DefaultHandler


1   // DefaultHandler.java - default implementation of the core handlers.
2   // http://www.saxproject.org
3   // Written by David Megginson
4   // NO WARRANTY!  This class is in the public domain.
5   // $Id: DefaultHandler.java,v 1.1.24.1 2004/05/01 08:34:45 jsuttor Exp $
6   
7   package org.xml.sax.helpers;
8   
9   import java.io.IOException  ;
10  
11  import org.xml.sax.InputSource  ;
12  import org.xml.sax.Locator  ;
13  import org.xml.sax.Attributes  ;
14  import org.xml.sax.EntityResolver  ;
15  import org.xml.sax.DTDHandler  ;
16  import org.xml.sax.ContentHandler  ;
17  import org.xml.sax.ErrorHandler  ;
18  import org.xml.sax.SAXException  ;
19  import org.xml.sax.SAXParseException  ;
20  
21  
22  /**
23   * Default base class for SAX2 event handlers.
24   *
25   * <blockquote>
26   * <em>This module, both source code and documentation, is in the
27   * Public Domain, and comes with <strong>NO WARRANTY</strong>.</em>
28   * See <a HREF='http://www.saxproject.org'>http://www.saxproject.org</a>
29   * for further information.
30   * </blockquote>
31   *
32   * <p>This class is available as a convenience base class for SAX2
33   * applications: it provides default implementations for all of the
34   * callbacks in the four core SAX2 handler classes:</p>
35   *
36   * <ul>
37   * <li>{@link org.xml.sax.EntityResolver EntityResolver}</li>
38   * <li>{@link org.xml.sax.DTDHandler DTDHandler}</li>
39   * <li>{@link org.xml.sax.ContentHandler ContentHandler}</li>
40   * <li>{@link org.xml.sax.ErrorHandler ErrorHandler}</li>
41   * </ul>
42   *
43   * <p>Application writers can extend this class when they need to
44   * implement only part of an interface; parser writers can
45   * instantiate this class to provide default handlers when the
46   * application has not supplied its own.</p>
47   *
48   * <p>This class replaces the deprecated SAX1
49   * {@link org.xml.sax.HandlerBase HandlerBase} class.</p>
50   *
51   * @since SAX 2.0
52   * @author David Megginson,
53   * @version 2.0.1 (sax2r2)
54   * @see org.xml.sax.EntityResolver
55   * @see org.xml.sax.DTDHandler
56   * @see org.xml.sax.ContentHandler
57   * @see org.xml.sax.ErrorHandler
58   */
59  public class DefaultHandler
60      implements EntityResolver  , DTDHandler  , ContentHandler  , ErrorHandler  
61  {
62      
63  
64      ////////////////////////////////////////////////////////////////////
65      // Default implementation of the EntityResolver interface.
66      ////////////////////////////////////////////////////////////////////
67      
68      /**
69       * Resolve an external entity.
70       *
71       * <p>Always return null, so that the parser will use the system
72       * identifier provided in the XML document.  This method implements
73       * the SAX default behaviour: application writers can override it
74       * in a subclass to do special translations such as catalog lookups
75       * or URI redirection.</p>
76       *
77       * @param publicId The public identifer, or null if none is
78       *                 available.
79       * @param systemId The system identifier provided in the XML 
80       *                 document.
81       * @return The new input source, or null to require the
82       *         default behaviour.
83       * @exception java.io.IOException If there is an error setting
84       *            up the new input source.
85       * @exception org.xml.sax.SAXException Any SAX exception, possibly
86       *            wrapping another exception.
87       * @see org.xml.sax.EntityResolver#resolveEntity
88       */
89      public InputSource   resolveEntity (String   publicId, String   systemId)
90      throws IOException  , SAXException  
91      {
92      return null;
93      }
94      
95      
96  
97      ////////////////////////////////////////////////////////////////////
98      // Default implementation of DTDHandler interface.
