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

   1 /* gnu.java.beans.decoder.SimpleHandler
   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 /** XML element handler that is specialized on tags that contains a simple string in their
  45  * body which has to be parsed in a specific way.
  46  * <p>All of these tags have in common that they do not accept attributes. A warning is
  47  * send to the parser's ExceptionListener when one or more attributes exist.</p>
  48  *
  49  * @author Robert Schuster
  50  */
  51 abstract class SimpleHandler extends AbstractElementHandler
  52 {
  53   private ObjectContext context;
  54
  55   /**
  56    * @param PersistenceParser
  57    */
  58   SimpleHandler(ElementHandler parent)
  59   {
  60     super(parent, false);
  61
  62     // SimpleHandler do not accept any subelements
  63   }
  64
  65   protected final Context startElement(Attributes attributes, ExceptionListener exceptionListener)
  66     throws AssemblyException
  67   {
  68
  69     // note: simple elements should not have any attributes. We inform
  70     // the user of this syntactical but uncritical problem by sending
  71     // an IllegalArgumentException for each unneccessary attribute
  72     int size = attributes.getLength();
  73     for (int i = 0; i < size; i++) {
  74             String attributeName = attributes.getQName(i);
  75             Exception e =
  76                     new IllegalArgumentException(
  77                             "Unneccessary attribute '"
  78                                     + attributeName
  79                                     + "' discarded.");
  80             exceptionListener.exceptionThrown(e);
  81     }
  82
  83     return context = new ObjectContext();
  84   }
  85
  86   public void endElement(String characters)
  87     throws AssemblyException, AssemblyException
  88   {
  89     // reports the number when the character data can be parsed
  90     try
  91       {
  92         context.setObject(parse(characters));
  93       }
  94     catch (NumberFormatException nfe)
  95       {
  96         throw new AssemblyException(nfe);
  97       }
  98   }
  99
 100   /** Returns an object that is created from the given characters. If the string is
 101    * converted into a number a NumberFormatException is cathed and reported
 102    * appropriately.
 103    *
 104    * @param characters A string of characters that has to be processed in some way.
 105    * @return An Object instance generated from the given data.
 106    * @throws AssemblerException When the string was invalid.
 107    * @throws NumberFormatException When the string could not be parsed into a number.
 108    */
 109   protected abstract Object parse(String characters)
 110     throws AssemblyException, NumberFormatException;
 111 }