001/* DocumentParser.java -- A parser for HTML documents.
002   Copyright (C) 2005 Free Software Foundation, Inc.
003
004This file is part of GNU Classpath.
005
006GNU Classpath is free software; you can redistribute it and/or modify
007it under the terms of the GNU General Public License as published by
008the Free Software Foundation; either version 2, or (at your option)
009any later version.
010
011GNU Classpath is distributed in the hope that it will be useful, but
012WITHOUT ANY WARRANTY; without even the implied warranty of
013MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014General Public License for more details.
015
016You should have received a copy of the GNU General Public License
017along with GNU Classpath; see the file COPYING.  If not, write to the
018Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
01902110-1301 USA.
020
021Linking this library statically or dynamically with other modules is
022making a combined work based on this library.  Thus, the terms and
023conditions of the GNU General Public License cover the whole
024combination.
025
026As a special exception, the copyright holders of this library give you
027permission to link this library with independent modules to produce an
028executable, regardless of the license terms of these independent
029modules, and to copy and distribute the resulting executable under
030terms of your choice, provided that you also meet, for each linked
031independent module, the terms and conditions of the license of that
032module.  An independent module is a module which is not derived from
033or based on this library.  If you modify this library, you may extend
034this exception to your version of the library, but you are not
035obligated to do so.  If you do not wish to do so, delete this
036exception statement from your version. */
037
038
039package javax.swing.text.html.parser;
040
041import javax.swing.text.html.parser.Parser;
042
043import java.io.IOException;
044import java.io.Reader;
045
046import javax.swing.text.BadLocationException;
047import javax.swing.text.SimpleAttributeSet;
048import javax.swing.text.html.HTMLEditorKit;
049
050/**
051 * <p>A simple error-tolerant HTML parser that uses a DTD document
052 * to access data on the possible tokens, arguments and syntax.</p>
053 * <p> The parser reads an HTML content from a Reader and calls various
054 * notifying methods (which should be overridden in a subclass)
055 * when tags or data are encountered.</p>
056 * <p>Some HTML elements need no opening or closing tags. The
057 * task of this parser is to invoke the tag handling methods also when
058 * the tags are not explicitly specified and must be supposed using
059 * information, stored in the DTD.
060 * For  example, parsing the document
061 * <p>&lt;table&gt;&lt;tr&gt;&lt;td&gt;a&lt;td&gt;b&lt;td&gt;c&lt;/tr&gt; <br>
062 * will invoke exactly the handling methods exactly in the same order
063 * (and with the same parameters) as if parsing the document: <br>
064 * <em>&lt;html&gt;&lt;head&gt;&lt;/head&gt;&lt;body&gt;&lt;table&gt;&lt;
065 * tbody&gt;</em>&lt;tr&gt;&lt;td&gt;a<em>&lt;/td&gt;</em>&lt;td&gt;b<em>
066 * &lt;/td&gt;</em>&lt;td&gt;c<em>&lt;/td&gt;&lt;/tr&gt;</em>&lt;
067 * <em>/tbody&gt;&lt;/table&gt;&lt;/body&gt;&lt;/html&gt;</em></p>
068 * (supposed tags are given in italics). The parser also supports
069 * obsolete elements of HTML syntax.<p>
070 * </p>
071 * In this implementation, DocumentParser is directly derived from its
072 * ancestor without changes of functionality.
073 * @author Audrius Meskauskas, Lithuania (AudriusA@Bioinformatics.org)
074 */
075public class DocumentParser
076  extends Parser
077  implements DTDConstants
078{
079  /**
080   * The enclosed working parser class.
081   */
082  private class gnuParser
083    extends gnu.javax.swing.text.html.parser.support.Parser
084  {
085    private gnuParser(DTD d)
086    {
087      super(d);
088    }
089
090    protected final void handleComment(char[] comment)
091    {
092      parser.handleComment(comment);
093      callBack.handleComment(comment, hTag.where.startPosition);
094    }
095
096    protected final void handleEmptyTag(TagElement tag)
097      throws javax.swing.text.ChangedCharSetException
098    {
099      parser.handleEmptyTag(tag);
100      callBack.handleSimpleTag(tag.getHTMLTag(), getAttributes(),
101                               hTag.where.startPosition
102                              );
103    }
104
105    protected final void handleEndTag(TagElement tag)
106    {
107      parser.handleEndTag(tag);
108      callBack.handleEndTag(tag.getHTMLTag(), hTag.where.startPosition);
109    }
110
111    protected final void handleError(int line, String message)
112    {
113      parser.handleError(line, message);
114      callBack.handleError(message, hTag.where.startPosition);
115    }
116
117    protected final void handleStartTag(TagElement tag)
118    {
119      parser.handleStartTag(tag);
120      SimpleAttributeSet attributes = gnu.getAttributes();
121
122      if (tag.fictional())
123        attributes.addAttribute(HTMLEditorKit.ParserCallback.IMPLIED,
124                                Boolean.TRUE
125                               );
126
127      callBack.handleStartTag(tag.getHTMLTag(), attributes,
128                              hTag.where.startPosition
129                             );
130    }
131
132    protected final void handleText(char[] text)
133    {
134      parser.handleText(text);
135      callBack.handleText(text, hTag.where.startPosition);
136    }
137
138    DTD getDTD()
139    {
140      return dtd;
141    }
142  }
143
144  /**
145   * This field is used to access the identically named
146   * methods of the outer class.
