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 * <h3>Specification for implementors</h3>
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 ZoneRulesProvider provider = ZoneRulesProvider.class.cast(c.newInstance());
151 registerProvider(provider);
152 loaded.add(provider);
153 } catch (Exception x) {
154 throw new Error(x);
155 }
156 } else {
157 registerProvider(new TzdbZoneRulesProvider());
158 }
159 return null;
160 }
161 });
162
163 ServiceLoader<ZoneRulesProvider> sl = ServiceLoader.load(ZoneRulesProvider.class, ClassLoader.getSystemClassLoader());
164 Iterator<ZoneRulesProvider> it = sl.iterator();
165 while (it.hasNext()) {
166 ZoneRulesProvider provider;
167 try {
168 provider = it.next();
169 } catch (ServiceConfigurationError ex) {
170 if (ex.getCause() instanceof SecurityException) {
171 continue; // ignore the security exception, try the next provider
172 }
173 throw ex;
174 }
175 boolean found = false;
176 for (ZoneRulesProvider p : loaded) {
177 if (p.getClass() == provider.getClass()) {
178 found = true;
179 }
180 }
181 if (!found) {
182 registerProvider0(provider);
183 loaded.add(provider);
184 }
185 }
186 // CopyOnWriteList could be slow if lots of providers and each added individually
187 PROVIDERS.addAll(loaded);
188 }
189
190 //-------------------------------------------------------------------------
191 /**
192 * Gets the set of available zone IDs.
193 * <p>
194 * These IDs are the string form of a {@link ZoneId}.
195 *
196 * @return a modifiable copy of the set of zone IDs, not null
197 */
198 public static Set<String> getAvailableZoneIds() {
199 return new HashSet<>(ZONES.keySet());
200 }
201
202 /**
203 * Gets the rules for the zone ID.
204 * <p>
205 * This returns the latest available rules for the zone ID.
206 * <p>
207 * This method relies on time-zone data provider files that are configured.
208 * These are loaded using a {@code ServiceLoader}.
209 * <p>
210 * The caching flag is designed to allow provider implementations to
211 * prevent the rules being cached in {@code ZoneId}.
212 * Under normal circumstances, the caching of zone rules is highly desirable
213 * as it will provide greater performance. However, there is a use case where
214 * the caching would not be desirable, see {@link #provideRules}.
215 *
216 * @param zoneId the zone ID as defined by {@code ZoneId}, not null
217 * @param forCaching whether the rules are being queried for caching,
218 * true if the returned rules will be cached by {@code ZoneId},
219 * false if they will be returned to the user without being cached in {@code ZoneId}
220 * @return the rules, null if {@code forCaching} is true and this
221 * is a dynamic provider that wants to prevent caching in {@code ZoneId},
222 * otherwise not null
223 * @throws ZoneRulesException if rules cannot be obtained for the zone ID
224 */
225 public static ZoneRules getRules(String zoneId, boolean forCaching) {
226 Objects.requireNonNull(zoneId, "zoneId");
227 return getProvider(zoneId).provideRules(zoneId, forCaching);
228 }
229
230 /**
231 * Gets the history of rules for the zone ID.
232 * <p>
233 * Time-zones are defined by governments and change frequently.
234 * This method allows applications to find the history of changes to the
235 * rules for a single zone ID. The map is keyed by a string, which is the
236 * version string associated with the rules.
237 * <p>
238 * The exact meaning and format of the version is provider specific.
239 * The version must follow lexicographical order, thus the returned map will
240 * be order from the oldest known rules to the newest available rules.
241 * The default 'TZDB' group uses version numbering consisting of the year
242 * followed by a letter, such as '2009e' or '2012f'.
243 * <p>
244 * Implementations must provide a result for each valid zone ID, however
245 * they do not have to provide a history of rules.
246 * Thus the map will always contain one element, and will only contain more
247 * than one element if historical rule information is available.
