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1 /*
2  * $Header: /home/projects/jaxen/scm/jaxen/src/java/main/org/jaxen/VariableContext.java,v 1.7 2005/05/05 14:04:19 elharo Exp $
3  * $Revision: 1.7 $
4  * $Date: 2005/05/05 14:04:19 $
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 1.7 2005/05/05 14:04:19 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
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 JavaDoc getVariableValue( String JavaDoc namespaceURI,
121                                     String JavaDoc prefix,
122                                     String JavaDoc localName )
123         throws UnresolvableException;
124 }
125
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