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. 
/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

// $Id: ErrorListener.java 569994 2007-08-27 04:28:57Z mrglavas $

package javax.xml.transform;


To provide customized error handling, implement this interface and
use the setErrorListener method to register an instance of the implementation with the Transformer. The Transformer then reports all errors and warnings through this
interface.


If an application does not register its own custom
ErrorListener, the default ErrorListener
is used which reports all warnings and errors to System.err
and does not throw any Exceptions.
Applications are strongly encouraged to register and use
ErrorListeners that insure proper behavior for warnings and
errors.


For transformation errors, a Transformer 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 the
Transformer is not required to continue with the transformation after a call to fatalError(TransformerException exception).


Transformers may use this mechanism to report XML parsing
errors as well as transformation errors.


/**
 * <p>To provide customized error handling, implement this interface and
 * use the <code>setErrorListener</code> method to register an instance of the
 * implementation with the {@link javax.xml.transform.Transformer}.  The
 * <code>Transformer</code> then reports all errors and warnings through this
 * interface.</p>
 *
 * <p>If an application does <em>not</em> register its own custom
 * <code>ErrorListener</code>, the default <code>ErrorListener</code>
 * is used which reports all warnings and errors to <code>System.err</code>
 * and does not throw any <code>Exception</code>s.
 * Applications are <em>strongly</em> encouraged to register and use
 * <code>ErrorListener</code>s that insure proper behavior for warnings and
 * errors.</p>
 *
 * <p>For transformation errors, a <code>Transformer</code> must use this
 * interface instead of throwing an <code>Exception</code>: it is up to the
 * application to decide whether to throw an <code>Exception</code> for
 * different types of errors and warnings.  Note however that the
 * <code>Transformer</code> is not required to continue with the transformation
 * after a call to {@link #fatalError(TransformerException exception)}.</p>
 *
 * <p><code>Transformer</code>s may use this mechanism to report XML parsing
 * errors as well as transformation errors.</p>
 */
public interface ErrorListener {

    
Receive notification of a warning.

Transformer can use this method to report conditions that are not errors or fatal errors. The default behaviour is to take no action.


After invoking this method, the Transformer must continue with
the transformation. It should still be possible for the
application to process the document through to the end.


Params:
  • exception – The warning information encapsulated in a
                 transformer exception.
Throws:
See Also:
/**
     * Receive notification of a warning.
     *
     * <p>{@link javax.xml.transform.Transformer} can use this method to report
     * conditions that are not errors or fatal errors.  The default behaviour
     * is to take no action.</p>
     *
     * <p>After invoking this method, the Transformer must continue with
     * the transformation. It should still be possible for the
     * application to process the document through to the end.</p>
     *
     * @param exception The warning information encapsulated in a
     *                  transformer exception.
     *
     * @throws javax.xml.transform.TransformerException if the application
     * chooses to discontinue the transformation.
     *
     * @see javax.xml.transform.TransformerException
     */
    public abstract void warning(TransformerException exception)
        throws TransformerException;

    
Receive notification of a recoverable error.

The transformer must continue to try and provide normal transformation
after invoking this method.  It should still be possible for the
application to process the document through to the end if no other errors
are encountered.


Params:
  • exception – The error information encapsulated in a
                 transformer exception.
Throws:
See Also:
/**
     * Receive notification of a recoverable error.
     *
     * <p>The transformer must continue to try and provide normal transformation
     * after invoking this method.  It should still be possible for the
     * application to process the document through to the end if no other errors
     * are encountered.</p>
     *
     * @param exception The error information encapsulated in a
     *                  transformer exception.
     *
     * @throws javax.xml.transform.TransformerException if the application
     * chooses to discontinue the transformation.
     *
     * @see javax.xml.transform.TransformerException
     */
    public abstract void error(TransformerException exception)
        throws TransformerException;

    
Receive notification of a non-recoverable error.


The Transformer must continue to try and provide normal
transformation after invoking this method.  It should still be possible for the
application to process the document through to the end if no other errors
are encountered, but there is no guarantee that the output will be
useable.


Params:
  • exception – The error information encapsulated in a
   TransformerException.
Throws:
See Also:
/**
     * <p>Receive notification of a non-recoverable error.</p>
     *
     * <p>The <code>Transformer</code> must continue to try and provide normal
     * transformation after invoking this method.  It should still be possible for the
     * application to process the document through to the end if no other errors
     * are encountered, but there is no guarantee that the output will be
     * useable.</p>
     *
     * @param exception The error information encapsulated in a
     *    <code>TransformerException</code>.
     *
     * @throws javax.xml.transform.TransformerException if the application
     * chooses to discontinue the transformation.
     *
     * @see javax.xml.transform.TransformerException
     */
    public abstract void fatalError(TransformerException exception)
        throws TransformerException;
}