View Javadoc

1   /*
2    * $Header: /home/projects/jaxen/scm/jaxen/src/java/main/org/jaxen/function/NamespaceUriFunction.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: NamespaceUriFunction.java,v 1.13 2006/02/05 21:47:41 elharo Exp $
46   */
47  
48  
49  package org.jaxen.function;
50  
51  import java.util.List;
52  
53  import org.jaxen.Context;
54  import org.jaxen.Function;
55  import org.jaxen.FunctionCallException;
56  import org.jaxen.Navigator;
57  
58  /***
59   * <p>
60   * <b>4.1</b>
61   * <code><i>string</i> namespace-uri(<i>node-set?</i>)</code>
62   * </p>
63   * 
64   * <blockquote src="http://www.w3.org/TR/xpath">
65   * <p>
66   * The <b>namespace-uri</b>
67   * function returns the namespace URI of the <a
68   * href="http://www.w3.org/TR/xpath#dt-expanded-name" target="_top">expanded-name</a> of the node in the
69   * argument node-set that is first in <a
70   * href="http://www.w3.org/TR/xpath#dt-document-order" target="_top">document order</a>. If the argument
71   * node-set is empty, the first node has no <a
72   * href="http://www.w3.org/TR/xpath#dt-expanded-name" target="_top">expanded-name</a>, or the namespace URI of
73   * the <a href="http://www.w3.org/TR/xpath#dt-expanded-name" target="_top">expanded-name</a> is null, an empty
74   * string is returned. If the argument is omitted, it defaults to a
75   * node-set with the context node as its only member.
76   * </p>
77   * 
78   * <blockquote> <b>NOTE: </b>The string returned by the <b>namespace-uri</b> function will
79   * be empty except for element nodes and attribute nodes.</blockquote>
80   * 
81   * </blockquote>
82   * 
83   * @author bob mcwhirter (bob @ werken.com)
84   * @see <a href="http://www.w3.org/TR/xpath#function-namespace-uri"
85   *      target="_top">Section 4.1 of the XPath Specification</a>
86   */
87  public class NamespaceUriFunction implements Function
88  {
89  
90      /***
91       * Create a new <code>NamespaceUriFunction</code> object.
92       */
93      public NamespaceUriFunction() {}
94  
95      /***
96       * Returns the namespace URI of the specified node or the namespace URI of the context node if 
97       * no arguments are provided.
98       * 
99       * @param context the context at the point in the
100      *         expression where the function is called
101      * @param args a <code>List</code> containing zero or one items
102      * 
103      * @return a <code>String</code> containing the namespace URI
104      * 
105      * @throws FunctionCallException if <code>args</code> has more than one item
106      */
107     public Object call(Context context,
108                        List args) throws FunctionCallException
109     {
110         if (args.size() == 0)
111         {
112             return evaluate( context.getNodeSet(),
113                              context.getNavigator() );
114         }
115 
116         if ( args.size() == 1 )
117         {
118             return evaluate( args,
119                              context.getNavigator() );
120         }
121 
122         throw new FunctionCallException( "namespace-uri() requires zero or one argument." );
123     }
124 
125     /***
126      * Returns the namespace URI of <code>list.get(0)</code>
127      * 
128      * @param list a list of nodes
129      * @param nav the <code>Navigator</code> used to retrieve the namespace
130      * 
131      * @return the namespace URI of <code>list.get(0)</code>
132      * 
133      * @throws FunctionCallException if <code>list.get(0)</code> is not a node
134      */
135     public static String evaluate(List list,
136                                   Navigator nav) throws FunctionCallException
137     {
138         if ( ! list.isEmpty() )
139         {
140             Object first = list.get(0);
141 
142             if ( first instanceof List )
143             {
144                 return evaluate( (List) first,
145                                  nav );
146             }
147             else if ( nav.isElement( first ) )
148             {
149                 return nav.getElementNamespaceUri( first );
150             }
151             else if ( nav.isAttribute( first ) )
152             {
153                 String uri = nav.getAttributeNamespaceUri( first );
154                 if (uri == null) return "";
155                 return uri;
156             }
157             else if ( nav.isProcessingInstruction( first ) )
158             {
159                 return "";
160             }
161             else if ( nav.isNamespace( first ) )
162             {
163                 return "";
164             }
165             else if ( nav.isDocument( first ) )
166             {
167                 return "";
168             }
169             else if ( nav.isComment( first ) )
170             {
171                 return "";
172             }
173             else if ( nav.isText( first ) )
174             {
175                 return "";
176             }
177             else {
178                 throw new FunctionCallException(
179                   "The argument to the namespace-uri function must be a node-set");   
180             }
181 
182         }
183 
184         return "";
185 
186     }
187 }
188