1 /*
2 * $Header: /home/projects/jaxen/scm/jaxen/src/java/main/org/jaxen/function/CountFunction.java,v 1.13 2005/06/28 13:44:45 elharo Exp $
3 * $Revision: 1.13 $
4 * $Date: 2005/06/28 13:44:45 $
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: CountFunction.java,v 1.13 2005/06/28 13:44:45 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
70 /***
71 * <p><b>4.1</b> <code><i>number</i> count(<i>node-set</i>)</code></p>
72 *
73 * <blockquote src="http://www.w3.org/TR/xpath#function-count">
74 * The <b>count</b> function returns the number of nodes in the argument node-set.
75 * </blockquote>
76 * @author bob mcwhirter (bob @ werken.com)
77 * @see <a href="http://www.w3.org/TR/xpath#function-count">Section 4.1 of the XPath Specification</a>
78 */
79 public class CountFunction implements Function
80 {
81
82 /***
83 * Create a new <code>CountFunction</code> object.
84 */
85 public CountFunction() {}
86
87 /***
88 * <p>
89 * Returns the number of nodes in the specified node-set.
90 * </p>
91 * @param context ignored
92 * @param args the function arguments
93 *
94 * @return a <code>Double</code> giving the integral number of items in the first argument
95 *
96 * @throws FunctionCallException if args does not have exactly one
97 * item; or that item is not a <code>List</code>
98 */
99 public Object call(Context context,
100 List args) throws FunctionCallException
101 {
102 if (args.size() == 1)
103 {
104 return evaluate( args.get(0) );
105 }
106
107 throw new FunctionCallException( "count() requires one argument." );
108 }
109
110 /***
111 * <p>
112 * Returns the number of nodes in the specified node-set.
113 * </p>
114 *
115 * @param obj a <code>List</code> of nodes
116 * @return the integral number of items in the list
117 * @throws FunctionCallException if obj is not a <code>List</code>
118 */
119 public static Double evaluate(Object obj) throws FunctionCallException
120 {
121
122 if (obj instanceof List)
123 {
124 return new Double( ((List) obj).size() );
125 }
126
127 throw new FunctionCallException("count() function can only be used for node-sets");
128
129 }
130
131 }