||
| 16 | * | ||
| 17 | * You should have received a copy of the GNU General Public License version | ||
| 18 | * 2 along with this work; if not, write to the Free Software Foundation, | ||
| 19 | * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. | ||
| 20 | * | ||
| 21 | * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA | ||
| 22 | * or visit www.oracle.com if you need additional information or have any | ||
| 23 | * questions. | ||
| 24 | */ | ||
| 25 | |||
| 26 | package java.io; | ||
| 27 | |||
| 28 | import java.io.ObjectOutput; | ||
| 29 | import java.io.ObjectInput; | ||
| 30 | |||
| 31 | /** | ||
| 32 | * Only the identity of the class of an Externalizable instance is | ||
| 33 | * written in the serialization stream and it is the responsibility | ||
| 34 | * of the class to save and restore the contents of its instances. | ||
| 35 | * | ||
| 36 | * The writeExternal and readExternal methods of the Externalizable | ||
| 37 | * interface are implemented by a class to give the class complete | ||
| 38 | * control over the format and contents of the stream for an object | ||
| 39 | * and its supertypes. These methods must explicitly | ||
| 40 | * coordinate with the supertype to save its state. These methods supersede | ||
| 41 | * customized implementations of writeObject and readObject methods.<br> | ||
| 42 | * | ||
| 43 | * Object Serialization uses the Serializable and Externalizable | ||
| 44 | * interfaces. Object persistence mechanisms can use them as well. Each | ||
| 45 | * object to be stored is tested for the Externalizable interface. If | ||
| 46 | * the object supports Externalizable, the writeExternal method is called. If the | ||
| 47 | * object does not support Externalizable and does implement | ||
| 48 | * Serializable, the object is saved using | ||
| 49 | * ObjectOutputStream. <br> When an Externalizable object is | ||
| 50 | * reconstructed, an instance is created using the public no-arg | ||
| 51 | * constructor, then the readExternal method called. Serializable | ||
| 52 | * objects are restored by reading them from an ObjectInputStream.<br> | ||
| 53 | * | ||
| 54 | * An Externalizable instance can designate a substitution object via | ||
| 55 | * the writeReplace and readResolve methods documented in the Serializable | ||
| 56 | * interface.<br> | ||
| 57 | * | ||
| 58 | * @author unascribed | ||
| 59 | * @see java.io.ObjectOutputStream | ||
| 60 | * @see java.io.ObjectInputStream | ||
| 61 | * @see java.io.ObjectOutput | ||
| 62 | * @see java.io.ObjectInput | ||
| 63 | * @see java.io.Serializable | ||
| 64 | * @since JDK1.1 | ||
| 65 | */ | ||
| 66 | public interface Externalizable extends java.io.Serializable { | ||
| 67 | /** | ||
| 68 | * The object implements the writeExternal method to save its contents | ||
| 69 | * by calling the methods of DataOutput for its primitive values or | ||
| 70 | * calling the writeObject method of ObjectOutput for objects, strings, | ||
| 71 | * and arrays. | ||
| 72 | * | ||
| 73 | * @serialData Overriding methods should use this tag to describe | ||
| 74 | * the data layout of this Externalizable object. | ||
| 75 | * List the sequence of element types and, if possible, | ||
| 76 | * relate the element to a public/protected field and/or | ||
| 77 | * method of this Externalizable class. | ||
| 78 | * | ||
| 79 | * @param out the stream to write the object to | ||
| 80 | * @exception IOException Includes any I/O exceptions that may occur | ||
| 81 | */ | ||
| 82 | void writeExternal(ObjectOutput out) throws IOException; | ||
| 83 | |||
| 84 | /** | ||
| 85 | * The object implements the readExternal method to restore its | ||
| 86 | * contents by calling the methods of DataInput for primitive | ||
| 87 | * types and readObject for objects, strings and arrays. The | ||
| 88 | * readExternal method must read the values in the same sequence | ||
| 89 | * and with the same types as were written by writeExternal. | ||
| 90 | * | ||
| 91 | * @param in the stream to read data from in order to restore the object | ||
| 92 | * @exception IOException if I/O errors occur | ||
| 93 | * @exception ClassNotFoundException If the class for an object being | ||
| 94 | * restored cannot be found. | ||
| 95 | */ | ||
| 96 | void readExternal(ObjectInput in) throws IOException, ClassNotFoundException; | ||
| 97 | } | ||