libjava/classpath/gnu/java/beans/encoder/ArrayPersistenceDelegate.java

   1 /* ArrayPersistenceDelegate.java - A PersistenceDelegate that handles arrays.
   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 gnu.java.beans.encoder;
  40
  41 import java.beans.Encoder;
  42 import java.beans.Expression;
  43 import java.beans.PersistenceDelegate;
  44 import java.beans.Statement;
  45
  46 import java.lang.reflect.Array;
  47 import java.util.HashMap;
  48
  49 public class ArrayPersistenceDelegate extends PersistenceDelegate
  50 {
  51   private static final HashMap NULL_VALUES = new HashMap();
  52
  53   static
  54     {
  55       NULL_VALUES.put(Boolean.TYPE, Boolean.FALSE);
  56       NULL_VALUES.put(Byte.TYPE, Byte.valueOf((byte) 0));
  57       NULL_VALUES.put(Short.TYPE, Short.valueOf((short) 0));
  58       NULL_VALUES.put(Integer.TYPE, Integer.valueOf(0));
  59       NULL_VALUES.put(Long.TYPE, Long.valueOf(0));
  60       NULL_VALUES.put(Float.TYPE, Float.valueOf(0.0f));
  61       NULL_VALUES.put(Double.TYPE, Double.valueOf(0.0));
  62     }
  63
  64   protected Expression instantiate(Object oldInstance, Encoder out)
  65   {
  66     Class type = oldInstance.getClass().getComponentType();
  67
  68     // oldInstance is expected to be an array, then
  69     // getClass().getComponentType() should lead
  70     // to its component type.
  71     assert (type != null);
  72
  73     // Not handling primitive types in a special way here
  74     // causes that Class.forName("int") is built as an Expression
  75     // later which would cause an exception if executed. A special
  76     // handling to avoid the execution for primitive types can be
  77     // java.beans.Encoder.writeExpression() .
  78     return new Expression(
  79                           oldInstance,
  80                           Array.class,
  81                           "newInstance",
  82                           new Object[] {
  83                             type,
  84                             new Integer(Array.getLength(oldInstance)) });
  85   }
  86
  87   protected void initialize(Class type, Object oldInstance, Object newInstance,
  88                             Encoder out)
  89   {
  90     int length = Array.getLength(oldInstance);
  91
  92     // Compares the array value against a prototypical
  93     // null value of the array's component type in order to skip
  94     // writing the default values of an array.
  95
  96     // Note: I have no idea why the persistence delegate for arrays writes
  97     // an Expression that reads the value and then writes a Statement that sets
  98     // the value. However it turned out that object arrays work better with the
  99     // get-Expression and primitive array work fine with the set-Statement.
 100
 101     type = type.getComponentType();
 102     if (type.isPrimitive())
 103       {
 104         Object nullValue = NULL_VALUES.get(type);
 105
 106         for (int i = 0; i < length; i++)
 107           {
 108             Object oldValue = Array.get(oldInstance, i);
 109
 110             if (!oldValue.equals(nullValue))
 111               {
 112                 out.writeExpression(new Expression(Array.class, "get",
 113                                                    new Object[] { oldInstance,
 114                                                                  Integer.valueOf(i),
 115                                                                  }));
 116
 117                 out.writeStatement(new Statement(Array.class, "set",
 118                                                new Object[] {
 119                                                  oldInstance,
 120                                                  Integer.valueOf(i),
 121                                                  oldValue
 122                                                  }));
 123               }
 124           }
 125
 126       }
 127     else
 128       {
 129
 130         for (int i = 0; i < length; i++)
 131           {
 132             Object oldValue = Array.get(oldInstance, i);
 133
 134             if (oldValue != null)
 135               {
 136                 out.writeExpression(new Expression(Array.class, "get",
 137                                                  new Object[] { oldInstance,
 138                                                                Integer.valueOf(i),
 139                                                                }));
 140
 141                 out.writeStatement(new Statement(Array.class, "set",
 142                                                    new Object[] {
 143                                                      oldInstance,
 144                                                      Integer.valueOf(i),
 145                                                      oldValue
 146                                                      }));
 147               }
 148           }
 149       }
 150
 151   }
 152
 153 }