http://xml.apache.org/commons/components/external/: xml-commons provides an Apache-hosted set of DOM, SAX, and JAXP interfaces for use in other xml-based projects. Our hope is that we can standardize on both a common version and packaging scheme for these critical XML standards interfaces to make the lives of both our developers and users easier. The External Components portion of xml-commons contains interfaces that are defined by external standards organizations. For DOM, that's the W3C; for SAX it's David Megginson and sax.sourceforge.net; for JAXP it's Sun. 
// ContentHandler.java - handle main document content.
// http://www.saxproject.org
// Written by David Megginson
// NO WARRANTY!  This class is in the public domain.
// $Id: ContentHandler.java 226184 2005-04-08 10:53:24Z neeraj $

package org.xml.sax;



Receive notification of the logical content of a document.


This module, both source code and documentation, is in the
Public Domain, and comes with NO WARRANTY.
See http://www.saxproject.org
for further information.



This is the main interface that most SAX applications implement: if the application needs to be informed of basic parsing events, it implements this interface and registers an instance with the SAX parser using the 
setContentHandler method. The parser uses the instance to report basic document-related events like the start and end of elements and character data.


The order of events in this interface is very important, and
mirrors the order of information in the document itself.  For
example, all of an element's content (character data, processing
instructions, and/or subelements) will appear, in order, between
the startElement event and the corresponding endElement event.


This interface is similar to the now-deprecated SAX 1.0
DocumentHandler interface, but it adds support for Namespaces
and for reporting skipped entities (in non-validating XML
processors).


Implementors should note that there is also a 
ContentHandler class in the java.net
package; that means that it's probably a bad idea to do


import java.net.*;
import org.xml.sax.*;



In fact, "import ...*" is usually a sign of sloppy programming
anyway, so the user should consider this a feature rather than a
bug.


Author:David Megginson
See Also:
Since:SAX 2.0
Version:2.0.1+ (sax2r3pre1)
/**
 * Receive notification of the logical content of a document.
 *
 * <blockquote>
 * <em>This module, both source code and documentation, is in the
 * Public Domain, and comes with <strong>NO WARRANTY</strong>.</em>
 * See <a href='http://www.saxproject.org'>http://www.saxproject.org</a>
 * for further information.
 * </blockquote>
 *
 * <p>This is the main interface that most SAX applications
 * implement: if the application needs to be informed of basic parsing 
 * events, it implements this interface and registers an instance with 
 * the SAX parser using the {@link org.xml.sax.XMLReader#setContentHandler 
 * setContentHandler} method.  The parser uses the instance to report 
 * basic document-related events like the start and end of elements 
 * and character data.</p>
 *
 * <p>The order of events in this interface is very important, and
 * mirrors the order of information in the document itself.  For
 * example, all of an element's content (character data, processing
 * instructions, and/or subelements) will appear, in order, between
 * the startElement event and the corresponding endElement event.</p>
 *
 * <p>This interface is similar to the now-deprecated SAX 1.0
 * DocumentHandler interface, but it adds support for Namespaces
 * and for reporting skipped entities (in non-validating XML
 * processors).</p>
 *
 * <p>Implementors should note that there is also a 
 * <code>ContentHandler</code> class in the <code>java.net</code>
 * package; that means that it's probably a bad idea to do</p>
 *
 * <pre>import java.net.*;
 * import org.xml.sax.*;
 * </pre>
 *
 * <p>In fact, "import ...*" is usually a sign of sloppy programming
 * anyway, so the user should consider this a feature rather than a
 * bug.</p>
 *
 * @since SAX 2.0
 * @author David Megginson
 * @version 2.0.1+ (sax2r3pre1)
 * @see org.xml.sax.XMLReader
 * @see org.xml.sax.DTDHandler
 * @see org.xml.sax.ErrorHandler
 */
public interface ContentHandler
{

    
Receive an object for locating the origin of SAX document events.

SAX parsers are strongly encouraged (though not absolutely
required) to supply a locator: if it does so, it must supply
the locator to the application by invoking this method before
invoking any of the other methods in the ContentHandler
interface.


The locator allows the application to determine the end
position of any document-related event, even if the parser is
not reporting an error.  Typically, the application will
use this information for reporting its own errors (such as
character content that does not match an application's
business rules).  The information returned by the locator
is probably not sufficient for use with a search engine.