99      ////////////////////////////////////////////////////////////////////
100     
101     
102     /**
103      * Receive notification of a notation declaration.
104      *
105      * <p>By default, do nothing.  Application writers may override this
106      * method in a subclass if they wish to keep track of the notations
107      * declared in a document.</p>
108      *
109      * @param name The notation name.
110      * @param publicId The notation public identifier, or null if not
111      *                 available.
112      * @param systemId The notation system identifier.
113      * @exception org.xml.sax.SAXException Any SAX exception, possibly
114      *            wrapping another exception.
115      * @see org.xml.sax.DTDHandler#notationDecl
116      */
117     public void notationDecl (String   name, String   publicId, String   systemId)
118     throws SAXException  
119     {
120     // no op
121     }
122     
123     
124     /**
125      * Receive notification of an unparsed entity declaration.
126      *
127      * <p>By default, do nothing.  Application writers may override this
128      * method in a subclass to keep track of the unparsed entities
129      * declared in a document.</p>
130      *
131      * @param name The entity name.
132      * @param publicId The entity public identifier, or null if not
133      *                 available.
134      * @param systemId The entity system identifier.
135      * @param notationName The name of the associated notation.
136      * @exception org.xml.sax.SAXException Any SAX exception, possibly
137      *            wrapping another exception.
138      * @see org.xml.sax.DTDHandler#unparsedEntityDecl
139      */
140     public void unparsedEntityDecl (String   name, String   publicId,
141                     String   systemId, String   notationName)
142     throws SAXException  
143     {
144     // no op
145     }
146     
147     
148 
149     ////////////////////////////////////////////////////////////////////
150     // Default implementation of ContentHandler interface.
151     ////////////////////////////////////////////////////////////////////
152     
153     
154     /**
155      * Receive a Locator object for document events.
156      *
157      * <p>By default, do nothing.  Application writers may override this
158      * method in a subclass if they wish to store the locator for use
159      * with other document events.</p>
160      *
161      * @param locator A locator for all SAX document events.
162      * @see org.xml.sax.ContentHandler#setDocumentLocator
163      * @see org.xml.sax.Locator
164      */
165     public void setDocumentLocator (Locator   locator)
166     {
167     // no op
168     }
169     
170     
171     /**
172      * Receive notification of the beginning of the document.
173      *
174      * <p>By default, do nothing.  Application writers may override this
175      * method in a subclass to take specific actions at the beginning
176      * of a document (such as allocating the root node of a tree or
177      * creating an output file).</p>
178      *
179      * @exception org.xml.sax.SAXException Any SAX exception, possibly
180      *            wrapping another exception.
181      * @see org.xml.sax.ContentHandler#startDocument
182      */
183     public void startDocument ()
184     throws SAXException  
185     {
186     // no op
187     }
188     
189     
190     /**
191      * Receive notification of the end of the document.
192      *
193      * <p>By default, do nothing.  Application writers may override this
194      * method in a subclass to take specific actions at the end
195      * of a document (such as finalising a tree or closing an output
196      * file).</p>
197      *
198      * @exception org.xml.sax.SAXException Any SAX exception, possibly
199      *            wrapping another exception.
200      * @see org.xml.sax.ContentHandler#endDocument
201      */
202     public void endDocument ()
203     throws SAXException  
204     {
205     // no op
206     }
207 
208 
209     /**
210      * Receive notification of the start of a Namespace mapping.
211      *
212      * <p>By default, do nothing.  Application writers may override this
213      * method in a subclass to take specific actions at the start of
214      * each Namespace prefix scope (such as storing the prefix mapping).</p>
215      *
216      * @param prefix The Namespace prefix being declared.
217      * @param uri The Namespace URI mapped to the prefix.
218      * @exception org.xml.sax.SAXException Any SAX exception, possibly
219      *            wrapping another exception.
