Classes in this File | Line Coverage | Branch Coverage | Complexity | ||||
BooleanFunction |
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1 | /* | |
2 | * $Header: /home/projects/jaxen/scm/jaxen/src/java/main/org/jaxen/function/BooleanFunction.java,v 1.17 2006/02/05 21:47:41 elharo Exp $ | |
3 | * $Revision: 1.17 $ | |
4 | * $Date: 2006/02/05 21:47:41 $ | |
5 | * | |
6 | * ==================================================================== | |
7 | * | |
8 | * Copyright 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 are | |
13 | * met: | |
14 | * | |
15 | * * Redistributions of source code must retain the above copyright | |
16 | * notice, this list of conditions and the following disclaimer. | |
17 | * | |
18 | * * Redistributions in binary form must reproduce the above copyright | |
19 | * notice, this list of conditions and the following disclaimer in the | |
20 | * documentation and/or other materials provided with the distribution. | |
21 | * | |
22 | * * Neither the name of the Jaxen Project nor the names of its | |
23 | * contributors may be used to endorse or promote products derived | |
24 | * from this software without specific prior written permission. | |
25 | * | |
26 | * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS | |
27 | * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED | |
28 | * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A | |
29 | * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER | |
30 | * OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, | |
31 | * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, | |
32 | * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR | |
33 | * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF | |
34 | * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING | |
35 | * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS | |
36 | * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | |
37 | * | |
38 | * ==================================================================== | |
39 | * This software consists of voluntary contributions made by many | |
40 | * individuals on behalf of the Jaxen Project and was originally | |
41 | * created by bob mcwhirter <bob@werken.com> and | |
42 | * James Strachan <jstrachan@apache.org>. For more information on the | |
43 | * Jaxen Project, please see <http://www.jaxen.org/>. | |
44 | * | |
45 | * $Id: BooleanFunction.java,v 1.17 2006/02/05 21:47:41 elharo Exp $ | |
46 | */ | |
47 | ||
48 | ||
49 | package org.jaxen.function; | |
50 | ||
51 | import java.util.List; | |
52 | ||
53 | import org.jaxen.Context; | |
54 | import org.jaxen.Function; | |
55 | import org.jaxen.FunctionCallException; | |
56 | import org.jaxen.Navigator; | |
57 | ||
58 | /** | |
59 | * <p> | |
60 | * <b>4.3</b> <code><i>boolean</i> boolean(<i>object</i>)</code> | |
61 | * </p> | |
62 | * | |
63 | * <blockquote | |
64 | * src="http://www.w3.org/TR/xpath#section-Boolean-Functions"> | |
65 | * <p> | |
66 | * The <b><a href="http://www.w3.org/TR/xpath#function-boolean" target="_top">boolean</a></b> | |
67 | * function converts its argument to a boolean as follows: | |
68 | * </p> | |
69 | * | |
70 | * <ul> | |
71 | * | |
72 | * <li> | |
73 | * <p> | |
74 | * a number is true if and only if it is neither positive or negative | |
75 | * zero nor NaN | |
76 | * </p> | |
77 | * </li> | |
78 | * | |
79 | * <li> | |
80 | * <p> | |
81 | * a node-set is true if and only if it is non-empty | |
82 | * </p> | |
83 | * </li> | |
84 | * | |
85 | * <li> | |
86 | * <p> | |
87 | * a string is true if and only if its length is non-zero | |
88 | * </p> | |
89 | * </li> | |
90 | * | |
91 | * <li> | |
92 | * | |
93 | * <p> | |
