// SAX document handler.
// http://www.saxproject.org
// No warranty; no copyright -- use this as you will.

package org.xml.sax;

import org.xml.sax.AttributeList;
import org.xml.sax.Locator;
import org.xml.sax.SAXException;

/**
 * Receive notification of general document events.
 *
 * <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 was the main event-handling interface for SAX1; in
 * SAX2, it has been replaced by {@link org.xml.sax.ContentHandler
 * ContentHandler}, which provides Namespace support and reporting
 * of skipped entities.  This interface is included in SAX2 only
 * to support legacy SAX1 applications.</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>Application writers who do not want to implement the entire
 * interface can derive a class from HandlerBase, which implements
 * the default functionality; parser writers can instantiate
 * HandlerBase to obtain a default handler.  The application can find
 * the location of any document event using the Locator interface
 * supplied by the Parser through the setDocumentLocator method.</p>
 *
 * @since SAX 1.0
 * @author David Megginson
 * @version 2.0.1 (sax2r2)
 * @see org.xml.sax.Parser#setDocumentHandler
 * @see org.xml.sax.Locator
 * @see org.xml.sax.HandlerBase
 */
public interface DocumentHandler {
    
    
    /**
     * 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 DocumentHandler
     * 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 abstract 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 methods in this interface or in DTDHandler (except for
     * setDocumentLocator).</p>
     *
     * @exception org.xml.sax.SAXException Any SAX exception, possibly
     *            wrapping another exception.
     */
    public abstract 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.
     */
    public abstract void endDocument ()
	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
     * 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>If the element name has a namespace prefix, the prefix will
     * still be attached.  Note that the attribute list provided will
     * contain only attributes with explicit values (specified or
     * defaulted): #IMPLIED attributes will be omitted.</p>
     *
     * @param name The element type name.
     * @param atts The attributes attached to the element, if any.
     * @exception org.xml.sax.SAXException Any SAX exception, possibly
     *            wrapping another exception.
     * @see #endElement
     * @see org.xml.sax.AttributeList 
     */
    public abstract void startElement (String name, AttributeList atts)
	throws SAXException;
    
    
    /**
     * 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
     * startElement() event for every endElement() event (even when the
     * element is empty).</p>
     *
     * <p>If the element name has a namespace prefix, the prefix will
     * still be attached to the name.</p>
     *
     * @param name The element type name
     * @exception org.xml.sax.SAXException Any SAX exception, possibly
     *            wrapping another exception.
     */
    public abstract void endElement (String name)
	throws SAXException;
    
    
    /**
     * 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>Note that some parsers will report whitespace using the
     * ignorableWhitespace() method rather than this one (validating
     * parsers must 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.
     * @exception org.xml.sax.SAXException Any SAX exception, possibly
     *            wrapping another exception.
     * @see #ignorableWhitespace 
     * @see org.xml.sax.Locator
     */
    public abstract void characters (char ch[], int start, int length)
	throws SAXException;
    
    
    /**
     * Receive notification of ignorable whitespace in element content.
     *
     * <p>Validating Parsers must use this method to report each chunk
     * of ignorable whitespace (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.
     * @exception org.xml.sax.SAXException Any SAX exception, possibly
     *            wrapping another exception.
     * @see #characters
     */
    public abstract void ignorableWhitespace (char ch[], int start, int length)
	throws SAXException;
    
    
    /**
     * 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 should 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>
     *
     * @param target The processing instruction target.
     * @param data The processing instruction data, or null if
     *        none was supplied.
     * @exception org.xml.sax.SAXException Any SAX exception, possibly
     *            wrapping another exception.
     */
    public abstract void processingInstruction (String target, String data)
	throws SAXException;
    
}

// end of DocumentHandler.java