Note that the locator will return correct information only during the invocation SAX event callbacks after startDocument returns and before endDocument is called. The application should not attempt to use it at any other time.


Params:
  • locator – an object that can return the location of
               any SAX document event
See Also:
/**
     * Receive an object for locating the origin of SAX document events.
     *
     * <p>SAX parsers are strongly encouraged (though not absolutely
     * required) to supply a locator: if it does so, it must supply
     * the locator to the application by invoking this method before
     * invoking any of the other methods in the ContentHandler
     * interface.</p>
     *
     * <p>The locator allows the application to determine the end
     * position of any document-related event, even if the parser is
     * not reporting an error.  Typically, the application will
     * use this information for reporting its own errors (such as
     * character content that does not match an application's
     * business rules).  The information returned by the locator
     * is probably not sufficient for use with a search engine.</p>
     *
     * <p>Note that the locator will return correct information only
     * during the invocation SAX event callbacks after
     * {@link #startDocument startDocument} returns and before
     * {@link #endDocument endDocument} is called.  The
     * application should not attempt to use it at any other time.</p>
     *
     * @param locator an object that can return the location of
     *                any SAX document event
     * @see org.xml.sax.Locator
     */
    public void setDocumentLocator (Locator locator);


    
Receive notification of the beginning of a document.

The SAX parser will invoke this method only once, before any other event callbacks (except for 
setDocumentLocator).


Throws:
  • SAXException – any SAX exception, possibly
           wrapping another exception
See Also:
/**
     * Receive notification of the beginning of a document.
     *
     * <p>The SAX parser will invoke this method only once, before any
     * other event callbacks (except for {@link #setDocumentLocator 
     * setDocumentLocator}).</p>
     *
     * @throws org.xml.sax.SAXException any SAX exception, possibly
     *            wrapping another exception
     * @see #endDocument
     */
    public void startDocument ()
	throws SAXException;


    
Receive notification of the end of a document.

There is an apparent contradiction between the documentation for this method and the documentation for ErrorHandler.fatalError. Until this ambiguity is resolved in a future major release, clients should make no assumptions about whether endDocument() will or will not be invoked when the parser has reported a fatalError() or thrown an exception.


The SAX parser will invoke this method only once, and it will
be the last method invoked during the parse.  The parser shall
not invoke this method until it has either abandoned parsing
(because of an unrecoverable error) or reached the end of
input.


Throws:
  • SAXException – any SAX exception, possibly
           wrapping another exception
See Also:
/**
     * Receive notification of the end of a document.
     *
     * <p><strong>There is an apparent contradiction between the
     * documentation for this method and the documentation for {@link
     * org.xml.sax.ErrorHandler#fatalError}.  Until this ambiguity is
     * resolved in a future major release, clients should make no
     * assumptions about whether endDocument() will or will not be
     * invoked when the parser has reported a fatalError() or thrown
     * an exception.</strong></p>
     *
     * <p>The SAX parser will invoke this method only once, and it will
     * be the last method invoked during the parse.  The parser shall
     * not invoke this method until it has either abandoned parsing
     * (because of an unrecoverable error) or reached the end of
     * input.</p>
     *
     * @throws org.xml.sax.SAXException any SAX exception, possibly
     *            wrapping another exception
     * @see #startDocument
     */
    public void endDocument()
	throws SAXException;


    
Begin the scope of a prefix-URI Namespace mapping.

The information from this event is not necessary for
normal Namespace processing: the SAX XML reader will 
automatically replace prefixes for element and attribute
names when the http://xml.org/sax/features/namespaces
feature is true (the default).


There are cases, however, when applications need to
use prefixes in character data or in attribute values,
where they cannot safely be expanded automatically; the
start/endPrefixMapping event supplies the information
to the application to expand prefixes in those contexts
itself, if necessary.


Note that start/endPrefixMapping events are not guaranteed to be properly nested relative to each other: all startPrefixMapping events will occur immediately before the corresponding startElement event, and all endPrefixMapping events will occur immediately after the corresponding endElement event, but their order is not otherwise guaranteed.


There should never be start/endPrefixMapping events for the
"xml" prefix, since it is predeclared and immutable.


