1 /*
2 * $Header: /home/projects/jaxen/scm/jaxen/src/java/main/org/jaxen/function/CountFunction.java,v 1.14 2006/02/05 21:47:41 elharo Exp $
3 * $Revision: 1.14 $
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: CountFunction.java,v 1.14 2006/02/05 21:47:41 elharo Exp $
46 */
47
48 package org.jaxen.function;
49
50 import java.util.List;
51
52 import org.jaxen.Context;
53 import org.jaxen.Function;
54 import org.jaxen.FunctionCallException;
55
56 /***
57 * <p><b>4.1</b> <code><i>number</i> count(<i>node-set</i>)</code></p>
58 *
59 * <blockquote src="http://www.w3.org/TR/xpath#function-count">
60 * The <b>count</b> function returns the number of nodes in the argument node-set.
61 * </blockquote>
62 * @author bob mcwhirter (bob @ werken.com)
63 * @see <a href="http://www.w3.org/TR/xpath#function-count">Section 4.1 of the XPath Specification</a>
64 */
65 public class CountFunction implements Function
66 {
67
68 /***
69 * Create a new <code>CountFunction</code> object.
70 */
71 public CountFunction() {}
72
73 /***
74 * <p>
75 * Returns the number of nodes in the specified node-set.
76 * </p>
77 * @param context ignored
78 * @param args the function arguments
79 *
80 * @return a <code>Double</code> giving the integral number of items in the first argument
81 *
82 * @throws FunctionCallException if args does not have exactly one
83 * item; or that item is not a <code>List</code>
84 */
85 public Object call(Context context,
86 List args) throws FunctionCallException
87 {
88 if (args.size() == 1)
89 {
90 return evaluate( args.get(0) );
91 }
92
93 throw new FunctionCallException( "count() requires one argument." );
94 }
95
96 /***
97 * <p>
98 * Returns the number of nodes in the specified node-set.
99 * </p>
100 *
101 * @param obj a <code>List</code> of nodes
102 * @return the integral number of items in the list
103 * @throws FunctionCallException if obj is not a <code>List</code>
104 */
105 public static Double evaluate(Object obj) throws FunctionCallException
106 {
107
108 if (obj instanceof List)
109 {
110 return new Double( ((List) obj).size() );
111 }
112
113 throw new FunctionCallException("count() function can only be used for node-sets");
114
115 }
116
117 }