001/* 002 * Copyright (C) 2012 The Guava Authors 003 * 004 * Licensed under the Apache License, Version 2.0 (the "License"); 005 * you may not use this file except in compliance with the License. 006 * You may obtain a copy of the License at 007 * 008 * http://www.apache.org/licenses/LICENSE-2.0 009 * 010 * Unless required by applicable law or agreed to in writing, software 011 * distributed under the License is distributed on an "AS IS" BASIS, 012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 013 * See the License for the specific language governing permissions and 014 * limitations under the License. 015 */ 016 017package com.google.common.testing; 018 019import static com.google.common.base.Preconditions.checkArgument; 020 021import com.google.common.annotations.Beta; 022import com.google.common.annotations.GwtIncompatible; 023import com.google.common.base.CharMatcher; 024import com.google.common.base.Charsets; 025import com.google.common.base.Defaults; 026import com.google.common.base.Equivalence; 027import com.google.common.base.Joiner; 028import com.google.common.base.Predicate; 029import com.google.common.base.Predicates; 030import com.google.common.base.Splitter; 031import com.google.common.base.Stopwatch; 032import com.google.common.base.Ticker; 033import com.google.common.collect.BiMap; 034import com.google.common.collect.ClassToInstanceMap; 035import com.google.common.collect.ImmutableBiMap; 036import com.google.common.collect.ImmutableClassToInstanceMap; 037import com.google.common.collect.ImmutableCollection; 038import com.google.common.collect.ImmutableList; 039import com.google.common.collect.ImmutableListMultimap; 040import com.google.common.collect.ImmutableMap; 041import com.google.common.collect.ImmutableMultimap; 042import com.google.common.collect.ImmutableMultiset; 043import com.google.common.collect.ImmutableSet; 044import com.google.common.collect.ImmutableSetMultimap; 045import com.google.common.collect.ImmutableSortedMap; 046import com.google.common.collect.ImmutableSortedMultiset; 047import com.google.common.collect.ImmutableSortedSet; 048import com.google.common.collect.ImmutableTable; 049import com.google.common.collect.Iterators; 050import com.google.common.collect.ListMultimap; 051import com.google.common.collect.MapDifference; 052import com.google.common.collect.Maps; 053import com.google.common.collect.Multimap; 054import com.google.common.collect.Multimaps; 055import com.google.common.collect.Multiset; 056import com.google.common.collect.Ordering; 057import com.google.common.collect.PeekingIterator; 058import com.google.common.collect.Range; 059import com.google.common.collect.RowSortedTable; 060import com.google.common.collect.SetMultimap; 061import com.google.common.collect.Sets; 062import com.google.common.collect.SortedMapDifference; 063import com.google.common.collect.SortedMultiset; 064import com.google.common.collect.SortedSetMultimap; 065import com.google.common.collect.Table; 066import com.google.common.collect.Tables; 067import com.google.common.collect.TreeBasedTable; 068import com.google.common.collect.TreeMultimap; 069import com.google.common.io.ByteSink; 070import com.google.common.io.ByteSource; 071import com.google.common.io.ByteStreams; 072import com.google.common.io.CharSink; 073import com.google.common.io.CharSource; 074import com.google.common.primitives.Primitives; 075import com.google.common.primitives.UnsignedInteger; 076import com.google.common.primitives.UnsignedLong; 077import java.io.ByteArrayInputStream; 078import java.io.ByteArrayOutputStream; 079import java.io.File; 080import java.io.InputStream; 081import java.io.OutputStream; 082import java.io.PrintStream; 083import java.io.PrintWriter; 