94 | * an object of a type other than the four basic types is converted to a | |
95 | * boolean in a way that is dependent on that type | |
96 | * </p></li></ul> | |
97 | * </blockquote> | |
98 | * | |
99 | * @author bob mcwhirter (bob @ werken.com) | |
100 | * @see <a href="http://www.w3.org/TR/xpath#function-boolean">Section 4.3 of the XPath Specification</a> | |
101 | */ | |
102 | public class BooleanFunction implements Function | |
103 | { | |
104 | ||
105 | ||
106 | /** | |
107 | * Create a new <code>BooleanFunction</code> object. | |
108 | */ | |
109 | 106 | public BooleanFunction() {} |
110 | ||
111 | /** Convert the argument to a <code>Boolean</code> | |
112 | * | |
113 | * @param context the context at the point in the | |
114 | * expression when the function is called | |
115 | * @param args a list with exactly one item which will be converted to a | |
116 | * <code>Boolean</code> | |
117 | * | |
118 | * @return the result of evaluating the function; | |
119 | * <code>Boolean.TRUE</code> or <code>Boolean.FALSE</code> | |
120 | * | |
121 | * @throws FunctionCallException if <code>args</code> has more or less than one item | |
122 | */ | |
123 | public Object call(Context context, | |
124 | List args) throws FunctionCallException | |
125 | { | |
126 | 16 | if ( args.size() == 1 ) |
127 | { | |
128 | 12 | return evaluate( args.get(0), context.getNavigator() ); |
129 | } | |
130 | ||
131 | 4 | throw new FunctionCallException("boolean() requires one argument"); |
132 | } | |
133 | ||
134 | /** | |
135 | * <p>Convert the argument <code>obj</code> to a <code>Boolean</code> | |
136 | * according to the following rules:</p> | |
137 | * | |
138 | * <ul> | |
139 | * <li>Lists are false if they're empty; true if they're not.</li> | |
140 | * <li>Booleans are false if they're false; true if they're true.</li> | |
141 | * <li>Strings are false if they're empty; true if they're not.</li> | |
142 | * <li>Numbers are false if they're 0 or NaN; true if they're not.</li> | |
143 | * <li>All other objects are true.</li> | |
144 | * </ul> | |
145 | * | |
146 | * @param obj the object to convert to a boolean | |
147 | * @param nav ignored | |
148 | * | |
149 | * @return <code>Boolean.TRUE</code> or <code>Boolean.FALSE</code> | |
150 | */ | |
151 | public static Boolean evaluate(Object obj, Navigator nav) | |
152 | { | |
153 | 7218 | if ( obj instanceof List ) |
154 | { | |
155 | 434 | List list = (List) obj; |
156 | ||
157 | // if it's an empty list, then we have a null node-set -> false | |
158 | 434 | if (list.size() == 0) |
159 | { | |
160 | 6 | return Boolean.FALSE; |
161 | } | |
162 | ||
163 | // otherwise, unwrap the list and check the primitive | |
164 | 428 | obj = list.get(0); |
165 | } | |
166 | ||
167 | // now check for primitive types | |
168 | // otherwise a non-empty node-set is true | |
169 | ||
170 | // if it's a Boolean, let it decide | |
171 | 7212 | if ( obj instanceof Boolean ) |
172 | { | |
173 | 6692 | return (Boolean) obj; |
174 | } | |
175 | // if it's a Number, != 0 -> true | |
176 | 520 | else if ( obj instanceof Number ) |
177 | { | |
178 | 90 | double d = ((Number) obj).doubleValue(); |
179 | 90 | if ( d == 0 || Double.isNaN(d) ) |
180 | { | |
181 | 16 | return Boolean.FALSE; |
182 | } | |
183 | 74 | return Boolean.TRUE; |
184 | } | |
185 | // if it's a String, "" -> false | |
186 | 430 | else if ( obj instanceof String ) |
187 | { | |
188 | 8 | return ( ((String)obj).length() > 0 |
189 | ? Boolean.TRUE | |
190 | : Boolean.FALSE ); | |
191 | } | |
192 | else | |
193 | { | |
194 | // assume it's a node so that this node-set is non-empty | |
195 | // and so it's true | |
196 | 422 | return ( obj != null ) ? Boolean.TRUE : Boolean.FALSE; |
197 | } | |
198 | ||
199 | } | |
200 | } |