1 /*
2 * $Header$
3 * $Revision$
4 * $Date$
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 * $Id$
46 */
47
48
49 package org.jaxen;
50
51 import java.util.List;
52
53 /** Interface for the extensible function framework.
54 *
55 * <p>
56 * <strong>NOTE:</strong> This class is not typically used directly,
57 * but is exposed for writers of extended XPath packages.
58 * </p>
59 *
60 * <p>
61 * Implementations of <code>Function</code> are functors
62 * which are used to evaluate a function-call within an
63 * XPath expression.
64 * </p>
65 *
66 * @see FunctionContext
67 *
68 * @author <a href="mailto:bob@werken.com">bob mcwhirter</a>
69 */
70 public interface Function
71 {
72 /** Evaluate this function.
73 *
74 * @param context the context at the point in the
75 * expression when the function is called
76 * @param args arguments provided to the function
77 *
78 * @return the result of evaluating the function; a <code>List</code>
79 * (node-set), <code>Double</code>, <code>Boolean</code>, or
80 * <code>String</code>
81 *
82 * @throws FunctionCallException if an XPath error occurs during evaluation;
83 * for instance, if the number or type of the arguments is incorrect
84 */
85 Object call(Context context,
86 List args) throws FunctionCallException;
87 }