1 /*
2 * Copyright (c) 2012, 2013, 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
18 * 2 along with this work; if not, write to the Free Software Foundation,
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
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
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
81 /**
82 * Provider of time-zone rules to the system.
83 * <p>
84 * This class manages the configuration of time-zone rules.
85 * The static methods provide the public API that can be used to manage the providers.
86 * The abstract methods provide the SPI that allows rules to be provided.
87 * <p>
88 * ZoneRulesProvider may be installed in an instance of the Java Platform as
89 * extension classes, that is, jar files placed into any of the usual extension
90 * directories. Installed providers are loaded using the service-provider loading
91 * facility defined by the {@link ServiceLoader} class. A ZoneRulesProvider
92 * identifies itself with a provider configuration file named
93 * {@code java.time.zone.ZoneRulesProvider} in the resource directory
94 * {@code META-INF/services}. The file should contain a line that specifies the
95 * fully qualified concrete zonerules-provider class name.
96 * Providers may also be made available by adding them to the class path or by
97 * registering themselves via {@link #registerProvider} method.
98 * <p>
99 * The Java virtual machine has a default provider that provides zone rules
100 * for the time-zones defined by IANA Time Zone Database (TZDB). If the system
101 * property {@code java.time.zone.DefaultZoneRulesProvider} is defined then
102 * it is taken to be the fully-qualified name of a concrete ZoneRulesProvider
103 * class to be loaded as the default provider, using the system class loader.
104 * If this system property is not defined, a system-default provider will be
105 * loaded to serve as the default provider.
106 * <p>
107 * Rules are looked up primarily by zone ID, as used by {@link ZoneId}.
108 * Only zone region IDs may be used, zone offset IDs are not used here.
109 * <p>
110 * Time-zone rules are political, thus the data can change at any time.
111 * Each provider will provide the latest rules for each zone ID, but they
112 * may also provide the history of how the rules changed.
113 *
114 * @implSpec
115 * This interface is a service provider that can be called by multiple threads.
116 * Implementations must be immutable and thread-safe.
117 * <p>
118 * Providers must ensure that once a rule has been seen by the application, the
119 * rule must continue to be available.
120 * <p>
121 * Providers are encouraged to implement a meaningful {@code toString} method.
122 * <p>
123 * Many systems would like to update time-zone rules dynamically without stopping the JVM.
124 * When examined in detail, this is a complex problem.
125 * Providers may choose to handle dynamic updates, however the default provider does not.
126 *
127 * @since 1.8
128 */
129 public abstract class ZoneRulesProvider {
130
131 /**
132 * The set of loaded providers.
133 */
134 private static final CopyOnWriteArrayList<ZoneRulesProvider> PROVIDERS = new CopyOnWriteArrayList<>();
135 /**
136 * The lookup from zone ID to provider.
137 */
138 private static final ConcurrentMap<String, ZoneRulesProvider> ZONES = new ConcurrentHashMap<>(512, 0.75f, 2);
139
140 static {
141 // if the property java.time.zone.DefaultZoneRulesProvider is
142 // set then its value is the class name of the default provider
143 final List<ZoneRulesProvider> loaded = new ArrayList<>();
144 AccessController.doPrivileged(new PrivilegedAction<>() {
145 public Object run() {
146 String prop = System.getProperty("java.time.zone.DefaultZoneRulesProvider");
147 if (prop != null) {
148 try {
149 Class<?> c = Class.forName(prop, true, ClassLoader.getSystemClassLoader());
150 @SuppressWarnings("deprecation")
151 ZoneRulesProvider provider = ZoneRulesProvider.class.cast(c.newInstance());
152 registerProvider(provider);
153 loaded.add(provider);
154 } catch (Exception x) {
155 throw new Error(x);
156 }
157 } else {
158 registerProvider(new TzdbZoneRulesProvider());
159 }
160 return null;
161 }
162 });
163
164 ServiceLoader<ZoneRulesProvider> sl = ServiceLoader.load(ZoneRulesProvider.class, ClassLoader.getSystemClassLoader());
165 Iterator<ZoneRulesProvider> it = sl.iterator();
166 while (it.hasNext()) {
167 ZoneRulesProvider provider;
168 try {
169 provider = it.next();
170 } catch (ServiceConfigurationError ex) {
171 if (ex.getCause() instanceof SecurityException) {
172 continue; // ignore the security exception, try the next provider
173 }
174 throw ex;
175 }
176 boolean found = false;
177 for (ZoneRulesProvider p : loaded) {
178 if (p.getClass() == provider.getClass()) {
179 found = true;
180 }
181 }
182 if (!found) {
183 registerProvider0(provider);
184 loaded.add(provider);
185 }
186 }
187 // CopyOnWriteList could be slow if lots of providers and each added individually
188 PROVIDERS.addAll(loaded);
189 }
190
191 //-------------------------------------------------------------------------
192 /**
193 * Gets the set of available zone IDs.
194 * <p>
195 * These IDs are the string form of a {@link ZoneId}.
