src/java/org/apache/commons/jxpath/ExpressionContext.java

/*
 * $Header: /home/jerenkrantz/tmp/commons/commons-convert/cvs/home/cvs/jakarta-commons//jxpath/src/java/org/apache/commons/jxpath/ExpressionContext.java,v 1.4 2002/04/24 04:05:41 dmitri Exp $
 * $Revision: 1.4 $
 * $Date: 2002/04/24 04:05:41 $
 *
 * ====================================================================
 * The Apache Software License, Version 1.1
 *
 *
 * Copyright (c) 1999-2001 The Apache Software Foundation.  All rights
 * reserved.
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 * modification, are permitted provided that the following conditions
 * are met:
 *
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 *    notice, this list of conditions and the following disclaimer.
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 *    any, must include the following acknowlegement:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowlegement may appear in the software itself,
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 * This software consists of voluntary contributions made by many
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 * originally based on software copyright (c) 2001, Plotnix, Inc,
 * <http://www.plotnix.com/>.
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package org.apache.commons.jxpath;

import java.util.List;

/**
 * If an extenstion function has an argument of type ExpressionContext,
 * it can gain access to the current node of an XPath expression context.
 * <p>
 * Example:
 * <blockquote><pre>
 * public class MyExtenstionFunctions {
 *    public static String objectType(ExpressionContext context){
 *       Object value = context.getContextNodePointer().getValue();
 *       if (value == null){
 *           return "null";
 *       }
 *       return value.getClass().getName();
 *    }
 * }
 * </pre></blockquote>
 *
 * You can then register this extension function using a {@link ClassFunctions
 * ClassFunctions} object and call it like this:
 * <blockquote><pre>
 *   "/descendent-or-self::node()[ns:objectType() = 'java.util.Date']"
 * </pre></blockquote>
 * This expression will find all nodes of the graph that are dates.
 */
public interface ExpressionContext
{
    /**
     * Get the JXPathContext in which this function is being evaluated.
     *
     * @return A list representing the current context nodes.
     */
    public JXPathContext getJXPathContext();

    /**
     * Get the current context node.
     *
     * @return The current context node pointer.
     */
    public Pointer getContextNodePointer();

    /**
     * Get the current context node list.  Each element of the list is
     * a Pointer.
     *
     * @return A list representing the current context nodes.
     */
    public List getContextNodeList();

    /**
     * Returns the current context position.
     */
    public int getPosition();
}