contenthandler.java

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// 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,v 1.2 2003/12/21 08:07:43 epr Exp $

package org.xml.sax;


/**
 * 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 Java class
 * {@link java.net.ContentHandler ContentHandler} in the java.net
 * package; that means that it's probably a bad idea to do</p>
 *
 * <blockquote>
 * import java.net.*;
 * import org.xml.sax.*;
 * </blockquote>
 *
 * <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 (sax2r2)
 * @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.
     *
     * <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 of the events in this interface.  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.
     *
     * <p>The SAX parser will invoke this method only once, before any
     * other event callbacks (except for {@link #setDocumentLocator 
     * setDocumentLocator}).</p>
     *
     * @exception 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.
     *
     * <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>
     *
     * @exception 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.
     *
     * <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.
     * @exception org.xml.sax.SAXException The client may throw
     *            an exception during processing.
     * @see #endPrefixMapping(String)
     * @see #startElement(String, String, String, Attributes)
     */
    public void startPrefixMapping (String prefix, String uri)
	throws SAXException;


    /**
     * 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.
     * @exception org.xml.sax.SAXException The client may throw
     *            an exception during processing.
     * @see #startPrefixMapping(String, String)
     * @see #endElement(String, String, String)
     */
    public void endPrefixMapping (String prefix)
	throws SAXException;


    /**
     * 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>