htmlelementlistimpl.java

来自「用Java写的面相对象的数据库管理系统」· Java 代码 · 共 123 行

/**
 * org/ozone-db/xml/dom/html/HTMLElementListImpl.java
 *
 * The contents of this file are subject to the OpenXML Public
 * License Version 1.0; you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at
 * http://www.openxml.org/license.html
 *
 * THIS SOFTWARE IS DISTRIBUTED ON AN "AS IS" BASIS WITHOUT WARRANTY
 * OF ANY KIND, EITHER EXPRESSED OR IMPLIED. THE INITIAL DEVELOPER
 * AND ALL CONTRIBUTORS SHALL NOT BE LIABLE FOR ANY DAMAGES AS A
 * RESULT OF USING, MODIFYING OR DISTRIBUTING THIS SOFTWARE OR ITS
 * DERIVATIVES. SEE THE LICENSE FOR THE SPECIFIC LANGUAGE GOVERNING
 * RIGHTS AND LIMITATIONS UNDER THE LICENSE.
 *
 * The Initial Developer of this code under the License is Assaf Arkin.
 * Portions created by Assaf Arkin are Copyright (C) 1998, 1999.
 * All Rights Reserved.
 */


package org.ozoneDB.xml.dom.html;


import java.util.*;
import org.w3c.dom.*;


/**
 * Implements a list of HTML elements extracted based on their name attribute.
 * The constructor recieves the root element and name. It then obtains all the
 * elements contained within that element that match with their <code>name</code>
 * attribute. The list is then accessible through the {@link #item} method.
 * <P>
 * The resulting list is a snapshot of the searched element at the time this
 * list was created. Updates to the document tree are not reflected in the list.
 * The list is implemented as a fast collection and access to elements in the
 * list is very rapid.
 *
 *
 * @version $Revision: 1.3 $ $Date: 2000/10/28 16:55:24 $
 * @author <a href="mailto:[e-mail]">Assaf Arkin</a>
 * @see org.w3c.dom.NodeList
 * @see HTMLElementImpl
 * @see HTMLDocumentImpl
 */
final class HTMLElementListImpl implements NodeList {
    
    
    public Node item( int index ) {
        return (Node)_elements.elementAt( index );
    } 
    
    
    public int getLength() {
        return _elements.size();
    } 
    
    
    /**
     * Add a single element to the list of elements.
     *
     * @param newElem The element to add
     */
    void addElement( Element newElem ) {
        _elements.addElement( newElem );
    } 
    
    
    /**
     * Add all the elements contained in the root element and matching the
     * <code>name</code> attribute. Each element is added by calling {@link
     * #addElement} and the method is recursed on all sub-elements.
     *
     * @param element The root element from which to extract all sub elements
     * @param name The <code>name</code> attribute to match
     */
    void addElements( Node element, String name ) {
        Node node;
        
        // Traverse all the child nodes of this element. Each node that is an
        // element is added to the list if its name attribute matches and this
        // method is recursed on that element.
        node = element.getFirstChild();
        while (node != null) {
            if (node instanceof Element) {
                if (((Element)node).getAttribute( "name" ).equals( name )) {
                    addElement( (Element)node );
                } 
                addElements( node, name );
            } 
            node = node.getNextSibling();
        } 
    } 
    
    
    /**
     * Constructor receieves an element and <code>name</code> attribute value and
     * extracts all the* sub elements based on that. After construction this object
     * is ready for element retrieval.
     *
     * @param element The root element from which to extract all sub elements
     * @param name The <code>name</code> attribute to match
     */
    HTMLElementListImpl( Node element, String name ) {
        if (name == null) {
            throw new NullPointerException( "Argument 'name' is null." );
        } 
        _elements = new Vector();
        addElements( element, name );
    }
    
    
    /**
     * Holds a list of all the matching elements. This list is accessed by
     * {@link #item} and {@link #getLength}. Note that this list is not live,
     * updates to the node tree are not reflected in this list.
     */
    private Vector _elements;
    
    
}