248 *
249 * @param zoneId the zone ID as defined by {@code ZoneId}, not null
250 * @return a modifiable copy of the history of the rules for the ID, sorted
251 * from oldest to newest, not null
252 * @throws ZoneRulesException if history cannot be obtained for the zone ID
253 */
254 public static NavigableMap<String, ZoneRules> getVersions(String zoneId) {
255 Objects.requireNonNull(zoneId, "zoneId");
256 return getProvider(zoneId).provideVersions(zoneId);
257 }
258
259 /**
260 * Gets the provider for the zone ID.
261 *
262 * @param zoneId the zone ID as defined by {@code ZoneId}, not null
263 * @return the provider, not null
264 * @throws ZoneRulesException if the zone ID is unknown
265 */
266 private static ZoneRulesProvider getProvider(String zoneId) {
267 ZoneRulesProvider provider = ZONES.get(zoneId);
268 if (provider == null) {
269 if (ZONES.isEmpty()) {
270 throw new ZoneRulesException("No time-zone data files registered");
271 }
272 throw new ZoneRulesException("Unknown time-zone ID: " + zoneId);
273 }
274 return provider;
275 }
276
277 //-------------------------------------------------------------------------
278 /**
279 * Registers a zone rules provider.
280 * <p>
281 * This adds a new provider to those currently available.
282 * A provider supplies rules for one or more zone IDs.
283 * A provider cannot be registered if it supplies a zone ID that has already been
284 * registered. See the notes on time-zone IDs in {@link ZoneId}, especially
285 * the section on using the concept of a "group" to make IDs unique.
286 * <p>
287 * To ensure the integrity of time-zones already created, there is no way
288 * to deregister providers.
289 *
290 * @param provider the provider to register, not null
291 * @throws ZoneRulesException if a zone ID is already registered
292 */
293 public static void registerProvider(ZoneRulesProvider provider) {
294 Objects.requireNonNull(provider, "provider");
295 registerProvider0(provider);
296 PROVIDERS.add(provider);
297 }
298
299 /**
300 * Registers the provider.
301 *
302 * @param provider the provider to register, not null
303 * @throws ZoneRulesException if unable to complete the registration
304 */
305 private static void registerProvider0(ZoneRulesProvider provider) {
306 for (String zoneId : provider.provideZoneIds()) {
307 Objects.requireNonNull(zoneId, "zoneId");
308 ZoneRulesProvider old = ZONES.putIfAbsent(zoneId, provider);
309 if (old != null) {
310 throw new ZoneRulesException(
311 "Unable to register zone as one already registered with that ID: " + zoneId +
312 ", currently loading from provider: " + provider);
313 }
314 }
315 }
316
317 /**
318 * Refreshes the rules from the underlying data provider.
319 * <p>
320 * This method allows an application to request that the providers check
321 * for any updates to the provided rules.
322 * After calling this method, the offset stored in any {@link ZonedDateTime}
323 * may be invalid for the zone ID.
324 * <p>
325 * Dynamic update of rules is a complex problem and most applications
326 * should not use this method or dynamic rules.
327 * To achieve dynamic rules, a provider implementation will have to be written
328 * as per the specification of this class.
329 * In addition, instances of {@code ZoneRules} must not be cached in the
330 * application as they will become stale. However, the boolean flag on
331 * {@link #provideRules(String, boolean)} allows provider implementations
332 * to control the caching of {@code ZoneId}, potentially ensuring that
333 * all objects in the system see the new rules.
334 * Note that there is likely to be a cost in performance of a dynamic rules
335 * provider. Note also that no dynamic rules provider is in this specification.
336 *
337 * @return true if the rules were updated
338 * @throws ZoneRulesException if an error occurs during the refresh
339 */
340 public static boolean refresh() {
341 boolean changed = false;
342 for (ZoneRulesProvider provider : PROVIDERS) {
343 changed |= provider.provideRefresh();
344 }
345 return changed;
346 }
347
348 /**
349 * Constructor.
