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 /**
56 * <p>
57 * A <em>builder</em> class for creating instances of {@code InterpolatorSpecification}.
58 * </p>
59 * <p>
60 * This class provides a fluent API for defining the various properties of an {@code InterpolatorSpecification} object.
61 * <em>Note:</em> This builder class is not thread-safe.
62 * </p>
63 */
64 public static class Builder {
65 /**
66 * Helper method for checking a lookup. Throws an exception if the lookup is <strong>null</strong>.
67 *
68 * @param lookup the lookup to be checked
69 * @throws IllegalArgumentException if the lookup is <strong>null</strong>
70 */
71 private static void checkLookup(final Lookup lookup) {
72 if (lookup == null) {
73 throw new IllegalArgumentException("Lookup must not be null!");
74 }
75 }
76
77 /** A map with prefix lookups. */
78 private final Map<String, Lookup> prefixLookups;
79
80 /** A collection with default lookups. */
81 private final Collection<Lookup> defLookups;
82
83 /** The {@code ConfigurationInterpolator}. */
84 private ConfigurationInterpolator interpolator;
85
86 /** The parent {@code ConfigurationInterpolator}. */
87 private ConfigurationInterpolator parentInterpolator;
88
89 /** Function used to convert interpolated values to strings. */
90 private Function<Object, String> stringConverter;
91
92 /**
93 * Constructs a new instance.
94 */
95 public Builder() {
96 prefixLookups = new HashMap<>();
97 defLookups = new LinkedList<>();
98 }
99
100 /**
101 * Creates a new {@code InterpolatorSpecification} instance with the properties set so far. After that this builder
102 * instance is reset so that it can be reused for creating further specification objects.
103 *
104 * @return the newly created {@code InterpolatorSpecification}
105 */
106 public InterpolatorSpecification create() {
107 final InterpolatorSpecification spec = new InterpolatorSpecification(this);
108 reset();
109 return spec;
110 }
111
112 /**
113 * Removes all data from this builder. Afterwards it can be used to define a brand new {@code InterpolatorSpecification}
114 * object.
115 */
116 public void reset() {
117 interpolator = null;
118 parentInterpolator = null;
119 prefixLookups.clear();
120 defLookups.clear();
121 stringConverter = null;
122 }
123
124 /**
125 * Adds the given {@code Lookup} object to the list of default lookups.
126 *
127 * @param lookup the {@code Lookup} (must not be <strong>null</strong>)
128 * @return a reference to this builder for method chaining
129 * @throws IllegalArgumentException if the {@code Lookup} is <strong>null</strong>
130 */
131 public Builder withDefaultLookup(final Lookup lookup) {
132 checkLookup(lookup);
133 defLookups.add(lookup);
134 return this;
135 }
136
137 /**
138 * Adds the content of the given collection to the default lookups managed by this builder. The collection can be
139 * <strong>null</strong>, then this method has no effect.
140 *
141 * @param lookups the collection with lookups to be added
142 * @return a reference to this builder for method chaining
143 * @throws IllegalArgumentException if the collection contains <strong>null</strong> entries
144 */
145 public Builder withDefaultLookups(final Collection<? extends Lookup> lookups) {
146 if (lookups != null) {
147 lookups.forEach(this::withDefaultLookup);
148 }
149 return this;
150 }
151
152 /**
153 * Sets the {@code ConfigurationInterpolator} instance for the {@code InterpolatorSpecification}. This means that a
154 * {@code ConfigurationInterpolator} has been created and set up externally and can be used directly.
155 *
156 * @param ci the {@code ConfigurationInterpolator} (can be <strong>null</strong>)
157 * @return a reference to this builder for method chaining
158 */
159 public Builder withInterpolator(final ConfigurationInterpolator ci) {
160 interpolator = ci;
161 return this;
162 }
163
164 /**
165 * Sets an optional parent {@code ConfigurationInterpolator}. If defined, this object is set as parent of a newly
166 * created {@code ConfigurationInterpolator} instance.
167 *
168 * @param parent the parent {@code ConfigurationInterpolator} (can be <strong>null</strong>)
169 * @return a reference to this builder for method chaining
170 */
171 public Builder withParentInterpolator(final ConfigurationInterpolator parent) {
172 parentInterpolator = parent;
173 return this;
174 }
175
176 /**
177 * Adds a {@code Lookup} object for a given prefix.
