001    // ContentHandler.java - handle main document content.
002    // http://www.saxproject.org
003    // Written by David Megginson
004    // NO WARRANTY!  This class is in the public domain.
005    // $Id: ContentHandler.java,v 1.1 2004/12/23 22:38:42 mark Exp $
006    
007    package org.xml.sax;
008    
009    
010    /**
011     * Receive notification of the logical content of a document.
012     *
013     * <blockquote>
014     * <em>This module, both source code and documentation, is in the
015     * Public Domain, and comes with <strong>NO WARRANTY</strong>.</em>
016     * See <a href='http://www.saxproject.org'>http://www.saxproject.org</a>
017     * for further information.
018     * </blockquote>
019     *
020     * <p>This is the main interface that most SAX applications
021     * implement: if the application needs to be informed of basic parsing 
022     * events, it implements this interface and registers an instance with 
023     * the SAX parser using the {@link org.xml.sax.XMLReader#setContentHandler 
024     * setContentHandler} method.  The parser uses the instance to report 
025     * basic document-related events like the start and end of elements 
026     * and character data.</p>
027     *
028     * <p>The order of events in this interface is very important, and
029     * mirrors the order of information in the document itself.  For
030     * example, all of an element's content (character data, processing
031     * instructions, and/or subelements) will appear, in order, between
032     * the startElement event and the corresponding endElement event.</p>
033     *
034     * <p>This interface is similar to the now-deprecated SAX 1.0
035     * DocumentHandler interface, but it adds support for Namespaces
036     * and for reporting skipped entities (in non-validating XML
037     * processors).</p>
038     *
039     * <p>Implementors should note that there is also a 
040     * <code>ContentHandler</code> class in the <code>java.net</code>
041     * package; that means that it's probably a bad idea to do</p>
042     *
043     * <pre>import java.net.*;
044     * import org.xml.sax.*;
045     * </pre>
046     *
047     * <p>In fact, "import ...*" is usually a sign of sloppy programming
048     * anyway, so the user should consider this a feature rather than a
049     * bug.</p>
050     *
051     * @since SAX 2.0
052     * @author David Megginson
053     * @version 2.0.1+ (sax2r3pre1)
054     * @see org.xml.sax.XMLReader
055     * @see org.xml.sax.DTDHandler
056     * @see org.xml.sax.ErrorHandler
057     */
058    public interface ContentHandler
059    {
060    
061        /**
062         * Receive an object for locating the origin of SAX document events.
063         *
064         * <p>SAX parsers are strongly encouraged (though not absolutely
065         * required) to supply a locator: if it does so, it must supply
066         * the locator to the application by invoking this method before
067         * invoking any of the other methods in the ContentHandler
068         * interface.</p>
069         *
070         * <p>The locator allows the application to determine the end
071         * position of any document-related event, even if the parser is
072         * not reporting an error.  Typically, the application will
073         * use this information for reporting its own errors (such as
074         * character content that does not match an application's
075         * business rules).  The information returned by the locator
076         * is probably not sufficient for use with a search engine.</p>
077         *
078         * <p>Note that the locator will return correct information only
079         * during the invocation SAX event callbacks after
080         * {@link #startDocument startDocument} returns and before
081         * {@link #endDocument endDocument} is called.  The
082         * application should not attempt to use it at any other time.</p>
083         *
084         * @param locator an object that can return the location of
085         *                any SAX document event
086         * @see org.xml.sax.Locator
087         */
088        public void setDocumentLocator (Locator locator);
089    
090    
091        /**
092         * Receive notification of the beginning of a document.
093         *
094         * <p>The SAX parser will invoke this method only once, before any
095         * other event callbacks (except for {@link #setDocumentLocator 
096         * setDocumentLocator}).</p>
097         *
098         * @throws org.xml.sax.SAXException any SAX exception, possibly
099         *            wrapping another exception
100         * @see #endDocument
101         */
102        public void startDocument ()
103            throws SAXException;
104    
105    
106        /**
107         * Receive notification of the end of a document.
