/*
* $Header: /home/projects/jaxen/scm/jaxen/src/java/main/org/jaxen/VariableContext.java,v 1.10 2006/02/05 21:47:41 elharo Exp $
* $Revision: 1.10 $
* $Date: 2006/02/05 21:47:41 $
*
* ====================================================================
*
* Copyright 2000-2002 bob mcwhirter & James Strachan.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* * Neither the name of the Jaxen Project nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
* IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
* PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
* OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* ====================================================================
* This software consists of voluntary contributions made by many
* individuals on behalf of the Jaxen Project and was originally
* created by bob mcwhirter <bob@werken.com> and
* James Strachan <jstrachan@apache.org>. For more information on the
* Jaxen Project, please see <http://www.jaxen.org/>.
*
* $Id: VariableContext.java,v 1.10 2006/02/05 21:47:41 elharo Exp $
*/
package org.orbeon.jaxen;
/** Resolves variable bindings within an XPath expression.
*
* <p>
* Variables within an XPath expression are denoted using
* notation such as <code>$varName</code> or
* <code>$nsPrefix:varName</code>, and may
* refer to a <code>Boolean</code>, <code>Double</code>, <code>String</code>,
* node-set (<code>List</code>) or individual XML node.
* </p>
*
* <p>
* When a variable is bound to a node-set, the
* actual Java object returned should be a <code>java.util.List</code>
* containing XML nodes from the object-model (e.g. dom4j, JDOM, DOM, etc.)
* being used with the XPath.
* </p>
*
* <p>
* A variable may validly be assigned the <code>null</code> value,
* but an unbound variable (one that this context does not know about)
* should cause an {@link UnresolvableException} to be thrown.
* </p>
*
* @see SimpleVariableContext
* @see NamespaceContext
*
* @author <a href="mailto:bob@werken.com">bob mcwhirter</a>
* @author <a href="mailto:jstrachan@apache.org">James Strachan</a>
*/
public interface VariableContext
{
/** An implementation should return the value of an XPath variable
* based on the namespace URI and local name of the variable-reference
* expression.
*
* <p>
* It must not use the prefix parameter to select a variable,
* because a prefix could be bound to any namespace; the prefix parameter
* could be used in debugging output or other generated information.
* The prefix may otherwise be ignored.
* </p>
*
* @param namespaceURI the namespace URI to which the prefix parameter
* is bound in the XPath expression. If the variable
* reference expression had no prefix, the namespace
* URI is <code>null</code>.
* @param prefix the prefix that was used in the variable reference
* expression; this value is ignored and has no effect
* @param localName the local name of the variable-reference
* expression. If there is no prefix, then this is
* the whole name of the variable.
*
* @return the variable's value (which can be <code>null</code>)
* @throws UnresolvableException when the variable cannot be resolved
*/
public Object getVariableValue( String namespaceURI,
String prefix,
String localName )
throws UnresolvableException;
}