220      * @see org.xml.sax.ContentHandler#startPrefixMapping
221      */
222     public void startPrefixMapping (String   prefix, String   uri)
223     throws SAXException  
224     {
225     // no op
226     }
227 
228 
229     /**
230      * Receive notification of the end of a Namespace mapping.
231      *
232      * <p>By default, do nothing.  Application writers may override this
233      * method in a subclass to take specific actions at the end of
234      * each prefix mapping.</p>
235      *
236      * @param prefix The Namespace prefix being declared.
237      * @exception org.xml.sax.SAXException Any SAX exception, possibly
238      *            wrapping another exception.
239      * @see org.xml.sax.ContentHandler#endPrefixMapping
240      */
241     public void endPrefixMapping (String   prefix)
242     throws SAXException  
243     {
244     // no op
245     }
246     
247     
248     /**
249      * Receive notification of the start of an element.
250      *
251      * <p>By default, do nothing.  Application writers may override this
252      * method in a subclass to take specific actions at the start of
253      * each element (such as allocating a new tree node or writing
254      * output to a file).</p>
255      *
256      * @param uri The Namespace URI, or the empty string if the
257      *        element has no Namespace URI or if Namespace
258      *        processing is not being performed.
259      * @param localName The local name (without prefix), or the
260      *        empty string if Namespace processing is not being
261      *        performed.
262      * @param qName The qualified name (with prefix), or the
263      *        empty string if qualified names are not available.
264      * @param attributes The attributes attached to the element.  If
265      *        there are no attributes, it shall be an empty
266      *        Attributes object.
267      * @exception org.xml.sax.SAXException Any SAX exception, possibly
268      *            wrapping another exception.
269      * @see org.xml.sax.ContentHandler#startElement
270      */
271     public void startElement (String   uri, String   localName,
272                   String   qName, Attributes   attributes)
273     throws SAXException  
274     {
275     // no op
276     }
277     
278     
279     /**
280      * Receive notification of the end of an element.
281      *
282      * <p>By default, do nothing.  Application writers may override this
283      * method in a subclass to take specific actions at the end of
284      * each element (such as finalising a tree node or writing
285      * output to a file).</p>
286      *
287      * @param uri The Namespace URI, or the empty string if the
288      *        element has no Namespace URI or if Namespace
289      *        processing is not being performed.
290      * @param localName The local name (without prefix), or the
291      *        empty string if Namespace processing is not being
292      *        performed.
293      * @param qName The qualified name (with prefix), or the
294      *        empty string if qualified names are not available.
295      * @exception org.xml.sax.SAXException Any SAX exception, possibly
296      *            wrapping another exception.
297      * @see org.xml.sax.ContentHandler#endElement
298      */
299     public void endElement (String   uri, String   localName, String   qName)
300     throws SAXException  
301     {
302     // no op
303     }
304     
305     
306     /**
307      * Receive notification of character data inside an element.
308      *
309      * <p>By default, do nothing.  Application writers may override this
310      * method to take specific actions for each chunk of character data
311      * (such as adding the data to a node or buffer, or printing it to
312      * a file).</p>
313      *
314      * @param ch The characters.
315      * @param start The start position in the character array.
316      * @param length The number of characters to use from the
317      *               character array.
318      * @exception org.xml.sax.SAXException Any SAX exception, possibly
319      *            wrapping another exception.
320      * @see org.xml.sax.ContentHandler#characters
321      */
322     public void characters (char ch[], int start, int length)
323     throws SAXException  
324     {
325     // no op
326     }
327     
328     
329     /**
330      * Receive notification of ignorable whitespace in element content.
331      *
332      * <p>By default, do nothing.  Application writers may override this
333      * method to take specific actions for each chunk of ignorable
334      * whitespace (such as adding data to a node or buffer, or printing
335      * it to a file).</p>
336      *
337      * @param ch The whitespace characters.
338      * @param start The start position in the character array.
339      * @param length The number of characters to use from the
340      *               character array.
341      * @exception org.xml.sax.SAXException Any SAX exception, possibly
342      *            wrapping another exception.
