Source for org.jfree.xml.parser.AbstractXmlReadHandler

   1: /* ========================================================================
   2:  * JCommon : a free general purpose class library for the Java(tm) platform
   3:  * ========================================================================
   4:  *
   5:  * (C) Copyright 2000-2005, by Object Refinery Limited and Contributors.
   6:  * 
   7:  * Project Info:  http://www.jfree.org/jcommon/index.html
   8:  *
   9:  * This library is free software; you can redistribute it and/or modify it 
  10:  * under the terms of the GNU Lesser General Public License as published by 
  11:  * the Free Software Foundation; either version 2.1 of the License, or 
  12:  * (at your option) any later version.
  13:  *
  14:  * This library is distributed in the hope that it will be useful, but 
  15:  * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 
  16:  * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public 
  17:  * License for more details.
  18:  *
  19:  * You should have received a copy of the GNU Lesser General Public
  20:  * License along with this library; if not, write to the Free Software
  21:  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, 
  22:  * USA.  
  23:  *
  24:  * [Java is a trademark or registered trademark of Sun Microsystems, Inc. 
  25:  * in the United States and other countries.]
  26:  * 
  27:  * ---------------------------
  28:  * AbstractXmlReadHandler.java
  29:  * ---------------------------
  30:  * (C)opyright 2003, 2004, by Thomas Morgner and Contributors.
  31:  *
  32:  * Original Author:  Thomas Morgner;
  33:  * Contributor(s):   David Gilbert (for Object Refinery Limited);
  34:  *
  35:  * $Id: AbstractXmlReadHandler.java,v 1.4 2005/10/18 13:32:52 mungady Exp $
  36:  *
  37:  * Changes (from 25-Nov-2003)
  38:  * --------------------------
  39:  * 25-Nov-2003 : Added Javadocs (DG);
  40:  *
  41:  */
  42: package org.jfree.xml.parser;
  43: 
  44: import org.xml.sax.Attributes;
  45: import org.xml.sax.SAXException;
  46: import org.jfree.util.Log;
  47: 
  48: /**
  49:  * A base class for implementing an {@link XmlReadHandler}.
  50:  */
  51: public abstract class AbstractXmlReadHandler implements XmlReadHandler {
  52:     /** The root handler. */
  53:     private RootXmlReadHandler rootHandler;
  54: 
  55:     /** The tag name. */
  56:     private String tagName;
  57: 
  58:     /** A flag indicating the first call. */
  59:     private boolean firstCall = true;
  60: 
  61:     /**
  62:      * Creates a new handler.
  63:      */
  64:     public AbstractXmlReadHandler() {
  65:     }
  66: 
  67:     /**
  68:      * Initialises the handler.
  69:      * 
  70:      * @param rootHandler  the root handler.
  71:      * @param tagName  the tag name.
  72:      */
  73:     public void init(final RootXmlReadHandler rootHandler, final String tagName) {
  74:         if (rootHandler == null) {
  75:             throw new NullPointerException("Root handler must not be null");
  76:         }
  77:         if (tagName == null) {
  78:             throw new NullPointerException("Tag name must not be null");
  79:         }
  80:         this.rootHandler = rootHandler;
  81:         this.tagName = tagName;
  82:     }
  83: 
  84:     /**
  85:      * This method is called at the start of an element.
  86:      *
  87:      * @param tagName  the tag name.
  88:      * @param attrs  the attributes.
  89:      *
  90:      * @throws SAXException if there is a parsing error.
  91:      * @throws XmlReaderException if there is a reader error.
  92:      */
  93:     public final void startElement(final String tagName, final Attributes attrs)
  94:         throws XmlReaderException, SAXException {
  95:         if (this.firstCall) {
  96:             if (!this.tagName.equals(tagName)) {
  97:                 throw new SAXException("Expected <" + this.tagName + ">, found <" + tagName + ">");
  98:             }
  99:             this.firstCall = false;
 100:             startParsing(attrs);
 101:         }
 102:         else {
 103:             final XmlReadHandler childHandler = getHandlerForChild(tagName, attrs);
 104:             if (childHandler == null) {
 105:                 Log.warn ("Unknown tag <" + tagName + ">");
 106:                 return;
 107:             }
 108:             childHandler.init(getRootHandler(), tagName);
 109:             this.rootHandler.recurse(childHandler, tagName, attrs);
 110:         }
 111:     }
 112: 
 113:     /**
 114:      * This method is called to process the character data between element tags.
 115:      *
 116:      * @param ch  the character buffer.
 117:      * @param start  the start index.
 118:      * @param length  the length.
 119:      *
 120:      * @throws SAXException if there is a parsing error.
 121:      */
 122:     public void characters(final char[] ch, final int start, final int length) throws SAXException {
 123:         // nothing required
 124:     }
 125: 
 126:     /**
 127:      * This method is called at the end of an element.
 128:      *
 129:      * @param tagName  the tag name.
 130:      *
 131:      * @throws SAXException if there is a parsing error.
 132:      */
 133:     public final void endElement(final String tagName) throws SAXException {
 134:         if (this.tagName.equals(tagName)) {
 135:             try {
 136:                 doneParsing();
 137:                 this.rootHandler.unwind(tagName);
 138:             }
 139:             catch (XmlReaderException xre) {
 140:                 throw new SAXException(xre);
 141:             }
 142:         }
 143:     }
 144: 
 145:     /**
 146:      * Starts parsing.
 147:      *
 148:      * @param attrs  the attributes.
 149:      *
 150:      * @throws SAXException if there is a parsing error.
 151:      */
 152:     protected void startParsing(final Attributes attrs) throws SAXException, XmlReaderException {
 153:         // nothing required
 154:     }
 155: 
 156:     /**
 157:      * Done parsing.
 158:      *
 159:      * @throws SAXException if there is a parsing error.
 160:      * @throws XmlReaderException if there is a reader error.
 161:      */
 162:     protected void doneParsing() throws SAXException, XmlReaderException {
 163:         // nothing required
 164:     }
 165: 
 166:     /**
 167:      * Returns the handler for a child element.
 168:      *
 169:      * @param tagName  the tag name.
 170:      * @param atts  the attributes.
 171:      *
 172:      * @return the handler or null, if the tagname is invalid.
 173:      *
 174:      * @throws SAXException  if there is a parsing error.
 175:      * @throws XmlReaderException if there is a reader error.
 176:      */
 177:     protected XmlReadHandler getHandlerForChild(final String tagName, final Attributes atts)
 178:         throws XmlReaderException, SAXException {
 179:         return null;
 180:     }
 181: 
 182:     /**
 183:      * Returns the tag name.
 184:      *
 185:      * @return the tag name.
 186:      */
 187:     public String getTagName() {
 188:         return this.tagName;
 189:     }
 190: 
 191:     /**
 192:      * Returns the root handler for the parsing.
 193:      *
 194:      * @return the root handler.
 195:      */
 196:     public RootXmlReadHandler getRootHandler() {
 197:         return this.rootHandler;
 198:     }
 199:     
 200: }