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 */
017
018 package org.apache.commons.configuration;
019
020 import java.math.BigDecimal;
021 import java.math.BigInteger;
022 import java.util.Iterator;
023 import java.util.List;
024 import java.util.Properties;
025
026 /**
027 * <p>The main Configuration interface.</p>
028 * <p>This interface allows accessing and manipulating a configuration object.
029 * The major part of the methods defined in this interface deals with accessing
030 * properties of various data types. There is a generic {@code getProperty()}
031 * method, which returns the value of the queried property in its raw data
032 * type. Other getter methods try to convert this raw data type into a specific
033 * data type. If this fails, a {@code ConversionException} will be thrown.</p>
034 * <p>For most of the property getter methods an overloaded version exists that
035 * allows to specify a default value, which will be returned if the queried
036 * property cannot be found in the configuration. The behavior of the methods
037 * that do not take a default value in case of a missing property is not defined
038 * by this interface and depends on a concrete implementation. E.g. the
039 * {@link AbstractConfiguration} class, which is the base class
040 * of most configuration implementations provided by this package, per default
041 * returns <b>null</b> if a property is not found, but provides the
042 * {@link AbstractConfiguration#setThrowExceptionOnMissing(boolean)
043 * setThrowExceptionOnMissing()}
044 * method, with which it can be configured to throw a {@code NoSuchElementException}
045 * exception in that case. (Note that getter methods for primitive types in
046 * {@code AbstractConfiguration} always throw an exception for missing
047 * properties because there is no way of overloading the return value.)</p>
048 * <p>With the {@code addProperty()} and {@code setProperty()} methods
049 * new properties can be added to a configuration or the values of properties
050 * can be changed. With {@code clearProperty()} a property can be removed.
051 * Other methods allow to iterate over the contained properties or to create
052 * a subset configuration.</p>
053 *
054 * @author Commons Configuration team
055 * @version $Id: Configuration.java 1204078 2011-11-19 21:28:49Z oheger $
056 */
057 public interface Configuration
058 {
059 /**
060 * Return a decorator Configuration containing every key from the current
061 * Configuration that starts with the specified prefix. The prefix is
062 * removed from the keys in the subset. For example, if the configuration
063 * contains the following properties:
064 *
065 * <pre>
066 * prefix.number = 1
067 * prefix.string = Apache
068 * prefixed.foo = bar
069 * prefix = Jakarta</pre>
070 *
071 * the Configuration returned by {@code subset("prefix")} will contain
072 * the properties:
073 *
074 * <pre>
075 * number = 1
076 * string = Apache
077 * = Jakarta</pre>
078 *
079 * (The key for the value "Jakarta" is an empty string)
080 * <p>
081 * Since the subset is a decorator and not a modified copy of the initial
082 * Configuration, any change made to the subset is available to the
083 * Configuration, and reciprocally.
084 *
085 * @param prefix The prefix used to select the properties.
086 * @return a subset configuration
087 *
088 * @see SubsetConfiguration
089 */
090 Configuration subset(String prefix);
091
092 /**
093 * Check if the configuration is empty.
094 *
095 * @return {@code true} if the configuration contains no property,
096 * {@code false} otherwise.
097 */
098 boolean isEmpty();
099
100 /**
101 * Check if the configuration contains the specified key.
102 *
103 * @param key the key whose presence in this configuration is to be tested
104 *
105 * @return {@code true} if the configuration contains a value for this
106 * key, {@code false} otherwise
107 */
108 boolean containsKey(String key);
109
110 /**
111 * Add a property to the configuration. If it already exists then the value
112 * stated here will be added to the configuration entry. For example, if
113 * the property:
114 *
115 * <pre>resource.loader = file</pre>
116 *
117 * is already present in the configuration and you call
118 *
119 * <pre>addProperty("resource.loader", "classpath")</pre>
120 *
121 * Then you will end up with a List like the following:
122 *
123 * <pre>["file", "classpath"]</pre>
124 *
125 * @param key The key to add the property to.
126 * @param value The value to add.
127 */
128 void addProperty(String key, Object value);
129
130 /**
131 * Set a property, this will replace any previously set values. Set values
132 * is implicitly a call to clearProperty(key), addProperty(key, value).
133 *
134 * @param key The key of the property to change
135 * @param value The new value
136 */
137 void setProperty(String key, Object value);
138
139 /**
140 * Remove a property from the configuration.
141 *
142 * @param key the key to remove along with corresponding value.
143 */
144 void clearProperty(String key);
145
146 /**
147 * Remove all properties from the configuration.
