1 /*
2 * Copyright (c) 2012, 2016, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
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19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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24 */
25
26 /*
27 * This file is available under and governed by the GNU General Public
28 * License version 2 only, as published by the Free Software Foundation.
29 * However, the following notice accompanied the original version of this
30 * file:
31 *
32 * Copyright (c) 2009-2012, Stephen Colebourne & Michael Nascimento Santos
33 *
34 * All rights reserved.
35 *
36 * Redistribution and use in source and binary forms, with or without
37 * modification, are permitted provided that the following conditions are met:
38 *
39 * * Redistributions of source code must retain the above copyright notice,
40 * this list of conditions and the following disclaimer.
41 *
42 * * Redistributions in binary form must reproduce the above copyright notice,
43 * this list of conditions and the following disclaimer in the documentation
44 * and/or other materials provided with the distribution.
45 *
46 * * Neither the name of JSR-310 nor the names of its contributors
47 * may be used to endorse or promote products derived from this software
48 * without specific prior written permission.
49 *
50 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
51 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
52 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
53 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
54 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
55 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
56 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
57 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
58 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
59 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
60 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
61 */
62 package java.time.zone;
63
64 import java.security.AccessController;
65 import java.security.PrivilegedAction;
66 import java.time.ZoneId;
67 import java.time.ZonedDateTime;
68 import java.util.ArrayList;
69 import java.util.HashSet;
70 import java.util.Iterator;
71 import java.util.List;
72 import java.util.NavigableMap;
73 import java.util.Objects;
74 import java.util.ServiceConfigurationError;
75 import java.util.ServiceLoader;
76 import java.util.Set;
77 import java.util.concurrent.ConcurrentHashMap;
78 import java.util.concurrent.ConcurrentMap;
79 import java.util.concurrent.CopyOnWriteArrayList;
80 import java.util.Collections;
81
82 /**
83 * Provider of time-zone rules to the system.
84 * <p>
85 * This class manages the configuration of time-zone rules.
86 * The static methods provide the public API that can be used to manage the providers.
87 * The abstract methods provide the SPI that allows rules to be provided.
88 * <p>
89 * ZoneRulesProvider may be installed in an instance of the Java Platform as
90 * extension classes, that is, jar files placed into any of the usual extension
91 * directories. Installed providers are loaded using the service-provider loading
92 * facility defined by the {@link ServiceLoader} class. A ZoneRulesProvider
93 * identifies itself with a provider configuration file named
94 * {@code java.time.zone.ZoneRulesProvider} in the resource directory
95 * {@code META-INF/services}. The file should contain a line that specifies the
96 * fully qualified concrete zonerules-provider class name.
97 * Providers may also be made available by adding them to the class path or by
98 * registering themselves via {@link #registerProvider} method.
99 * <p>
100 * The Java virtual machine has a default provider that provides zone rules
101 * for the time-zones defined by IANA Time Zone Database (TZDB). If the system
102 * property {@code java.time.zone.DefaultZoneRulesProvider} is defined then
103 * it is taken to be the fully-qualified name of a concrete ZoneRulesProvider
104 * class to be loaded as the default provider, using the system class loader.
105 * If this system property is not defined, a system-default provider will be
106 * loaded to serve as the default provider.
107 * <p>
108 * Rules are looked up primarily by zone ID, as used by {@link ZoneId}.
109 * Only zone region IDs may be used, zone offset IDs are not used here.
110 * <p>
111 * Time-zone rules are political, thus the data can change at any time.
112 * Each provider will provide the latest rules for each zone ID, but they
113 * may also provide the history of how the rules changed.
114 *
115 * @implSpec
116 * This interface is a service provider that can be called by multiple threads.
117 * Implementations must be immutable and thread-safe.
118 * <p>
119 * Providers must ensure that once a rule has been seen by the application, the
120 * rule must continue to be available.
121 * <p>
122 * Providers are encouraged to implement a meaningful {@code toString} method.
123 * <p>
124 * Many systems would like to update time-zone rules dynamically without stopping the JVM.
125 * When examined in detail, this is a complex problem.
126 * Providers may choose to handle dynamic updates, however the default provider does not.
127 *
128 * @since 1.8
129 */
130 public abstract class ZoneRulesProvider {
131
132 /**
133 * The set of loaded providers.