Params:
  • prefix – the Namespace prefix being declared.
An empty string is used for the default element namespace,
which has no prefix.
  • uri – the Namespace URI the prefix is mapped to
Throws:
  • SAXException – the client may throw
           an exception during processing
See Also:
/**
     * Begin the scope of a prefix-URI Namespace mapping.
     *
     * <p>The information from this event is not necessary for
     * normal Namespace processing: the SAX XML reader will 
     * automatically replace prefixes for element and attribute
     * names when the <code>http://xml.org/sax/features/namespaces</code>
     * feature is <var>true</var> (the default).</p>
     *
     * <p>There are cases, however, when applications need to
     * use prefixes in character data or in attribute values,
     * where they cannot safely be expanded automatically; the
     * start/endPrefixMapping event supplies the information
     * to the application to expand prefixes in those contexts
     * itself, if necessary.</p>
     *
     * <p>Note that start/endPrefixMapping events are not
     * guaranteed to be properly nested relative to each other:
     * all startPrefixMapping events will occur immediately before the
     * corresponding {@link #startElement startElement} event, 
     * and all {@link #endPrefixMapping endPrefixMapping}
     * events will occur immediately after the corresponding
     * {@link #endElement endElement} event,
     * but their order is not otherwise 
     * guaranteed.</p>
     *
     * <p>There should never be start/endPrefixMapping events for the
     * "xml" prefix, since it is predeclared and immutable.</p>
     *
     * @param prefix the Namespace prefix being declared.
     *	An empty string is used for the default element namespace,
     *	which has no prefix.
     * @param uri the Namespace URI the prefix is mapped to
     * @throws org.xml.sax.SAXException the client may throw
     *            an exception during processing
     * @see #endPrefixMapping
     * @see #startElement
     */
    public void startPrefixMapping (String prefix, String uri)
	throws SAXException;


    
End the scope of a prefix-URI mapping.

See startPrefixMapping for details. These events will always occur immediately after the corresponding endElement event, but the order of endPrefixMapping events is not otherwise guaranteed.


Params:
  • prefix – the prefix that was being mapped.
This is the empty string when a default mapping scope ends.
Throws:
  • SAXException – the client may throw
           an exception during processing
See Also:
/**
     * End the scope of a prefix-URI mapping.
     *
     * <p>See {@link #startPrefixMapping startPrefixMapping} for 
     * details.  These events will always occur immediately after the
     * corresponding {@link #endElement endElement} event, but the order of 
     * {@link #endPrefixMapping endPrefixMapping} events is not otherwise
     * guaranteed.</p>
     *
     * @param prefix the prefix that was being mapped.
     *	This is the empty string when a default mapping scope ends.
     * @throws org.xml.sax.SAXException the client may throw
     *            an exception during processing
     * @see #startPrefixMapping
     * @see #endElement
     */
    public void endPrefixMapping (String prefix)
	throws SAXException;


    
Receive notification of the beginning of an element.

The Parser will invoke this method at the beginning of every element in the XML document; there will be a corresponding endElement event for every startElement event (even when the element is empty). All of the element's content will be reported, in order, before the corresponding endElement event.


This event allows up to three name components for each
element:


    

  1. the Namespace URI;
    2. 

  2. the local name; and
    3. 

  3. the qualified (prefixed) name.
    4. 



Any or all of these may be provided, depending on the
values of the http://xml.org/sax/features/namespaces
and the http://xml.org/sax/features/namespace-prefixes
properties:


    

  • the Namespace URI and local name are required when 
the namespaces property is true (the default), and are
optional when the namespaces property is false (if one is
specified, both must be);
    • 

  • the qualified name is required when the namespace-prefixes property
is true, and is optional when the namespace-prefixes property
is false (the default).
    • 



Note that the attribute list provided will contain only
attributes with explicit values (specified or defaulted):
#IMPLIED attributes will be omitted.  The attribute list
will contain attributes used for Namespace declarations
(xmlns* attributes) only if the
http://xml.org/sax/features/namespace-prefixes
property is true (it is false by default, and support for a 
true value is optional).


Like characters(), attribute values may have characters that need more than one char value.  


