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    1   /*
    2    * $Header: /home/projects/jaxen/scm/jaxen/src/java/main/org/jaxen/function/IdFunction.java,v 1.12 2005/09/23 13:58:46 elharo Exp $
    3    * $Revision: 1.12 $
    4    * $Date: 2005/09/23 13:58:46 $
    5    *
    6    * ====================================================================
    7    *
    8    * Copyright (C) 2000-2002 bob mcwhirter & James Strachan.
    9    * All rights reserved.
    10   *
    11   * Redistribution and use in source and binary forms, with or without
    12   * modification, are permitted provided that the following conditions
    13   * are met:
    14   *
    15   * 1. Redistributions of source code must retain the above copyright
    16   *    notice, this list of conditions, and the following disclaimer.
    17   *
    18   * 2. Redistributions in binary form must reproduce the above copyright
    19   *    notice, this list of conditions, and the disclaimer that follows
    20   *    these conditions in the documentation and/or other materials
    21   *    provided with the distribution.
    22   *
    23   * 3. The name "Jaxen" must not be used to endorse or promote products
    24   *    derived from this software without prior written permission.  For
    25   *    written permission, please contact license@jaxen.org.
    26   *
    27   * 4. Products derived from this software may not be called "Jaxen", nor
    28   *    may "Jaxen" appear in their name, without prior written permission
    29   *    from the Jaxen Project Management (pm@jaxen.org).
    30   *
    31   * In addition, we request (but do not require) that you include in the
    32   * end-user documentation provided with the redistribution and/or in the
    33   * software itself an acknowledgement equivalent to the following:
    34   *     "This product includes software developed by the
    35   *      Jaxen Project <http://www.jaxen.org/>."
    36   * Alternatively, the acknowledgment may be graphical using the logos
    37   * available at http://www.jaxen.org/
    38   *
    39   * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
    40   * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
    41   * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
    42   * DISCLAIMED.  IN NO EVENT SHALL THE Jaxen AUTHORS OR THE PROJECT
    43   * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
    44   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
    45   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
    46   * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
    47   * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
    48   * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
    49   * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
    50   * SUCH DAMAGE.
    51   *
    52   * ====================================================================
    53   * This software consists of voluntary contributions made by many
    54   * individuals on behalf of the Jaxen Project and was originally
    55   * created by bob mcwhirter <bob@werken.com> and
    56   * James Strachan <jstrachan@apache.org>.  For more information on the
    57   * Jaxen Project, please see <http://www.jaxen.org/>.
    58   *
    59   * $Id: IdFunction.java,v 1.12 2005/09/23 13:58:46 elharo Exp $
    60   */
    61
    62  package org.jaxen.function;
    63
    64  import java.util.ArrayList;
    65  import java.util.Collections;
    66  import java.util.Iterator;
    67  import java.util.List;
    68  import java.util.StringTokenizer;
    69
    70  import org.jaxen.Context;
    71  import org.jaxen.Function;
    72  import org.jaxen.FunctionCallException;
    73  import org.jaxen.Navigator;
    74
    75  /***
    76   * <p><b>4.1</b> <code><i>node-set</i> id(<i>object</i>)</code> </p>
    77   *
    78   * <p>The <b>id</b> function returns a <code>List</code>
    79   * of all the elements in the context document that have an ID
    80   * matching one of a specified list of IDs. How an attribute is determined
    81   * to be of type ID depends on the navigator, but it normally requires that
    82   * the attribute be declared to have type ID in the DTD.
    83   * </p>
    84   *
    85   * <p>
    86   * There should be no more than one element in any document with a
    87   * certain ID. However, if there are multiple such elements--i.e. if
    88   * there are duplicate IDs--then this function selects only the first element
    89   * in document order with the specified ID.
    90   * </p>
    91   *
    92   * @author Erwin Bolwidt (ejb @ klomp.org)
    93   * @author J\u00e9r\u00f4me N\u00e8gre (jerome.negre @ e-xmlmedia.fr)
    94   *
    95   * @see <a href="http://www.w3.org/TR/xpath#function-id" target="_top">Section 4.1 of the XPath Specification</a>
    96   */
    97  public class IdFunction implements Function
    98  {
    99
    100     /***
    101      * Create a new <code>IdFunction</code> object.
    102      */
    103     public IdFunction() {}
    104
    105     /***
    106      * Returns a list of the nodes with the specified IDs.
    107      *
    108      * @param context the context at the point in the
    109      *         expression when the function is called
    110      * @param args a list with exactly one item which is either a string
    111      *     a node-set
    112      *
    113      * @return a <code>List</code> containing the first node in document
    114      *     with each of the specified IDs; or
    115      *     an empty list if there are no such nodes
    116      *
    117      * @throws FunctionCallException if <code>args</code> has more or less than one item
    118      */
    119     public Object call(Context context, List args) throws FunctionCallException
    120     {
    121         if ( args.size() == 1 ) {
    122             return evaluate( context.getNodeSet(),
    123                              args.get(0), context.getNavigator() );
    124         }
    125
    126         throw new FunctionCallException( "id() requires one argument" );
    127     }
    128
    129     /***
    130      * Returns a list of the nodes with the specified IDs.
    131      *
    132      * @param contextNodes the context node-set. The first item in this list
    133      *     determines the document in which the search is performed.
    134      * @param arg the ID or IDs to search for
    135      * @param nav the navigator used to calculate string-values and search
    136      *     by ID
    137      *
    138      * @return a <code>List</code> containing the first node in document
    139      *     with each of the specified IDs; or
    140      *     an empty list if there are no such nodes
    141      *
    142      */
    143     public static List evaluate(List contextNodes, Object arg, Navigator nav)
    144     {
    145         if (contextNodes.size() == 0) return Collections.EMPTY_LIST;
    146
    147         List nodes = new ArrayList();
    148
    149         Object contextNode = contextNodes.get(0);
    150
    151         if (arg instanceof List) {
    152             Iterator iter = ((List)arg).iterator();
    153             while (iter.hasNext()) {
    154                 String id = StringFunction.evaluate(iter.next(), nav);
    155                 nodes.addAll( evaluate( contextNodes, id, nav ) );
    156             }
    157         }
    158         else {
    159             String ids = StringFunction.evaluate(arg, nav);
    160             StringTokenizer tok = new StringTokenizer(ids, " \t\n\r");
    161             while (tok.hasMoreTokens()) {
    162                 String id = tok.nextToken();
    163                 Object node = nav.getElementById(contextNode, id);
    164                 if (node != null) {
    165                     nodes.add(node);
    166                 }
    167             }
    168         }
    169         return nodes;
    170     }
    171
    172 }
    173