StartsWithFunction


1   /*
2    * $Header: /home/projects/jaxen/scm/jaxen/src/java/main/org/jaxen/function/StartsWithFunction.java,v 1.8 2005/06/26 16:07:23 elharo Exp $
3    * $Revision: 1.8 $
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
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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).
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31   * In addition, we request (but do not require) that you include in the 
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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 
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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
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43   * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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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: StartsWithFunction.java,v 1.8 2005/06/26 16:07:23 elharo Exp $
60   */
61  
62  
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><b>4.2</b> <code><i>boolean</i> starts-with(<i>string</i>,<i>string</i>)</code> 
74   * 
75   * 
76   * <blockquote SRC="http://www.w3.org/TR/xpath">
77   * The <b>starts-with</b> function returns true if the first argument string starts 
78   * with the second argument string, and otherwise returns false.
79   * </blockquote>
80   * 
81   * @author bob mcwhirter (bob @ werken.com)
82   * @see <a HREF="http://www.w3.org/TR/xpath#function-starts-with" target="_top">Section 4.2 of the XPath Specification</a>
83   */
84  public class StartsWithFunction implements Function
85  {
86      
87      /**
88       * Create a new <code>StartsWithFunction</code> object.
89       */
90      public StartsWithFunction() {}
91      
92      /** 
93       * Returns true if the string-value of the first item in <code>args</code>
94       * starts with the string-value of the second item in <code>args</code>. 
95       * Otherwise it returns false.
96       *
97       * @param context the context at the point in the
98       *         expression when the function is called
99       * @param args a list that contains two items
100      * 
101      * @return <code>Boolean.TRUE</code> if the first item in <code>args</code>
102      *     starts with the string-value of the second item in <code>args</code>;
103      *     otherwise <code>Boolean.FALSE</code>
104      * 
105      * @throws FunctionCallException if <code>args</code> does not have length two
106      */
107     public Object   call(Context context,
108                        List   args) throws FunctionCallException
109     {
110         if (args.size() == 2)
111         {
112             return evaluate( args.get(0),
113                              args.get(1),
114                              context.getNavigator() );
115         }
116 
117         throw new FunctionCallException( "starts-with() requires two arguments." );
118     }
119 
120     /** 
121      * Returns true if the string-value of <code>strArg</code>
122      * starts with the string-value of <code>matchArg</code>. 
123      * Otherwise it returns false.
124      * 
125      * @param strArg the object whose string-value searched for the prefix
126      * @param matchArg the object whose string-value becomes the prefix string to compare against
127      * @param nav the navigator used to calculate the string-values of the arguments
128      * 
129      * @return <code>Boolean.TRUE</code> if the string-value of <code>strArg</code>
130      *     starts with the string-value of <code>matchArg</code>;
131      *     otherwise <code>Boolean.FALSE</code>
132      * 
133      */
134     public static Boolean   evaluate(Object   strArg,
135                                    Object   matchArg,
136                                    Navigator nav)
137     {
138         String   str   = StringFunction.evaluate( strArg,
139                                                 nav );
140 
141         String   match = StringFunction.evaluate( matchArg,
142                                                 nav );
143 
144         return ( str.startsWith(match)
145                  ? Boolean.TRUE
146                  : Boolean.FALSE
147                  );
148     }
149      
150 }
151
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