Params:
  • uri – the Namespace URI, or the empty string if the
       element has no Namespace URI or if Namespace
       processing is not being performed
  • localName – the local name (without prefix), or the
       empty string if Namespace processing is not being
       performed
  • qName – the qualified name (with prefix), or the
       empty string if qualified names are not available
  • atts – the attributes attached to the element.  If
       there are no attributes, it shall be an empty
       Attributes object.  The value of this object after
       startElement returns is undefined
Throws:
  • SAXException – any SAX exception, possibly
           wrapping another exception
See Also:
/**
     * Receive notification of the beginning of an element.
     *
     * <p>The Parser will invoke this method at the beginning of every
     * element in the XML document; there will be a corresponding
     * {@link #endElement endElement} event for every startElement event
     * (even when the element is empty). All of the element's content will be
     * reported, in order, before the corresponding endElement
     * event.</p>
     *
     * <p>This event allows up to three name components for each
     * element:</p>
     *
     * <ol>
     * <li>the Namespace URI;</li>
     * <li>the local name; and</li>
     * <li>the qualified (prefixed) name.</li>
     * </ol>
     *
     * <p>Any or all of these may be provided, depending on the
     * values of the <var>http://xml.org/sax/features/namespaces</var>
     * and the <var>http://xml.org/sax/features/namespace-prefixes</var>
     * properties:</p>
     *
     * <ul>
     * <li>the Namespace URI and local name are required when 
     * the namespaces property is <var>true</var> (the default), and are
     * optional when the namespaces property is <var>false</var> (if one is
     * specified, both must be);</li>
     * <li>the qualified name is required when the namespace-prefixes property
     * is <var>true</var>, and is optional when the namespace-prefixes property
     * is <var>false</var> (the default).</li>
     * </ul>
     *
     * <p>Note that the attribute list provided will contain only
     * attributes with explicit values (specified or defaulted):
     * #IMPLIED attributes will be omitted.  The attribute list
     * will contain attributes used for Namespace declarations
     * (xmlns* attributes) only if the
     * <code>http://xml.org/sax/features/namespace-prefixes</code>
     * property is true (it is false by default, and support for a 
     * true value is optional).</p>
     *
     * <p>Like {@link #characters characters()}, attribute values may have
     * characters that need more than one <code>char</code> value.  </p>
     *
     * @param uri the Namespace URI, or the empty string if the
     *        element has no Namespace URI or if Namespace
     *        processing is not being performed
     * @param localName the local name (without prefix), or the
     *        empty string if Namespace processing is not being
     *        performed
     * @param qName the qualified name (with prefix), or the
     *        empty string if qualified names are not available
     * @param atts the attributes attached to the element.  If
     *        there are no attributes, it shall be an empty
     *        Attributes object.  The value of this object after
     *        startElement returns is undefined
     * @throws org.xml.sax.SAXException any SAX exception, possibly
     *            wrapping another exception
     * @see #endElement
     * @see org.xml.sax.Attributes
     * @see org.xml.sax.helpers.AttributesImpl
     */
    public void startElement (String uri, String localName,
			      String qName, Attributes atts)
	throws SAXException;


    
Receive notification of the end of an element.

The SAX parser will invoke this method at the end of every element in the XML document; there will be a corresponding startElement event for every endElement event (even when the element is empty).


For information on the names, see startElement.


Params:
  • uri – the Namespace URI, or the empty string if the
       element has no Namespace URI or if Namespace
       processing is not being performed
  • localName – the local name (without prefix), or the
       empty string if Namespace processing is not being
       performed
  • qName – the qualified XML name (with prefix), or the
       empty string if qualified names are not available
Throws:
  • SAXException – any SAX exception, possibly
           wrapping another exception
/**
     * Receive notification of the end of an element.
     *
     * <p>The SAX parser will invoke this method at the end of every
     * element in the XML document; there will be a corresponding
     * {@link #startElement startElement} event for every endElement 
     * event (even when the element is empty).</p>
     *
     * <p>For information on the names, see startElement.</p>
     *
     * @param uri the Namespace URI, or the empty string if the
     *        element has no Namespace URI or if Namespace
     *        processing is not being performed
     * @param localName the local name (without prefix), or the
     *        empty string if Namespace processing is not being
     *        performed
     * @param qName the qualified XML name (with prefix), or the
     *        empty string if qualified names are not available
     * @throws org.xml.sax.SAXException any SAX exception, possibly
     *            wrapping another exception
     */
    public void endElement (String uri, String localName,
			    String qName)
	throws SAXException;


    
Receive notification of character data.

