gomp-20050608-branch/libjava/classpath/gnu/java/beans/decoder/ObjectHandler.java

   1 /* gnu.java.beans.decoder.ObjectHandler
   2    Copyright (C) 2004 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 gnu.java.beans.decoder;
  39
  40 import java.beans.ExceptionListener;
  41
  42 import org.xml.sax.Attributes;
  43
  44 /** An ObjectHandler parses the &lt;object&gt; tag and thereby creates various
  45  * Context implementations.
  46  *
  47  * @author Robert Schuster
  48  *
  49  */
  50 public class ObjectHandler extends AbstractElementHandler
  51 {
  52   /**
  53    * XXX: Can all results be stored with an object id?
  54    *
  55    *
  56    * @param PersistenceParser
  57    */
  58   ObjectHandler(ElementHandler parent)
  59   {
  60     super(parent, true);
  61   }
  62
  63   protected Context startElement(Attributes attributes, ExceptionListener exceptionListener)
  64     throws AssemblyException
  65   {
  66     String className = attributes.getValue("class");
  67     String methodName = attributes.getValue("method");
  68     String fieldName = attributes.getValue("field");
  69     String index = attributes.getValue("index");
  70     String propertyName = attributes.getValue("property");
  71     String id = attributes.getValue("id");
  72     String idRef = attributes.getValue("idref");
  73
  74     /* first check if we just want to access an existing object (idref present)
  75      *
  76      * note: <object idref="foo" method="bar"/> is not valid to call method "bar"
  77      * on the object with id "foo". Instead this should return the object "foo"
  78      * itself. The right way to this is:
  79      * <object idref="foo">
  80      *         <object method="bar"/>
  81      * </object>
  82      *
  83      * This means that if idref is present class, method, field, index and
  84      * property are obsolete.
  85      */
  86     if (idRef != null)
  87       // reactivates an existing object and giving it another name if id exists
  88       return new ObjectContext(id, getObject(idRef));
  89
  90     // decides whether we are in a static (className present) or dynamic context
  91     if (className != null)
  92       {
  93         try
  94           {
  95             Class klass = instantiateClass(className);
  96
  97             // class name exists which means that we are in a static context.
  98             // so we may want to ...
  99             // access a static field if the fieldName exists
 100             if (fieldName != null)
 101               {
 102                 try
 103                   {
 104                     return new ObjectContext(id,
 105                                              klass.getField(fieldName).get(null));
 106                   }
 107                 catch (NoSuchFieldException nsfe)
 108                   {
 109                     throw new AssemblyException(nsfe);
 110                   }
 111                 catch (IllegalAccessException iae)
 112                   {
 113                     throw new AssemblyException(iae);
 114                   }
 115               }
 116
 117             // (falling through is important!)
 118             // run a constructor if methodName is "new" or null
 119             if (methodName == null || methodName.equals("new"))
 120               return new ConstructorContext(id, klass);
 121
 122             // (falling through is important!)
 123             // run a static method on the given class (if methodName exists, which is implied already)
 124             return new StaticMethodContext(id, klass, methodName);
 125             // XXX: should fail if unexpected attributes are present?
 126           }
 127         catch (ClassNotFoundException cnfe)
 128           {
 129             throw new AssemblyException(cnfe);
 130           }
 131       }
 132     else
 133       {
 134         // className does not exist which means we are in the context of
 135         // some object and want to ...
 136         // access the get(int index) method if index != null
 137         if (index != null)
 138           {
 139             try
 140               {
 141                 // Note: http://java.sun.com/products/jfc/tsc/articles/persistence3/ says
 142                 // that <void index="4"/> will make up a get()-call. But this is wrong because
 143                 // <void/> tags never return values (to the surrounding context)
 144                 return new IndexContext(id, Integer.parseInt(index));
 145               }
 146             catch (NumberFormatException nfe)
 147               {
 148                 throw new AssemblyException(nfe);
 149               }
 150           }
 151
 152         // access a method if methodName exists
 153         if (methodName != null)
 154           return new MethodContext(id, methodName);
 155
 156         // (falling through is important!)
 157         // access a property if a propertyName exists
 158         if (propertyName != null && propertyName.length() > 0)
 159           // this is reported as an ordinary method access where the propertyName is
 160           // converted into a 'getter'-method name: convert first character of property name
 161           // to upper case and prepend 'get'
 162           // Note: This will be a getter-method because the <object> tag implies that a return
 163           // value is expected.
 164           return new PropertyContext(id, propertyName);
 165       }
 166
 167     throw new AssemblyException(new IllegalArgumentException("Wrong or missing attributes for <object> tag."));
 168   }
 169 }