ContentHandler


1   // ContentHandler.java - handle main document content.
2   // http://www.saxproject.org
3   // Written by David Megginson
4   // NO WARRANTY!  This class is in the public domain.
5   // $Id: ContentHandler.java,v 1.1.24.1 2004/05/01 08:34:39 jsuttor Exp $
6   
7   package org.xml.sax;
8   
9   
10  /**
11   * Receive notification of the logical content of a document.
12   *
13   * <blockquote>
14   * <em>This module, both source code and documentation, is in the
15   * Public Domain, and comes with <strong>NO WARRANTY</strong>.</em>
16   * See <a HREF='http://www.saxproject.org'>http://www.saxproject.org</a>
17   * for further information.
18   * </blockquote>
19   *
20   * <p>This is the main interface that most SAX applications
21   * implement: if the application needs to be informed of basic parsing 
22   * events, it implements this interface and registers an instance with 
23   * the SAX parser using the {@link org.xml.sax.XMLReader#setContentHandler 
24   * setContentHandler} method.  The parser uses the instance to report 
25   * basic document-related events like the start and end of elements 
26   * and character data.</p>
27   *
28   * <p>The order of events in this interface is very important, and
29   * mirrors the order of information in the document itself.  For
30   * example, all of an element's content (character data, processing
31   * instructions, and/or subelements) will appear, in order, between
32   * the startElement event and the corresponding endElement event.</p>
33   *
34   * <p>This interface is similar to the now-deprecated SAX 1.0
35   * DocumentHandler interface, but it adds support for Namespaces
36   * and for reporting skipped entities (in non-validating XML
37   * processors).</p>
38   *
39   * <p>Implementors should note that there is also a 
40   * <code>ContentHandler</code> class in the <code>java.net</code>
41   * package; that means that it's probably a bad idea to do</p>
42   *
43   * <pre>import java.net.*;
44   * import org.xml.sax.*;
45   * </pre>
46   *
47   * <p>In fact, "import ...*" is usually a sign of sloppy programming
48   * anyway, so the user should consider this a feature rather than a
49   * bug.</p>
50   *
51   * @since SAX 2.0
52   * @author David Megginson
53   * @version 2.0.1+ (sax2r3pre1)
54   * @see org.xml.sax.XMLReader
55   * @see org.xml.sax.DTDHandler
56   * @see org.xml.sax.ErrorHandler
57   */
58  public interface ContentHandler
59  {
60  
61      /**
62       * Receive an object for locating the origin of SAX document events.
63       *
64       * <p>SAX parsers are strongly encouraged (though not absolutely
65       * required) to supply a locator: if it does so, it must supply
66       * the locator to the application by invoking this method before
67       * invoking any of the other methods in the ContentHandler
68       * interface.</p>
69       *
70       * <p>The locator allows the application to determine the end
71       * position of any document-related event, even if the parser is
72       * not reporting an error.  Typically, the application will
73       * use this information for reporting its own errors (such as
74       * character content that does not match an application's
75       * business rules).  The information returned by the locator
76       * is probably not sufficient for use with a search engine.</p>
77       *
78       * <p>Note that the locator will return correct information only
79       * during the invocation SAX event callbacks after
80       * {@link #startDocument startDocument} returns and before
81       * {@link #endDocument endDocument} is called.  The
82       * application should not attempt to use it at any other time.</p>
83       *
84       * @param locator an object that can return the location of
85       *                any SAX document event
86       * @see org.xml.sax.Locator
87       */
88      public void setDocumentLocator (Locator   locator);
89  
90  
91      /**
92       * Receive notification of the beginning of a document.
93       *
94       * <p>The SAX parser will invoke this method only once, before any
95       * other event callbacks (except for {@link #setDocumentLocator 
96       * setDocumentLocator}).</p>
97       *
98       * @throws org.xml.sax.SAXException any SAX exception, possibly
99       *            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
420
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