001/* 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017package org.apache.commons.configuration2.builder.combined; 018 019import java.util.Collection; 020import java.util.LinkedList; 021import java.util.Map; 022 023import org.apache.commons.configuration2.CombinedConfiguration; 024import org.apache.commons.configuration2.HierarchicalConfiguration; 025import org.apache.commons.configuration2.XMLConfiguration; 026import org.apache.commons.configuration2.builder.BuilderParameters; 027import org.apache.commons.configuration2.builder.ConfigurationBuilder; 028import org.apache.commons.configuration2.builder.ReloadingFileBasedConfigurationBuilder; 029import org.apache.commons.configuration2.ex.ConfigurationException; 030import org.apache.commons.configuration2.reloading.CombinedReloadingController; 031import org.apache.commons.configuration2.reloading.ReloadingController; 032import org.apache.commons.configuration2.reloading.ReloadingControllerSupport; 033 034/** 035 * <p> 036 * An extension of {@code CombinedConfigurationBuilder} which also supports reloading operations. 037 * </p> 038 * <p> 039 * This class differs from its super class in the following aspects: 040 * </p> 041 * <ul> 042 * <li>A {@link ReloadingController} is created which manages all child configuration builders supporting reloading 043 * operations.</li> 044 * <li>If no {@code ConfigurationBuilder} is provided for the definition configuration, a builder with reloading support 045 * is created.</li> 046 * </ul> 047 * <p> 048 * This class can be used exactly as its super class for creating combined configurations from multiple configuration 049 * sources. In addition, the combined reloading controller managed by an instance can be used to react on changes in one 050 * of these configuration sources or in the definition configuration. 051 * </p> 052 * 053 * @since 2.0 054 */ 055public class ReloadingCombinedConfigurationBuilder extends CombinedConfigurationBuilder implements ReloadingControllerSupport { 056 /** The reloading controller used by this builder. */ 057 private ReloadingController reloadingController; 058 059 /** 060 * Creates a new instance of {@code ReloadingCombinedConfigurationBuilder}. No parameters are set. 061 */ 062 public ReloadingCombinedConfigurationBuilder() { 063 } 064 065 /** 066 * Creates a new instance of {@code ReloadingCombinedConfigurationBuilder} and sets the specified initialization 067 * parameters and the <em>allowFailOnInit</em> flag. 068 * 069 * @param params a map with initialization parameters 070 * @param allowFailOnInit the <em>allowFailOnInit</em> flag 071 */ 072 public ReloadingCombinedConfigurationBuilder(final Map<String, Object> params, final boolean allowFailOnInit) { 073 super(params, allowFailOnInit); 074 } 075 076 /** 077 * Creates a new instance of {@code ReloadingCombinedConfigurationBuilder} and sets the specified initialization 078 * parameters. 079 * 080 * @param params a map with initialization parameters 081 */ 082 public ReloadingCombinedConfigurationBuilder(final Map<String, Object> params) { 083 super(params); 084 } 085 086 /** 087 * {@inheritDoc} This method is overridden to adapt the return type. 088 */ 089 @Override 090 public ReloadingCombinedConfigurationBuilder configure(final BuilderParameters... params) { 091 super.configure(params); 092 return this; 093 } 094 095 /** 096 * {@inheritDoc} This implementation returns a {@link CombinedReloadingController} which contains sub controllers for 097 * all child configuration sources with reloading support. If the definition builder supports reloading, its controller 098 * is contained, too. Note that the combined reloading controller is initialized when the result configuration is 099 * 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}