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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