libjava/classpath/java/beans/DefaultPersistenceDelegate.java

   1 /* DefaultPersistenceDelegate.java
   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
  39 package java.beans;
  40
  41 import java.lang.reflect.InvocationTargetException;
  42 import java.lang.reflect.Method;
  43
  44 /** <p><code>DefaultPersistenceDelegate</code> is a {@link PersistenceDelegate}
  45  * implementation that can be used to serialize objects which adhere to the
  46  * Java Beans naming convention.</p>
  47  *
  48  * @author Robert Schuster (robertschuster@fsfe.org)
  49  * @since 1.4
  50  */
  51 public class DefaultPersistenceDelegate extends PersistenceDelegate
  52 {
  53
  54   private String[] constructorPropertyNames;
  55
  56   /** Using this constructor the object to be serialized will be instantiated
  57    * with the default non-argument constructor.
  58    */
  59   public DefaultPersistenceDelegate()
  60   {
  61   }
  62
  63   /** This constructor allows to specify which Bean properties appear
  64    * in the constructor.
  65    *
  66    * <p>The implementation reads the mentioned properties from the Bean
  67    * instance and applies it in the given order to a corresponding
  68    * constructor.</p>
  69    *
  70    * @param constructorPropertyNames The properties the Bean's constructor
  71    * should be given to.
  72    */
  73   public DefaultPersistenceDelegate(String[] constructorPropertyNames)
  74   {
  75     this.constructorPropertyNames = constructorPropertyNames;
  76   }
  77
  78   protected boolean mutatesTo(Object oldInstance, Object newInstance)
  79   {
  80     try
  81       {
  82
  83         return (constructorPropertyNames != null
  84                && constructorPropertyNames.length > 0
  85                && oldInstance.getClass()
  86                .getDeclaredMethod("equals",
  87                                   new Class[] { Object.class }) != null)
  88                                   ? oldInstance.equals(newInstance)
  89                                   : super.mutatesTo(oldInstance, newInstance);
  90       }
  91     catch (NoSuchMethodException nsme)
  92       {
  93         return super.mutatesTo(oldInstance, newInstance);
  94       }
  95   }
  96
  97   protected Expression instantiate(Object oldInstance, Encoder out)
  98   {
  99     Object[] args = null;
 100
 101     try
 102       {
 103         // If there are property names in the array, then we create
 104         // a corresponding argument array and store every
 105         // argument in it. To retrieve an argument object we have
 106         // dig up the right property in the bean class' BeanInfo
 107         // object.
 108         // This is so costly in terms of execution time I better
 109         // not think twice about it ...
 110         if (constructorPropertyNames != null)
 111           {
 112             args = new Object[constructorPropertyNames.length];
 113
 114             // Look up the properties of oldInstance's class to find matches for
 115             // the
 116             // names given in the constructor.
 117             PropertyDescriptor[] propertyDescs = Introspector.getBeanInfo(
 118                                                                           oldInstance.getClass()).getPropertyDescriptors();
 119
 120             for (int i = 0; i < constructorPropertyNames.length; i++)
 121               {
 122                 // Scan the property descriptions for a matching name.
 123                 for (int j = 0; j < propertyDescs.length; j++)
 124                   {
 125                     if (propertyDescs[i].getName().equals(
 126                                                           constructorPropertyNames[i]))
 127                       {
 128                         Method readMethod = propertyDescs[i].getReadMethod();
 129
 130                         args[i] = readMethod.invoke(oldInstance);
 131                       }
 132                   }
 133               }
 134           }
 135
 136       }
 137     catch (IllegalAccessException iae)
 138       {
 139         out.getExceptionListener().exceptionThrown(iae);
 140       }
 141     catch (IllegalArgumentException iarge)
 142       {
 143         out.getExceptionListener().exceptionThrown(iarge);
 144       }
 145     catch (InvocationTargetException ite)
 146       {
 147         out.getExceptionListener().exceptionThrown(ite);
 148       }
 149     catch (IntrospectionException ie)
 150       {
 151         out.getExceptionListener().exceptionThrown(ie);
 152       }
 153
 154     return new Expression(oldInstance, oldInstance.getClass(), "new", args);
 155   }
 156
 157   protected void initialize(Class<?> type, Object oldInstance,
 158                             Object newInstance, Encoder out)
 159   {
 160     // Calling the supertype's implementation of initialize makes it
 161     // possible that descendants of classes like AbstractHashMap
 162     // or Hashtable are serialized correctly. This mechanism grounds on
 163     // two other facts:
 164     // * Each class which has not registered a special purpose
 165     //   PersistenceDelegate is handled by a DefaultPersistenceDelegate
 166     //   instance.
 167     // * PersistenceDelegate.initialize() is implemented in a way that it
 168     //   calls the initialize method of the superclass' persistence delegate.
 169     super.initialize(type, oldInstance, newInstance, out);
 170
 171     // Suppresses the writing of property setting statements when this delegate
 172     // is not used for the exact instance type. By doing so the following code
 173     // is called only once per object.
 174     if (type != oldInstance.getClass())
 175       return;
 176
 177     try
 178       {
 179         PropertyDescriptor[] propertyDescs = Introspector.getBeanInfo(
 180                                                                       oldInstance.getClass()).getPropertyDescriptors();
 181
 182         for (int i = 0; i < propertyDescs.length; i++)
 183           {
 184             Method readMethod = propertyDescs[i].getReadMethod();
 185             Method writeMethod = propertyDescs[i].getWriteMethod();
 186
 187             if (readMethod != null && writeMethod != null)
 188               {
 189                 Object oldValue = readMethod.invoke(oldInstance);
 190
 191                 if (oldValue != null)
 192                   out.writeStatement(new Statement(oldInstance,
 193                                                    writeMethod.getName(),
 194                                                    new Object[] { oldValue }));
 195               }
 196           }
 197       }
 198     catch (IntrospectionException ie)
 199       {
 200         out.getExceptionListener().exceptionThrown(ie);
 201       }
 202     catch (IllegalAccessException iae)
 203       {
 204         out.getExceptionListener().exceptionThrown(iae);
 205       }
 206     catch (InvocationTargetException ite)
 207       {
 208         out.getExceptionListener().exceptionThrown(ite);
 209       }
 210   }
 211 }