1 /*
2 * $Header: /home/projects/jaxen/scm/jaxen/src/java/main/org/jaxen/function/BooleanFunction.java,v 1.10 2005/01/14 02:52:17 elharo Exp $
3 * $Revision: 1.10 $
4 * $Date: 2005/01/14 02:52:17 $
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: BooleanFunction.java,v 1.10 2005/01/14 02:52:17 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>4.3</b> <code><i>boolean</i> boolean(<i>object</i>)</code>
74 *
75 * @author bob mcwhirter (bob @ werken.com)
76 */
77 public class BooleanFunction implements Function
78 {
79
80 public Object call(Context context,
81 List args) throws FunctionCallException
82 {
83 if ( args.size() == 1 )
84 {
85 return evaluate( args.get(0), context.getNavigator() );
86 }
87
88 throw new FunctionCallException("boolean() requires one argument");
89 }
90
91 public static Boolean evaluate(Object obj, Navigator nav)
92 {
93 if ( obj instanceof List )
94 {
95 List list = (List) obj;
96
97 // if it's an empty list, then we have a null node-set -> false
98 if (list.size() == 0)
99 {
100 return Boolean.FALSE;
101 }
102
103 // otherwise, unwrap the list and check the primitive
104 obj = list.get(0);
105 }
106
107 // now check for primitive types
108 // otherwise a non-empty node-set is true
109
110 // if it's a Boolean, let it decide
111 if ( obj instanceof Boolean )
112 {
113 return (Boolean) obj;
114 }
115 // if it's a Number, != 0 -> true
116 else if ( obj instanceof Number )
117 {
118 double d = ((Number) obj).doubleValue();
119 if ( d == 0 || Double.isNaN(d) )
120 {
121 return Boolean.FALSE;
122 }
123 return Boolean.TRUE;
124 }
125 // if it's a String, "" -> false
126 else if ( obj instanceof String )
127 {
128 return ( ((String)obj).length() > 0
129 ? Boolean.TRUE
130 : Boolean.FALSE );
131 }
132 else
133 {
134 // assume it's a node so that this node-set is non-empty
135 // and so it's true
136 return ( obj != null ) ? Boolean.TRUE : Boolean.FALSE;
137 }
138
139 }
140 }