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 package org.apache.commons.configuration2.builder.combined;
18
19 import java.util.Collection;
20 import java.util.LinkedList;
21 import java.util.Map;
22
23 import org.apache.commons.configuration2.CombinedConfiguration;
24 import org.apache.commons.configuration2.HierarchicalConfiguration;
25 import org.apache.commons.configuration2.XMLConfiguration;
26 import org.apache.commons.configuration2.builder.BuilderParameters;
27 import org.apache.commons.configuration2.builder.ConfigurationBuilder;
28 import org.apache.commons.configuration2.builder.ReloadingFileBasedConfigurationBuilder;
29 import org.apache.commons.configuration2.ex.ConfigurationException;
30 import org.apache.commons.configuration2.reloading.CombinedReloadingController;
31 import org.apache.commons.configuration2.reloading.ReloadingController;
32 import org.apache.commons.configuration2.reloading.ReloadingControllerSupport;
33
34 /**
35 * <p>
36 * An extension of {@code CombinedConfigurationBuilder} which also supports reloading operations.
37 * </p>
38 * <p>
39 * This class differs from its super class in the following aspects:
40 * </p>
41 * <ul>
42 * <li>A {@link ReloadingController} is created which manages all child configuration builders supporting reloading
43 * operations.</li>
44 * <li>If no {@code ConfigurationBuilder} is provided for the definition configuration, a builder with reloading support
45 * is created.</li>
46 * </ul>
47 * <p>
48 * This class can be used exactly as its super class for creating combined configurations from multiple configuration
49 * sources. In addition, the combined reloading controller managed by an instance can be used to react on changes in one
50 * of these configuration sources or in the definition configuration.
51 * </p>
52 *
53 * @since 2.0
54 */
55 public class ReloadingCombinedConfigurationBuilder extends CombinedConfigurationBuilder implements ReloadingControllerSupport {
56 /** The reloading controller used by this builder. */
57 private ReloadingController reloadingController;
58
59 /**
60 * Creates a new instance of {@code ReloadingCombinedConfigurationBuilder}. No parameters are set.
61 */
62 public ReloadingCombinedConfigurationBuilder() {
63 }
64
65 /**
66 * Creates a new instance of {@code ReloadingCombinedConfigurationBuilder} and sets the specified initialization
67 * parameters and the <em>allowFailOnInit</em> flag.
68 *
69 * @param params a map with initialization parameters
70 * @param allowFailOnInit the <em>allowFailOnInit</em> flag
71 */
72 public ReloadingCombinedConfigurationBuilder(final Map<String, Object> params, final boolean allowFailOnInit) {
73 super(params, allowFailOnInit);
74 }
75
76 /**
77 * Creates a new instance of {@code ReloadingCombinedConfigurationBuilder} and sets the specified initialization
78 * parameters.
79 *
80 * @param params a map with initialization parameters
81 */
82 public ReloadingCombinedConfigurationBuilder(final Map<String, Object> params) {
83 super(params);
84 }
85
86 /**
87 * {@inheritDoc} This method is overridden to adapt the return type.
88 */
89 @Override
90 public ReloadingCombinedConfigurationBuilder configure(final BuilderParameters... params) {
91 super.configure(params);
92 return this;
93 }
94
95 /**
96 * {@inheritDoc} This implementation returns a {@link CombinedReloadingController} which contains sub controllers for
97 * all child configuration sources with reloading support. If the definition builder supports reloading, its controller
98 * is contained, too. Note that the combined reloading controller is initialized when the result configuration is
99 * created (i.e. when calling {@code getConfiguration()} for the first time). So this method does not return a
100 * meaningful result before.
101 */
102 @Override
103 public synchronized ReloadingController getReloadingController() {
104 return reloadingController;
105 }
106
107 /**
108 * {@inheritDoc} This implementation makes sure that the reloading state of the managed reloading controller is reset.
109 * Note that this has to be done here and not in {@link #initResultInstance(CombinedConfiguration)} because it must be
110 * outside of a synchronized block; otherwise, a dead-lock situation can occur.
111 */
112 @Override
113 public CombinedConfiguration getConfiguration() throws ConfigurationException {
114 final CombinedConfiguration result = super.getConfiguration();
115 reloadingController.resetReloadingState();
116 return result;
117 }
118
119 /**
120 * {@inheritDoc} This implementation creates a builder for XML configurations with reloading support.
121 */
122 @Override
123 protected ConfigurationBuilder<? extends HierarchicalConfiguration<?>> createXMLDefinitionBuilder(final BuilderParameters builderParams) {
124 return new ReloadingFileBasedConfigurationBuilder<>(XMLConfiguration.class).configure(builderParams);
125 }
126
127 /**
128 * {@inheritDoc} This implementation first calls the super method to actually initialize the result configuration. Then
129 * it creates the {@link CombinedReloadingController} for all child configuration sources with reloading support.
130 */
131 @Override
132 protected void initResultInstance(final CombinedConfiguration result) throws ConfigurationException {
133 super.initResultInstance(result);
134 if (reloadingController == null) {
135 reloadingController = createReloadingController();
136 }
137 }
138
139 /**
140 * Creates the {@code ReloadingController} for this builder. This method is called after the result configuration has
141 * been created and initialized. It is called from a synchronized block. This implementation creates a
142 * {@link CombinedReloadingController}.
143 *
144 * @return the {@code ReloadingController} for this builder
145 * @throws ConfigurationException if an error occurs
146 */
147 protected ReloadingController createReloadingController() throws ConfigurationException {
148 final Collection<ReloadingController> subControllers = new LinkedList<>();
149 final ConfigurationBuilder<? extends HierarchicalConfiguration<?>> defBuilder = getDefinitionBuilder();
150 obtainReloadingController(subControllers, defBuilder);
151
152 getChildBuilders().forEach(b -> obtainReloadingController(subControllers, b));
153
154 final CombinedReloadingController ctrl = new CombinedReloadingController(subControllers);
155 ctrl.resetInitialReloadingState();
156 return ctrl;
157 }
158
159 /**
160 * Checks whether the passed in builder object supports reloading. If yes, its reloading controller is obtained and
161 * added to the given list.
162 *
163 * @param subControllers the list with sub controllers
164 * @param builder the builder object to be checked
165 */
166 public static void obtainReloadingController(final Collection<ReloadingController> subControllers, final Object builder) {
167 if (builder instanceof ReloadingControllerSupport) {
168 subControllers.add(((ReloadingControllerSupport) builder).getReloadingController());
169 }
170 }
171 }