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18 package org.apache.commons.configuration;
19
20 import java.math.BigDecimal;
21 import java.math.BigInteger;
22 import java.util.Iterator;
23 import java.util.List;
24 import java.util.Properties;
25
26 /***
27 * <p>The main Configuration interface.</p>
28 * <p>This interface allows accessing and manipulating a configuration object.
29 * The major part of the methods defined in this interface deals with accessing
30 * properties of various data types. There is a generic <code>getProperty()</code>
31 * method, which returns the value of the queried property in its raw data
32 * type. Other getter methods try to convert this raw data type into a specific
33 * data type. If this fails, a <code>ConversionException</code> will be thrown.</p>
34 * <p>For most of the property getter methods an overloaded version exists that
35 * allows to specify a default value, which will be returned if the queried
36 * property cannot be found in the configuration. The behavior of the methods
37 * that do not take a default value in case of a missing property is not defined
38 * by this interface and depends on a concrete implementation. E.g. the
39 * <code>{@link AbstractConfiguration}</code> class, which is the base class
40 * of most configuration implementations provided by this package, per default
41 * returns <b>null</b> if a property is not found, but provides the
42 * <code>{@link org.apache.commons.configuration.AbstractConfiguration#setThrowExceptionOnMissing(boolean)
43 * setThrowExceptionOnMissing()}</code>
44 * method, with which it can be configured to throw a <code>NoSuchElementException</code>
45 * exception in that case. (Note that getter methods for primitive types in
46 * <code>AbstractConfiguration</code> always throw an exception for missing
47 * properties because there is no way of overloading the return value.)</p>
48 * <p>With the <code>addProperty()</code> and <code>setProperty()</code> methods
49 * new properties can be added to a configuration or the values of properties
50 * can be changed. With <code>clearProperty()</code> a property can be removed.
51 * Other methods allow to iterate over the contained properties or to create
52 * a subset configuration.</p>
53 *
54 * @author Commons Configuration team
55 * @version $Id: Configuration.java 449017 2006-09-22 17:27:00Z oheger $
56 */
57 public interface Configuration
58 {
59 /***
60 * Return a decorator Configuration containing every key from the current
61 * Configuration that starts with the specified prefix. The prefix is
62 * removed from the keys in the subset. For example, if the configuration
63 * contains the following properties:
64 *
65 * <pre>
66 * prefix.number = 1
67 * prefix.string = Apache
68 * prefixed.foo = bar
69 * prefix = Jakarta</pre>
70 *
71 * the Configuration returned by <code>subset("prefix")</code> will contain
72 * the properties:
73 *
74 * <pre>
75 * number = 1
76 * string = Apache
77 * = Jakarta</pre>
78 *
79 * (The key for the value "Jakarta" is an empty string)
80 * <p>
81 * Since the subset is a decorator and not a modified copy of the initial
82 * Configuration, any change made to the subset is available to the
83 * Configuration, and reciprocally.
84 *
85 * @param prefix The prefix used to select the properties.
86 * @return a subset configuration
87 *
88 * @see SubsetConfiguration
89 */
90 Configuration subset(String prefix);
91
92 /***
93 * Check if the configuration is empty.
94 *
95 * @return <code>true</code> if the configuration contains no property,
96 * <code>false</code> otherwise.
97 */
98 boolean isEmpty();
99
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</code> if the configuration contains a value for this
106 * key, <code>false</code> 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</code> 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</code> 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.
172 *
173 * @param prefix The prefix to test against.
174 * @return An Iterator of keys that match the prefix.
175 * @see #getKeys()
176 */
177 Iterator getKeys(String prefix);
178
179 /***
180 * Get the list of the keys contained in the configuration. The returned
181 * iterator can be used to obtain all defined keys. Note that the exact
182 * behavior of the iterator's <code>remove()</code> method is specific to
183 * a concrete implementation. It <em>may</em> remove the corresponding
184 * property from the configuration, but this is not guaranteed. In any case
185 * it is no replacement for calling
186 * <code>{@link #clearProperty(String)}</code> for this property. So it is
187 * highly recommended to avoid using the iterator's <code>remove()</code>
188 * method.