The Parser will call this method to report each chunk of
character data.  SAX parsers may return all contiguous character
data in a single chunk, or they may split it into several
chunks; however, all of the characters in any single event
must come from the same external entity so that the Locator
provides useful information.


The application must not attempt to read from the array
outside of the specified range.


Individual characters may consist of more than one Java
char value.  There are two important cases where this
happens, because characters can't be represented in just sixteen bits.
In one case, characters are represented in a Surrogate Pair,
using two special Unicode values. Such characters are in the so-called
"Astral Planes", with a code point above U+FFFF.  A second case involves
composite characters, such as a base character combining with one or
more accent characters. 


 Your code should not assume that algorithms using
char-at-a-time idioms will be working in character
units; in some cases they will split characters.  This is relevant
wherever XML permits arbitrary characters, such as attribute values,
processing instruction data, and comments as well as in data reported
from this method.  It's also generally relevant whenever Java code
manipulates internationalized text; the issue isn't unique to XML.


Note that some parsers will report whitespace in element content using the ignorableWhitespace method rather than this one (validating parsers must 
do so).


Params:
  • ch – the characters from the XML document
  • start – the start position in the array
  • length – the number of characters to read from the array
Throws:
  • SAXException – any SAX exception, possibly
           wrapping another exception
See Also:
/**
     * Receive notification of character data.
     *
     * <p>The Parser will call this method to report each chunk of
     * character data.  SAX parsers may return all contiguous character
     * data in a single chunk, or they may split it into several
     * chunks; however, all of the characters in any single event
     * must come from the same external entity so that the Locator
     * provides useful information.</p>
     *
     * <p>The application must not attempt to read from the array
     * outside of the specified range.</p>
     *
     * <p>Individual characters may consist of more than one Java
     * <code>char</code> value.  There are two important cases where this
     * happens, because characters can't be represented in just sixteen bits.
     * In one case, characters are represented in a <em>Surrogate Pair</em>,
     * using two special Unicode values. Such characters are in the so-called
     * "Astral Planes", with a code point above U+FFFF.  A second case involves
     * composite characters, such as a base character combining with one or
     * more accent characters. </p>
     *
     * <p> Your code should not assume that algorithms using
     * <code>char</code>-at-a-time idioms will be working in character
     * units; in some cases they will split characters.  This is relevant
     * wherever XML permits arbitrary characters, such as attribute values,
     * processing instruction data, and comments as well as in data reported
     * from this method.  It's also generally relevant whenever Java code
     * manipulates internationalized text; the issue isn't unique to XML.</p>
     *
     * <p>Note that some parsers will report whitespace in element
     * content using the {@link #ignorableWhitespace ignorableWhitespace}
     * method rather than this one (validating parsers <em>must</em> 
     * do so).</p>
     *
     * @param ch the characters from the XML document
     * @param start the start position in the array
     * @param length the number of characters to read from the array
     * @throws org.xml.sax.SAXException any SAX exception, possibly
     *            wrapping another exception
     * @see #ignorableWhitespace 
     * @see org.xml.sax.Locator
     */
    public void characters (char ch[], int start, int length)
	throws SAXException;


    
Receive notification of ignorable whitespace in element content.

Validating Parsers must use this method to report each chunk
of whitespace in element content (see the W3C XML 1.0
recommendation, section 2.10): non-validating parsers may also
use this method if they are capable of parsing and using
content models.


SAX parsers may return all contiguous whitespace in a single
chunk, or they may split it into several chunks; however, all of
the characters in any single event must come from the same
external entity, so that the Locator provides useful
information.


The application must not attempt to read from the array
outside of the specified range.