148 */
149 void clear();
150
151 /**
152 * Gets a property from the configuration. This is the most basic get
153 * method for retrieving values of properties. In a typical implementation
154 * of the {@code Configuration} interface the other get methods (that
155 * return specific data types) will internally make use of this method. On
156 * this level variable substitution is not yet performed. The returned
157 * object is an internal representation of the property value for the passed
158 * in key. It is owned by the {@code Configuration} object. So a caller
159 * should not modify this object. It cannot be guaranteed that this object
160 * will stay constant over time (i.e. further update operations on the
161 * configuration may change its internal state).
162 *
163 * @param key property to retrieve
164 * @return the value to which this configuration maps the specified key, or
165 * null if the configuration contains no mapping for this key.
166 */
167 Object getProperty(String key);
168
169 /**
170 * Get the list of the keys contained in the configuration that match the
171 * specified prefix. For instance, if the configuration contains the
172 * following keys:<br>
173 * {@code db.user, db.pwd, db.url, window.xpos, window.ypos},<br>
174 * an invocation of {@code getKeys("db");}<br>
175 * will return the keys below:<br>
176 * {@code db.user, db.pwd, db.url}.<br>
177 * Note that the prefix itself is included in the result set if there is a
178 * matching key. The exact behavior - how the prefix is actually
179 * interpreted - depends on a concrete implementation.
180 *
181 * @param prefix The prefix to test against.
182 * @return An Iterator of keys that match the prefix.
183 * @see #getKeys()
184 */
185 Iterator<String> getKeys(String prefix);
186
187 /**
188 * Get the list of the keys contained in the configuration. The returned
189 * iterator can be used to obtain all defined keys. Note that the exact
190 * behavior of the iterator's {@code remove()} method is specific to
191 * a concrete implementation. It <em>may</em> remove the corresponding
192 * property from the configuration, but this is not guaranteed. In any case
193 * it is no replacement for calling
194 * {@link #clearProperty(String)} for this property. So it is
195 * highly recommended to avoid using the iterator's {@code remove()}
196 * method.
197 *
198 * @return An Iterator.
199 */
200 Iterator<String> getKeys();
201
202 /**
203 * Get a list of properties associated with the given configuration key.
204 * This method expects the given key to have an arbitrary number of String
205 * values, each of which is of the form {code key=value}. These
206 * strings are split at the equals sign, and the key parts will become
207 * keys of the returned {@code Properties} object, the value parts
208 * become values.
209 *
210 * @param key The configuration key.
211 * @return The associated properties if key is found.
212 *
213 * @throws ConversionException is thrown if the key maps to an
214 * object that is not a String/List.
215 *
216 * @throws IllegalArgumentException if one of the tokens is
217 * malformed (does not contain an equals sign).
218 */
219 Properties getProperties(String key);
220
221 /**
222 * Get a boolean associated with the given configuration key.
223 *
224 * @param key The configuration key.
225 * @return The associated boolean.
226 *
227 * @throws ConversionException is thrown if the key maps to an
228 * object that is not a Boolean.
229 */
230 boolean getBoolean(String key);
231
232 /**
233 * Get a boolean associated with the given configuration key.
234 * If the key doesn't map to an existing object, the default value
235 * is returned.
236 *
237 * @param key The configuration key.
238 * @param defaultValue The default value.
239 * @return The associated boolean.
240 *
241 * @throws ConversionException is thrown if the key maps to an
242 * object that is not a Boolean.
243 */
244 boolean getBoolean(String key, boolean defaultValue);
245
246 /**
247 * Get a {@link Boolean} associated with the given configuration key.
248 *
249 * @param key The configuration key.
250 * @param defaultValue The default value.
251 * @return The associated boolean if key is found and has valid
252 * format, default value otherwise.
253 *
254 * @throws ConversionException is thrown if the key maps to an
255 * object that is not a Boolean.
256 */
257 Boolean getBoolean(String key, Boolean defaultValue);
258
259 /**
260 * Get a byte associated with the given configuration key.
261 *
262 * @param key The configuration key.
263 * @return The associated byte.
264 *
265 * @throws ConversionException is thrown if the key maps to an
266 * object that is not a Byte.
267 */
268 byte getByte(String key);
269
270 /**
271 * Get a byte associated with the given configuration key.
272 * If the key doesn't map to an existing object, the default value
273 * is returned.
274 *
275 * @param key The configuration key.
276 * @param defaultValue The default value.
277 * @return The associated byte.
278 *
279 * @throws ConversionException is thrown if the key maps to an
280 * object that is not a Byte.
