    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.configuration2;
    019
    020import org.apache.commons.configuration2.tree.ConfigurationNodeVisitorAdapter;
    021import org.apache.commons.configuration2.tree.NodeHandler;
    022import org.apache.commons.configuration2.tree.NodeTreeWalker;
    023import org.xml.sax.Attributes;
    024import org.xml.sax.helpers.AttributesImpl;
    025
    026/**
    027 * <p>
    028 * A specialized SAX2 XML parser that "parses" hierarchical configuration objects.
    029 * </p>
    030 * <p>
    031 * This class mimics to be a SAX conform XML parser. Instead of parsing XML documents it processes a
    032 * {@code Configuration} object and generates SAX events for the single properties defined there. This enables the whole
    033 * world of XML processing for configuration objects.
    034 * </p>
    035 * <p>
    036 * The {@code HierarchicalConfiguration} object to be parsed can be specified using a constructor or the
    037 * {@code setConfiguration()} method. This object will be processed by the {@code parse()} methods. Note that these
    038 * methods ignore their argument.
    039 * </p>
    040 *
    041 * @param <T> the type of the nodes supported by this reader
    042 */
    043public class HierarchicalConfigurationXMLReader<T> extends ConfigurationXMLReader {
    044    /**
    045     * A specialized visitor class for generating SAX events for a hierarchical node structure.
    046     */
    047    private final class SAXVisitor extends ConfigurationNodeVisitorAdapter<T> {
    048        /** Constant for the attribute type. */
    049        private static final String ATTR_TYPE = "CDATA";
    050
    051        /**
    052         * Returns an object with all attributes for the specified node.
    053         *
    054         * @param node the current node
    055         * @param handler the node handler
    056         * @return an object with all attributes of this node
    057         */
    058        protected Attributes fetchAttributes(final T node, final NodeHandler<T> handler) {
    059            final AttributesImpl attrs = new AttributesImpl();
    060
    061            handler.getAttributes(node).forEach(attr -> {
    062                final Object value = handler.getAttributeValue(node, attr);
    063                if (value != null) {
    064                    attrs.addAttribute(NS_URI, attr, attr, ATTR_TYPE, value.toString());
    065                }
    066            });
    067
    068            return attrs;
    069        }
    070
    071        /**
    072         * Helper method for determining the name of a node. If a node has no name (which is true for the root node), the
    073         * specified default name will be used.
    074         *
    075         * @param node the node to be checked
    076         * @param handler the node handler
    077         * @return the name for this node
    078         */
    079        private String nodeName(final T node, final NodeHandler<T> handler) {
    080            final String nodeName = handler.nodeName(node);
    081            return nodeName == null ? getRootName() : nodeName;
    082        }
    083
    084        /**
    085         * Checks if iteration should be terminated. This implementation stops iteration after an exception has occurred.
    086         *
    087         * @return a flag if iteration should be stopped
    088         */
    089        @Override
    090        public boolean terminate() {
    091            return getException() != null;
    092        }
    093
    094        /**
    095         * Visits the specified node after its children have been processed.
    096         *
    097         * @param node the actual node
    098         * @param handler the node handler
    099         */
    100        @Override
    101        public void visitAfterChildren(final T node, final NodeHandler<T> handler) {
    102            fireElementEnd(nodeName(node, handler));
    103        }
    104
    105        /**
    106         * Visits the specified node.
    107         *
    108         * @param node the actual node
    109         * @param handler the node handler
    110         */
    111        @Override
    112        public void visitBeforeChildren(final T node, final NodeHandler<T> handler) {
    113            fireElementStart(nodeName(node, handler), fetchAttributes(node, handler));
    114
    115            final Object value = handler.getValue(node);
    116            if (value != null) {
    117                fireCharacters(value.toString());
    118            }
    119        }
    120    }
    121
    122    /** Stores the configuration object to be parsed. */
    123    private HierarchicalConfiguration<T> configuration;
    124
    125    /**
    126     * Creates a new instance of {@code HierarchicalConfigurationXMLReader}.
    127     */
    128    public HierarchicalConfigurationXMLReader() {
    129    }
    130
    131    /**
    132     * Creates a new instance of {@code HierarchicalConfigurationXMLReader} and sets the configuration to be parsed.
    133     *
    134     * @param config the configuration object
    135     */
    136    public HierarchicalConfigurationXMLReader(final HierarchicalConfiguration<T> config) {
    137        this();
    138        setConfiguration(config);
    139    }
    140
    141    /**
    142     * Gets the configuration object to be parsed.
    143     *
    144     * @return the configuration object to be parsed
    145     */
    146    public HierarchicalConfiguration<T> getConfiguration() {
    147        return configuration;
    148    }
    149
    150    /**
    151     * Gets the configuration object to be processed.
    152     *
    153     * @return the actual configuration object
    154     */
    155    @Override
    156    public Configuration getParsedConfiguration() {
    157        return getConfiguration();
    158    }
    159
    160    /**
    161     * Processes the actual configuration object to generate SAX parsing events.
    162     */
    163    @Override
    164    protected void processKeys() {
    165        final NodeHandler<T> nodeHandler = getConfiguration().getNodeModel().getNodeHandler();
    166        NodeTreeWalker.INSTANCE.walkDFS(nodeHandler.getRootNode(), new SAXVisitor(), nodeHandler);
    167    }
    168
    169    /**
    170     * Sets the configuration object to be parsed.
    171     *
    172     * @param config the configuration object to be parsed
    173     */
    174    public void setConfiguration(final HierarchicalConfiguration<T> config) {
    175        configuration = config;
    176    }
    177}