##### Coverage Report - org.apache.commons.configuration.SubnodeConfiguration

Classes in this File | Line Coverage | Branch Coverage | Complexity
SubnodeConfiguration |
100% | 52/52
100% | 8/8
| 2.2;2,2

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.
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      * The ASF licenses this file to You under the Apache License, Version 2.0
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      * (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,
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      * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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      * See the License for the specific language governing permissions and
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      * limitations under the License.
16 |  |
      */
17 |  |
     package org.apache.commons.configuration;
18 |  |
19 |  |
     import java.util.ArrayList;
20 |  |
     import java.util.Collections;
21 |  |
     import java.util.Iterator;
22 |  |
     import java.util.List;
23 |  |
24 |  |
     import org.apache.commons.configuration.tree.ConfigurationNode;
25 |  |
26 |  |
     /**
27 |  |
      * <p>
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      * A specialized hierarchical configuration class that wraps a single node of
29 |  |
      * its parent configuration.
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      * </p>
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      * <p>
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      * Configurations of this type are initialized with a parent configuration and a
33 |  |
      * configuration node of this configuration. This node becomes the root node of
34 |  |
      * the subnode configuration. All property accessor methods are evaluated
35 |  |
      * relative to this root node. A good use case for a
36 |  |
      * <code>SubnodeConfiguration</code> is when multiple properties from a
37 |  |
      * specific sub tree of the whole configuration need to be accessed. Then a
38 |  |
      * <code>SubnodeConfiguration</code> can be created with the parent node of
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      * the affected sub tree as root node. This allows for simpler property keys and
40 |  |
      * is also more efficient.
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      * </p>
42 |  |
      * <p>
43 |  |
      * A subnode configuration and its parent configuration operate on the same
44 |  |
      * hierarchy of configuration nodes. So if modifications are performed at the
45 |  |
      * subnode configuration, these changes are immideately visible in the parent
46 |  |
      * configuration. Analogously will updates of the parent configuration affect
47 |  |
      * the subnode configuration if the sub tree spanned by the subnode
48 |  |
      * configuration's root node is involved.
49 |  |
      * </p>
50 |  |
      * <p>
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      * There are however changes at the parent configuration, which cause the
52 |  |
      * subnode configuration to become detached. An example for such a change is a
53 |  |
      * reload operation of a file-based configuration, which replaces all nodes of
54 |  |
      * the parent configuration. The subnode configuration per default still
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      * references the old nodes. Another example are list structures: a subnode
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      * configuration can be created to point on the <em>i</em>th element of the
57 |  |
      * list. Now list elements can be added or removed, so that the list elements'
58 |  |
      * indices change. In such a scenario the subnode configuration would always
59 |  |
      * point to the same list element, regardless of its current index.
60 |  |
      * </p>
61 |  |
      * <p>
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      * To solve these problems and make a subnode configuration aware of
63 |  |
      * such structural changes of its parent, it is possible to associate a
64 |  |
      * subnode configuration with a configuration key. This can be done by calling
65 |  |
      * the <code>setSubnodeKey()</code> method. If here a key is set, the subnode
66 |  |
      * configuration will evaluate it on each access, thus ensuring that it is
67 |  |
      * always in sync with its parent. In this mode the subnode configuration really
68 |  |
      * behaves like a live-view on its parent. The price for this is a decreased
69 |  |
      * performance because now an additional evaluation has to be performed on each
70 |  |
      * property access. So this mode should only be used if necessary; if for
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      * instance a subnode configuration is only used for a temporary convenient
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      * access to a complex configuration, there is no need to make it aware for
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      * structural changes of its parent. If a subnode configuration is created
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      * using the <code>{@link HierarchicalConfiguration#configurationAt(String, boolean)
75 |  |
      * configurationAt()}</code> method of <code>HierarchicalConfiguration</code>
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      * (which should be the preferred way), with an additional boolean parameter it
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      * can be specified whether the resulting subnode configuration should be
78 |  |
      * aware of structural changes or not. Then the configuration key will be
79 |  |
      * automatically set.
