Source for java.beans.PersistenceDelegate

   1: /* java.beans.PersistenceDelegate
   2:    Copyright (C) 2005 Free Software Foundation, Inc.
   3: 
   4: This file is part of GNU Classpath.
   5: 
   6: GNU Classpath is free software; you can redistribute it and/or modify
   7: it under the terms of the GNU General Public License as published by
   8: the Free Software Foundation; either version 2, or (at your option)
   9: any later version.
  10:  
  11: GNU Classpath is distributed in the hope that it will be useful, but
  12: WITHOUT ANY WARRANTY; without even the implied warranty of
  13: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14: General Public License for more details.
  15: 
  16: You should have received a copy of the GNU General Public License
  17: along with GNU Classpath; see the file COPYING.  If not, write to the
  18: Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  19: 02110-1301 USA.
  20: 
  21: Linking this library statically or dynamically with other modules is
  22: making a combined work based on this library.  Thus, the terms and
  23: conditions of the GNU General Public License cover the whole
  24: combination.
  25: 
  26: As a special exception, the copyright holders of this library give you
  27: permission to link this library with independent modules to produce an
  28: executable, regardless of the license terms of these independent
  29: modules, and to copy and distribute the resulting executable under
  30: terms of your choice, provided that you also meet, for each linked
  31: independent module, the terms and conditions of the license of that
  32: module.  An independent module is a module which is not derived from
  33: or based on this library.  If you modify this library, you may extend
  34: this exception to your version of the library, but you are not
  35: obligated to do so.  If you do not wish to do so, delete this
  36: exception statement from your version. */
  37: 
  38: package java.beans;
  39: 
  40: /** <p>A <code>PersistenceDelegate</code> describes how a another object
  41:  * has to constructed and transformed in order to create a complete
  42:  * replicate.</p>
  43:  * 
  44:  * <p>For custom classes you will need to implement
  45:  * <code>PersistenceDelegate</code> in a way that is suitable for them.
  46:  * To make use of the implementation you have to register it with an
  47:  * {@link Encoder} using the {Encoder#setPersistenceDelegate} method.</p>
  48:  * 
  49:  * @author Robert Schuster (robertschuster@fsfe.org)
  50:  * @since 1.4
  51:  */
  52: public abstract class PersistenceDelegate
  53: {
  54: 
  55:   protected void initialize(Class<?> type, Object oldInstance,
  56:                             Object newInstance, Encoder out)
  57:   {
  58:     if (type != Object.class)
  59:       {
  60:         type = type.getSuperclass();
  61: 
  62:         PersistenceDelegate pd = out.getPersistenceDelegate(type);
  63:         
  64:         pd.initialize(type, oldInstance, newInstance, out);
  65:       }
  66:   }
  67: 
  68:   public void writeObject(Object oldInstance, Encoder out)
  69:   {
  70:     Object streamCandidate = out.get(oldInstance);
  71: 
  72:     if (mutatesTo(oldInstance, streamCandidate))
  73:       {
  74:         initialize(oldInstance.getClass(), oldInstance, streamCandidate, out);
  75:       }
  76:     else
  77:       {
  78:         out.remove(oldInstance);
  79:         out.writeExpression(instantiate(oldInstance, out));
  80:       }
  81:   }
  82: 
  83:   protected boolean mutatesTo(Object oldInstance, Object newInstance)
  84:   {
  85:     return (newInstance != null)
  86:            && oldInstance.getClass() == newInstance.getClass();
  87:   }
  88: 
  89:   protected abstract Expression instantiate(Object oldInstance, Encoder out);
  90: }