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63 package org.jaxen.function;
64
65 import java.util.List;
66
67 import org.jaxen.Context;
68 import org.jaxen.Function;
69 import org.jaxen.FunctionCallException;
70 import org.jaxen.Navigator;
71
72 /***
73 * <p>
74 * <b>4.1</b>
75 * <code><i>string</i> namespace-uri(<i>node-set?</i>)</code>
76 * </p>
77 *
78 * <blockquote src="http://www.w3.org/TR/xpath">
79 * <p>
80 * The <b>namespace-uri</b>
81 * function returns the namespace URI of the <a
82 * href="http://www.w3.org/TR/xpath#dt-expanded-name" target="_top">expanded-name</a> of the node in the
83 * argument node-set that is first in <a
84 * href="http://www.w3.org/TR/xpath#dt-document-order" target="_top">document order</a>. If the argument
85 * node-set is empty, the first node has no <a
86 * href="http://www.w3.org/TR/xpath#dt-expanded-name" target="_top">expanded-name</a>, or the namespace URI of
87 * the <a href="http://www.w3.org/TR/xpath#dt-expanded-name" target="_top">expanded-name</a> is null, an empty
88 * string is returned. If the argument is omitted, it defaults to a
89 * node-set with the context node as its only member.
90 * </p>
91 *
92 * <blockquote> <b>NOTE: </b>The string returned by the <b>namespace-uri</b> function will
93 * be empty except for element nodes and attribute nodes.</blockquote>
94 *
95 * </blockquote>
96 *
97 * @author bob mcwhirter (bob @ werken.com)
98 * @see <a href="http://www.w3.org/TR/xpath#function-namespace-uri"
99 * target="_top">Section 4.1 of the XPath Specification</a>
100 */
101 public class NamespaceUriFunction implements Function
102 {
103
104 /***
105 * Create a new <code>NamespaceUriFunction</code> object.
106 */
107 public NamespaceUriFunction() {}
108
109 /***
110 * Returns the namespace URI of the specified node or the namespace URI of the context node if
111 * no arguments are provided.
112 *
113 * @param context the context at the point in the
114 * expression where the function is called
115 * @param args a <code>List</code> containing zero or one items
116 *
117 * @return a <code>String</code> containing the namespace URI
118 *
119 * @throws FunctionCallException if <code>args</code> has more than one item
120 */
121 public Object call(Context context,
122 List args) throws FunctionCallException
123 {
124 if (args.size() == 0)
125 {
126 return evaluate( context.getNodeSet(),
127 context.getNavigator() );
128 }
129
130 if ( args.size() == 1 )
131 {
132 return evaluate( args,
133 context.getNavigator() );
134 }
135
136 throw new FunctionCallException( "namespace-uri() requires zero or one argument." );
137 }
138
139 /***
140 * Returns the namespace URI of <code>list.get(0)</code>
141 *
142 * @param list a list of nodes
143 * @param nav the <code>Navigator</code> used to retrieve the namespace
144 *
145 * @return the namespace URI of <code>list.get(0)</code>
146 *
147 * @throws FunctionCallException if <code>list.get(0)</code> is not a node
148 */
149 public static String evaluate(List list,
150 Navigator nav) throws FunctionCallException
151 {
152 if ( ! list.isEmpty() )
153 {
154 Object first = list.get(0);
155
156 if ( first instanceof List )
157 {
158 return evaluate( (List) first,
159 nav );
160 }
161 else if ( nav.isElement( first ) )
162 {
163 return nav.getElementNamespaceUri( first );
164 }
165 else if ( nav.isAttribute( first ) )
166 {
167 String uri = nav.getAttributeNamespaceUri( first );
168 if (uri == null) return "";
169 return uri;
170 }
171 else if ( nav.isProcessingInstruction( first ) )
172 {
173 return "";
174 }
175 else if ( nav.isNamespace( first ) )
176 {
177 return "";
178 }
179 else if ( nav.isDocument( first ) )
180 {
181 return "";
182 }
183 else if ( nav.isComment( first ) )
184 {
185 return "";
186 }
187 else if ( nav.isText( first ) )
188 {
189 return "";
190 }
191 else {
192 throw new FunctionCallException(
193 "The argument to the namespace-uri function must be a node-set");
194 }
195
196 }
197
198 return "";
199
200 }
201 }
202