ozoneiterator.java

Java的面向对象数据库系统的源代码

// This file is
// Copyright (C) 2002-@year@ Leo Mekenkamp. All rights reserved.
// $Id: OzoneCollection.java,v 1.4 2003/10/28 13:01:42 leomekenkamp Exp $
// 
// This file is part of the Ozone Collections package.
// 
// Ozone Collections 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.
// 
// Ozone Collections 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
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package org.ozoneDB.collections;

import java.util.Iterator;
import org.ozoneDB.OzoneRemote;

/**
 * <p>Used by implementations of <code>FullXxx</code> Ozone collections. <code>NodeXxx</code>
 * have no need for server side iterators. All <code>FullXxx</code> use non-Ozone
 * objects for 'nodes' inside, all <code>NodeXxx</code> <i>do</i> use Ozone
 * objects for their internal structure. As an <code>Iterator</code> has direct
 * links to these internal node objects, it is possible for <code>NodeXxx</code>
 * collections to have non-Ozone iterators, since they only reference Ozone objects.
 * This means these iterators can simply be serializable and can leave the
 * Ozone server. Iterators for <code>FullXxx</code> collections however can not
 * leave the server since they reference non-Ozone objects; simply serializing
 * them and sending them to the client would cause the internal node structure
 * to be copied and send to the client as well. Therefor <code>FullXxx</code>
 * collections need a server side iterator.</p>
 * <p>Because an <code>OzoneIterator</code> references non-Ozone objects that
 * 'belong' to an other Ozone object special precautions have to be taken to
 * assure that if the collection that an iterator is connected to is serialized,
 * that the iterator itself does not continue using the non-Ozone objects that
 * are serialized in the same container as the collection (or vice versa: the 
 * iterator is serialized but the collection is not). One such a precaution
 * can be throwing a <code>ConcurrentModificationException</code> when one of
 * the two have been serialized. This is slightly abusing the specs as layed out
 * by Sun, but there is no other workaround IMHO, at least not until Ozone
 * supports a way of storing 2 objects in 1 container or keeping objects forced
 * in main memory.</p>
 * 
 * @author <a href="mailto:ozoneATmekenkampD0Tcom">Leo Mekenkamp (mind the anti-sp@m)</a>
 */
public interface OzoneIterator extends Iterator, OzoneRemote {
    
    public Object next(); /*update*/
    
    public void remove(); /*update*/
    
}