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 */
017package org.apache.commons.jxpath;
018
019import java.util.List;
020
021/**
022 * If an extenstion function has an argument of type ExpressionContext,
023 * it can gain access to the current node of an XPath expression context.
024 * <p>
025 * Example:
026 * <blockquote><pre>
027 * public class MyExtenstionFunctions {
028 *    public static String objectType(ExpressionContext context){
029 *       Object value = context.getContextNodePointer().getValue();
030 *       if (value == null){
031 *           return "null";
032 *       }
033 *       return value.getClass().getName();
034 *    }
035 * }
036 * </pre></blockquote>
037 *
038 * You can then register this extension function using a {@link ClassFunctions
039 * ClassFunctions} object and call it like this:
040 * <blockquote><pre>
041 *   "/descendent-or-self::node()[ns:objectType() = 'java.util.Date']"
042 * </pre></blockquote>
043 * This expression will find all nodes of the graph that are dates.
044 */
045public interface ExpressionContext {
046
047    /**
048     * Get the JXPathContext in which this function is being evaluated.
049     *
050     * @return A list representing the current context nodes.
051     */
052    JXPathContext getJXPathContext();
053
054    /**
055     * Get the current context node.
056     *
057     * @return The current context node pointer.
058     */
059    Pointer getContextNodePointer();
060
061    /**
062     * Get the current context node list.  Each element of the list is
063     * a Pointer.
064     *
065     * @return A list representing the current context nodes.
066     */
067    List getContextNodeList();
068
069    /**
070     * Returns the current context position.
071     * @return int
072     */
073    int getPosition();
074}