147   * This is package-private to avoid an accessor method.
148   */
149  DocumentParser parser = this;
150
151  /**
152   * The callback.
153   * This is package-private to avoid an accessor method.
154   */
155  HTMLEditorKit.ParserCallback callBack;
156
157  /**
158   * The reference to the working class of HTML parser that is
159   * actually used to parse the document.
160   * This is package-private to avoid an accessor method.
161   */
162  gnuParser gnu;
163
164  /**
165   * Creates a new parser that uses the given DTD to access data on the
166   * possible tokens, arguments and syntax. There is no single - step way
167   * to get a default DTD; you must either refer to the implementation -
168   * specific packages, write your own DTD or obtain the working instance
169   * of parser in other way, for example, by calling
170   * {@link javax.swing.text.html.HTMLEditorKit#getParser()}.
171   *
172   * @param a_dtd a DTD to use.
173   */
174  public DocumentParser(DTD a_dtd)
175  {
176    super(a_dtd);
177    gnu = new gnuParser(a_dtd);
178  }
179
180  /**
181   * Parses the HTML document, calling methods of the provided
182   * callback. This method must be multithread - safe.
183   * @param reader The reader to read the HTML document from
184   * @param aCallback The callback that is notifyed about the presence
185   * of HTML elements in the document.
186   * @param ignoreCharSet If thrue, any charset changes during parsing
187   * are ignored.
188   * @throws java.io.IOException
189   */
190  public void parse(Reader reader, HTMLEditorKit.ParserCallback aCallback,
191                    boolean ignoreCharSet
192                   )
193             throws IOException
194  {
195    callBack = aCallback;
196    gnu.parse(reader);
197
198    callBack.handleEndOfLineString(gnu.getEndOfLineSequence());
199    try
200      {
201        callBack.flush();
202      }
203    catch (BadLocationException ex)
204      {
205        // Convert this into the supported type of exception.
206        throw new IOException(ex.getMessage());
207      }
208  }
209
210  /**
211   * Handle HTML comment. The default method returns without action.
212   * @param comment the comment being handled
213   */
214  protected void handleComment(char[] comment)
215  {
216    // This default implementation does nothing.
217  }
218
219  /**
220   * Handle the tag with no content, like &lt;br&gt;. The method is
221   * called for the elements that, in accordance with the current DTD,
222   * has an empty content.
223   * @param tag the tag being handled.
224   * @throws javax.swing.text.ChangedCharSetException
225   */
226  protected void handleEmptyTag(TagElement tag)
227                         throws javax.swing.text.ChangedCharSetException
228  {
229    // This default implementation does nothing.
230  }
231
232  /**
233   * The method is called when the HTML closing tag ((like &lt;/table&gt;)
234   * is found or if the parser concludes that the one should be present
235   * in the current position.
236   * @param tag The tag being handled
237   */
238  protected void handleEndTag(TagElement tag)
239  {
240    // This default implementation does nothing.
241  }
242
243  /* Handle error that has occured in the given line. */
244  protected void handleError(int line, String message)
245  {
246    // This default implementation does nothing.
247  }
248
249  /**
250   * The method is called when the HTML opening tag ((like &lt;table&gt;)
251   * is found or if the parser concludes that the one should be present
252   * in the current position.
253   * @param tag The tag being handled
254   */
255  protected void handleStartTag(TagElement tag)
256  {
257    // This default implementation does nothing.
258  }
259
260  /**
261   * Handle the text section.
262   * @param text a section text.
263   */
264  protected void handleText(char[] text)
265  {
266    // This default implementation does nothing.
267  }
268}