281 */
282 byte getByte(String key, byte defaultValue);
283
284 /**
285 * Get a {@link Byte} associated with the given configuration key.
286 *
287 * @param key The configuration key.
288 * @param defaultValue The default value.
289 * @return The associated byte if key is found and has valid format, default
290 * value otherwise.
291 *
292 * @throws ConversionException is thrown if the key maps to an object that
293 * is not a Byte.
294 */
295 Byte getByte(String key, Byte defaultValue);
296
297 /**
298 * Get a double associated with the given configuration key.
299 *
300 * @param key The configuration key.
301 * @return The associated double.
302 *
303 * @throws ConversionException is thrown if the key maps to an
304 * object that is not a Double.
305 */
306 double getDouble(String key);
307
308 /**
309 * Get a double associated with the given configuration key.
310 * If the key doesn't map to an existing object, the default value
311 * is returned.
312 *
313 * @param key The configuration key.
314 * @param defaultValue The default value.
315 * @return The associated double.
316 *
317 * @throws ConversionException is thrown if the key maps to an
318 * object that is not a Double.
319 */
320 double getDouble(String key, double defaultValue);
321
322 /**
323 * Get a {@link Double} associated with the given configuration key.
324 *
325 * @param key The configuration key.
326 * @param defaultValue The default value.
327 * @return The associated double if key is found and has valid
328 * format, default value otherwise.
329 *
330 * @throws ConversionException is thrown if the key maps to an
331 * object that is not a Double.
332 */
333 Double getDouble(String key, Double defaultValue);
334
335 /**
336 * Get a float associated with the given configuration key.
337 *
338 * @param key The configuration key.
339 * @return The associated float.
340 * @throws ConversionException is thrown if the key maps to an
341 * object that is not a Float.
342 */
343 float getFloat(String key);
344
345 /**
346 * Get a float associated with the given configuration key.
347 * If the key doesn't map to an existing object, the default value
348 * is returned.
349 *
350 * @param key The configuration key.
351 * @param defaultValue The default value.
352 * @return The associated float.
353 *
354 * @throws ConversionException is thrown if the key maps to an
355 * object that is not a Float.
356 */
357 float getFloat(String key, float defaultValue);
358
359 /**
360 * Get a {@link Float} associated with the given configuration key.
361 * If the key doesn't map to an existing object, the default value
362 * is returned.
363 *
364 * @param key The configuration key.
365 * @param defaultValue The default value.
366 * @return The associated float if key is found and has valid
367 * format, default value otherwise.
368 *
369 * @throws ConversionException is thrown if the key maps to an
370 * object that is not a Float.
371 */
372 Float getFloat(String key, Float defaultValue);
373
374 /**
375 * Get a int associated with the given configuration key.
376 *
377 * @param key The configuration key.
378 * @return The associated int.
379 *
380 * @throws ConversionException is thrown if the key maps to an
381 * object that is not a Integer.
382 */
383 int getInt(String key);
384
385 /**
386 * Get a int associated with the given configuration key.
387 * If the key doesn't map to an existing object, the default value
388 * is returned.
389 *
390 * @param key The configuration key.
391 * @param defaultValue The default value.
392 * @return The associated int.
393 *
394 * @throws ConversionException is thrown if the key maps to an
395 * object that is not a Integer.
396 */
397 int getInt(String key, int defaultValue);
398
399 /**
400 * Get an {@link Integer} associated with the given configuration key.
401 * If the key doesn't map to an existing object, the default value
402 * is returned.
403 *
404 * @param key The configuration key.
405 * @param defaultValue The default value.
406 * @return The associated int if key is found and has valid format, default
407 * value otherwise.
408 *
409 * @throws ConversionException is thrown if the key maps to an object that
410 * is not a Integer.
411 */
412 Integer getInteger(String key, Integer defaultValue);
413
414 /**
415 * Get a long associated with the given configuration key.
416 *
417 * @param key The configuration key.
418 * @return The associated long.
419 *
420 * @throws ConversionException is thrown if the key maps to an
421 * object that is not a Long.
422 */
423 long getLong(String key);
424
425 /**
426 * Get a long associated with the given configuration key.
427 * If the key doesn't map to an existing object, the default value
428 * is returned.
429 *
430 * @param key The configuration key.
431 * @param defaultValue The default value.
432 * @return The associated long.
433 *
434 * @throws ConversionException is thrown if the key maps to an
435 * object that is not a Long.
436 */
437 long getLong(String key, long defaultValue);
438
439 /**
440 * Get a {@link Long} associated with the given configuration key.
441 * If the key doesn't map to an existing object, the default value
442 * is returned.