084import java.io.Reader; 085import java.io.Serializable; 086import java.io.StringReader; 087import java.io.StringWriter; 088import java.io.Writer; 089import java.lang.reflect.AnnotatedElement; 090import java.lang.reflect.Array; 091import java.lang.reflect.Constructor; 092import java.lang.reflect.Field; 093import java.lang.reflect.GenericDeclaration; 094import java.lang.reflect.InvocationTargetException; 095import java.lang.reflect.Modifier; 096import java.lang.reflect.Type; 097import java.math.BigDecimal; 098import java.math.BigInteger; 099import java.nio.Buffer; 100import java.nio.ByteBuffer; 101import java.nio.CharBuffer; 102import java.nio.DoubleBuffer; 103import java.nio.FloatBuffer; 104import java.nio.IntBuffer; 105import java.nio.LongBuffer; 106import java.nio.ShortBuffer; 107import java.nio.charset.Charset; 108import java.util.ArrayDeque; 109import java.util.Arrays; 110import java.util.Collection; 111import java.util.Comparator; 112import java.util.Currency; 113import java.util.Deque; 114import java.util.Iterator; 115import java.util.List; 116import java.util.ListIterator; 117import java.util.Locale; 118import java.util.Map; 119import java.util.NavigableMap; 120import java.util.NavigableSet; 121import java.util.Optional; 122import java.util.OptionalDouble; 123import java.util.OptionalInt; 124import java.util.OptionalLong; 125import java.util.Queue; 126import java.util.Random; 127import java.util.Set; 128import java.util.SortedMap; 129import java.util.SortedSet; 130import java.util.concurrent.BlockingDeque; 131import java.util.concurrent.BlockingQueue; 132import java.util.concurrent.ConcurrentHashMap; 133import java.util.concurrent.ConcurrentMap; 134import java.util.concurrent.ConcurrentNavigableMap; 135import java.util.concurrent.ConcurrentSkipListMap; 136import java.util.concurrent.CountDownLatch; 137import java.util.concurrent.Executor; 138import java.util.concurrent.LinkedBlockingDeque; 139import java.util.concurrent.ScheduledThreadPoolExecutor; 140import java.util.concurrent.ThreadFactory; 141import java.util.concurrent.ThreadPoolExecutor; 142import java.util.concurrent.TimeUnit; 143import java.util.logging.Level; 144import java.util.logging.Logger; 145import java.util.regex.MatchResult; 146import java.util.regex.Matcher; 147import java.util.regex.Pattern; 148import java.util.stream.Stream; 149import org.checkerframework.checker.nullness.compatqual.NullableDecl; 150 151/** 152 * Supplies an arbitrary "default" instance for a wide range of types, often useful in testing 153 * utilities. 154 * 155 * <p>Covers arrays, enums and common types defined in {@code java.lang}, {@code java.lang.reflect}, 156 * {@code java.io}, {@code java.nio}, {@code java.math}, {@code java.util}, {@code 157 * java.util.concurrent}, {@code java.util.regex}, {@code com.google.common.base}, {@code 158 * com.google.common.collect} and {@code com.google.common.primitives}. In addition, if the type 159 * exposes at least one public static final constant of the same type, one of the constants will be 160 * used; or if the class exposes a public parameter-less constructor then it will be "new"d and 161 * returned. 162 * 163 * <p>All default instances returned by {@link #get} are generics-safe. Clients won't get type 164 * errors for using {@code get(Comparator.class)} as a {@code Comparator<Foo>}, for example. 165 * Immutable empty instances are returned for collection types; {@code ""} for string; {@code 0} for 166 * number types; reasonable default instance for other stateless types. For mutable types, a fresh 167 * instance is created each time {@code get()} is called. 