108         *
109         * <p><strong>There is an apparent contradiction between the
110         * documentation for this method and the documentation for {@link
111         * org.xml.sax.ErrorHandler#fatalError}.  Until this ambiguity is
112         * resolved in a future major release, clients should make no
113         * assumptions about whether endDocument() will or will not be
114         * invoked when the parser has reported a fatalError() or thrown
115         * an exception.</strong></p>
116         *
117         * <p>The SAX parser will invoke this method only once, and it will
118         * be the last method invoked during the parse.  The parser shall
119         * not invoke this method until it has either abandoned parsing
120         * (because of an unrecoverable error) or reached the end of
121         * input.</p>
122         *
123         * @throws org.xml.sax.SAXException any SAX exception, possibly
124         *            wrapping another exception
125         * @see #startDocument
126         */
127        public void endDocument()
128            throws SAXException;
129    
130    
131        /**
132         * Begin the scope of a prefix-URI Namespace mapping.
133         *
134         * <p>The information from this event is not necessary for
135         * normal Namespace processing: the SAX XML reader will 
136         * automatically replace prefixes for element and attribute
137         * names when the <code>http://xml.org/sax/features/namespaces</code>
138         * feature is <var>true</var> (the default).</p>
139         *
140         * <p>There are cases, however, when applications need to
141         * use prefixes in character data or in attribute values,
142         * where they cannot safely be expanded automatically; the
143         * start/endPrefixMapping event supplies the information
144         * to the application to expand prefixes in those contexts
145         * itself, if necessary.</p>
146         *
147         * <p>Note that start/endPrefixMapping events are not
148         * guaranteed to be properly nested relative to each other:
149         * all startPrefixMapping events will occur immediately before the
150         * corresponding {@link #startElement startElement} event, 
151         * and all {@link #endPrefixMapping endPrefixMapping}
152         * events will occur immediately after the corresponding
153         * {@link #endElement endElement} event,
154         * but their order is not otherwise 
155         * guaranteed.</p>
156         *
157         * <p>There should never be start/endPrefixMapping events for the
158         * "xml" prefix, since it is predeclared and immutable.</p>
159         *
160         * @param prefix the Namespace prefix being declared.
161         *  An empty string is used for the default element namespace,
162         *  which has no prefix.
163         * @param uri the Namespace URI the prefix is mapped to
164         * @throws org.xml.sax.SAXException the client may throw
165         *            an exception during processing
166         * @see #endPrefixMapping
167         * @see #startElement
168         */
169        public void startPrefixMapping (String prefix, String uri)
170            throws SAXException;
171    
172    
173        /**
174         * End the scope of a prefix-URI mapping.
175         *
176         * <p>See {@link #startPrefixMapping startPrefixMapping} for 
177         * details.  These events will always occur immediately after the
178         * corresponding {@link #endElement endElement} event, but the order of 
179         * {@link #endPrefixMapping endPrefixMapping} events is not otherwise
180         * guaranteed.</p>
181         *
182         * @param prefix the prefix that was being mapped.
183         *  This is the empty string when a default mapping scope ends.
184         * @throws org.xml.sax.SAXException the client may throw
185         *            an exception during processing
186         * @see #startPrefixMapping
187         * @see #endElement
188         */
189        public void endPrefixMapping (String prefix)
190            throws SAXException;
191    
192    
193        /**
194         * Receive notification of the beginning of an element.
