Identity.java

/*
 * Copyright 2002-2009 Andy Clark, Marc Guillemot
 * 
 * Licensed 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.
 */

package com.googlecode.html.filters;

import com.googlecode.html.HTMLEventInfo;
import org.apache.xerces.xni.Augmentations;
import org.apache.xerces.xni.QName;
import org.apache.xerces.xni.XMLAttributes;
import org.apache.xerces.xni.XNIException;

/**
 * This filter performs the identity operation of the original document event stream generated by
 * the HTML scanner by removing events that are synthesized by the tag balancer. This operation is
 * essentially the same as turning off tag-balancing in the parser. However, this filter is useful
 * when you want the tag balancer to report "errors" but do not want the synthesized events in the
 * output.
 * <p>
 * <strong>Note:</strong> This filter requires the augmentations feature to be turned on. For
 * example:
 * <p>
 * <pre>
 *  XMLParserConfiguration parser = new HTMLConfiguration();
 *  parser.setFeature("http://cyberneko.org/html/features/augmentations", true);
 * </pre>
 * <p>
 * <strong>Note:</strong> This isn't <em>exactly</em> the identify transform because the element and
 * attributes names may have been modified from the original document. For example, by default,
 * NekoHTML converts element names to upper-case and attribute names to lower-case.
 *
 * @author Andy Clark
 * @version $Id: Identity.java,v 1.4 2005/02/14 03:56:54 andyc Exp $
 */
public class Identity extends DefaultFilter {

    //
    // Constants
    //

    /**
     * Augmentations feature identifier.
     */
    protected static final String AUGMENTATIONS = "http://cyberneko.org/html/features/augmentations";

    /**
     * Filters property identifier.
     */
    protected static final String FILTERS = "http://cyberneko.org/html/properties/filters";

    //
    // XMLDocumentHandler methods
    //

    /**
     * Returns true if the information provided is synthesized.
     */
    protected static boolean synthesized(Augmentations augs) {
        HTMLEventInfo info = (HTMLEventInfo) augs.getItem(AUGMENTATIONS);
        return info != null ? info.isSynthesized() : false;
    } // synthesized(Augmentations):boolean

    /**
     * Empty element.
     */
    public void emptyElement(QName element, XMLAttributes attributes, Augmentations augs)
            throws XNIException {
        if (augs == null || !synthesized(augs)) {
            super.emptyElement(element, attributes, augs);
        }
    } // emptyElement(QName,XMLAttributes,Augmentations)

    /**
     * End element.
     */
    public void endElement(QName element, Augmentations augs) throws XNIException {
        if (augs == null || !synthesized(augs)) {
            super.endElement(element, augs);
        }
    } // endElement(QName,XMLAttributes,Augmentations)

    //
    // Protected static methods
    //

    /**
     * Start element.
     */
    public void startElement(QName element, XMLAttributes attributes, Augmentations augs)
            throws XNIException {
        if (augs == null || !synthesized(augs)) {
            super.startElement(element, attributes, augs);
        }
    } // startElement(QName,XMLAttributes,Augmentations)

} // class Identity