168 * 169 * @author Kevin Bourrillion 170 * @author Ben Yu 171 * @since 12.0 172 */ 173@Beta 174@GwtIncompatible 175public final class ArbitraryInstances { 176 177 private static final Ordering<Field> BY_FIELD_NAME = 178 new Ordering<Field>() { 179 @Override 180 public int compare(Field left, Field right) { 181 return left.getName().compareTo(right.getName()); 182 } 183 }; 184 185 /** 186 * Returns a new {@code MatchResult} that corresponds to a successful match. Apache Harmony (used 187 * in Android) requires a successful match in order to generate a {@code MatchResult}: 188 * http://goo.gl/5VQFmC 189 */ 190 private static MatchResult newMatchResult() { 191 Matcher matcher = Pattern.compile(".").matcher("X"); 192 matcher.find(); 193 return matcher.toMatchResult(); 194 } 195 196 private static final ClassToInstanceMap<Object> DEFAULTS = 197 ImmutableClassToInstanceMap.builder() 198 // primitives 199 .put(Object.class, "") 200 .put(Number.class, 0) 201 .put(UnsignedInteger.class, UnsignedInteger.ZERO) 202 .put(UnsignedLong.class, UnsignedLong.ZERO) 203 .put(BigInteger.class, BigInteger.ZERO) 204 .put(BigDecimal.class, BigDecimal.ZERO) 205 .put(CharSequence.class, "") 206 .put(String.class, "") 207 .put(Pattern.class, Pattern.compile("")) 208 .put(MatchResult.class, newMatchResult()) 209 .put(TimeUnit.class, TimeUnit.SECONDS) 210 .put(Charset.class, Charsets.UTF_8) 211 .put(Currency.class, Currency.getInstance(Locale.US)) 212 .put(Locale.class, Locale.US) 213 .put(Optional.class, Optional.empty()) 214 .put(OptionalInt.class, OptionalInt.empty()) 215 .put(OptionalLong.class, OptionalLong.empty()) 216 .put(OptionalDouble.class, OptionalDouble.empty()) 217 // common.base 218 .put(CharMatcher.class, CharMatcher.none()) 219 .put(Joiner.class, Joiner.on(',')) 220 .put(Splitter.class, Splitter.on(',')) 221 .put(com.google.common.base.Optional.class, com.google.common.base.Optional.absent()) 222 .put(Predicate.class, Predicates.alwaysTrue()) 223 .put(Equivalence.class, Equivalence.equals()) 224 .put(Ticker.class, Ticker.systemTicker()) 225 .put(Stopwatch.class, Stopwatch.createUnstarted()) 226 // io types 227 .put(InputStream.class, new ByteArrayInputStream(new byte[0])) 228 .put(ByteArrayInputStream.class, new ByteArrayInputStream(new byte[0])) 229 .put(Readable.class, new StringReader("")) 230 .put(Reader.class, new StringReader("")) 231 .put(StringReader.class, new StringReader("")) 232 .put(Buffer.class, ByteBuffer.allocate(0)) 233 .put(CharBuffer.class, CharBuffer.allocate(0)) 234 .put(ByteBuffer.class, ByteBuffer.allocate(0)) 235 .put(ShortBuffer.class, ShortBuffer.allocate(0)) 236 .put(IntBuffer.class, IntBuffer.allocate(0)) 237 .put(LongBuffer.class, LongBuffer.allocate(0)) 238 .put(FloatBuffer.class, FloatBuffer.allocate(0)) 239 .put(DoubleBuffer.class, DoubleBuffer.allocate(0)) 240 .put(File.class, new File("")) 241 .put(ByteSource.class, ByteSource.empty()) 242 .put(CharSource.class, CharSource.empty()) 243 .put(ByteSink.class, NullByteSink.INSTANCE) 244 .put(CharSink.class, NullByteSink.INSTANCE.asCharSink(Charsets.UTF_8)) 245 // All collections are immutable empty. So safe for any type parameter. 246 .put(Iterator.class, ImmutableSet.of().iterator()) 247 .put(PeekingIterator.class, Iterators.peekingIterator(ImmutableSet.of().iterator())) 248 .put(ListIterator.class, ImmutableList.of().listIterator()) 249 .put(Iterable.class, ImmutableSet.of()) 250 .put(Collection.class, ImmutableList.of()) 251 .put(ImmutableCollection.class, ImmutableList.of()) 252 .put(List.class, ImmutableList.of()) 253 .put(ImmutableList.class, ImmutableList.of()) 254 .put(Set.class, ImmutableSet.of()) 255 .put(ImmutableSet.class, ImmutableSet.of()) 256 .put(SortedSet.class, ImmutableSortedSet.of()) 257 .put(ImmutableSortedSet.class, ImmutableSortedSet.of()) 258 .put(NavigableSet.class, Sets.unmodifiableNavigableSet(Sets.newTreeSet())) 