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.interpol; 18 19 import java.util.ArrayList; 20 import java.util.Collection; 21 import java.util.Collections; 22 import java.util.HashMap; 23 import java.util.LinkedList; 24 import java.util.Map; 25 import java.util.function.Function; 26 27 /** 28 * <p> 29 * A simple value class defining a {@link ConfigurationInterpolator}. 30 * </p> 31 * <p> 32 * Objects of this class can be used for creating new {@code ConfigurationInterpolator} instances; they contain all 33 * required properties. It is either possible to set a fully initialized {@code ConfigurationInterpolator} directly 34 * which can be used as is. Alternatively, some or all properties of an instance to be newly created can be set. These 35 * properties include 36 * </p> 37 * <ul> 38 * <li>a map with {@code Lookup} objects associated with a specific prefix</li> 39 * <li>a collection with default {@code Lookup} objects (without a prefix)</li> 40 * <li>a parent {@code ConfigurationInterpolator}</li> 41 * <li>a function used to convert interpolated values into strings</li> 42 * </ul> 43 * <p> 44 * When setting up a configuration it is possible to define the {@code ConfigurationInterpolator} in terms of this 45 * class. The configuration will then either use the {@code ConfigurationInterpolator} instance explicitly defined in 46 * the {@code InterpolatorSpecification} instance or create a new one. 47 * </p> 48 * <p> 49 * Instances are not created directly, but using the nested {@code Builder} class. They are then immutable. 50 * </p> 51 * 52 * @since 2.0 53 */ 54 public final class InterpolatorSpecification { 55 /** The {@code ConfigurationInterpolator} instance to be used directly. */ 56 private final ConfigurationInterpolator interpolator; 57 58 /** The parent {@code ConfigurationInterpolator}. */ 59 private final ConfigurationInterpolator parentInterpolator; 60 61 /** The map with prefix lookups. */ 62 private final Map<String, Lookup> prefixLookups; 63 64 /** The collection with default lookups. */ 65 private final Collection<Lookup> defaultLookups; 66 67 /** Function used to convert interpolated values to strings. */ 68 private final Function<Object, String> stringConverter; 69 70 /** 71 * Creates a new instance of {@code InterpolatorSpecification} with the properties defined by the given builder object. 72 * 73 * @param builder the builder 74 */ 75 private InterpolatorSpecification(final Builder builder) { 76 interpolator = builder.interpolator; 77 parentInterpolator = builder.parentInterpolator; 78 prefixLookups = Collections.unmodifiableMap(new HashMap<>(builder.prefixLookups)); 79 defaultLookups = Collections.unmodifiableCollection(new ArrayList<>(builder.defLookups)); 80 stringConverter = builder.stringConverter; 81 } 82 83 /** 84 * Gets the {@code ConfigurationInterpolator} instance to be used directly. 85 * 86 * @return the {@code ConfigurationInterpolator} (can be <b>null</b>) 87 */ 88 public ConfigurationInterpolator getInterpolator() { 89 return interpolator; 90 } 91 92 /** 93 * Gets the parent {@code ConfigurationInterpolator} object. 94 * 95 * @return the parent {@code ConfigurationInterpolator} (can be <b>null</b>) 96 */ 97 public ConfigurationInterpolator getParentInterpolator() { 98 return parentInterpolator; 99 } 100 101 /** 102 * Gets a map with prefix lookups. The keys of the map are the prefix strings, its values are the corresponding 103 * {@code Lookup} objects. 104 * 105 * @return the prefix lookups for a new {@code ConfigurationInterpolator} instance (never <b>null</b>) 106 */ 107 public Map<String, Lookup> getPrefixLookups() { 108 return prefixLookups; 109 } 110 111 /** 112 * Gets a collection with the default lookups. 113 * 114 * @return the default lookups for a new {@code ConfigurationInterpolator} instance (never <b>null</b>) 115 */ 116 public Collection<Lookup> getDefaultLookups() { 117 return defaultLookups; 118 } 119 120 /** 121 * Gets the function used to convert interpolated values to strings or {@code null} 122 * if the default conversion function is to be used. 123 * 124 * @return function used to convert interpolated values to strings or {@code null} if 125 * the default conversion function is to be used 126 */ 127 public Function<Object, String> getStringConverter() { 128 return stringConverter; 129 } 130 131 /** 132 * <p> 133 * A <em>builder</em> class for creating instances of {@code InterpolatorSpecification}. 134 * </p> 135 * <p> 136 * This class provides a fluent API for defining the various properties of an {@code InterpolatorSpecification} object. 137 * <em>Note:</em> This builder class is not thread-safe. 138 * </p> 139 */ 140 public static class Builder { 141 /** A map with prefix lookups. */ 142 private final Map<String, Lookup> prefixLookups; 143 144 /** A collection with default lookups. */ 145 private final Collection<Lookup> defLookups; 146 147 /** The {@code ConfigurationInterpolator}. */ 148 private ConfigurationInterpolator interpolator; 149 150 /** The parent {@code ConfigurationInterpolator}. */ 151 private ConfigurationInterpolator parentInterpolator; 152 153 /** Function used to convert interpolated values to strings. */ 154 private Function<Object, String> stringConverter; 155 156 public Builder() { 157 prefixLookups = new HashMap<>(); 158 defLookups = new LinkedList<>(); 159 } 160 161 /** 162 * Adds a {@code Lookup} object for a given prefix. 