LangFunction


1   /*
2    * $Header: /home/projects/jaxen/scm/jaxen/src/java/main/org/jaxen/function/LangFunction.java,v 1.11 2005/06/26 16:07:23 elharo Exp $
3    * $Revision: 1.11 $
4    * $Date: 2005/06/26 16:07:23 $
5    *
6    * ====================================================================
7    *
8    * Copyright (C) 2000-2002 bob mcwhirter & James Strachan.
9    * All rights reserved.
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12   * modification, are permitted provided that the following conditions
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20   *    these conditions in the documentation and/or other materials 
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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
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29   *    from the Jaxen Project Management (pm@jaxen.org).
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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: LangFunction.java,v 1.11 2005/06/26 16:07:23 elharo Exp $
60   */
61  
62  
63  package org.jaxen.function;
64  
65  import java.util.Iterator  ;
66  import java.util.List  ;
67  
68  import org.jaxen.Context;
69  import org.jaxen.Function;
70  import org.jaxen.FunctionCallException;
71  import org.jaxen.Navigator;
72  import org.jaxen.UnsupportedAxisException;
73  
74  /**
75   * <p>
76   * <b>4.3</b> <code><i>boolean</i> lang(<i>string</i>)</code>
77   * </p>
78   * 
79   * <blockquote SRC="http://www.w3.org/TR/xpath#function-lang">
80   * <p>
81   * The <b>lang</b> function returns true or false depending on whether
82   * the language of the context node as specified by
83   * <code>xml:lang</code> attributes is the same as or is a sublanguage
84   * of the language specified by the argument string. The language of the
85   * context node is determined by the value of the <code>xml:lang</code>
86   * 
87   * attribute on the context node, or, if the context node has no
88   * <code>xml:lang</code> attribute, by the value of the
89   * <code>xml:lang</code> attribute on the nearest ancestor of the
90   * context node that has an <code>xml:lang</code> attribute. If there
91   * is no such attribute, then <b><a HREF="#function-lang">lang</a></b>
92   * returns false. If there is such an attribute, then <b><a
93   * HREF="#function-lang">lang</a></b> returns true if the attribute
94   * value is equal to the argument ignoring case, or if there is some
95   * suffix starting with <code>-</code> such that the attribute value
96   * is equal to the argument ignoring that suffix of the attribute value
97   * and ignoring case. For example, <code>lang("en")</code> would
98   * return true if the context node is any of these five elements:
99   * </p>
100  * 
101  * <pre>
102  *  &lt;para xml:lang=&quot;en&quot;/&gt;
103  *  &lt;div xml:lang=&quot;en&quot;&gt;&lt;para/&gt;&lt;/div&gt;
104  *  &lt;para xml:lang=&quot;EN&quot;/&gt;
105  *  &lt;para xml:lang=&quot;en-us&quot;/&gt;
106  * </pre>
107  * 
108  * </blockquote>
109  * 
110  * @author Attila Szegedi (szegedia @ freemail.hu)
111  * @see <a HREF="http://www.w3.org/TR/xpath#function-lang"
112  *      target="_top">XPath Specification</a>
113  */
114 public class LangFunction implements Function
115 {
116     private static final String   LANG_LOCALNAME = "lang";
117     private static final String   XMLNS_URI = 
118         "http://www.w3.org/XML/1998/namespace";
119     
120 
121     /**
122      * Create a new <code>LangFunction</code> object.
123      */
124     public LangFunction() {}
125     
126     
127     /**
128      * <p>
129      * Determines whether or not the context node is written in the language specified
130      * by the XPath string-value of <code>args.get(0)</code>,
131      * as determined by the nearest <code>xml:lang</code> attribute in scope. 
132      * </p>
133      * 
134      * @param context the context in which to evaluate the <code>lang()</code> function
135      * @param args the arguments to the lang function
136      * @return a <code>Boolean</code> indicating whether the context node is written in
137      *     the specified language
138      * @throws FunctionCallException if <code>args</code> does not have length one
139      * 
140      */
141     public Object   call(Context context,
142                        List   args) throws FunctionCallException
143     {
144         if (args.size() != 1) {
145             throw new FunctionCallException("lang() requires exactly one argument.");   
146         }
147         
148         Object   arg = args.get(0);
149             
150         try {
151             return evaluate(context.getNodeSet(), arg, context.getNavigator() );
152         }
153         catch(UnsupportedAxisException e) {
154             throw new FunctionCallException("Can't evaluate lang()", 
155                                                  e);
156         }
157        
158     }
159 
160     private static Boolean   evaluate(List   contextNodes, Object   lang, Navigator nav)
161       throws UnsupportedAxisException
162     {
163         return evaluate(contextNodes.get(0), 
164             StringFunction.evaluate(lang, nav), nav)
165             ? Boolean.TRUE : Boolean.FALSE;
166     }
167 
168     private static boolean evaluate(Object   node, String   lang, Navigator nav)
169       throws UnsupportedAxisException
170     {
171         
172         Object   element = node;
173         if (! nav.isElement(element)) {
174             element = nav.getParentNode(node);
175         }
176         while (element != null && nav.isElement(element)) 
177         {
178             Iterator   attrs = nav.getAttributeAxisIterator(element);
179             while(attrs.hasNext())
180             {
181                 Object   attr = attrs.next();
182                 if(LANG_LOCALNAME.equals(nav.getAttributeName(attr)) && 
183                    XMLNS_URI.equals(nav.getAttributeNamespaceUri(attr)))
184                 {
185                     return 
186                         isSublang(nav.getAttributeStringValue(attr), lang);
187                 }
188             }
189             element = nav.getParentNode(element);
190         }
191         return false;
192     }
193     
194     private static boolean isSublang(String   sublang, String   lang)
195     {
196         if(sublang.equalsIgnoreCase(lang))
197         {
198             return true;
199         }
200         int ll = lang.length();
201         return 
202             sublang.length() > ll && 
203             sublang.charAt(ll) == '-' && 
204             sublang.substring(0, ll).equalsIgnoreCase(lang);
205     }
206     
207 }
208 
209
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