Params:
  • ch – the characters from the XML document
  • start – the start position in the array
  • length – the number of characters to read from the array
Throws:
  • SAXException – any SAX exception, possibly
           wrapping another exception
See Also:
/**
     * Receive notification of ignorable whitespace in element content.
     *
     * <p>Validating Parsers must use this method to report each chunk
     * of whitespace in element content (see the W3C XML 1.0
     * recommendation, section 2.10): non-validating parsers may also
     * use this method if they are capable of parsing and using
     * content models.</p>
     *
     * <p>SAX parsers may return all contiguous whitespace in a single
     * chunk, or they may split it into several chunks; however, all of
     * the characters in any single event must come from the same
     * external entity, so that the Locator provides useful
     * information.</p>
     *
     * <p>The application must not attempt to read from the array
     * outside of the specified range.</p>
     *
     * @param ch the characters from the XML document
     * @param start the start position in the array
     * @param length the number of characters to read from the array
     * @throws org.xml.sax.SAXException any SAX exception, possibly
     *            wrapping another exception
     * @see #characters
     */
    public void ignorableWhitespace (char ch[], int start, int length)
	throws SAXException;


    
Receive notification of a processing instruction.

The Parser will invoke this method once for each processing
instruction found: note that processing instructions may occur
before or after the main document element.


A SAX parser must never report an XML declaration (XML 1.0,
section 2.8) or a text declaration (XML 1.0, section 4.3.1)
using this method.


Like characters(), processing instruction data may have characters that need more than one char
value. 


Params:
  • target – the processing instruction target
  • data – the processing instruction data, or null if
       none was supplied.  The data does not include any
       whitespace separating it from the target
Throws:
  • SAXException – any SAX exception, possibly
           wrapping another exception
/**
     * Receive notification of a processing instruction.
     *
     * <p>The Parser will invoke this method once for each processing
     * instruction found: note that processing instructions may occur
     * before or after the main document element.</p>
     *
     * <p>A SAX parser must never report an XML declaration (XML 1.0,
     * section 2.8) or a text declaration (XML 1.0, section 4.3.1)
     * using this method.</p>
     *
     * <p>Like {@link #characters characters()}, processing instruction
     * data may have characters that need more than one <code>char</code>
     * value. </p>
     *
     * @param target the processing instruction target
     * @param data the processing instruction data, or null if
     *        none was supplied.  The data does not include any
     *        whitespace separating it from the target
     * @throws org.xml.sax.SAXException any SAX exception, possibly
     *            wrapping another exception
     */
    public void processingInstruction (String target, String data)
	throws SAXException;


    
Receive notification of a skipped entity.
This is not called for entity references within markup constructs
such as element start tags or markup declarations.  (The XML
recommendation requires reporting skipped external entities.
SAX also reports internal entity expansion/non-expansion, except
within markup constructs.)

The Parser will invoke this method each time the entity is
skipped.  Non-validating processors may skip entities if they
have not seen the declarations (because, for example, the
entity was declared in an external DTD subset).  All processors
may skip external entities, depending on the values of the
http://xml.org/sax/features/external-general-entities
and the
http://xml.org/sax/features/external-parameter-entities
properties.


Params:
  • name – the name of the skipped entity.  If it is a 
       parameter entity, the name will begin with '%', and if
       it is the external DTD subset, it will be the string
       "[dtd]"
Throws:
  • SAXException – any SAX exception, possibly
           wrapping another exception
/**
     * Receive notification of a skipped entity.
     * This is not called for entity references within markup constructs
     * such as element start tags or markup declarations.  (The XML
     * recommendation requires reporting skipped external entities.
     * SAX also reports internal entity expansion/non-expansion, except
     * within markup constructs.)
     *
     * <p>The Parser will invoke this method each time the entity is
     * skipped.  Non-validating processors may skip entities if they
     * have not seen the declarations (because, for example, the
     * entity was declared in an external DTD subset).  All processors
     * may skip external entities, depending on the values of the
     * <code>http://xml.org/sax/features/external-general-entities</code>
     * and the
     * <code>http://xml.org/sax/features/external-parameter-entities</code>
     * properties.</p>
     *
     * @param name the name of the skipped entity.  If it is a 
     *        parameter entity, the name will begin with '%', and if
     *        it is the external DTD subset, it will be the string
     *        "[dtd]"
     * @throws org.xml.sax.SAXException any SAX exception, possibly
     *            wrapping another exception
     */
    public void skippedEntity (String name)
	throws SAXException;
}

// end of ContentHandler.java