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A lib to access XML via XPath
There is a newer version: 1.0.5
/*
 * $Header: /cvs/jaxen/jaxen/src/java/main/org/jaxen/function/IdFunction.java,v 1.13 2006/02/05 21:47:41 elharo Exp $
 * $Revision: 1.13 $
 * $Date: 2006/02/05 21:47:41 $
 *
 * ====================================================================
 *
 * Copyright 2000-2002 bob mcwhirter & James Strachan.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 * 
 *   * Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 * 
 *   * Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 * 
 *   * Neither the name of the Jaxen Project nor the names of its
 *     contributors may be used to endorse or promote products derived 
 *     from this software without specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
 * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
 * OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * ====================================================================
 * This software consists of voluntary contributions made by many 
 * individuals on behalf of the Jaxen Project and was originally 
 * created by bob mcwhirter  and 
 * James Strachan .  For more information on the 
 * Jaxen Project, please see .
 * 
 * $Id: IdFunction.java,v 1.13 2006/02/05 21:47:41 elharo Exp $
 */

package org.navimatrix.jaxen.function;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.StringTokenizer;

import org.navimatrix.jaxen.Context;
import org.navimatrix.jaxen.Function;
import org.navimatrix.jaxen.FunctionCallException;
import org.navimatrix.jaxen.Navigator;

/**
 * 4.1 node-set id(object) 
 *  
 * The id function returns a List
 * of all the elements in the context document that have an ID
 * matching one of a specified list of IDs. How an attribute is determined
 * to be of type ID depends on the navigator, but it normally requires that
 * the attribute be declared to have type ID in the DTD. 
 * 
 * 
 * 
 * There should be no more than one element in any document with a 
 * certain ID. However, if there are multiple such elements--i.e. if 
 * there are duplicate IDs--then this function selects only the first element 
 * in document order with the specified ID. 
 * 
 * 
 * @author Erwin Bolwidt (ejb @ klomp.org)
 * @author J\u00e9r\u00f4me N\u00e8gre (jerome.negre @ e-xmlmedia.fr)
 * 
 * @see Section 4.1 of the XPath Specification
 */
public class IdFunction implements Function
{

    /**
     * Create a new IdFunction object.
     */
    public IdFunction() {}
    
    /** 
     * Returns a list of the nodes with the specified IDs.
     *
     * @param context the context at the point in the
     *         expression when the function is called
     * @param args a list with exactly one item which is either a string
     *     a node-set
     * 
     * @return a List containing the first node in document 
     *     with each of the specified IDs; or 
     *     an empty list if there are no such nodes
     * 
     * @throws FunctionCallException if args has more or less than one item
     */
    public Object call(Context context, List args) throws FunctionCallException
    {
        if ( args.size() == 1 ) {
            return evaluate( context.getNodeSet(),
                             args.get(0), context.getNavigator() );
        }

        throw new FunctionCallException( "id() requires one argument" );
    }

    /** 
     * Returns a list of the nodes with the specified IDs.
     * 
     * @param contextNodes the context node-set. The first item in this list
     *     determines the document in which the search is performed.
     * @param arg the ID or IDs to search for
     * @param nav the navigator used to calculate string-values and search
     *     by ID
     * 
     * @return a List containing the first node in document 
     *     with each of the specified IDs; or 
     *     an empty list if there are no such nodes
     * 
     */
    public static List evaluate(List contextNodes, Object arg, Navigator nav)
    {
        if (contextNodes.size() == 0) return Collections.EMPTY_LIST;
      
        List nodes = new ArrayList();

        Object contextNode = contextNodes.get(0);

        if (arg instanceof List) {
            Iterator iter = ((List)arg).iterator();
            while (iter.hasNext()) {
                String id = StringFunction.evaluate(iter.next(), nav);
                nodes.addAll( evaluate( contextNodes, id, nav ) );
            }
        } 
        else {
            String ids = StringFunction.evaluate(arg, nav);
            StringTokenizer tok = new StringTokenizer(ids, " \t\n\r");
            while (tok.hasMoreTokens()) {
                String id = tok.nextToken();
                Object node = nav.getElementById(contextNode, id);
                if (node != null) {
                    nodes.add(node);
                }
            }
        }
        return nodes;
    }
    
}