189 *
190 * @return An Iterator.
191 */
192 Iterator getKeys();
193
194 /***
195 * Get a list of properties associated with the given configuration key.
196 * This method expects the given key to have an arbitrary number of String
197 * values, each of which is of the form <code>key=value</code>. These
198 * strings are splitted at the equals sign, and the key parts will become
199 * keys of the returned <code>Properties</code> object, the value parts
200 * become values.
201 *
202 * @param key The configuration key.
203 * @return The associated properties if key is found.
204 *
205 * @throws ConversionException is thrown if the key maps to an
206 * object that is not a String/List.
207 *
208 * @throws IllegalArgumentException if one of the tokens is
209 * malformed (does not contain an equals sign).
210 */
211 Properties getProperties(String key);
212
213 /***
214 * Get a boolean associated with the given configuration key.
215 *
216 * @param key The configuration key.
217 * @return The associated boolean.
218 *
219 * @throws ConversionException is thrown if the key maps to an
220 * object that is not a Boolean.
221 */
222 boolean getBoolean(String key);
223
224 /***
225 * Get a boolean associated with the given configuration key.
226 * If the key doesn't map to an existing object, the default value
227 * is returned.
228 *
229 * @param key The configuration key.
230 * @param defaultValue The default value.
231 * @return The associated boolean.
232 *
233 * @throws ConversionException is thrown if the key maps to an
234 * object that is not a Boolean.
235 */
236 boolean getBoolean(String key, boolean defaultValue);
237
238 /***
239 * Get a {@link Boolean} associated with the given configuration key.
240 *
241 * @param key The configuration key.
242 * @param defaultValue The default value.
243 * @return The associated boolean if key is found and has valid
244 * format, default value otherwise.
245 *
246 * @throws ConversionException is thrown if the key maps to an
247 * object that is not a Boolean.
248 */
249 Boolean getBoolean(String key, Boolean defaultValue);
250
251 /***
252 * Get a byte associated with the given configuration key.
253 *
254 * @param key The configuration key.
255 * @return The associated byte.
256 *
257 * @throws ConversionException is thrown if the key maps to an
258 * object that is not a Byte.
259 */
260 byte getByte(String key);
261
262 /***
263 * Get a byte associated with the given configuration key.
264 * If the key doesn't map to an existing object, the default value
265 * is returned.
266 *
267 * @param key The configuration key.
268 * @param defaultValue The default value.
269 * @return The associated byte.
270 *
271 * @throws ConversionException is thrown if the key maps to an
272 * object that is not a Byte.
273 */
274 byte getByte(String key, byte defaultValue);
275
276 /***
277 * Get a {@link Byte} associated with the given configuration key.
278 *
279 * @param key The configuration key.
280 * @param defaultValue The default value.
281 * @return The associated byte if key is found and has valid format, default
282 * value otherwise.
283 *
284 * @throws ConversionException is thrown if the key maps to an object that
285 * is not a Byte.
286 */
287 Byte getByte(String key, Byte defaultValue);
288
289 /***
290 * Get a double associated with the given configuration key.
291 *
292 * @param key The configuration key.
293 * @return The associated double.
294 *
295 * @throws ConversionException is thrown if the key maps to an
296 * object that is not a Double.
297 */
298 double getDouble(String key);
299
300 /***
301 * Get a double associated with the given configuration key.
302 * If the key doesn't map to an existing object, the default value
303 * is returned.
304 *
305 * @param key The configuration key.
306 * @param defaultValue The default value.
307 * @return The associated double.
308 *
309 * @throws ConversionException is thrown if the key maps to an
310 * object that is not a Double.
311 */
312 double getDouble(String key, double defaultValue);
313
314 /***
315 * Get a {@link Double} associated with the given configuration key.
316 *
317 * @param key The configuration key.
