001 /**
002 * Java Gui Builder - A library to build GUIs using an XML file.
003 * Copyright 2002, 2003 (C) François Beausoleil
004 *
005 * This library is free software; you can redistribute it and/or
006 * modify it under the terms of the GNU Lesser General Public
007 * License as published by the Free Software Foundation; either
008 * version 2.1 of the License, or (at your option) any later version.
009 *
010 * This library is distributed in the hope that it will be useful,
011 * but WITHOUT ANY WARRANTY; without even the implied warranty of
012 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
013 * Lesser General Public License for more details.
014 *
015 * You should have received a copy of the GNU Lesser General Public
016 * License along with this library; if not, write to the Free Software
017 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
018 */
019
020 package jgb.handlers.swing;
021
022 import jgb.builder.TagHandler;
023 import org.xml.sax.SAXException;
024
025 import java.lang.reflect.Field;
026 import java.util.HashMap;
027 import java.util.Map;
028
029 /**
030 * @since 0.1a
031 * @author Francois Beausoleil, <a href="mailto:fbos@users.sourceforge.net">fbos@users.sourceforge.net</a>
032 */
033 public class ConstantTagHandler extends AbstractValueTagHandler {
034 /**
035 * The suffix to use when searching for the current constant's class in the context.
036 */
037 public static final String CLASS_SUFFIX = ".class";
038
039 /**
040 * The suffix to use when searching for the current constant's value in the context.
041 */
042 public static final String VALUE_SUFFIX = ".value";
043
044 /**
045 * The name of the name attribute.
046 */
047 protected static final String ATTR_NAME = "name";
048
049 public void enterElement(Map atts) throws SAXException {
050 String constantName = (String)atts.get(ATTR_NAME);
051
052 if (false == getConstantsMap().containsKey(constantName + CLASS_SUFFIX)
053 || false == getConstantsMap().containsKey(constantName + VALUE_SUFFIX)) {
054 try {
055 findConstantThroughReflection(constantName);
056 return;
057 } catch (Exception e) {
058 throwParsingException("Could not find constant named " + constantName, e);
059 }
060 }
061
062 Class constantClass = (Class)getConstantsMap().get(constantName + CLASS_SUFFIX);
063 Object constantValue = getConstantsMap().get(constantName + VALUE_SUFFIX);
064
065 updateContextParameters(constantClass, constantValue);
066 }
067
068 protected void exitElement() throws SAXException {
069 // NOP
070 }
071
072 private Map getConstantsMap() {
073 Map constantsMap = (Map)tagContext.get(TagHandler.CONSTANTS_MAP_KEY);
074 if (constantsMap == null) {
075 constantsMap = new HashMap();
076 tagContext.put(TagHandler.CONSTANTS_MAP_KEY, constantsMap);
077 }
078 return constantsMap;
079 }
080
081 private void findConstantThroughReflection(String constantName) throws ClassNotFoundException, NoSuchFieldException, IllegalAccessException {
082 int lastPeriod = constantName.lastIndexOf('.');
083 String className = constantName.substring(0, lastPeriod);
084
085 Class constantDeclClass = Class.forName(className);
086 Field constantField = constantDeclClass.getField(constantName.substring(lastPeriod + 1));
087 Object constantValue = constantField.get(null);
088
089 putConstant(constantName, constantField.getType(), constantValue);
090 updateContextParameters(constantField.getType(), constantValue);
091 }
092
093 private void putConstant(String constantName, Class constantClass, Object constantValue) {
094 getConstantsMap().put(constantName + CLASS_SUFFIX, constantClass);
095 getConstantsMap().put(constantName + VALUE_SUFFIX, constantValue);
096 }
097 }