350 */
351 protected ZoneRulesProvider() {
352 }
353
354 //-----------------------------------------------------------------------
355 /**
356 * SPI method to get the available zone IDs.
357 * <p>
358 * This obtains the IDs that this {@code ZoneRulesProvider} provides.
359 * A provider should provide data for at least one zone ID.
360 * <p>
361 * The returned zone IDs remain available and valid for the lifetime of the application.
362 * A dynamic provider may increase the set of IDs as more data becomes available.
363 *
364 * @return the set of zone IDs being provided, not null
365 * @throws ZoneRulesException if a problem occurs while providing the IDs
366 */
367 protected abstract Set<String> provideZoneIds();
368
369 /**
370 * SPI method to get the rules for the zone ID.
371 * <p>
372 * This loads the rules for the specified zone ID.
373 * The provider implementation must validate that the zone ID is valid and
374 * available, throwing a {@code ZoneRulesException} if it is not.
375 * The result of the method in the valid case depends on the caching flag.
376 * <p>
377 * If the provider implementation is not dynamic, then the result of the
378 * method must be the non-null set of rules selected by the ID.
379 * <p>
380 * If the provider implementation is dynamic, then the flag gives the option
381 * of preventing the returned rules from being cached in {@link ZoneId}.
382 * When the flag is true, the provider is permitted to return null, where
383 * null will prevent the rules from being cached in {@code ZoneId}.
384 * When the flag is false, the provider must return non-null rules.
385 *
386 * @param zoneId the zone ID as defined by {@code ZoneId}, not null
387 * @param forCaching whether the rules are being queried for caching,
388 * true if the returned rules will be cached by {@code ZoneId},
389 * false if they will be returned to the user without being cached in {@code ZoneId}
390 * @return the rules, null if {@code forCaching} is true and this
391 * is a dynamic provider that wants to prevent caching in {@code ZoneId},
392 * otherwise not null
393 * @throws ZoneRulesException if rules cannot be obtained for the zone ID
394 */
395 protected abstract ZoneRules provideRules(String zoneId, boolean forCaching);
396
397 /**
398 * SPI method to get the history of rules for the zone ID.
399 * <p>
400 * This returns a map of historical rules keyed by a version string.
401 * The exact meaning and format of the version is provider specific.
402 * The version must follow lexicographical order, thus the returned map will
403 * be order from the oldest known rules to the newest available rules.
404 * The default 'TZDB' group uses version numbering consisting of the year
405 * followed by a letter, such as '2009e' or '2012f'.
406 * <p>
407 * Implementations must provide a result for each valid zone ID, however
408 * they do not have to provide a history of rules.
409 * Thus the map will contain at least one element, and will only contain
410 * more than one element if historical rule information is available.
411 * <p>
412 * The returned versions remain available and valid for the lifetime of the application.
413 * A dynamic provider may increase the set of versions as more data becomes available.
414 *
415 * @param zoneId the zone ID as defined by {@code ZoneId}, not null
416 * @return a modifiable copy of the history of the rules for the ID, sorted
417 * from oldest to newest, not null
418 * @throws ZoneRulesException if history cannot be obtained for the zone ID
419 */
420 protected abstract NavigableMap<String, ZoneRules> provideVersions(String zoneId);
421
422 /**
423 * SPI method to refresh the rules from the underlying data provider.
424 * <p>
425 * This method provides the opportunity for a provider to dynamically
426 * recheck the underlying data provider to find the latest rules.
427 * This could be used to load new rules without stopping the JVM.
428 * Dynamic behavior is entirely optional and most providers do not support it.
429 * <p>
430 * This implementation returns false.
431 *
432 * @return true if the rules were updated
433 * @throws ZoneRulesException if an error occurs during the refresh
434 */
435 protected boolean provideRefresh() {
436 return false;
437 }
438
439 }