134 */
135 private static final CopyOnWriteArrayList<ZoneRulesProvider> PROVIDERS = new CopyOnWriteArrayList<>();
136 /**
137 * The lookup from zone ID to provider.
138 */
139 private static final ConcurrentMap<String, ZoneRulesProvider> ZONES = new ConcurrentHashMap<>(512, 0.75f, 2);
140
141 /**
142 * The zone ID data
143 */
144 private static volatile Set<String> ZONE_IDS;
145
146 static {
147 // if the property java.time.zone.DefaultZoneRulesProvider is
148 // set then its value is the class name of the default provider
149 final List<ZoneRulesProvider> loaded = new ArrayList<>();
150 AccessController.doPrivileged(new PrivilegedAction<>() {
151 public Object run() {
152 String prop = System.getProperty("java.time.zone.DefaultZoneRulesProvider");
153 if (prop != null) {
154 try {
155 Class<?> c = Class.forName(prop, true, ClassLoader.getSystemClassLoader());
156 @SuppressWarnings("deprecation")
157 ZoneRulesProvider provider = ZoneRulesProvider.class.cast(c.newInstance());
158 registerProvider(provider);
159 loaded.add(provider);
160 } catch (Exception x) {
161 throw new Error(x);
162 }
163 } else {
164 registerProvider(new TzdbZoneRulesProvider());
165 }
166 return null;
167 }
168 });
169
170 ServiceLoader<ZoneRulesProvider> sl = ServiceLoader.load(ZoneRulesProvider.class, ClassLoader.getSystemClassLoader());
171 Iterator<ZoneRulesProvider> it = sl.iterator();
172 while (it.hasNext()) {
173 ZoneRulesProvider provider;
174 try {
175 provider = it.next();
176 } catch (ServiceConfigurationError ex) {
177 if (ex.getCause() instanceof SecurityException) {
178 continue; // ignore the security exception, try the next provider
179 }
180 throw ex;
181 }
182 boolean found = false;
183 for (ZoneRulesProvider p : loaded) {
184 if (p.getClass() == provider.getClass()) {
185 found = true;
186 }
187 }
188 if (!found) {
189 registerProvider0(provider);
190 loaded.add(provider);
191 }
192 }
193 // CopyOnWriteList could be slow if lots of providers and each added individually
194 PROVIDERS.addAll(loaded);
195 }
196
197 //-------------------------------------------------------------------------
198 /**
199 * Gets the set of available zone IDs.
200 * <p>
201 * These IDs are the string form of a {@link ZoneId}.
202 *
203 * @return the unmodifiable set of zone IDs, not null
204 */
205 public static Set<String> getAvailableZoneIds() {
206 return ZONE_IDS;
207 }
208
209 /**
210 * Gets the rules for the zone ID.
211 * <p>
212 * This returns the latest available rules for the zone ID.
213 * <p>
214 * This method relies on time-zone data provider files that are configured.
215 * These are loaded using a {@code ServiceLoader}.
216 * <p>
217 * The caching flag is designed to allow provider implementations to
218 * prevent the rules being cached in {@code ZoneId}.
219 * Under normal circumstances, the caching of zone rules is highly desirable
220 * as it will provide greater performance. However, there is a use case where
221 * the caching would not be desirable, see {@link #provideRules}.
222 *
223 * @param zoneId the zone ID as defined by {@code ZoneId}, not null
224 * @param forCaching whether the rules are being queried for caching,
225 * true if the returned rules will be cached by {@code ZoneId},
226 * false if they will be returned to the user without being cached in {@code ZoneId}
227 * @return the rules, null if {@code forCaching} is true and this
228 * is a dynamic provider that wants to prevent caching in {@code ZoneId},
229 * otherwise not null
230 * @throws ZoneRulesException if rules cannot be obtained for the zone ID
231 */
232 public static ZoneRules getRules(String zoneId, boolean forCaching) {
233 Objects.requireNonNull(zoneId, "zoneId");
234 return getProvider(zoneId).provideRules(zoneId, forCaching);
235 }
236
237 /**
238 * Gets the history of rules for the zone ID.
239 * <p>
240 * Time-zones are defined by governments and change frequently.
241 * This method allows applications to find the history of changes to the
242 * rules for a single zone ID. The map is keyed by a string, which is the
243 * version string associated with the rules.
