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; 18 19 import java.util.Collection; 20 import java.util.List; 21 22 import org.apache.commons.configuration2.tree.ExpressionEngine; 23 import org.apache.commons.configuration2.tree.NodeModelSupport; 24 25 /** 26 * <p> 27 * An interface for mutable hierarchical configurations. 28 * </p> 29 * <p> 30 * This interface introduces methods for manipulating tree-like structured configuration sources. Also, all methods 31 * defined by the {@code Configuration} interface are available. 32 * </p> 33 * <p> 34 * This interface does not make any assumptions about the concrete type of nodes used by an implementation; this is 35 * reflected by a generic type parameter. Concrete implementations may therefore define their own hierarchical 36 * structures. 37 * </p> 38 * 39 * @since 2.0 40 * @param <T> the type of the nodes used by this hierarchical configuration 41 */ 42 public interface HierarchicalConfiguration<T> extends Configuration, ImmutableHierarchicalConfiguration, NodeModelSupport<T> { 43 /** 44 * Adds a collection of nodes at the specified position of the configuration tree. This method works similar to 45 * {@code addProperty()}, but instead of a single property a whole collection of nodes can be added - and thus complete 46 * configuration sub trees. E.g. with this method it is possible to add parts of another 47 * {@code BaseHierarchicalConfiguration} object to this object. If the passed in key refers to an existing and unique 48 * node, the new nodes are added to this node. Otherwise a new node will be created at the specified position in the 49 * hierarchy. 50 * 51 * @param key the key where the nodes are to be added; can be <b>null </b>, then they are added to the root node 52 * @param nodes a collection with the {@code Node} objects to be added 53 */ 54 void addNodes(String key, Collection<? extends T> nodes); 55 56 /** 57 * Returns a list with sub configurations for all child nodes of the node selected by the given key. This method works 58 * like {@link #immutableChildConfigurationsAt(String)}, but returns a list with mutable configuration objects. The 59 * configuration objects returned are <strong>not</strong> connected to the parent configuration. 60 * 61 * @param key the key for selecting the desired parent node 62 * @return a collection with {@code HierarchicalConfiguration} objects for all child nodes of the selected parent node 63 */ 64 List<HierarchicalConfiguration<T>> childConfigurationsAt(String key); 65 66 /** 67 * Returns a list with sub configurations for all child nodes of the node selected by the given key allowing the caller 68 * to specify the {@code supportUpdates} flag. 69 * 70 * @param key the key for selecting the desired parent node 71 * @param supportUpdates a flag whether the returned sub configuration should be directly connected to its parent 72 * @return a collection with {@code HierarchicalConfiguration} objects for all child nodes of the selected parent node 73 */ 74 List<HierarchicalConfiguration<T>> childConfigurationsAt(String key, boolean supportUpdates); 75 76 /** 77 * Removes all values of the property with the given name and of keys that start with this name. So if there is a 78 * property with the key "foo" and a property with the key "foo.bar", a call of 79 * {@code clearTree("foo")} would remove both properties. 80 * 81 * @param key the key of the property to be removed 82 */ 83 void clearTree(String key); 84 85 /** 86 * Returns a hierarchical subnode configuration for the node specified by the given key. This is a short form for 87 * {@code configurationAt(key, 88 * <b>false</b>)}. 89 * 90 * @param key the key that selects the sub tree 91 * @return a hierarchical configuration that contains this sub tree 92 * @see SubnodeConfiguration 93 */ 94 HierarchicalConfiguration<T> configurationAt(String key); 95 96 /** 97 * <p> 98 * Returns a hierarchical sub configuration object that wraps the configuration node specified by the given key. This 99 * method provides an easy means of accessing sub trees of a hierarchical configuration. In the returned configuration 100 * the sub tree can directly be accessed, it becomes the root node of this configuration. Because of this the passed in 101 * key must select exactly one configuration node; otherwise an {@code IllegalArgumentException} will be thrown. 