    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.ri.axes;
    018
    019    import org.apache.commons.jxpath.Pointer;
    020    import org.apache.commons.jxpath.ri.EvalContext;
    021    import org.apache.commons.jxpath.ri.compiler.NodeTest;
    022    import org.apache.commons.jxpath.ri.model.NodeIterator;
    023    import org.apache.commons.jxpath.ri.model.NodePointer;
    024
    025    /**
    026     * EvalContext that can walk the "child::", "following-sibling::" and
    027     * "preceding-sibling::" axes.
    028     *
    029     * @author Dmitri Plotnikov
    030     * @version $Revision: 652903 $ $Date: 2008-05-02 15:46:32 -0500 (Fri, 02 May 2008) $
    031     */
    032    public class ChildContext extends EvalContext {
    033        private NodeTest nodeTest;
    034        private boolean startFromParentLocation;
    035        private boolean reverse;
    036        private NodeIterator iterator;
    037
    038        /**
    039         * Create a new ChildContext.
    040         * @param parentContext parent EvalContext
    041         * @param nodeTest NodeTest
    042         * @param startFromParentLocation whether to start from parent location
    043         * @param reverse whether to iterate in reverse
    044         */
    045        public ChildContext(EvalContext parentContext, NodeTest nodeTest,
    046                boolean startFromParentLocation, boolean reverse) {
    047            super(parentContext);
    048            this.nodeTest = nodeTest;
    049            this.startFromParentLocation = startFromParentLocation;
    050            this.reverse = reverse;
    051        }
    052
    053        public NodePointer getCurrentNodePointer() {
    054            if (position == 0 && !setPosition(1)) {
    055                return null;
    056            }
    057            return iterator == null ? null : iterator.getNodePointer();
    058        }
    059
    060        /**
    061         * This method is called on the last context on the path when only
    062         * one value is needed.  Note that this will return the whole property,
    063         * even if it is a collection. It will not extract the first element
    064         * of the collection.  For example, "books" will return the collection
    065         * of books rather than the first book from that collection.
    066         * @return Pointer
    067         */
    068        public Pointer getSingleNodePointer() {
    069            if (position == 0) {
    070                while (nextSet()) {
    071                    prepare();
    072                    if (iterator == null) {
    073                        return null;
    074                    }
    075                    // See if there is a property there, singular or collection
    076                    NodePointer pointer = iterator.getNodePointer();
    077                    if (pointer != null) {
    078                        return pointer;
    079                    }
    080                }
    081                return null;
    082            }
    083            return getCurrentNodePointer();
    084        }
    085
    086        public boolean nextNode() {
    087            return setPosition(getCurrentPosition() + 1);
    088        }
    089
    090        public void reset() {
    091            super.reset();
    092            iterator = null;
    093        }
    094
    095        public boolean setPosition(int position) {
    096            int oldPosition = getCurrentPosition();
    097            super.setPosition(position);
    098            if (oldPosition == 0) {
    099                prepare();
    100            }
    101            return iterator == null ? false : iterator.setPosition(position);
    102        }
    103
    104        /**
    105         * Allocates a PropertyIterator.
    106         */
    107        private void prepare() {
    108            NodePointer parent = parentContext.getCurrentNodePointer();
    109            if (parent == null) {
    110                return;
    111            }
    112            NodePointer useParent = startFromParentLocation ? parent.getParent() : parent;
    113            iterator = useParent.childIterator(nodeTest, reverse,
    114                    startFromParentLocation ? parent : null);
    115        }
    116    }