318 * @param defaultValue The default value.
319 * @return The associated double if key is found and has valid
320 * format, default value otherwise.
321 *
322 * @throws ConversionException is thrown if the key maps to an
323 * object that is not a Double.
324 */
325 Double getDouble(String key, Double defaultValue);
326
327 /***
328 * Get a float associated with the given configuration key.
329 *
330 * @param key The configuration key.
331 * @return The associated float.
332 * @throws ConversionException is thrown if the key maps to an
333 * object that is not a Float.
334 */
335 float getFloat(String key);
336
337 /***
338 * Get a float associated with the given configuration key.
339 * If the key doesn't map to an existing object, the default value
340 * is returned.
341 *
342 * @param key The configuration key.
343 * @param defaultValue The default value.
344 * @return The associated float.
345 *
346 * @throws ConversionException is thrown if the key maps to an
347 * object that is not a Float.
348 */
349 float getFloat(String key, float defaultValue);
350
351 /***
352 * Get a {@link Float} associated with the given configuration key.
353 * If the key doesn't map to an existing object, the default value
354 * is returned.
355 *
356 * @param key The configuration key.
357 * @param defaultValue The default value.
358 * @return The associated float if key is found and has valid
359 * format, default value otherwise.
360 *
361 * @throws ConversionException is thrown if the key maps to an
362 * object that is not a Float.
363 */
364 Float getFloat(String key, Float defaultValue);
365
366 /***
367 * Get a int associated with the given configuration key.
368 *
369 * @param key The configuration key.
370 * @return The associated int.
371 *
372 * @throws ConversionException is thrown if the key maps to an
373 * object that is not a Integer.
374 */
375 int getInt(String key);
376
377 /***
378 * Get a int associated with the given configuration key.
379 * If the key doesn't map to an existing object, the default value
380 * is returned.
381 *
382 * @param key The configuration key.
383 * @param defaultValue The default value.
384 * @return The associated int.
385 *
386 * @throws ConversionException is thrown if the key maps to an
387 * object that is not a Integer.
388 */
389 int getInt(String key, int defaultValue);
390
391 /***
392 * Get an {@link Integer} associated with the given configuration key.
393 * If the key doesn't map to an existing object, the default value
394 * is returned.
395 *
396 * @param key The configuration key.
397 * @param defaultValue The default value.
398 * @return The associated int if key is found and has valid format, default
399 * value otherwise.
400 *
401 * @throws ConversionException is thrown if the key maps to an object that
402 * is not a Integer.
403 */
404 Integer getInteger(String key, Integer defaultValue);
405
406 /***
407 * Get a long associated with the given configuration key.
408 *
409 * @param key The configuration key.
410 * @return The associated long.
411 *
412 * @throws ConversionException is thrown if the key maps to an
413 * object that is not a Long.
414 */
415 long getLong(String key);
416
417 /***
418 * Get a long associated with the given configuration key.
419 * If the key doesn't map to an existing object, the default value
420 * is returned.
421 *
422 * @param key The configuration key.
423 * @param defaultValue The default value.
424 * @return The associated long.
425 *
426 * @throws ConversionException is thrown if the key maps to an
427 * object that is not a Long.
428 */
429 long getLong(String key, long defaultValue);
430
431 /***
432 * Get a {@link Long} associated with the given configuration key.
433 * If the key doesn't map to an existing object, the default value
434 * is returned.
435 *
436 * @param key The configuration key.
437 * @param defaultValue The default value.
438 * @return The associated long if key is found and has valid
439 * format, default value otherwise.
440 *
441 * @throws ConversionException is thrown if the key maps to an
442 * object that is not a Long.
443 */
444 Long getLong(String key, Long defaultValue);
445
446 /***
447 * Get a short associated with the given configuration key.
448 *
449 * @param key The configuration key.
450 * @return The associated short.
451 *
452 * @throws ConversionException is thrown if the key maps to an
453 * object that is not a Short.
