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    package org.apache.commons.jxpath;
018    
019    import 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     */
045    public 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    }