443 *
444 * @param key The configuration key.
445 * @param defaultValue The default value.
446 * @return The associated long if key is found and has valid
447 * format, default value otherwise.
448 *
449 * @throws ConversionException is thrown if the key maps to an
450 * object that is not a Long.
451 */
452 Long getLong(String key, Long defaultValue);
453
454 /**
455 * Get a short associated with the given configuration key.
456 *
457 * @param key The configuration key.
458 * @return The associated short.
459 *
460 * @throws ConversionException is thrown if the key maps to an
461 * object that is not a Short.
462 */
463 short getShort(String key);
464
465 /**
466 * Get a short associated with the given configuration key.
467 *
468 * @param key The configuration key.
469 * @param defaultValue The default value.
470 * @return The associated short.
471 *
472 * @throws ConversionException is thrown if the key maps to an
473 * object that is not a Short.
474 */
475 short getShort(String key, short defaultValue);
476
477 /**
478 * Get a {@link Short} associated with the given configuration key.
479 * If the key doesn't map to an existing object, the default value
480 * is returned.
481 *
482 * @param key The configuration key.
483 * @param defaultValue The default value.
484 * @return The associated short if key is found and has valid
485 * format, default value otherwise.
486 *
487 * @throws ConversionException is thrown if the key maps to an
488 * object that is not a Short.
489 */
490 Short getShort(String key, Short defaultValue);
491
492 /**
493 * Get a {@link BigDecimal} associated with the given configuration key.
494 *
495 * @param key The configuration key.
496 * @return The associated BigDecimal if key is found and has valid format
497 */
498 BigDecimal getBigDecimal(String key);
499
500 /**
501 * Get a {@link BigDecimal} associated with the given configuration key.
502 * If the key doesn't map to an existing object, the default value
503 * is returned.
504 *
505 * @param key The configuration key.
506 * @param defaultValue The default value.
507 *
508 * @return The associated BigDecimal if key is found and has valid
509 * format, default value otherwise.
510 */
511 BigDecimal getBigDecimal(String key, BigDecimal defaultValue);
512
513 /**
514 * Get a {@link BigInteger} associated with the given configuration key.
515 *
516 * @param key The configuration key.
517 *
518 * @return The associated BigInteger if key is found and has valid format
519 */
520 BigInteger getBigInteger(String key);
521
522 /**
523 * Get a {@link BigInteger} associated with the given configuration key.
524 * If the key doesn't map to an existing object, the default value
525 * is returned.
526 *
527 * @param key The configuration key.
528 * @param defaultValue The default value.
529 *
530 * @return The associated BigInteger if key is found and has valid
531 * format, default value otherwise.
532 */
533 BigInteger getBigInteger(String key, BigInteger defaultValue);
534
535 /**
536 * Get a string associated with the given configuration key.
537 *
538 * @param key The configuration key.
539 * @return The associated string.
540 *
541 * @throws ConversionException is thrown if the key maps to an object that
542 * is not a String.
543 */
544 String getString(String key);
545
546 /**
547 * Get a string associated with the given configuration key.
548 * If the key doesn't map to an existing object, the default value
549 * is returned.
550 *
551 * @param key The configuration key.
552 * @param defaultValue The default value.
553 * @return The associated string if key is found and has valid
554 * format, default value otherwise.
555 *
556 * @throws ConversionException is thrown if the key maps to an object that
557 * is not a String.
558 */
559 String getString(String key, String defaultValue);
560
561 /**
562 * Get an array of strings associated with the given configuration key.
563 * If the key doesn't map to an existing object an empty array is returned
564 *
565 * @param key The configuration key.
566 * @return The associated string array if key is found.
567 *
568 * @throws ConversionException is thrown if the key maps to an
569 * object that is not a String/List of Strings.
570 */
571 String[] getStringArray(String key);
572
573 /**
574 * Get a List of strings associated with the given configuration key.
575 * If the key doesn't map to an existing object an empty List is returned.
576 *
577 * @param key The configuration key.
578 * @return The associated List.
579 *
580 * @throws ConversionException is thrown if the key maps to an
581 * object that is not a List.
582 */
583 List<Object> getList(String key);
584
585 /**
586 * Get a List of strings associated with the given configuration key.
587 * If the key doesn't map to an existing object, the default value
588 * is returned.
589 *
590 * @param key The configuration key.
591 * @param defaultValue The default value.
592 * @return The associated List of strings.
593 *
594 * @throws ConversionException is thrown if the key maps to an
595 * object that is not a List.
596 */
597 List<Object> getList(String key, List<Object> defaultValue);
598 }