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 * https://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 /**
46 * A specialized visitor class for generating SAX events for a hierarchical node structure.
47 */
48 private final class SAXVisitor extends ConfigurationNodeVisitorAdapter<T> {
49
50 /** Constant for the attribute type. */
51 private static final String ATTR_TYPE = "CDATA";
52
53 /**
54 * Returns an object with all attributes for the specified node.
55 *
56 * @param node the current node
57 * @param handler the node handler
58 * @return an object with all attributes of this node
59 */
60 protected Attributes fetchAttributes(final T node, final NodeHandler<T> handler) {
61 final AttributesImpl attrs = new AttributesImpl();
62
63 handler.getAttributes(node).forEach(attr -> {
64 final Object value = handler.getAttributeValue(node, attr);
65 if (value != null) {
66 attrs.addAttribute(NS_URI, attr, attr, ATTR_TYPE, value.toString());
67 }
68 });
69
70 return attrs;
71 }
72
73 /**
74 * Helper method for determining the name of a node. If a node has no name (which is true for the root node), the
75 * specified default name will be used.
76 *
77 * @param node the node to be checked
78 * @param handler the node handler
79 * @return the name for this node
80 */
81 private String nodeName(final T node, final NodeHandler<T> handler) {
82 final String nodeName = handler.nodeName(node);
83 return nodeName == null ? getRootName() : nodeName;
84 }
85
86 /**
87 * Checks if iteration should be terminated. This implementation stops iteration after an exception has occurred.
88 *
89 * @return a flag if iteration should be stopped
90 */
91 @Override
92 public boolean terminate() {
93 return getException() != null;
94 }
95
96 /**
97 * Visits the specified node after its children have been processed.
98 *
99 * @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 }