195         *
196         * <p>The Parser will invoke this method at the beginning of every
197         * element in the XML document; there will be a corresponding
198         * {@link #endElement endElement} event for every startElement event
199         * (even when the element is empty). All of the element's content will be
200         * reported, in order, before the corresponding endElement
201         * event.</p>
202         *
203         * <p>This event allows up to three name components for each
204         * element:</p>
205         *
206         * <ol>
207         * <li>the Namespace URI;</li>
208         * <li>the local name; and</li>
209         * <li>the qualified (prefixed) name.</li>
210         * </ol>
211         *
212         * <p>Any or all of these may be provided, depending on the
213         * values of the <var>http://xml.org/sax/features/namespaces</var>
214         * and the <var>http://xml.org/sax/features/namespace-prefixes</var>
215         * properties:</p>
216         *
217         * <ul>
218         * <li>the Namespace URI and local name are required when 
219         * the namespaces property is <var>true</var> (the default), and are
220         * optional when the namespaces property is <var>false</var> (if one is
221         * specified, both must be);</li>
222         * <li>the qualified name is required when the namespace-prefixes property
223         * is <var>true</var>, and is optional when the namespace-prefixes property
224         * is <var>false</var> (the default).</li>
225         * </ul>
226         *
227         * <p>Note that the attribute list provided will contain only
228         * attributes with explicit values (specified or defaulted):
229         * #IMPLIED attributes will be omitted.  The attribute list
230         * will contain attributes used for Namespace declarations
231         * (xmlns* attributes) only if the
232         * <code>http://xml.org/sax/features/namespace-prefixes</code>
233         * property is true (it is false by default, and support for a 
234         * true value is optional).</p>
235         *
236         * <p>Like {@link #characters characters()}, attribute values may have
237         * characters that need more than one <code>char</code> value.  </p>
238         *
239         * @param uri the Namespace URI, or the empty string if the
240         *        element has no Namespace URI or if Namespace
241         *        processing is not being performed
242         * @param localName the local name (without prefix), or the
243         *        empty string if Namespace processing is not being
244         *        performed
245         * @param qName the qualified name (with prefix), or the
246         *        empty string if qualified names are not available
247         * @param atts the attributes attached to the element.  If
248         *        there are no attributes, it shall be an empty
249         *        Attributes object.  The value of this object after
250         *        startElement returns is undefined
251         * @throws org.xml.sax.SAXException any SAX exception, possibly
252         *            wrapping another exception
253         * @see #endElement
254         * @see org.xml.sax.Attributes
255         * @see org.xml.sax.helpers.AttributesImpl
256         */
257        public void startElement (String uri, String localName,
258                                  String qName, Attributes atts)
259            throws SAXException;
260    
261    
262        /**
263         * Receive notification of the end of an element.
264         *
265         * <p>The SAX parser will invoke this method at the end of every
266         * element in the XML document; there will be a corresponding
267         * {@link #startElement startElement} event for every endElement 
268         * event (even when the element is empty).</p>
269         *
270         * <p>For information on the names, see startElement.</p>
271         *
272         * @param uri the Namespace URI, or the empty string if the
273         *        element has no Namespace URI or if Namespace
274         *        processing is not being performed
275         * @param localName the local name (without prefix), or the
276         *        empty string if Namespace processing is not being
277         *        performed
278         * @param qName the qualified XML name (with prefix), or the
279         *        empty string if qualified names are not available
280         * @throws org.xml.sax.SAXException any SAX exception, possibly
281         *            wrapping another exception
282         */
283        public void endElement (String uri, String localName,
284                                String qName)
285            throws SAXException;
286    
287    
288        /**
289         * Receive notification of character data.
290         *
291         * <p>The Parser will call this method to report each chunk of
292         * character data.  SAX parsers may return all contiguous character
293         * data in a single chunk, or they may split it into several
294         * chunks; however, all of the characters in any single event
295         * must come from the same external entity so that the Locator
296         * provides useful information.</p>
297         *
298         * <p>The application must not attempt to read from the array
299         * outside of the specified range.</p>
300         *
301         * <p>Individual characters may consist of more than one Java
302         * <code>char</code> value.  There are two important cases where this
303         * happens, because characters can't be represented in just sixteen bits.
