1 /*
2 * $Header: /home/projects/jaxen/scm/jaxen/src/java/main/org/jaxen/VariableContext.java,v 1.9 2005/09/25 11:40:36 elharo Exp $
3 * $Revision: 1.9 $
4 * $Date: 2005/09/25 11:40:36 $
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: VariableContext.java,v 1.9 2005/09/25 11:40:36 elharo Exp $
60 */
61
62
63 package org.jaxen;
64
65 /*** Resolves variable bindings within an XPath expression.
66 *
67 * <p>
68 * Variables within an XPath expression are denoted using
69 * notation such as <code>$varName</code> or
70 * <code>$nsPrefix:varName</code>, and may
71 * refer to a <code>Boolean</code>, <code>Double</code>, <code>String</code>,
72 * node-set (<code>List</code>) or individual XML node.
73 * </p>
74 *
75 * <p>
76 * When a variable is bound to a node-set, the
77 * actual Java object returned should be a <code>java.util.List</code>
78 * containing XML nodes from the object-model (e.g. dom4j, JDOM, DOM, etc.)
79 * being used with the XPath.
80 * </p>
81 *
82 * <p>
83 * A variable may validly be assigned the <code>null</code> value,
84 * but an unbound variable (one that this context does not know about)
85 * should cause an {@link UnresolvableException} to be thrown.
86 * </p>
87 *
88 * @see SimpleVariableContext
89 * @see NamespaceContext
90 *
91 * @author <a href="mailto:bob@werken.com">bob mcwhirter</a>
92 * @author <a href="mailto:jstrachan@apache.org">James Strachan</a>
93 */
94 public interface VariableContext
95 {
96 /*** An implementation should return the value of an XPath variable
97 * based on the namespace URI and local name of the variable-reference
98 * expression.
99 *
100 * <p>
101 * It must not use the prefix parameter to select a variable,
102 * because a prefix could be bound to any namespace; the prefix parameter
103 * could be used in debugging output or other generated information.
104 * The prefix may otherwise be ignored.
105 * </p>
106 *
107 * @param namespaceURI the namespace URI to which the prefix parameter
108 * is bound in the XPath expression. If the variable
109 * reference expression had no prefix, the namespace
110 * URI is <code>null</code>.
111 * @param prefix the prefix that was used in the variable reference
112 * expression; this value is ignored and has no effect
113 * @param localName the local name of the variable-reference
114 * expression. If there is no prefix, then this is
115 * the whole name of the variable.
116 *
117 * @return the variable's value (which can be <code>null</code>)
118 * @throws UnresolvableException when the variable cannot be resolved
119 */
120 public Object getVariableValue( String namespaceURI,
121 String prefix,
122 String localName )
123 throws UnresolvableException;
124 }