244 * <p>
245 * The exact meaning and format of the version is provider specific.
246 * The version must follow lexicographical order, thus the returned map will
247 * be order from the oldest known rules to the newest available rules.
248 * The default 'TZDB' group uses version numbering consisting of the year
249 * followed by a letter, such as '2009e' or '2012f'.
250 * <p>
251 * Implementations must provide a result for each valid zone ID, however
252 * they do not have to provide a history of rules.
253 * Thus the map will always contain one element, and will only contain more
254 * than one element if historical rule information is available.
255 *
256 * @param zoneId the zone ID as defined by {@code ZoneId}, not null
257 * @return a modifiable copy of the history of the rules for the ID, sorted
258 * from oldest to newest, not null
259 * @throws ZoneRulesException if history cannot be obtained for the zone ID
260 */
261 public static NavigableMap<String, ZoneRules> getVersions(String zoneId) {
262 Objects.requireNonNull(zoneId, "zoneId");
263 return getProvider(zoneId).provideVersions(zoneId);
264 }
265
266 /**
267 * Gets the provider for the zone ID.
268 *
269 * @param zoneId the zone ID as defined by {@code ZoneId}, not null
270 * @return the provider, not null
271 * @throws ZoneRulesException if the zone ID is unknown
272 */
273 private static ZoneRulesProvider getProvider(String zoneId) {
274 ZoneRulesProvider provider = ZONES.get(zoneId);
275 if (provider == null) {
276 if (ZONES.isEmpty()) {
277 throw new ZoneRulesException("No time-zone data files registered");
278 }
279 throw new ZoneRulesException("Unknown time-zone ID: " + zoneId);
280 }
281 return provider;
282 }
283
284 //-------------------------------------------------------------------------
285 /**
286 * Registers a zone rules provider.
287 * <p>
288 * This adds a new provider to those currently available.
289 * A provider supplies rules for one or more zone IDs.
290 * A provider cannot be registered if it supplies a zone ID that has already been
291 * registered. See the notes on time-zone IDs in {@link ZoneId}, especially
292 * the section on using the concept of a "group" to make IDs unique.
293 * <p>
294 * To ensure the integrity of time-zones already created, there is no way
295 * to deregister providers.
296 *
297 * @param provider the provider to register, not null
298 * @throws ZoneRulesException if a zone ID is already registered
299 */
300 public static void registerProvider(ZoneRulesProvider provider) {
301 Objects.requireNonNull(provider, "provider");
302 registerProvider0(provider);
303 PROVIDERS.add(provider);
304 }
305
306 /**
307 * Registers the provider.
308 *
309 * @param provider the provider to register, not null
310 * @throws ZoneRulesException if unable to complete the registration
311 */
312 private static synchronized void registerProvider0(ZoneRulesProvider provider) {
313 for (String zoneId : provider.provideZoneIds()) {
314 Objects.requireNonNull(zoneId, "zoneId");
315 ZoneRulesProvider old = ZONES.putIfAbsent(zoneId, provider);
316 if (old != null) {
317 throw new ZoneRulesException(
318 "Unable to register zone as one already registered with that ID: " + zoneId +
319 ", currently loading from provider: " + provider);
320 }
321 }
322 Set<String> combinedSet = new HashSet<String>(ZONES.keySet());
323 ZONE_IDS = Collections.unmodifiableSet(combinedSet);
324 }
325
326 /**
327 * Refreshes the rules from the underlying data provider.
328 * <p>
329 * This method allows an application to request that the providers check
330 * for any updates to the provided rules.
331 * After calling this method, the offset stored in any {@link ZonedDateTime}
332 * may be invalid for the zone ID.
333 * <p>
334 * Dynamic update of rules is a complex problem and most applications
335 * should not use this method or dynamic rules.
336 * To achieve dynamic rules, a provider implementation will have to be written
337 * as per the specification of this class.
338 * In addition, instances of {@code ZoneRules} must not be cached in the
339 * application as they will become stale. However, the boolean flag on
340 * {@link #provideRules(String, boolean)} allows provider implementations
341 * to control the caching of {@code ZoneId}, potentially ensuring that
342 * all objects in the system see the new rules.