304         * In one case, characters are represented in a <em>Surrogate Pair</em>,
305         * using two special Unicode values. Such characters are in the so-called
306         * "Astral Planes", with a code point above U+FFFF.  A second case involves
307         * composite characters, such as a base character combining with one or
308         * more accent characters. </p>
309         *
310         * <p> Your code should not assume that algorithms using
311         * <code>char</code>-at-a-time idioms will be working in character
312         * units; in some cases they will split characters.  This is relevant
313         * wherever XML permits arbitrary characters, such as attribute values,
314         * processing instruction data, and comments as well as in data reported
315         * from this method.  It's also generally relevant whenever Java code
316         * manipulates internationalized text; the issue isn't unique to XML.</p>
317         *
318         * <p>Note that some parsers will report whitespace in element
319         * content using the {@link #ignorableWhitespace ignorableWhitespace}
320         * method rather than this one (validating parsers <em>must</em> 
321         * do so).</p>
322         *
323         * @param ch the characters from the XML document
324         * @param start the start position in the array
325         * @param length the number of characters to read from the array
326         * @throws org.xml.sax.SAXException any SAX exception, possibly
327         *            wrapping another exception
328         * @see #ignorableWhitespace 
329         * @see org.xml.sax.Locator
330         */
331        public void characters (char ch[], int start, int length)
332            throws SAXException;
333    
334    
335        /**
336         * Receive notification of ignorable whitespace in element content.
337         *
338         * <p>Validating Parsers must use this method to report each chunk
339         * of whitespace in element content (see the W3C XML 1.0
340         * recommendation, section 2.10): non-validating parsers may also
341         * use this method if they are capable of parsing and using
342         * content models.</p>
343         *
344         * <p>SAX parsers may return all contiguous whitespace in a single
345         * chunk, or they may split it into several chunks; however, all of
346         * the characters in any single event must come from the same
347         * external entity, so that the Locator provides useful
348         * information.</p>
349         *
350         * <p>The application must not attempt to read from the array
351         * outside of the specified range.</p>
352         *
353         * @param ch the characters from the XML document
354         * @param start the start position in the array
355         * @param length the number of characters to read from the array
356         * @throws org.xml.sax.SAXException any SAX exception, possibly
357         *            wrapping another exception
358         * @see #characters
359         */
360        public void ignorableWhitespace (char ch[], int start, int length)
361            throws SAXException;
362    
363    
364        /**
365         * Receive notification of a processing instruction.
366         *
367         * <p>The Parser will invoke this method once for each processing
368         * instruction found: note that processing instructions may occur
369         * before or after the main document element.</p>
370         *
371         * <p>A SAX parser must never report an XML declaration (XML 1.0,
372         * section 2.8) or a text declaration (XML 1.0, section 4.3.1)
373         * using this method.</p>
374         *
375         * <p>Like {@link #characters characters()}, processing instruction
376         * data may have characters that need more than one <code>char</code>
377         * value. </p>
378         *
379         * @param target the processing instruction target
380         * @param data the processing instruction data, or null if
381         *        none was supplied.  The data does not include any
382         *        whitespace separating it from the target
383         * @throws org.xml.sax.SAXException any SAX exception, possibly
384         *            wrapping another exception
385         */
386        public void processingInstruction (String target, String data)
387            throws SAXException;
388    
389    
390        /**
391         * Receive notification of a skipped entity.
392         * This is not called for entity references within markup constructs
393         * such as element start tags or markup declarations.  (The XML
394         * recommendation requires reporting skipped external entities.
395         * SAX also reports internal entity expansion/non-expansion, except
396         * within markup constructs.)
397         *
398         * <p>The Parser will invoke this method each time the entity is
399         * skipped.  Non-validating processors may skip entities if they
400         * have not seen the declarations (because, for example, the
401         * entity was declared in an external DTD subset).  All processors
402         * may skip external entities, depending on the values of the
403         * <code>http://xml.org/sax/features/external-general-entities</code>
404         * and the
405         * <code>http://xml.org/sax/features/external-parameter-entities</code>
406         * properties.</p>
407         *
408         * @param name the name of the skipped entity.  If it is a 
409         *        parameter entity, the name will begin with '%', and if
410         *        it is the external DTD subset, it will be the string
411         *        "[dtd]"
412         * @throws org.xml.sax.SAXException any SAX exception, possibly
413         *            wrapping another exception
414         */
415        public void skippedEntity (String name)
416            throws SAXException;
417    }
418    
419    // end of ContentHandler.java