80 |  |
      * </p>
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      * <p>
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      * <em>Note:</em> At the moment support for creating a subnode configuration
83 |  |
      * that is aware of structural changes of its parent from another subnode
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      * configuration (a "sub subnode configuration") is limited. This only works if
85 |  |
      * <ol><li>the subnode configuration that serves as the parent for the new
86 |  |
      * subnode configuration is itself associated with a configuration key and</li>
87 |  |
      * <li>the key passed in to create the new subnode configuration is not too
88 |  |
      * complex (if configuration keys are used that contain indices, a corresponding
89 |  |
      * key that is valid from the parent configuration's point of view cannot be
90 |  |
      * constructed).</li></ol>
91 |  |
      * </p>
92 |  |
      * <p>
93 |  |
      * When a subnode configuration is created, it inherits the settings of its
94 |  |
      * parent configuration, e.g. some flags like the
95 |  |
      * <code>throwExceptionOnMissing</code> flag or the settings for handling list
96 |  |
      * delimiters) or the expression engine. If these settings are changed later in
97 |  |
      * either the subnode or the parent configuration, the changes are not visible
98 |  |
      * for each other. So you could create a subnode configuration, change its
99 |  |
      * expression engine without affecting the parent configuration.
100 |  |
      * </p>
101 |  |
      * <p>
102 |  |
      * From its purpose this class is quite similar to
103 |  |
      * <code>{@link SubsetConfiguration}</code>. The difference is that a subset
104 |  |
      * configuration of a hierarchical configuration may combine multiple
105 |  |
      * configuration nodes from different sub trees of the configuration, while all
106 |  |
      * nodes in a subnode configuration belong to the same sub tree. If an
107 |  |
      * application can live with this limitation, it is recommended to use this
108 |  |
      * class instead of <code>SubsetConfiguration</code> because creating a subset
109 |  |
      * configuration is more expensive than creating a subnode configuration.
110 |  |
      * </p>
111 |  |
      *
112 |  |
      * @since 1.3
113 |  |
      * @author Oliver Heger
114 |  |
      * @version $Id: SubnodeConfiguration.java 531254 2007-04-22 18:54:57Z oheger $
115 |  |
      */
116 |  |
     public class SubnodeConfiguration extends HierarchicalConfiguration
117 |  |
     {
118 |  |
         /**
119 |  |
          * The serial version UID.
120 |  |
          */
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         private static final long serialVersionUID = 3105734147019386480L;
122 |  |
123 |  |
         /** Stores the parent configuration. */
124 |  |
         private HierarchicalConfiguration parent;
125 |  |
126 |  |
         /** Stores the key that was used to construct this configuration.*/
127 |  |
         private String subnodeKey;
128 |  |
129 |  |
         /**
130 |  |
          * Creates a new instance of <code>SubnodeConfiguration</code> and
131 |  |
          * initializes it with the parent configuration and the new root node.
132 |  |
          *
133 |  |
          * @param parent the parent configuration
134 |  |
          * @param root the root node of this subnode configuration
135 |  |
          */
136 |  |
         public SubnodeConfiguration(HierarchicalConfiguration parent, ConfigurationNode root)
137 | 240 |
         {
138 | 240 |
             if (parent == null)
139 |  |
             {
140 | 1 |
                 throw new IllegalArgumentException(
141 |  |
                         "Parent configuration must not be null!");
142 |  |
             }
143 | 239 |
             if (root == null)
144 |  |
             {
145 | 1 |
                 throw new IllegalArgumentException("Root node must not be null!");
146 |  |
             }
147 |  |
148 | 238 |
             setRootNode(root);
149 | 238 |
             this.parent = parent;
150 | 238 |
             initFromParent(parent);
151 | 238 |
         }
152 |  |
153 |  |
         /**
154 |  |
          * Returns the parent configuration of this subnode configuration.
