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Java > Open Source Codes > org > apache > commons > configuration > HierarchicalConfigurationXMLReader


1 /*
2  * Copyright 2001-2004 The Apache Software Foundation.
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License")
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  * http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16
17 package org.apache.commons.configuration;
18
19 import java.util.List JavaDoc;
20
21 import org.apache.commons.configuration.HierarchicalConfiguration.Node;
22 import org.xml.sax.Attributes JavaDoc;
23 import org.xml.sax.helpers.AttributesImpl JavaDoc;
24
25 /**
26  * <p>A specialized SAX2 XML parser that "parses" hierarchical
27  * configuration objects.</p>
28  * <p>This class mimics to be a SAX conform XML parser. Instead of parsing
29  * XML documents it processes a <code>Configuration</code> object and
30  * generates SAX events for the single properties defined there. This enables
31  * the whole world of XML processing for configuration objects.</p>
32  * <p>The <code>HierarchicalConfiguration</code> object to be parsed can be
33  * specified using a constructor or the <code>setConfiguration()</code> method.
34  * This object will be processed by the <code>parse()</code> methods. Note
35  * that these methods ignore their argument.</p>
36  *
37  * @author <a HREF="mailto:oliver.heger@t-online.de">Oliver Heger</a>
38  * @version $Id: HierarchicalConfigurationXMLReader.java 155408 2005-02-26 12:56:39Z dirkv $
39  */
40 public class HierarchicalConfigurationXMLReader extends ConfigurationXMLReader
41 {
42     /** Stores the configuration object to be parsed.*/
43     private HierarchicalConfiguration configuration;
44
45     /**
46      * Creates a new instance of
47      * <code>HierarchicalConfigurationXMLReader</code>.
48      */
49     public HierarchicalConfigurationXMLReader()
50     {
51         super();
52     }
53
54     /**
55      * Creates a new instance of
56      * <code>HierarchicalConfigurationXMLReader</code> and sets the
57      * configuration to be parsed.
58      *
59      * @param config the configuration object
60      */
61     public HierarchicalConfigurationXMLReader(HierarchicalConfiguration config)
62     {
63         this();
64         setConfiguration(config);
65     }
66
67     /**
68      * Returns the configuration object to be parsed.
69      *
70      * @return the configuration object to be parsed
71      */
72     public HierarchicalConfiguration getConfiguration()
73     {
74         return configuration;
75     }
76
77     /**
78      * Sets the configuration object to be parsed.
79      *
80      * @param config the configuration object to be parsed
81      */
82     public void setConfiguration(HierarchicalConfiguration config)
83     {
84         configuration = config;
85     }
86
87     /**
88      * Returns the configuration object to be processed.
89      *
90      * @return the actual configuration object
91      */
92     public Configuration getParsedConfiguration()
93     {
94         return getConfiguration();
95     }
96
97     /**
98      * Processes the actual configuration object to generate SAX parsing events.
99      */
100     protected void processKeys()
101     {
102         getConfiguration().getRoot().visit(new SAXVisitor(), null);
103     }
104
105     /**
106      * A specialized visitor class for generating SAX events for a
107      * hierarchical node structure.
108      *
109      */
110     class SAXVisitor extends HierarchicalConfiguration.NodeVisitor
111     {
112         /** Constant for the attribute type.*/
113         private static final String JavaDoc ATTR_TYPE = "CDATA";
114
115         /**
116          * Visits the specified node after its children have been processed.
117          *
118          * @param node the actual node
119          * @param key the key of this node
120          */
121         public void visitAfterChildren(Node node, ConfigurationKey key)
122         {
123             if (!isAttributeNode(node))
124             {
125                 fireElementEnd(nodeName(node));
126             }
127         }
128
129         /**
130          * Visits the specified node.
131          *
132          * @param node the actual node
133          * @param key the key of this node
134          */
135         public void visitBeforeChildren(Node node, ConfigurationKey key)
136         {
137             if (!isAttributeNode(node))
138             {
139                 fireElementStart(nodeName(node), fetchAttributes(node));
140
141                 if (node.getValue() != null)
142                 {
143                     fireCharacters(node.getValue().toString());
144                 }
145             }
146         }
147
148         /**
149          * Checks if iteration should be terminated. This implementation stops
150          * iteration after an exception has occurred.
151          *
152          * @return a flag if iteration should be stopped
153          */
154         public boolean terminate()
155         {
156             return getException() != null;
157         }
158
159         /**
160          * Returns an object with all attributes for the specified node.
161          *
162          * @param node the actual node
163          * @return an object with all attributes of this node
164          */
165         protected Attributes JavaDoc fetchAttributes(Node node)
166         {
167             AttributesImpl JavaDoc attrs = new AttributesImpl JavaDoc();
168             List JavaDoc children = node.getChildren();
169
170             for (int i = 0; i < children.size(); i++)
171             {
172                 Node child = (Node) children.get(i);
173                 if (isAttributeNode(child) && child.getValue() != null)
174                 {
175                     String JavaDoc attr = ConfigurationKey.attributeName(child.getName());
176                     attrs.addAttribute(NS_URI, attr, attr, ATTR_TYPE, child.getValue().toString());
177                 }
178             }
179
180             return attrs;
181         }
182
183         /**
184          * Helper method for determining the name of a node. If a node has no
185          * name (which is true for the root node), the specified default name
186          * will be used.
187          *
188          * @param node the node to be checked
189          * @return the name for this node
190          */
191         private String JavaDoc nodeName(Node node)
192         {
193             return (node.getName() == null) ? getRootName() : node.getName();
194         }
195
196         /**
197          * Checks if the specified node is an attribute node. In the node
198          * hierarchy attributes are stored as normal child nodes, but with
199          * special names.
200          *
201          * @param node the node to be checked
202          * @return a flag if this is an attribute node
203          */
204         private boolean isAttributeNode(Node node)
205         {
206             return ConfigurationKey.isAttributeKey(node.getName());
207         }
208     }
209 }
210
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