1/*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements.  See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License.  You may obtain a copy of the License at
8 *
9 *     http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17// $Id: XPathFunctionResolver.java 446598 2006-09-15 12:55:40Z jeremias $
18
19package javax.xml.xpath;
20
21import javax.xml.namespace.QName;
22
23/**
24 * <p><code>XPathFunctionResolver</code> provides access to the set of user defined <code>XPathFunction</code>s.</p>
25 *
26 * <p>XPath functions are resolved by name and arity.
27 * The resolver is not needed for XPath built-in functions and the resolver
28 * <strong><em>cannot</em></strong> be used to override those functions.</p>
29 *
30 * <p>In particular, the resolver is only called for functions in an another
31 * namespace (functions with an explicit prefix). This means that you cannot
32 * use the <code>XPathFunctionResolver</code> to implement specifications
33 * like <a href="http://www.w3.org/TR/xmldsig-core/">XML-Signature Syntax
34 * and Processing</a> which extend the function library of XPath 1.0 in the
35 * same namespace. This is a consequence of the design of the resolver.</p>
36 *
37 * <p>If you wish to implement additional built-in functions, you will have to
38 * extend the underlying implementation directly.</p>
39 *
40 * @author  <a href="mailto:Norman.Walsh@Sun.com">Norman Walsh</a>
41 * @author  <a href="mailto:Jeff.Suttor@Sun.com">Jeff Suttor</a>
42 * @version $Revision: 446598 $, $Date: 2006-09-15 05:55:40 -0700 (Fri, 15 Sep 2006) $
43 * @see <a href="http://www.w3.org/TR/xpath#corelib">XML Path Language (XPath) Version 1.0, Core Function Library</a>
44 * @since 1.5
45 */
46public interface XPathFunctionResolver {
47  /**
48   * <p>Find a function in the set of available functions.</p>
49   *
50   * <p>If <code>functionName</code> or <code>arity</code> is <code>null</code>, then a <code>NullPointerException</code> is thrown.</p>
51   *
52   * @param functionName The function name.
53   * @param arity The number of arguments that the returned function must accept.
54   *
55   * @return The function or <code>null</code> if no function named <code>functionName</code> with <code>arity</code> arguments exists.
56   *
57   * @throws NullPointerException If <code>functionName</code> or <code>arity</code> is <code>null</code>.
58   */
59  public XPathFunction resolveFunction(QName functionName, int arity);
60}
61