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.
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  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 }
--- EOF ---