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