163 * 164 * @param prefix the prefix (must not be <b>null</b>) 165 * @param lookup the {@code Lookup} (must not be <b>null</b>) 166 * @return a reference to this builder for method chaining 167 * @throws IllegalArgumentException if a required parameter is missing 168 */ 169 public Builder withPrefixLookup(final String prefix, final Lookup lookup) { 170 if (prefix == null) { 171 throw new IllegalArgumentException("Prefix must not be null!"); 172 } 173 checkLookup(lookup); 174 prefixLookups.put(prefix, lookup); 175 return this; 176 } 177 178 /** 179 * Adds the content of the given map to the prefix lookups managed by this builder. The map can be <b>null</b>, then 180 * this method has no effect. 181 * 182 * @param lookups the map with prefix lookups to be added 183 * @return a reference to this builder for method chaining 184 * @throws IllegalArgumentException if the map contains <b>null</b> values 185 */ 186 public Builder withPrefixLookups(final Map<String, ? extends Lookup> lookups) { 187 if (lookups != null) { 188 lookups.forEach(this::withPrefixLookup); 189 } 190 return this; 191 } 192 193 /** 194 * Adds the given {@code Lookup} object to the list of default lookups. 195 * 196 * @param lookup the {@code Lookup} (must not be <b>null</b>) 197 * @return a reference to this builder for method chaining 198 * @throws IllegalArgumentException if the {@code Lookup} is <b>null</b> 199 */ 200 public Builder withDefaultLookup(final Lookup lookup) { 201 checkLookup(lookup); 202 defLookups.add(lookup); 203 return this; 204 } 205 206 /** 207 * Adds the content of the given collection to the default lookups managed by this builder. The collection can be 208 * <b>null</b>, then this method has no effect. 209 * 210 * @param lookups the collection with lookups to be added 211 * @return a reference to this builder for method chaining 212 * @throws IllegalArgumentException if the collection contains <b>null</b> entries 213 */ 214 public Builder withDefaultLookups(final Collection<? extends Lookup> lookups) { 215 if (lookups != null) { 216 lookups.forEach(this::withDefaultLookup); 217 } 218 return this; 219 } 220 221 /** 222 * Sets the {@code ConfigurationInterpolator} instance for the {@code InterpolatorSpecification}. This means that a 223 * {@code ConfigurationInterpolator} has been created and set up externally and can be used directly. 224 * 225 * @param ci the {@code ConfigurationInterpolator} (can be <b>null</b>) 226 * @return a reference to this builder for method chaining 227 */ 228 public Builder withInterpolator(final ConfigurationInterpolator ci) { 229 interpolator = ci; 230 return this; 231 } 232 233 /** 234 * Sets an optional parent {@code ConfigurationInterpolator}. If defined, this object is set as parent of a newly 235 * created {@code ConfigurationInterpolator} instance. 236 * 237 * @param parent the parent {@code ConfigurationInterpolator} (can be <b>null</b>) 238 * @return a reference to this builder for method chaining 239 */ 240 public Builder withParentInterpolator(final ConfigurationInterpolator parent) { 241 parentInterpolator = parent; 242 return this; 243 } 244 245 /** 246 * Sets the function used to convert interpolated values to strings. Pass {@code null} 247 * if the default conversion function is to be used. 248 * 249 * @param fn function used to convert interpolated values to string or {@code null} if the 250 * default conversion function is to be used 251 * @return a reference to this builder for method chaining 252 */ 253 public Builder withStringConverter(final Function<Object, String> fn) { 254 this.stringConverter = fn; 255 return this; 256 } 257 258 /** 259 * Creates a new {@code InterpolatorSpecification} instance with the properties set so far. After that this builder 260 * instance is reset so that it can be reused for creating further specification objects. 261 * 262 * @return the newly created {@code InterpolatorSpecification} 263 */ 264 public InterpolatorSpecification create() { 265 final InterpolatorSpecification spec = new InterpolatorSpecification(this); 266 reset(); 267 return spec; 268 } 269 270 /** 271 * Removes all data from this builder. Afterwards it can be used to define a brand new {@code InterpolatorSpecification} 272 * object. 273 */ 274 public void reset() { 275 interpolator = null; 276 parentInterpolator = null; 277 prefixLookups.clear(); 278 defLookups.clear(); 279 stringConverter = null; 280 } 281 282 /** 283 * Helper method for checking a lookup. Throws an exception if the lookup is <b>null</b>. 284 * 285 * @param lookup the lookup to be checked 286 * @throws IllegalArgumentException if the lookup is <b>null</b> 287 */ 288 private static void checkLookup(final Lookup lookup) { 289 if (lookup == null) { 290 throw new IllegalArgumentException("Lookup must not be null!"); 291 } 292 } 293 } 294 }