    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    }