// SAX error handler.
// No warranty; no copyright -- use this as you will.
// $Id$

package org.xml.sax;


/**
 * Basic interface for SAX error handlers.
 *
 * <blockquote>
 * <em>This module, both source code and documentation, is in the
 * Public Domain, and comes with <strong>NO WARRANTY</strong>.</em>
 * </blockquote>
 *
 * <p>If a SAX application needs to implement customized error
 * handling, it must implement this interface and then register an
 * instance with the XML reader using the
 * {@link org.xml.sax.XMLReader#setErrorHandler setErrorHandler}
 * method.  The parser will then report all errors and warnings
 * through this interface.</p>
 *
 * <p><strong>WARNING:</strong> If an application does <em>not</em>
 * register an ErrorHandler, XML parsing errors will go unreported
 * and bizarre behaviour may result.</p>
 *
 * <p>For XML processing errors, a SAX driver must use this interface 
 * instead of throwing an exception: it is up to the application 
 * to decide whether to throw an exception for different types of 
 * errors and warnings.  Note, however, that there is no requirement that 
 * the parser continue to provide useful information after a call to 
 * {@link #fatalError fatalError} (in other words, a SAX driver class 
 * could catch an exception and report a fatalError).</p>
 *
 * @since SAX 1.0
 * @author David Megginson, 
 *         <a href="mailto:sax@megginson.com">sax@megginson.com</a>
 * @version 2.0
 * @see org.xml.sax.Parser#setErrorHandler
 * @see org.xml.sax.SAXParseException 
 */
public interface ErrorHandler {
    
    
    /**
     * Receive notification of a warning.
     *
     * <p>SAX parsers will use this method to report conditions that
     * are not errors or fatal errors as defined by the XML 1.0
     * recommendation.  The default behaviour is to take no action.</p>
     *
     * <p>The SAX parser must continue to provide normal parsing events
     * after invoking this method: it should still be possible for the
     * application to process the document through to the end.</p>
     *
     * <p>Filters may use this method to report other, non-XML warnings
     * as well.</p>
     *
     * @param exception The warning information encapsulated in a
     *                  SAX parse exception.
     * @exception org.xml.sax.SAXException Any SAX exception, possibly
     *            wrapping another exception.
     * @see org.xml.sax.SAXParseException 
     */
    public abstract void warning (SAXParseException exception)
	throws SAXException;
    
    
    /**
     * Receive notification of a recoverable error.
     *
     * <p>This corresponds to the definition of "error" in section 1.2
     * of the W3C XML 1.0 Recommendation.  For example, a validating
     * parser would use this callback to report the violation of a
     * validity constraint.  The default behaviour is to take no
     * action.</p>
     *
     * <p>The SAX parser must continue to provide normal parsing events
     * after invoking this method: it should still be possible for the
     * application to process the document through to the end.  If the
     * application cannot do so, then the parser should report a fatal
     * error even if the XML 1.0 recommendation does not require it to
     * do so.</p>
     *
     * <p>Filters may use this method to report other, non-XML errors
     * as well.</p>
     *
     * @param exception The error information encapsulated in a
     *                  SAX parse exception.
     * @exception org.xml.sax.SAXException Any SAX exception, possibly
     *            wrapping another exception.
     * @see org.xml.sax.SAXParseException 
     */
    public abstract void error (SAXParseException exception)
	throws SAXException;
    
    
    /**
     * Receive notification of a non-recoverable error.
     *
     * <p>This corresponds to the definition of "fatal error" in
     * section 1.2 of the W3C XML 1.0 Recommendation.  For example, a
     * parser would use this callback to report the violation of a
     * well-formedness constraint.</p>
     *
     * <p>The application must assume that the document is unusable
     * after the parser has invoked this method, and should continue
     * (if at all) only for the sake of collecting addition error
     * messages: in fact, SAX parsers are free to stop reporting any
     * other events once this method has been invoked.</p>
     *
     * @param exception The error information encapsulated in a
     *                  SAX parse exception.  
     * @exception org.xml.sax.SAXException Any SAX exception, possibly
     *            wrapping another exception.
     * @see org.xml.sax.SAXParseException
     */
    public abstract void fatalError (SAXParseException exception)
	throws SAXException;
    
}

// end of ErrorHandler.java