    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 *     https://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    /**
    046     * A specialized visitor class for generating SAX events for a hierarchical node structure.
    047     */
    048    private final class SAXVisitor extends ConfigurationNodeVisitorAdapter<T> {
    049
    050        /** Constant for the attribute type. */
    051        private static final String ATTR_TYPE = "CDATA";
    052
    053        /**
    054         * Returns an object with all attributes for the specified node.
    055         *
    056         * @param node the current node
    057         * @param handler the node handler
    058         * @return an object with all attributes of this node
    059         */
    060        protected Attributes fetchAttributes(final T node, final NodeHandler<T> handler) {
    061            final AttributesImpl attrs = new AttributesImpl();
    062
    063            handler.getAttributes(node).forEach(attr -> {
    064                final Object value = handler.getAttributeValue(node, attr);
    065                if (value != null) {
    066                    attrs.addAttribute(NS_URI, attr, attr, ATTR_TYPE, value.toString());
    067                }
    068            });
    069
    070            return attrs;
    071        }
    072
    073        /**
    074         * Helper method for determining the name of a node. If a node has no name (which is true for the root node), the
    075         * specified default name will be used.
    076         *
    077         * @param node the node to be checked
    078         * @param handler the node handler
    079         * @return the name for this node
    080         */
    081        private String nodeName(final T node, final NodeHandler<T> handler) {
    082            final String nodeName = handler.nodeName(node);
    083            return nodeName == null ? getRootName() : nodeName;
    084        }
    085
    086        /**
    087         * Checks if iteration should be terminated. This implementation stops iteration after an exception has occurred.
    088         *
    089         * @return a flag if iteration should be stopped
    090         */
    091        @Override
    092        public boolean terminate() {
    093            return getException() != null;
    094        }
    095
    096        /**
    097         * Visits the specified node after its children have been processed.
    098         *
    099         * @param node the actual node
    100         * @param handler the node handler
    101         */
    102        @Override
    103        public void visitAfterChildren(final T node, final NodeHandler<T> handler) {
    104            fireElementEnd(nodeName(node, handler));
    105        }
    106
    107        /**
    108         * Visits the specified node.
    109         *
    110         * @param node the actual node
    111         * @param handler the node handler
    112         */
    113        @Override
    114        public void visitBeforeChildren(final T node, final NodeHandler<T> handler) {
    115            fireElementStart(nodeName(node, handler), fetchAttributes(node, handler));
    116
    117            final Object value = handler.getValue(node);
    118            if (value != null) {
    119                fireCharacters(value.toString());
    120            }
    121        }
    122    }
    123
    124    /** Stores the configuration object to be parsed. */
    125    private HierarchicalConfiguration<T> configuration;
    126
    127    /**
    128     * Creates a new instance of {@code HierarchicalConfigurationXMLReader}.
    129     */
    130    public HierarchicalConfigurationXMLReader() {
    131    }
    132
    133    /**
    134     * Creates a new instance of {@code HierarchicalConfigurationXMLReader} and sets the configuration to be parsed.
    135     *
    136     * @param config the configuration object
    137     */
    138    public HierarchicalConfigurationXMLReader(final HierarchicalConfiguration<T> config) {
    139        this();
    140        setConfiguration(config);
    141    }
    142
    143    /**
    144     * Gets the configuration object to be parsed.
    145     *
    146     * @return the configuration object to be parsed
    147     */
    148    public HierarchicalConfiguration<T> getConfiguration() {
    149        return configuration;
    150    }
    151
    152    /**
    153     * Gets the configuration object to be processed.
    154     *
    155     * @return the actual configuration object
    156     */
    157    @Override
    158    public Configuration getParsedConfiguration() {
    159        return getConfiguration();
    160    }
    161
    162    /**
    163     * Processes the actual configuration object to generate SAX parsing events.
    164     */
    165    @Override
    166    protected void processKeys() {
    167        final NodeHandler<T> nodeHandler = getConfiguration().getNodeModel().getNodeHandler();
    168        NodeTreeWalker.INSTANCE.walkDFS(nodeHandler.getRootNode(), new SAXVisitor(), nodeHandler);
    169    }
    170
    171    /**
    172     * Sets the configuration object to be parsed.
    173     *
    174     * @param config the configuration object to be parsed
    175     */
    176    public void setConfiguration(final HierarchicalConfiguration<T> config) {
    177        configuration = config;
    178    }
    179}