155 |  |
          *
156 |  |
          * @return the parent configuration
157 |  |
          */
158 |  |
         public HierarchicalConfiguration getParent()
159 |  |
         {
160 | 574 |
             return parent;
161 |  |
         }
162 |  |
163 |  |
         /**
164 |  |
          * Returns the key that was used to construct this configuration. If here a
165 |  |
          * non-<b>null</b> value is returned, the subnode configuration will
166 |  |
          * always check its parent for structural changes and reconstruct itself if
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          * necessary.
168 |  |
          *
169 |  |
          * @return the key for selecting this configuration's root node
170 |  |
          * @since 1.5
171 |  |
          */
172 |  |
         public String getSubnodeKey()
173 |  |
         {
174 | 611 |
             return subnodeKey;
175 |  |
         }
176 |  |
177 |  |
         /**
178 |  |
          * Sets the key to the root node of this subnode configuration. If here a
179 |  |
          * key is set, the subnode configuration will behave like a live-view on its
180 |  |
          * parent for this key. See the class comment for more details.
181 |  |
          *
182 |  |
          * @param subnodeKey the key used to construct this configuration
183 |  |
          * @since 1.5
184 |  |
          */
185 |  |
         public void setSubnodeKey(String subnodeKey)
186 |  |
         {
187 | 8 |
             this.subnodeKey = subnodeKey;
188 | 8 |
         }
189 |  |
190 |  |
         /**
191 |  |
          * Returns the root node for this configuration. If a subnode key is set,
192 |  |
          * this implementation re-evaluates this key to find out if this subnode
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          * configuration needs to be reconstructed. This ensures that the subnode
194 |  |
          * configuration is always synchronized with its parent configuration.
195 |  |
          *
196 |  |
          * @return the root node of this configuration
197 |  |
          * @since 1.5
198 |  |
          * @see #setSubnodeKey(String)
199 |  |
          */
200 |  |
         public ConfigurationNode getRootNode()
201 |  |
         {
202 | 593 |
             if (getSubnodeKey() != null)
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             {
204 |  |
                 try
205 |  |
                 {
206 | 10 |
                     List nodes = getParent().fetchNodeList(getSubnodeKey());
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                     if (nodes.size() != 1)
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                     {
209 |  |
                         // key is invalid, so detach this subnode configuration
210 | 1 |
                         setSubnodeKey(null);
211 | 1 |
                     }
212 |  |
                     else
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                     {
214 | 8 |
                         ConfigurationNode currentRoot = (ConfigurationNode) nodes
215 |  |
                                 .get(0);
216 | 8 |
                         if (currentRoot != super.getRootNode())
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                         {
218 |  |
                             // the root node was changed due to a change of the
219 |  |
                             // parent
220 | 4 |
                             setRootNode(currentRoot);
221 |  |
                         }
222 | 8 |
                         return currentRoot;
223 |  |
                     }
224 |  |
                 }
225 | 1 |
                 catch (Exception ex)
226 |  |
                 {
227 |  |
                     // Evaluation of the key caused an exception. Probably the
228 |  |
                     // expression engine has changed on the parent. Detach this
229 |  |
                     // configuration, there is not much we can do about this.
230 | 1 |
                     setSubnodeKey(null);
231 | 1 |
                 }
232 |  |
             }
233 |  |
234 | 585 |
             return super.getRootNode(); // use stored root node
235 |  |
         }
236 |  |
237 |  |
         /**
238 |  |
          * Returns a hierarchical configuration object for the given sub node.
239 |  |
          * This implementation will ensure that the returned
240 |  |
          * <code>SubnodeConfiguration</code> object will have the same parent than
241 |  |
          * this object.
242 |  |
          *
243 |  |
          * @param node the sub node, for which the configuration is to be created
244 |  |
          * @return a hierarchical configuration for this sub node
245 |  |
          */
246 |  |
         protected SubnodeConfiguration createSubnodeConfiguration(ConfigurationNode node)
247 |  |
         {
248 | 84 |
             SubnodeConfiguration result = new SubnodeConfiguration(getParent(), node);
249 | 84 |
             getParent().registerSubnodeConfiguration(result);
250 | 84 |
             return result;
251 |  |
         }
252 |  |
253 |  |
         /**
254 |  |
          * Returns a hierarchical configuration object for the given sub node that
255 |  |
          * is aware of structural changes of its parent. Works like the method with
256 |  |
          * the same name, but also sets the subnode key for the new subnode
257 |  |
          * configuration, so it can check whether the parent has been changed. This
258 |  |
          * only works if this subnode configuration has itself a valid subnode key.