343      * @see org.xml.sax.ContentHandler#ignorableWhitespace
344      */
345     public void ignorableWhitespace (char ch[], int start, int length)
346     throws SAXException  
347     {
348     // no op
349     }
350     
351     
352     /**
353      * Receive notification of a processing instruction.
354      *
355      * <p>By default, do nothing.  Application writers may override this
356      * method in a subclass to take specific actions for each
357      * processing instruction, such as setting status variables or
358      * invoking other methods.</p>
359      *
360      * @param target The processing instruction target.
361      * @param data The processing instruction data, or null if
362      *             none is supplied.
363      * @exception org.xml.sax.SAXException Any SAX exception, possibly
364      *            wrapping another exception.
365      * @see org.xml.sax.ContentHandler#processingInstruction
366      */
367     public void processingInstruction (String   target, String   data)
368     throws SAXException  
369     {
370     // no op
371     }
372 
373 
374     /**
375      * Receive notification of a skipped entity.
376      *
377      * <p>By default, do nothing.  Application writers may override this
378      * method in a subclass to take specific actions for each
379      * processing instruction, such as setting status variables or
380      * invoking other methods.</p>
381      *
382      * @param name The name of the skipped entity.
383      * @exception org.xml.sax.SAXException Any SAX exception, possibly
384      *            wrapping another exception.
385      * @see org.xml.sax.ContentHandler#processingInstruction
386      */
387     public void skippedEntity (String   name)
388     throws SAXException  
389     {
390     // no op
391     }
392     
393     
394 
395     ////////////////////////////////////////////////////////////////////
396     // Default implementation of the ErrorHandler interface.
397     ////////////////////////////////////////////////////////////////////
398     
399     
400     /**
401      * Receive notification of a parser warning.
402      *
403      * <p>The default implementation does nothing.  Application writers
404      * may override this method in a subclass to take specific actions
405      * for each warning, such as inserting the message in a log file or
406      * printing it to the console.</p>
407      *
408      * @param e The warning information encoded as an exception.
409      * @exception org.xml.sax.SAXException Any SAX exception, possibly
410      *            wrapping another exception.
411      * @see org.xml.sax.ErrorHandler#warning
412      * @see org.xml.sax.SAXParseException
413      */
414     public void warning (SAXParseException   e)
415     throws SAXException  
416     {
417     // no op
418     }
419     
420     
421     /**
422      * Receive notification of a recoverable parser error.
423      *
424      * <p>The default implementation does nothing.  Application writers
425      * may override this method in a subclass to take specific actions
426      * for each error, such as inserting the message in a log file or
427      * printing it to the console.</p>
428      *
429      * @param e The warning information encoded as an exception.
430      * @exception org.xml.sax.SAXException Any SAX exception, possibly
431      *            wrapping another exception.
432      * @see org.xml.sax.ErrorHandler#warning
433      * @see org.xml.sax.SAXParseException
434      */
435     public void error (SAXParseException   e)
436     throws SAXException  
437     {
438     // no op
439     }
440     
441     
442     /**
443      * Report a fatal XML parsing error.
444      *
445      * <p>The default implementation throws a SAXParseException.
446      * Application writers may override this method in a subclass if
447      * they need to take specific actions for each fatal error (such as
448      * collecting all of the errors into a single report): in any case,
449      * the application must stop all regular processing when this
450      * method is invoked, since the document is no longer reliable, and
451      * the parser may no longer report parsing events.</p>
452      *
453      * @param e The error information encoded as an exception.
454      * @exception org.xml.sax.SAXException Any SAX exception, possibly
455      *            wrapping another exception.
456      * @see org.xml.sax.ErrorHandler#fatalError
457      * @see org.xml.sax.SAXParseException
458      */
459     public void fatalError (SAXParseException   e)
460     throws SAXException  
461     {
462     throw e;
463     }
464     
465 }
466 
467 // end of DefaultHandler.java
468
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