178 *
179 * @param prefix the prefix (must not be <strong>null</strong>)
180 * @param lookup the {@code Lookup} (must not be <strong>null</strong>)
181 * @return a reference to this builder for method chaining
182 * @throws IllegalArgumentException if a required parameter is missing
183 */
184 public Builder withPrefixLookup(final String prefix, final Lookup lookup) {
185 if (prefix == null) {
186 throw new IllegalArgumentException("Prefix must not be null!");
187 }
188 checkLookup(lookup);
189 prefixLookups.put(prefix, lookup);
190 return this;
191 }
192
193 /**
194 * Adds the content of the given map to the prefix lookups managed by this builder. The map can be <strong>null</strong>, then
195 * this method has no effect.
196 *
197 * @param lookups the map with prefix lookups to be added
198 * @return a reference to this builder for method chaining
199 * @throws IllegalArgumentException if the map contains <strong>null</strong> values
200 */
201 public Builder withPrefixLookups(final Map<String, ? extends Lookup> lookups) {
202 if (lookups != null) {
203 lookups.forEach(this::withPrefixLookup);
204 }
205 return this;
206 }
207
208 /**
209 * Sets the function used to convert interpolated values to strings. Pass {@code null}
210 * if the default conversion function is to be used.
211 *
212 * @param fn function used to convert interpolated values to string or {@code null} if the
213 * default conversion function is to be used
214 * @return a reference to this builder for method chaining
215 */
216 public Builder withStringConverter(final Function<Object, String> fn) {
217 this.stringConverter = fn;
218 return this;
219 }
220 }
221
222 /** The {@code ConfigurationInterpolator} instance to be used directly. */
223 private final ConfigurationInterpolator interpolator;
224
225 /** The parent {@code ConfigurationInterpolator}. */
226 private final ConfigurationInterpolator parentInterpolator;
227
228 /** The map with prefix lookups. */
229 private final Map<String, Lookup> prefixLookups;
230
231 /** The collection with default lookups. */
232 private final Collection<Lookup> defaultLookups;
233
234 /** Function used to convert interpolated values to strings. */
235 private final Function<Object, String> stringConverter;
236
237 /**
238 * Creates a new instance of {@code InterpolatorSpecification} with the properties defined by the given builder object.
239 *
240 * @param builder the builder
241 */
242 private InterpolatorSpecification(final Builder builder) {
243 interpolator = builder.interpolator;
244 parentInterpolator = builder.parentInterpolator;
245 prefixLookups = Collections.unmodifiableMap(new HashMap<>(builder.prefixLookups));
246 defaultLookups = Collections.unmodifiableCollection(new ArrayList<>(builder.defLookups));
247 stringConverter = builder.stringConverter;
248 }
249
250 /**
251 * Gets a collection with the default lookups.
252 *
253 * @return the default lookups for a new {@code ConfigurationInterpolator} instance (never <strong>null</strong>)
254 */
255 public Collection<Lookup> getDefaultLookups() {
256 return defaultLookups;
257 }
258
259 /**
260 * Gets the {@code ConfigurationInterpolator} instance to be used directly.
261 *
262 * @return the {@code ConfigurationInterpolator} (can be <strong>null</strong>)
263 */
264 public ConfigurationInterpolator getInterpolator() {
265 return interpolator;
266 }
267
268 /**
269 * Gets the parent {@code ConfigurationInterpolator} object.
270 *
271 * @return the parent {@code ConfigurationInterpolator} (can be <strong>null</strong>)
272 */
273 public ConfigurationInterpolator getParentInterpolator() {
274 return parentInterpolator;
275 }
276
277 /**
278 * Gets a map with prefix lookups. The keys of the map are the prefix strings, its values are the corresponding
279 * {@code Lookup} objects.
280 *
281 * @return the prefix lookups for a new {@code ConfigurationInterpolator} instance (never <strong>null</strong>)
282 */
283 public Map<String, Lookup> getPrefixLookups() {
284 return prefixLookups;
285 }
286
287 /**
288 * Gets the function used to convert interpolated values to strings or {@code null}
289 * if the default conversion function is to be used.
290 *
291 * @return function used to convert interpolated values to strings or {@code null} if
292 * the default conversion function is to be used
293 */
294 public Function<Object, String> getStringConverter() {
295 return stringConverter;
296 }
297 }