196 *
197 * @return a modifiable copy of the set of zone IDs, not null
198 */
199 public static Set<String> getAvailableZoneIds() {
200 return new HashSet<>(ZONES.keySet());
201 }
202
203 /**
204 * Gets the rules for the zone ID.
205 * <p>
206 * This returns the latest available rules for the zone ID.
207 * <p>
208 * This method relies on time-zone data provider files that are configured.
209 * These are loaded using a {@code ServiceLoader}.
210 * <p>
211 * The caching flag is designed to allow provider implementations to
212 * prevent the rules being cached in {@code ZoneId}.
213 * Under normal circumstances, the caching of zone rules is highly desirable
214 * as it will provide greater performance. However, there is a use case where
215 * the caching would not be desirable, see {@link #provideRules}.
216 *
217 * @param zoneId the zone ID as defined by {@code ZoneId}, not null
218 * @param forCaching whether the rules are being queried for caching,
219 * true if the returned rules will be cached by {@code ZoneId},
220 * false if they will be returned to the user without being cached in {@code ZoneId}
221 * @return the rules, null if {@code forCaching} is true and this
222 * is a dynamic provider that wants to prevent caching in {@code ZoneId},
223 * otherwise not null
224 * @throws ZoneRulesException if rules cannot be obtained for the zone ID
225 */
226 public static ZoneRules getRules(String zoneId, boolean forCaching) {
227 Objects.requireNonNull(zoneId, "zoneId");
228 return getProvider(zoneId).provideRules(zoneId, forCaching);
229 }
230
231 /**
232 * Gets the history of rules for the zone ID.
233 * <p>
234 * Time-zones are defined by governments and change frequently.
235 * This method allows applications to find the history of changes to the
236 * rules for a single zone ID. The map is keyed by a string, which is the
237 * version string associated with the rules.
238 * <p>
239 * The exact meaning and format of the version is provider specific.
240 * The version must follow lexicographical order, thus the returned map will
241 * be order from the oldest known rules to the newest available rules.
242 * The default 'TZDB' group uses version numbering consisting of the year
243 * followed by a letter, such as '2009e' or '2012f'.
244 * <p>
245 * Implementations must provide a result for each valid zone ID, however
246 * they do not have to provide a history of rules.
247 * Thus the map will always contain one element, and will only contain more
248 * than one element if historical rule information is available.
249 *
250 * @param zoneId the zone ID as defined by {@code ZoneId}, not null
251 * @return a modifiable copy of the history of the rules for the ID, sorted
252 * from oldest to newest, not null
253 * @throws ZoneRulesException if history cannot be obtained for the zone ID
254 */
255 public static NavigableMap<String, ZoneRules> getVersions(String zoneId) {
256 Objects.requireNonNull(zoneId, "zoneId");
257 return getProvider(zoneId).provideVersions(zoneId);
258 }
259
260 /**
261 * Gets the provider for the zone ID.
262 *
263 * @param zoneId the zone ID as defined by {@code ZoneId}, not null
264 * @return the provider, not null
265 * @throws ZoneRulesException if the zone ID is unknown
266 */
267 private static ZoneRulesProvider getProvider(String zoneId) {
268 ZoneRulesProvider provider = ZONES.get(zoneId);
269 if (provider == null) {
270 if (ZONES.isEmpty()) {
271 throw new ZoneRulesException("No time-zone data files registered");
272 }
273 throw new ZoneRulesException("Unknown time-zone ID: " + zoneId);
274 }
275 return provider;
276 }
277
278 //-------------------------------------------------------------------------
279 /**
280 * Registers a zone rules provider.
281 * <p>
282 * This adds a new provider to those currently available.
283 * A provider supplies rules for one or more zone IDs.
284 * A provider cannot be registered if it supplies a zone ID that has already been
285 * registered. See the notes on time-zone IDs in {@link ZoneId}, especially
286 * the section on using the concept of a "group" to make IDs unique.
287 * <p>
288 * To ensure the integrity of time-zones already created, there is no way
289 * to deregister providers.
290 *
291 * @param provider the provider to register, not null
292 * @throws ZoneRulesException if a zone ID is already registered
293 */
294 public static void registerProvider(ZoneRulesProvider provider) {
295 Objects.requireNonNull(provider, "provider");
296 registerProvider0(provider);
297 PROVIDERS.add(provider);
298 }
299
300 /**
301 * Registers the provider.
302 *
303 * @param provider the provider to register, not null
304 * @throws ZoneRulesException if unable to complete the registration
305 */
306 private static void registerProvider0(ZoneRulesProvider provider) {
307 for (String zoneId : provider.provideZoneIds()) {
308 Objects.requireNonNull(zoneId, "zoneId");
309 ZoneRulesProvider old = ZONES.putIfAbsent(zoneId, provider);
310 if (old != null) {
311 throw new ZoneRulesException(
312 "Unable to register zone as one already registered with that ID: " + zoneId +
313 ", currently loading from provider: " + provider);
314 }
315 }
316 }
317
318 /**
319 * Refreshes the rules from the underlying data provider.