343 * Note that there is likely to be a cost in performance of a dynamic rules
344 * provider. Note also that no dynamic rules provider is in this specification.
345 *
346 * @return true if the rules were updated
347 * @throws ZoneRulesException if an error occurs during the refresh
348 */
349 public static boolean refresh() {
350 boolean changed = false;
351 for (ZoneRulesProvider provider : PROVIDERS) {
352 changed |= provider.provideRefresh();
353 }
354 return changed;
355 }
356
357 /**
358 * Constructor.
359 */
360 protected ZoneRulesProvider() {
361 }
362
363 //-----------------------------------------------------------------------
364 /**
365 * SPI method to get the available zone IDs.
366 * <p>
367 * This obtains the IDs that this {@code ZoneRulesProvider} provides.
368 * A provider should provide data for at least one zone ID.
369 * <p>
370 * The returned zone IDs remain available and valid for the lifetime of the application.
371 * A dynamic provider may increase the set of IDs as more data becomes available.
372 *
373 * @return the set of zone IDs being provided, not null
374 * @throws ZoneRulesException if a problem occurs while providing the IDs
375 */
376 protected abstract Set<String> provideZoneIds();
377
378 /**
379 * SPI method to get the rules for the zone ID.
380 * <p>
381 * This loads the rules for the specified zone ID.
382 * The provider implementation must validate that the zone ID is valid and
383 * available, throwing a {@code ZoneRulesException} if it is not.
384 * The result of the method in the valid case depends on the caching flag.
385 * <p>
386 * If the provider implementation is not dynamic, then the result of the
387 * method must be the non-null set of rules selected by the ID.
388 * <p>
389 * If the provider implementation is dynamic, then the flag gives the option
390 * of preventing the returned rules from being cached in {@link ZoneId}.
391 * When the flag is true, the provider is permitted to return null, where
392 * null will prevent the rules from being cached in {@code ZoneId}.
393 * When the flag is false, the provider must return non-null rules.
394 *
395 * @param zoneId the zone ID as defined by {@code ZoneId}, not null
396 * @param forCaching whether the rules are being queried for caching,
397 * true if the returned rules will be cached by {@code ZoneId},
398 * false if they will be returned to the user without being cached in {@code ZoneId}
399 * @return the rules, null if {@code forCaching} is true and this
400 * is a dynamic provider that wants to prevent caching in {@code ZoneId},
401 * otherwise not null
402 * @throws ZoneRulesException if rules cannot be obtained for the zone ID
403 */
404 protected abstract ZoneRules provideRules(String zoneId, boolean forCaching);
405
406 /**
407 * SPI method to get the history of rules for the zone ID.
408 * <p>
409 * This returns a map of historical rules keyed by a version string.
410 * The exact meaning and format of the version is provider specific.
411 * The version must follow lexicographical order, thus the returned map will
412 * be order from the oldest known rules to the newest available rules.
413 * The default 'TZDB' group uses version numbering consisting of the year
414 * followed by a letter, such as '2009e' or '2012f'.
415 * <p>
416 * Implementations must provide a result for each valid zone ID, however
417 * they do not have to provide a history of rules.
418 * Thus the map will contain at least one element, and will only contain
419 * more than one element if historical rule information is available.
420 * <p>
421 * The returned versions remain available and valid for the lifetime of the application.
422 * A dynamic provider may increase the set of versions as more data becomes available.
423 *
424 * @param zoneId the zone ID as defined by {@code ZoneId}, not null
425 * @return a modifiable copy of the history of the rules for the ID, sorted
426 * from oldest to newest, not null
427 * @throws ZoneRulesException if history cannot be obtained for the zone ID
428 */
429 protected abstract NavigableMap<String, ZoneRules> provideVersions(String zoneId);
430
431 /**
432 * SPI method to refresh the rules from the underlying data provider.
433 * <p>
434 * This method provides the opportunity for a provider to dynamically
435 * recheck the underlying data provider to find the latest rules.
436 * This could be used to load new rules without stopping the JVM.
437 * Dynamic behavior is entirely optional and most providers do not support it.
438 * <p>
439 * This implementation returns false.
440 *
441 * @return true if the rules were updated
442 * @throws ZoneRulesException if an error occurs during the refresh
443 */
444 protected boolean provideRefresh() {
445 return false;
446 }
447
448 }