| /* Externalizable.java -- Interface for saving and restoring object data |
| Copyright (C) 1998 Free Software Foundation, Inc. |
| |
| This file is part of GNU Classpath. |
| |
| GNU Classpath is free software; you can redistribute it and/or modify |
| it under the terms of the GNU General Public License as published by |
| the Free Software Foundation; either version 2, or (at your option) |
| any later version. |
| |
| GNU Classpath 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 for more details. |
| |
| You should have received a copy of the GNU General Public License |
| along with GNU Classpath; see the file COPYING. If not, write to the |
| Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA |
| 02111-1307 USA. |
| |
| Linking this library statically or dynamically with other modules is |
| making a combined work based on this library. Thus, the terms and |
| conditions of the GNU General Public License cover the whole |
| combination. |
| |
| As a special exception, the copyright holders of this library give you |
| permission to link this library with independent modules to produce an |
| executable, regardless of the license terms of these independent |
| modules, and to copy and distribute the resulting executable under |
| terms of your choice, provided that you also meet, for each linked |
| independent module, the terms and conditions of the license of that |
| module. An independent module is a module which is not derived from |
| or based on this library. If you modify this library, you may extend |
| this exception to your version of the library, but you are not |
| obligated to do so. If you do not wish to do so, delete this |
| exception statement from your version. */ |
| |
| |
| package java.io; |
| |
| /** |
| * This interface provides a way that classes can completely control how |
| * the data of their object instances are written and read to and from |
| * streams. It has two methods which are used to write the data to a stream |
| * and to read the data from a stream. The read method must read the data |
| * in exactly the way it was written by the write method. |
| * <p> |
| * Note that classes which implement this interface must take into account |
| * that all superclass data must also be written to the stream as well. |
| * The class implementing this interface must figure out how to make that |
| * happen. |
| * <p> |
| * This interface can be used to provide object persistence. When an |
| * object is to be stored externally, the <code>writeExternal</code> method is |
| * called to save state. When the object is restored, an instance is |
| * created using the default no-argument constructor and the |
| * <code>readExternal</code> method is used to restore the state. |
| * |
| * @author Aaron M. Renn (arenn@urbanophile.com) |
| */ |
| public interface Externalizable extends Serializable |
| { |
| /** |
| * This method restores an object's state by reading in the instance data |
| * for the object from the passed in stream. Note that this stream is not |
| * a subclass of <code>InputStream</code>, but rather is a class that |
| * implements |
| * the <code>ObjectInput</code> interface. That interface provides a |
| * mechanism for |
| * reading in Java data types from a stream. |
| * <p> |
| * Note that this method must be compatible with <code>writeExternal</code>. |
| * It must read back the exact same types that were written by that |
| * method in the exact order they were written. |
| * <p> |
| * If this method needs to read back an object instance, then the class |
| * for that object must be found and loaded. If that operation fails, |
| * then this method throws a <code>ClassNotFoundException</code> |
| * |
| * @param in An <code>ObjectInput</code> instance for reading in the object |
| * state |
| * |
| * @exception ClassNotFoundException If the class of an object being |
| * restored cannot be found |
| * @exception IOException If any other error occurs |
| */ |
| void readExternal(ObjectInput in) |
| throws ClassNotFoundException, IOException; |
| |
| /** |
| * This method is responsible for writing the instance data of an object |
| * to the passed in stream. Note that this stream is not a subclass of |
| * <code>OutputStream</code>, but rather is a class that implements the |
| * <code>ObjectOutput</code> interface. That interface provides a |
| * number of methods |
| * for writing Java data values to a stream. |
| * <p> |
| * Not that the implementation of this method must be coordinated with |
| * the implementation of <code>readExternal</code>. |
| * |
| * @param out An <code>ObjectOutput</code> instance for writing the |
| * object state |
| * |
| * @exception IOException If an error occurs |
| */ |
| void writeExternal(ObjectOutput out) throws IOException; |
| } |