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1   /*
2    * $Header: /home/projects/jaxen/scm/jaxen/src/java/main/org/jaxen/function/IdFunction.java,v 1.13 2006/02/05 21:47:41 elharo Exp $
3    * $Revision: 1.13 $
4    * $Date: 2006/02/05 21:47:41 $
5    *
6    * ====================================================================
7    *
8    * Copyright 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 are
13   * met:
14   * 
15   *   * Redistributions of source code must retain the above copyright
16   *     notice, this list of conditions and the following disclaimer.
17   * 
18   *   * Redistributions in binary form must reproduce the above copyright
19   *     notice, this list of conditions and the following disclaimer in the
20   *     documentation and/or other materials provided with the distribution.
21   * 
22   *   * Neither the name of the Jaxen Project nor the names of its
23   *     contributors may be used to endorse or promote products derived 
24   *     from this software without specific prior written permission.
25   * 
26   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
27   * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
28   * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
29   * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
30   * OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
31   * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
32   * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
33   * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
34   * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
35   * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
36   * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
37   *
38   * ====================================================================
39   * This software consists of voluntary contributions made by many 
40   * individuals on behalf of the Jaxen Project and was originally 
41   * created by bob mcwhirter <bob@werken.com> and 
42   * James Strachan <jstrachan@apache.org>.  For more information on the 
43   * Jaxen Project, please see <http://www.jaxen.org/>.
44   * 
45   * $Id: IdFunction.java,v 1.13 2006/02/05 21:47:41 elharo Exp $
46   */
47  
48  package org.jaxen.function;
49  
50  import java.util.ArrayList;
51  import java.util.Collections;
52  import java.util.Iterator;
53  import java.util.List;
54  import java.util.StringTokenizer;
55  
56  import org.jaxen.Context;
57  import org.jaxen.Function;
58  import org.jaxen.FunctionCallException;
59  import org.jaxen.Navigator;
60  
61  /***
62   * <p><b>4.1</b> <code><i>node-set</i> id(<i>object</i>)</code> </p>
63   *  
64   * <p>The <b>id</b> function returns a <code>List</code>
65   * of all the elements in the context document that have an ID
66   * matching one of a specified list of IDs. How an attribute is determined
67   * to be of type ID depends on the navigator, but it normally requires that
68   * the attribute be declared to have type ID in the DTD. 
69   * </p>
70   * 
71   * <p>
72   * There should be no more than one element in any document with a 
73   * certain ID. However, if there are multiple such elements--i.e. if 
74   * there are duplicate IDs--then this function selects only the first element 
75   * in document order with the specified ID. 
76   * </p>
77   * 
78   * @author Erwin Bolwidt (ejb @ klomp.org)
79   * @author J\u00e9r\u00f4me N\u00e8gre (jerome.negre @ e-xmlmedia.fr)
80   * 
81   * @see <a href="http://www.w3.org/TR/xpath#function-id" target="_top">Section 4.1 of the XPath Specification</a>
82   */
83  public class IdFunction implements Function
84  {
85  
86      /***
87       * Create a new <code>IdFunction</code> object.
88       */
89      public IdFunction() {}
90      
91      /*** 
92       * Returns a list of the nodes with the specified IDs.
93       *
94       * @param context the context at the point in the
95       *         expression when the function is called
96       * @param args a list with exactly one item which is either a string
97       *     a node-set
98       * 
99       * @return a <code>List</code> containing the first node in document 
100      *     with each of the specified IDs; or 
101      *     an empty list if there are no such nodes
102      * 
103      * @throws FunctionCallException if <code>args</code> has more or less than one item
104      */
105     public Object call(Context context, List args) throws FunctionCallException
106     {
107         if ( args.size() == 1 ) {
108             return evaluate( context.getNodeSet(),
109                              args.get(0), context.getNavigator() );
110         }
111 
112         throw new FunctionCallException( "id() requires one argument" );
113     }
114 
115     /*** 
116      * Returns a list of the nodes with the specified IDs.
117      * 
118      * @param contextNodes the context node-set. The first item in this list
119      *     determines the document in which the search is performed.
120      * @param arg the ID or IDs to search for
121      * @param nav the navigator used to calculate string-values and search
122      *     by ID
123      * 
124      * @return a <code>List</code> containing the first node in document 
125      *     with each of the specified IDs; or 
126      *     an empty list if there are no such nodes
127      * 
128      */
129     public static List evaluate(List contextNodes, Object arg, Navigator nav)
130     {
131         if (contextNodes.size() == 0) return Collections.EMPTY_LIST;
132       
133         List nodes = new ArrayList();
134 
135         Object contextNode = contextNodes.get(0);
136 
137         if (arg instanceof List) {
138             Iterator iter = ((List)arg).iterator();
139             while (iter.hasNext()) {
140                 String id = StringFunction.evaluate(iter.next(), nav);
141                 nodes.addAll( evaluate( contextNodes, id, nav ) );
142             }
143         } 
144         else {
145             String ids = StringFunction.evaluate(arg, nav);
146             StringTokenizer tok = new StringTokenizer(ids, " \t\n\r");
147             while (tok.hasMoreTokens()) {
148                 String id = tok.nextToken();
149                 Object node = nav.getElementById(contextNode, id);
150                 if (node != null) {
151                     nodes.add(node);
152                 }
153             }
154         }
155         return nodes;
156     }
157     
158 }
159