001 /* DefaultPersistenceDelegate.java 002 Copyright (C) 2005 Free Software Foundation, Inc. 003 004 This file is part of GNU Classpath. 005 006 GNU Classpath is free software; you can redistribute it and/or modify 007 it under the terms of the GNU General Public License as published by 008 the Free Software Foundation; either version 2, or (at your option) 009 any later version. 010 011 GNU Classpath is distributed in the hope that it will be useful, but 012 WITHOUT ANY WARRANTY; without even the implied warranty of 013 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 014 General Public License for more details. 015 016 You should have received a copy of the GNU General Public License 017 along with GNU Classpath; see the file COPYING. If not, write to the 018 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 019 02110-1301 USA. 020 021 Linking this library statically or dynamically with other modules is 022 making a combined work based on this library. Thus, the terms and 023 conditions of the GNU General Public License cover the whole 024 combination. 025 026 As a special exception, the copyright holders of this library give you 027 permission to link this library with independent modules to produce an 028 executable, regardless of the license terms of these independent 029 modules, and to copy and distribute the resulting executable under 030 terms of your choice, provided that you also meet, for each linked 031 independent module, the terms and conditions of the license of that 032 module. An independent module is a module which is not derived from 033 or based on this library. If you modify this library, you may extend 034 this exception to your version of the library, but you are not 035 obligated to do so. If you do not wish to do so, delete this 036 exception statement from your version. */ 037 038 039 package java.beans; 040 041 import java.lang.reflect.InvocationTargetException; 042 import java.lang.reflect.Method; 043 044 /** <p><code>DefaultPersistenceDelegate</code> is a {@link PersistenceDelegate} 045 * implementation that can be used to serialize objects which adhere to the 046 * Java Beans naming convention.</p> 047 * 048 * @author Robert Schuster (robertschuster@fsfe.org) 049 * @since 1.4 050 */ 051 public class DefaultPersistenceDelegate extends PersistenceDelegate 052 { 053 054 private String[] constructorPropertyNames; 055 056 /** Using this constructor the object to be serialized will be instantiated 057 * with the default non-argument constructor. 058 */ 059 public DefaultPersistenceDelegate() 060 { 061 } 062 063 /** This constructor allows to specify which Bean properties appear 064 * in the constructor. 065 * 066 * <p>The implementation reads the mentioned properties from the Bean 067 * instance and applies it in the given order to a corresponding 068 * constructor.</p> 069 * 070 * @param constructorPropertyNames The properties the Bean's constructor 071 * should be given to. 072 */ 073 public DefaultPersistenceDelegate(String[] constructorPropertyNames) 074 { 075 this.constructorPropertyNames = constructorPropertyNames; 076 } 077 078 protected boolean mutatesTo(Object oldInstance, Object newInstance) 079 { 080 try 081 { 082 083 return (constructorPropertyNames != null 084 && constructorPropertyNames.length > 0 085 && oldInstance.getClass() 086 .getDeclaredMethod("equals", 087 new Class[] { Object.class }) != null) 088 ? oldInstance.equals(newInstance) 089 : super.mutatesTo(oldInstance, newInstance); 090 } 091 catch (NoSuchMethodException nsme) 092 { 093 return super.mutatesTo(oldInstance, newInstance); 094 } 095 } 096 097 protected Expression instantiate(Object oldInstance, Encoder out) 098 { 099 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 }