    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
    029 * objects.
    030 * </p>
    031 * <p>
    032 * This class mimics to be a SAX conform XML parser. Instead of parsing XML
    033 * documents it processes a {@code Configuration} object and generates SAX
    034 * events for the single properties defined there. This enables the whole world
    035 * of XML processing for configuration objects.
    036 * </p>
    037 * <p>
    038 * The {@code HierarchicalConfiguration} object to be parsed can be specified
    039 * using a constructor or the {@code setConfiguration()} method. This object
    040 * will be processed by the {@code parse()} methods. Note that these methods
    041 * ignore their argument.
    042 * </p>
    043 *
    044 * @param <T> the type of the nodes supported by this reader
    045 */
    046public class HierarchicalConfigurationXMLReader<T> extends
    047        ConfigurationXMLReader
    048{
    049    /** Stores the configuration object to be parsed. */
    050    private HierarchicalConfiguration<T> configuration;
    051
    052    /**
    053     * Creates a new instance of {@code HierarchicalConfigurationXMLReader}.
    054     */
    055    public HierarchicalConfigurationXMLReader()
    056    {
    057        super();
    058    }
    059
    060    /**
    061     * Creates a new instance of {@code HierarchicalConfigurationXMLReader} and
    062     * sets the configuration to be parsed.
    063     *
    064     * @param config the configuration object
    065     */
    066    public HierarchicalConfigurationXMLReader(
    067            final HierarchicalConfiguration<T> config)
    068    {
    069        this();
    070        setConfiguration(config);
    071    }
    072
    073    /**
    074     * Returns the configuration object to be parsed.
    075     *
    076     * @return the configuration object to be parsed
    077     */
    078    public HierarchicalConfiguration<T> getConfiguration()
    079    {
    080        return configuration;
    081    }
    082
    083    /**
    084     * Sets the configuration object to be parsed.
    085     *
    086     * @param config the configuration object to be parsed
    087     */
    088    public void setConfiguration(final HierarchicalConfiguration<T> config)
    089    {
    090        configuration = config;
    091    }
    092
    093    /**
    094     * Returns the configuration object to be processed.
    095     *
    096     * @return the actual configuration object
    097     */
    098    @Override
    099    public Configuration getParsedConfiguration()
    100    {
    101        return getConfiguration();
    102    }
    103
    104    /**
    105     * Processes the actual configuration object to generate SAX parsing events.
    106     */
    107    @Override
    108    protected void processKeys()
    109    {
    110        final NodeHandler<T> nodeHandler =
    111                getConfiguration().getNodeModel().getNodeHandler();
    112        NodeTreeWalker.INSTANCE.walkDFS(nodeHandler.getRootNode(),
    113                new SAXVisitor(), nodeHandler);
    114    }
    115
    116    /**
    117     * A specialized visitor class for generating SAX events for a hierarchical
    118     * node structure.
    119     */
    120    private class SAXVisitor extends ConfigurationNodeVisitorAdapter<T>
    121    {
    122        /** Constant for the attribute type. */
    123        private static final String ATTR_TYPE = "CDATA";
    124
    125        /**
    126         * Visits the specified node after its children have been processed.
    127         *
    128         * @param node the actual node
    129         * @param handler the node handler
    130         */
    131        @Override
    132        public void visitAfterChildren(final T node, final NodeHandler<T> handler)
    133        {
    134            fireElementEnd(nodeName(node, handler));
    135        }
    136
    137        /**
    138         * Visits the specified node.
    139         *
    140         * @param node the actual node
    141         * @param handler the node handler
    142         */
    143        @Override
    144        public void visitBeforeChildren(final T node, final NodeHandler<T> handler)
    145        {
    146            fireElementStart(nodeName(node, handler),
    147                    fetchAttributes(node, handler));
    148
    149            final Object value = handler.getValue(node);
    150            if (value != null)
    151            {
    152                fireCharacters(value.toString());
    153            }
    154        }
    155
    156        /**
    157         * Checks if iteration should be terminated. This implementation stops
    158         * iteration after an exception has occurred.
    159         *
    160         * @return a flag if iteration should be stopped
    161         */
    162        @Override
    163        public boolean terminate()
    164        {
    165            return getException() != null;
    166        }
    167
    168        /**
    169         * Returns an object with all attributes for the specified node.
    170         *
    171         * @param node the current node
    172         * @param handler the node handler
    173         * @return an object with all attributes of this node
    174         */
    175        protected Attributes fetchAttributes(final T node, final NodeHandler<T> handler)
    176        {
    177            final AttributesImpl attrs = new AttributesImpl();
    178
    179            for (final String attr : handler.getAttributes(node))
    180            {
    181                final Object value = handler.getAttributeValue(node, attr);
    182                if (value != null)
    183                {
    184                    attrs.addAttribute(NS_URI, attr, attr, ATTR_TYPE,
    185                            value.toString());
    186                }
    187            }
    188
    189            return attrs;
    190        }
    191
    192        /**
    193         * Helper method for determining the name of a node. If a node has no
    194         * name (which is true for the root node), the specified default name
    195         * will be used.
    196         *
    197         * @param node the node to be checked
    198         * @param handler the node handler
    199         * @return the name for this node
    200         */
    201        private String nodeName(final T node, final NodeHandler<T> handler)
    202        {
    203            final String nodeName = handler.nodeName(node);
    204            return nodeName == null ? getRootName() : nodeName;
    205        }
    206    }
    207}