454 */
455 short getShort(String key);
456
457 /***
458 * Get a short associated with the given configuration key.
459 *
460 * @param key The configuration key.
461 * @param defaultValue The default value.
462 * @return The associated short.
463 *
464 * @throws ConversionException is thrown if the key maps to an
465 * object that is not a Short.
466 */
467 short getShort(String key, short defaultValue);
468
469 /***
470 * Get a {@link Short} associated with the given configuration key.
471 * If the key doesn't map to an existing object, the default value
472 * is returned.
473 *
474 * @param key The configuration key.
475 * @param defaultValue The default value.
476 * @return The associated short if key is found and has valid
477 * format, default value otherwise.
478 *
479 * @throws ConversionException is thrown if the key maps to an
480 * object that is not a Short.
481 */
482 Short getShort(String key, Short defaultValue);
483
484 /***
485 * Get a {@link BigDecimal} associated with the given configuration key.
486 *
487 * @param key The configuration key.
488 * @return The associated BigDecimal if key is found and has valid format
489 */
490 BigDecimal getBigDecimal(String key);
491
492 /***
493 * Get a {@link BigDecimal} associated with the given configuration key.
494 * If the key doesn't map to an existing object, the default value
495 * is returned.
496 *
497 * @param key The configuration key.
498 * @param defaultValue The default value.
499 *
500 * @return The associated BigDecimal if key is found and has valid
501 * format, default value otherwise.
502 */
503 BigDecimal getBigDecimal(String key, BigDecimal defaultValue);
504
505 /***
506 * Get a {@link BigInteger} associated with the given configuration key.
507 *
508 * @param key The configuration key.
509 *
510 * @return The associated BigInteger if key is found and has valid format
511 */
512 BigInteger getBigInteger(String key);
513
514 /***
515 * Get a {@link BigInteger} associated with the given configuration key.
516 * If the key doesn't map to an existing object, the default value
517 * is returned.
518 *
519 * @param key The configuration key.
520 * @param defaultValue The default value.
521 *
522 * @return The associated BigInteger if key is found and has valid
523 * format, default value otherwise.
524 */
525 BigInteger getBigInteger(String key, BigInteger defaultValue);
526
527 /***
528 * Get a string associated with the given configuration key.
529 *
530 * @param key The configuration key.
531 * @return The associated string.
532 *
533 * @throws ConversionException is thrown if the key maps to an object that
534 * is not a String.
535 */
536 String getString(String key);
537
538 /***
539 * Get a string associated with the given configuration key.
540 * If the key doesn't map to an existing object, the default value
541 * is returned.
542 *
543 * @param key The configuration key.
544 * @param defaultValue The default value.
545 * @return The associated string if key is found and has valid
546 * format, default value otherwise.
547 *
548 * @throws ConversionException is thrown if the key maps to an object that
549 * is not a String.
550 */
551 String getString(String key, String defaultValue);
552
553 /***
554 * Get an array of strings associated with the given configuration key.
555 * If the key doesn't map to an existing object an empty array is returned
556 *
557 * @param key The configuration key.
558 * @return The associated string array if key is found.
559 *
560 * @throws ConversionException is thrown if the key maps to an
561 * object that is not a String/List of Strings.
562 */
563 String[] getStringArray(String key);
564
565 /***
566 * Get a List of strings associated with the given configuration key.
567 * If the key doesn't map to an existing object an empty List is returned.
568 *
569 * @param key The configuration key.
570 * @return The associated List.
571 *
572 * @throws ConversionException is thrown if the key maps to an
573 * object that is not a List.
574 */
575 List getList(String key);
576
577 /***
578 * Get a List of strings associated with the given configuration key.
579 * If the key doesn't map to an existing object, the default value
580 * is returned.
581 *
582 * @param key The configuration key.
583 * @param defaultValue The default value.
584 * @return The associated List of strings.
585 *
586 * @throws ConversionException is thrown if the key maps to an
587 * object that is not a List.
588 */
589 List getList(String key, List defaultValue);
590 }