1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17
18 package org.apache.commons.configuration2;
19
20 import org.apache.commons.configuration2.tree.ConfigurationNodeVisitorAdapter;
21 import org.apache.commons.configuration2.tree.NodeHandler;
22 import org.apache.commons.configuration2.tree.NodeTreeWalker;
23 import org.xml.sax.Attributes;
24 import org.xml.sax.helpers.AttributesImpl;
25
26 /**
27 * <p>
28 * A specialized SAX2 XML parser that "parses" hierarchical configuration objects.
29 * </p>
30 * <p>
31 * This class mimics to be a SAX conform XML parser. Instead of parsing XML documents it processes a
32 * {@code Configuration} object and generates SAX events for the single properties defined there. This enables the whole
33 * world of XML processing for configuration objects.
34 * </p>
35 * <p>
36 * The {@code HierarchicalConfiguration} object to be parsed can be specified using a constructor or the
37 * {@code setConfiguration()} method. This object will be processed by the {@code parse()} methods. Note that these
38 * methods ignore their argument.
39 * </p>
40 *
41 * @param <T> the type of the nodes supported by this reader
42 */
43 public class HierarchicalConfigurationXMLReader<T> extends ConfigurationXMLReader {
44 /**
45 * A specialized visitor class for generating SAX events for a hierarchical node structure.
46 */
47 private final class SAXVisitor extends ConfigurationNodeVisitorAdapter<T> {
48 /** Constant for the attribute type. */
49 private static final String ATTR_TYPE = "CDATA";
50
51 /**
52 * Returns an object with all attributes for the specified node.
53 *
54 * @param node the current node
55 * @param handler the node handler
56 * @return an object with all attributes of this node
57 */
58 protected Attributes fetchAttributes(final T node, final NodeHandler<T> handler) {
59 final AttributesImpl attrs = new AttributesImpl();
60
61 handler.getAttributes(node).forEach(attr -> {
62 final Object value = handler.getAttributeValue(node, attr);
63 if (value != null) {
64 attrs.addAttribute(NS_URI, attr, attr, ATTR_TYPE, value.toString());
65 }
66 });
67
68 return attrs;
69 }
70
71 /**
72 * Helper method for determining the name of a node. If a node has no name (which is true for the root node), the
73 * specified default name will be used.
74 *
75 * @param node the node to be checked
76 * @param handler the node handler
77 * @return the name for this node
78 */
79 private String nodeName(final T node, final NodeHandler<T> handler) {
80 final String nodeName = handler.nodeName(node);
81 return nodeName == null ? getRootName() : nodeName;
82 }
83
84 /**
85 * Checks if iteration should be terminated. This implementation stops iteration after an exception has occurred.
86 *
87 * @return a flag if iteration should be stopped
88 */
89 @Override
90 public boolean terminate() {
91 return getException() != null;
92 }
93
94 /**
95 * Visits the specified node after its children have been processed.
96 *
97 * @param node the actual node
98 * @param handler the node handler
99 */
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 }