102 * </p> 103 * <p> 104 * The difference between this method and the {@link #subset(String)} method is that {@code subset()} supports arbitrary 105 * subsets of configuration nodes while {@code configurationAt()} only returns a single sub tree. Please refer to the 106 * documentation of the {@link SubnodeConfiguration} class to obtain further information about sub configurations and 107 * when they should be used. 108 * </p> 109 * <p> 110 * With the {@code supportUpdate} flag the behavior of the returned sub configuration regarding updates of its parent 111 * configuration can be determined. If set to <b>false</b>, the configurations return on independent nodes structures. 112 * So changes made on one configuration cannot be seen by the other one. A value of <b>true</b> in contrast creates a 113 * direct connection between both configurations - they are then using the same underlying data structures as much as 114 * possible. There are however changes which break this connection; for instance, if the sub tree the sub configuration 115 * belongs to is completely removed from the parent configuration. If such a change happens, the sub configuration 116 * becomes detached from its parent. It can still be used in a normal way, but changes on it are not reflected by the 117 * parent and vice verse. Also, it is not possible to reattach a once detached sub configuration. 118 * </p> 119 * 120 * @param key the key that selects the sub tree 121 * @param supportUpdates a flag whether the returned sub configuration should be directly connected to its parent 122 * @return a hierarchical configuration that contains this sub tree 123 * @see SubnodeConfiguration 124 */ 125 HierarchicalConfiguration<T> configurationAt(String key, boolean supportUpdates); 126 127 /** 128 * Returns a list of sub configurations for all configuration nodes selected by the given key. This method will evaluate 129 * the passed in key (using the current {@code ExpressionEngine}) and then create a sub configuration for each returned 130 * node (like {@link #configurationAt(String)} ). This is especially useful when dealing with list-like structures. As 131 * an example consider the configuration that contains data about database tables and their fields. If you need access 132 * to all fields of a certain table, you can simply do 133 * 134 * <pre> 135 * List fields = config.configurationsAt("tables.table(0).fields.field"); 136 * for(Iterator it = fields.iterator(); it.hasNext();) 137 * { 138 * BaseHierarchicalConfiguration sub = (BaseHierarchicalConfiguration) it.next(); 139 * // now the children and attributes of the field node can be 140 * // directly accessed 141 * String fieldName = sub.getString("name"); 142 * String fieldType = sub.getString("type"); 143 * ... 144 * </pre> 145 * 146 * The configuration objects returned are <strong>not</strong> connected to the parent configuration. 147 * 148 * @param key the key for selecting the desired nodes 149 * @return a list with hierarchical configuration objects; each configuration represents one of the nodes selected by 150 * the passed in key 151 */ 152 List<HierarchicalConfiguration<T>> configurationsAt(String key); 153 154 /** 155 * Returns a list of sub configurations for all configuration nodes selected by the given key allowing the caller to 156 * specify the {@code supportUpdates} flag. This method works like {@link #configurationsAt(String)}, but with the 157 * additional boolean parameter it can be specified whether the returned configurations react on updates of the parent 158 * configuration. 159 * 160 * @param key the key for selecting the desired nodes 161 * @param supportUpdates a flag whether the returned sub configuration should be directly connected to its parent 162 * @return a list with hierarchical configuration objects; each configuration represents one of the nodes selected by 163 * the passed in key 164 * @see #configurationsAt(String, boolean) 165 */ 166 List<HierarchicalConfiguration<T>> configurationsAt(String key, boolean supportUpdates); 167 168 /** 169 * Sets the expression engine to be used by this configuration. All property keys this configuration has to deal with 170 * will be interpreted by this engine. 171 * 172 * @param expressionEngine the new expression engine; can be <b>null</b>, then the default expression engine will be 173 * used 174 */ 175 void setExpressionEngine(ExpressionEngine expressionEngine); 176 }