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1   /*
2    * $Header: /home/projects/jaxen/scm/jaxen/src/java/main/org/jaxen/function/IdFunction.java,v 1.10 2005/06/26 16:07:23 elharo Exp $
3    * $Revision: 1.10 $
4    * $Date: 2005/06/26 16:07:23 $
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 1.10 2005/06/26 16:07:23 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   * @author Erwin Bolwidt (ejb @ klomp.org)
86   * @author J\u00e9r\u00f4me N\u00e8gre (jerome.negre @ e-xmlmedia.fr)
87   * 
88   * @see <a href="http://www.w3.org/TR/xpath#function-id" target="_top">Section 4.1 of the XPath Specification</a>
89   */
90  public class IdFunction implements Function
91  {
92  
93      /***
94       * Create a new <code>IdFunction</code> object.
95       */
96      public IdFunction() {}
97      
98      /*** 
99       * Returns the node with the specified ID.
100      *
101      * @param context the context at the point in the
102      *         expression when the function is called
103      * @param args a list with exactly one item which is either a string
104      *     a node-set
105      * 
106      * @return a <code>List</code> containing the node with the specified ID; or 
107      *     an empty list if there is no such node
108      * 
109      * @throws FunctionCallException if <code>args</code> has more or less than one item
110      */
111     public Object call(Context context, List args) throws FunctionCallException
112     {
113         if ( args.size() == 1 ) {
114             return evaluate( context.getNodeSet(),
115                              args.get(0), context.getNavigator() );
116         }
117 
118         throw new FunctionCallException( "id() requires one argument" );
119     }
120 
121     /*** 
122      * Returns the node with the specified ID.
123      * @param contextNodes the context node-set. The first item in this list
124      *     determines the document in which the search is performed.
125      * @param arg the ID or IDs to search for
126      * @param nav the navigator used to calculate string-values and search
127      *     by ID
128      * 
129      * @return a <code>List</code> containing the node with the specified ID; or 
130      *     an empty list if there is no such node
131      * 
132      */
133     public static List evaluate(List contextNodes, Object arg, Navigator nav)
134     {
135         if (contextNodes.size() == 0) return Collections.EMPTY_LIST;
136       
137         List nodes = new ArrayList();
138 
139         Object contextNode = contextNodes.get(0);
140 
141         if (arg instanceof List) {
142             Iterator iter = ((List)arg).iterator();
143             while (iter.hasNext()) {
144                 String id = StringFunction.evaluate(iter.next(), nav);
145                 nodes.addAll( evaluate( contextNodes, id, nav ) );
146             }
147         } 
148         else {
149             String ids = StringFunction.evaluate(arg, nav);
150             StringTokenizer tok = new StringTokenizer(ids, " \t\n\r");
151             while (tok.hasMoreTokens()) {
152                 String id = tok.nextToken();
153                 Object node = nav.getElementById(contextNode, id);
154                 if (node != null) {
155                     nodes.add(node);
156                 }
157             }
158         }
159         return nodes;
160     }
161     
162 }
163