1 /*
2 * $Header: /home/projects/jaxen/scm/jaxen/src/java/main/org/jaxen/function/NotFunction.java,v 1.7 2005/06/26 16:07:22 elharo Exp $
3 * $Revision: 1.7 $
4 * $Date: 2005/06/26 16:07:22 $
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
16 * notice, this list of conditions, and the following disclaimer.
17 *
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).
30 *
31 * In addition, we request (but do not require) that you include in the
32 * end-user documentation provided with the redistribution and/or in the
33 * software itself an acknowledgement equivalent to the following:
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
37 * available at http://www.jaxen.org/
38 *
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
42 * DISCLAIMED. IN NO EVENT SHALL THE Jaxen AUTHORS OR THE PROJECT
43 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
44 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
45 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
46 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
47 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
48 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
49 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
50 * SUCH DAMAGE.
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: NotFunction.java,v 1.7 2005/06/26 16:07:22 elharo Exp $
60 */
61
62 package org.jaxen.function;
63
64 import java.util.List;
65
66 import org.jaxen.Context;
67 import org.jaxen.Function;
68 import org.jaxen.FunctionCallException;
69 import org.jaxen.Navigator;
70
71 /***
72 * <p><b>4.3</b> <code><i>boolean</i> not(<i>boolean</i>)</code> </p>
73 *
74 *
75 * <blockquote src="http://www.w3.org/TR/xpath#function-not">
76 * The <b>not</b> function returns true if its argument is false, and false otherwise.
77 * </blockquote>
78 *
79 * @author bob mcwhirter (bob @ werken.com)
80 * @see <a href="http://www.w3.org/TR/xpath#function-not" target="_top">Section 4.3 of the XPath Specification</a>
81 */
82 public class NotFunction implements Function
83 {
84
85 /***
86 * Create a new <code>NotFunction</code> object.
87 */
88 public NotFunction() {}
89
90 /***
91 * Returns <code>Boolean.TRUE</code> if the boolean value of
92 * <code>args.get(0)</code> is false, and <code>Boolean.FALSE</code> otherwise.
93 * The boolean value is calculated as if by the XPath <code>boolean</code>
94 * function.
95 *
96 * @param context the context at the point in the
97 * expression where the function is called
98 * @param args a single element list
99 *
100 * @return <code>Boolean.TRUE</code> if the boolean value of
101 * <code>obj</code> is false, and <code>Boolean.FALSE</code> otherwise
102 *
103 * @throws FunctionCallException if <code>args</code> does not have exactly one argument
104 */
105 public Object call(Context context,
106 List args) throws FunctionCallException
107 {
108 if (args.size() == 1)
109 {
110 return evaluate( args.get(0), context.getNavigator() );
111 }
112
113 throw new FunctionCallException( "not() requires one argument." );
114 }
115
116 /***
117 * Returns <code>Boolean.TRUE</code> if the boolean value of
118 * <code>obj</code> is false, and <code>Boolean.FALSE</code> otherwise.
119 * The boolean value is calculated as if by the XPath <code>boolean</code>
120 * function.
121 *
122 * @param obj the object whose boolean value is inverted
123 * @param nav the <code>Navigator</code> used to calculate the boolean value of <code>obj</code>
124 *
125 * @return <code>Boolean.TRUE</code> if the boolean value of
126 * <code>obj</code> is false, and <code>Boolean.FALSE</code> otherwise
127 */
128 public static Boolean evaluate(Object obj, Navigator nav)
129 {
130 return ( ( BooleanFunction.evaluate( obj, nav ).booleanValue() )
131 ? Boolean.FALSE
132 : Boolean.TRUE
133 );
134 }
135
136 }