259 |  |
          * So if a subnode configuration that should be aware of structural changes
260 |  |
          * is created from an already existing subnode configuration, this subnode
261 |  |
          * configuration must also be aware of such changes.
262 |  |
          *
263 |  |
          * @param node the sub node, for which the configuration is to be created
264 |  |
          * @param subnodeKey the construction key
265 |  |
          * @return a hierarchical configuration for this sub node
266 |  |
          * @since 1.5
267 |  |
          */
268 |  |
         protected SubnodeConfiguration createSubnodeConfiguration(
269 |  |
                 ConfigurationNode node, String subnodeKey)
270 |  |
         {
271 | 2 |
             SubnodeConfiguration result = createSubnodeConfiguration(node);
272 |  |
273 | 2 |
             if (getSubnodeKey() != null)
274 |  |
             {
275 |  |
                 // construct the correct subnode key
276 |  |
                 // determine path to root node
277 | 1 |
                 List lstPathToRoot = new ArrayList();
278 | 1 |
                 ConfigurationNode top = super.getRootNode();
279 | 1 |
                 ConfigurationNode nd = node;
280 | 2 |
                 while (nd != top)
281 |  |
                 {
282 | 1 |
                     lstPathToRoot.add(nd);
283 | 1 |
                     nd = nd.getParentNode();
284 | 1 |
                 }
285 |  |
286 |  |
                 // construct the keys for the nodes on this path
287 | 1 |
                 Collections.reverse(lstPathToRoot);
288 | 1 |
                 String key = getSubnodeKey();
289 | 1 |
                 for (Iterator it = lstPathToRoot.iterator(); it.hasNext();)
290 |  |
                 {
291 | 1 |
                     key = getParent().getExpressionEngine().nodeKey(
292 |  |
                             (ConfigurationNode) it.next(), key);
293 | 1 |
                 }
294 | 1 |
                 result.setSubnodeKey(key);
295 |  |
             }
296 |  |
297 | 2 |
             return result;
298 |  |
         }
299 |  |
300 |  |
         /**
301 |  |
          * Creates a new node. This task is delegated to the parent.
302 |  |
          *
303 |  |
          * @param name the node's name
304 |  |
          * @return the new node
305 |  |
          */
306 |  |
         protected Node createNode(String name)
307 |  |
         {
308 | 5 |
             return getParent().createNode(name);
309 |  |
         }
310 |  |
311 |  |
         /**
312 |  |
          * Initializes this subnode configuration from the given parent
313 |  |
          * configuration. This method is called by the constructor. It will copy
314 |  |
          * many settings from the parent.
315 |  |
          *
316 |  |
          * @param parentConfig the parent configuration
317 |  |
          */
318 |  |
         protected void initFromParent(HierarchicalConfiguration parentConfig)
319 |  |
         {
320 | 238 |
             setExpressionEngine(parentConfig.getExpressionEngine());
321 | 238 |
             setListDelimiter(parentConfig.getListDelimiter());
322 | 238 |
             setDelimiterParsingDisabled(parentConfig.isDelimiterParsingDisabled());
323 | 238 |
             setThrowExceptionOnMissing(parentConfig.isThrowExceptionOnMissing());
324 | 238 |
         }
325 |  |
326 |  |
         /**
327 |  |
          * Performs interpolation. This implementation will ask the parent
328 |  |
          * configuration to perform the interpolation so that variables can be
329 |  |
          * evaluated in the global context.
330 |  |
          *
331 |  |
          * @param value the value to be interpolated
332 |  |
          */
333 |  |
         protected Object interpolate(Object value)
334 |  |
         {
335 | 346 |
             return getParent().interpolate(value);
336 |  |
         }
337 |  |
     }