J. Duke | 319a3b9 | 2007-12-01 00:00:00 +0000 | [diff] [blame^] | 1 | /* |
| 2 | * Copyright 1996-2004 Sun Microsystems, Inc. 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. Sun designates this |
| 8 | * particular file as subject to the "Classpath" exception as provided |
| 9 | * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, |
| 22 | * CA 95054 USA or visit www.sun.com if you need additional information or |
| 23 | * have any 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 | } |