001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *     http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017
018package org.apache.commons.jxpath;
019
020import java.util.List;
021
022/**
023 * If an extenstion function has an argument of type ExpressionContext, it can gain access to the current node of an XPath expression context.
024 * <p>
025 * Example: <blockquote>
026 *
027 * <pre>
028 * public class MyExtenstionFunctions {
029 *
030 *     public static String objectType(ExpressionContext context) {
031 *         Object value = context.getContextNodePointer().getValue();
032 *         if (value == null) {
033 *             return "null";
034 *         }
035 *         return value.getClass().getName();
036 *     }
037 * }
038 * </pre>
039 *
040 * </blockquote>
041 *
042 * You can then register this extension function using a {@link ClassFunctions ClassFunctions} object and call it like this: <blockquote>
043 *
044 * <pre>
045 * "/descendent-or-self::node()[ns:objectType() = 'java.util.Date']"
046 * </pre>
047 *
048 * </blockquote> This expression will find all nodes of the graph that are dates.
049 */
050public interface ExpressionContext {
051
052    /**
053     * Gets the current context node list. Each element of the list is a Pointer.
054     *
055     * @return A list representing the current context nodes.
056     */
057    List<Pointer> getContextNodeList();
058
059    /**
060     * Gets the current context node.
061     *
062     * @return The current context node pointer.
063     */
064    Pointer getContextNodePointer();
065
066    /**
067     * Gets the JXPathContext in which this function is being evaluated.
068     *
069     * @return A list representing the current context nodes.
070     */
071    JXPathContext getJXPathContext();
072
073    /**
074     * Returns the current context position.
075     *
076     * @return int
077     */
078    int getPosition();
079}