320 * <p>
321 * This method allows an application to request that the providers check
322 * for any updates to the provided rules.
323 * After calling this method, the offset stored in any {@link ZonedDateTime}
324 * may be invalid for the zone ID.
325 * <p>
326 * Dynamic update of rules is a complex problem and most applications
327 * should not use this method or dynamic rules.
328 * To achieve dynamic rules, a provider implementation will have to be written
329 * as per the specification of this class.
330 * In addition, instances of {@code ZoneRules} must not be cached in the
331 * application as they will become stale. However, the boolean flag on
332 * {@link #provideRules(String, boolean)} allows provider implementations
333 * to control the caching of {@code ZoneId}, potentially ensuring that
334 * all objects in the system see the new rules.
335 * Note that there is likely to be a cost in performance of a dynamic rules
336 * provider. Note also that no dynamic rules provider is in this specification.
337 *
338 * @return true if the rules were updated
339 * @throws ZoneRulesException if an error occurs during the refresh
340 */
341 public static boolean refresh() {
342 boolean changed = false;
343 for (ZoneRulesProvider provider : PROVIDERS) {
344 changed |= provider.provideRefresh();
345 }
346 return changed;
347 }
348
349 /**
350 * Constructor.
351 */
352 protected ZoneRulesProvider() {
353 }
354
355 //-----------------------------------------------------------------------
356 /**
357 * SPI method to get the available zone IDs.
358 * <p>
359 * This obtains the IDs that this {@code ZoneRulesProvider} provides.
360 * A provider should provide data for at least one zone ID.
361 * <p>
362 * The returned zone IDs remain available and valid for the lifetime of the application.
363 * A dynamic provider may increase the set of IDs as more data becomes available.
364 *
365 * @return the set of zone IDs being provided, not null
366 * @throws ZoneRulesException if a problem occurs while providing the IDs
367 */
368 protected abstract Set<String> provideZoneIds();
369
370 /**
371 * SPI method to get the rules for the zone ID.
372 * <p>
373 * This loads the rules for the specified zone ID.
374 * The provider implementation must validate that the zone ID is valid and
375 * available, throwing a {@code ZoneRulesException} if it is not.
376 * The result of the method in the valid case depends on the caching flag.
377 * <p>
378 * If the provider implementation is not dynamic, then the result of the
379 * method must be the non-null set of rules selected by the ID.
380 * <p>
381 * If the provider implementation is dynamic, then the flag gives the option
382 * of preventing the returned rules from being cached in {@link ZoneId}.
383 * When the flag is true, the provider is permitted to return null, where
384 * null will prevent the rules from being cached in {@code ZoneId}.
385 * When the flag is false, the provider must return non-null rules.
386 *
387 * @param zoneId the zone ID as defined by {@code ZoneId}, not null
388 * @param forCaching whether the rules are being queried for caching,
389 * true if the returned rules will be cached by {@code ZoneId},
390 * false if they will be returned to the user without being cached in {@code ZoneId}
391 * @return the rules, null if {@code forCaching} is true and this
392 * is a dynamic provider that wants to prevent caching in {@code ZoneId},
393 * otherwise not null
394 * @throws ZoneRulesException if rules cannot be obtained for the zone ID
395 */
396 protected abstract ZoneRules provideRules(String zoneId, boolean forCaching);
397
398 /**
399 * SPI method to get the history of rules for the zone ID.
400 * <p>
401 * This returns a map of historical rules keyed by a version string.
402 * The exact meaning and format of the version is provider specific.
403 * The version must follow lexicographical order, thus the returned map will
404 * be order from the oldest known rules to the newest available rules.
405 * The default 'TZDB' group uses version numbering consisting of the year
406 * followed by a letter, such as '2009e' or '2012f'.
407 * <p>
408 * Implementations must provide a result for each valid zone ID, however
409 * they do not have to provide a history of rules.
410 * Thus the map will contain at least one element, and will only contain
411 * more than one element if historical rule information is available.
412 * <p>
413 * The returned versions remain available and valid for the lifetime of the application.
414 * A dynamic provider may increase the set of versions as more data becomes available.
415 *
416 * @param zoneId the zone ID as defined by {@code ZoneId}, not null
417 * @return a modifiable copy of the history of the rules for the ID, sorted
418 * from oldest to newest, not null
419 * @throws ZoneRulesException if history cannot be obtained for the zone ID
420 */
421 protected abstract NavigableMap<String, ZoneRules> provideVersions(String zoneId);
422
423 /**
424 * SPI method to refresh the rules from the underlying data provider.
425 * <p>
426 * This method provides the opportunity for a provider to dynamically
427 * recheck the underlying data provider to find the latest rules.
428 * This could be used to load new rules without stopping the JVM.
429 * Dynamic behavior is entirely optional and most providers do not support it.
430 * <p>
431 * This implementation returns false.
432 *
433 * @return true if the rules were updated
434 * @throws ZoneRulesException if an error occurs during the refresh
435 */
436 protected boolean provideRefresh() {
437 return false;
438 }
439
440 }