259 .put(Map.class, ImmutableMap.of()) 260 .put(ImmutableMap.class, ImmutableMap.of()) 261 .put(SortedMap.class, ImmutableSortedMap.of()) 262 .put(ImmutableSortedMap.class, ImmutableSortedMap.of()) 263 .put(NavigableMap.class, Maps.unmodifiableNavigableMap(Maps.newTreeMap())) 264 .put(Multimap.class, ImmutableMultimap.of()) 265 .put(ImmutableMultimap.class, ImmutableMultimap.of()) 266 .put(ListMultimap.class, ImmutableListMultimap.of()) 267 .put(ImmutableListMultimap.class, ImmutableListMultimap.of()) 268 .put(SetMultimap.class, ImmutableSetMultimap.of()) 269 .put(ImmutableSetMultimap.class, ImmutableSetMultimap.of()) 270 .put( 271 SortedSetMultimap.class, 272 Multimaps.unmodifiableSortedSetMultimap(TreeMultimap.create())) 273 .put(Multiset.class, ImmutableMultiset.of()) 274 .put(ImmutableMultiset.class, ImmutableMultiset.of()) 275 .put(SortedMultiset.class, ImmutableSortedMultiset.of()) 276 .put(ImmutableSortedMultiset.class, ImmutableSortedMultiset.of()) 277 .put(BiMap.class, ImmutableBiMap.of()) 278 .put(ImmutableBiMap.class, ImmutableBiMap.of()) 279 .put(Table.class, ImmutableTable.of()) 280 .put(ImmutableTable.class, ImmutableTable.of()) 281 .put(RowSortedTable.class, Tables.unmodifiableRowSortedTable(TreeBasedTable.create())) 282 .put(ClassToInstanceMap.class, ImmutableClassToInstanceMap.builder().build()) 283 .put(ImmutableClassToInstanceMap.class, ImmutableClassToInstanceMap.builder().build()) 284 .put(Comparable.class, ByToString.INSTANCE) 285 .put(Comparator.class, AlwaysEqual.INSTANCE) 286 .put(Ordering.class, AlwaysEqual.INSTANCE) 287 .put(Range.class, Range.all()) 288 .put(MapDifference.class, Maps.difference(ImmutableMap.of(), ImmutableMap.of())) 289 .put( 290 SortedMapDifference.class, 291 Maps.difference(ImmutableSortedMap.of(), ImmutableSortedMap.of())) 292 // reflect 293 .put(AnnotatedElement.class, Object.class) 294 .put(GenericDeclaration.class, Object.class) 295 .put(Type.class, Object.class) 296 .build(); 297 298 /** 299 * type → implementation. Inherently mutable interfaces and abstract classes are mapped to their 300 * default implementations and are "new"d upon get(). 301 */ 302 private static final ConcurrentMap<Class<?>, Class<?>> implementations = Maps.newConcurrentMap(); 303 304 private static <T> void setImplementation(Class<T> type, Class<? extends T> implementation) { 305 checkArgument(type != implementation, "Don't register %s to itself!", type); 306 checkArgument( 307 !DEFAULTS.containsKey(type), "A default value was already registered for %s", type); 308 checkArgument( 309 implementations.put(type, implementation) == null, 310 "Implementation for %s was already registered", 311 type); 312 } 313 314 static { 315 setImplementation(Appendable.class, StringBuilder.class); 316 setImplementation(BlockingQueue.class, LinkedBlockingDeque.class); 317 setImplementation(BlockingDeque.class, LinkedBlockingDeque.class); 318 setImplementation(ConcurrentMap.class, ConcurrentHashMap.class); 319 setImplementation(ConcurrentNavigableMap.class, ConcurrentSkipListMap.class); 320 setImplementation(CountDownLatch.class, Dummies.DummyCountDownLatch.class); 321 setImplementation(Deque.class, ArrayDeque.class); 322 setImplementation(OutputStream.class, ByteArrayOutputStream.class); 323 setImplementation(PrintStream.class, Dummies.InMemoryPrintStream.class); 324 setImplementation(PrintWriter.class, Dummies.InMemoryPrintWriter.class); 325 setImplementation(Queue.class, ArrayDeque.class); 326 setImplementation(Random.class, Dummies.DeterministicRandom.class); 327 setImplementation( 328 ScheduledThreadPoolExecutor.class, Dummies.DummyScheduledThreadPoolExecutor.class); 329 setImplementation(ThreadPoolExecutor.class, Dummies.DummyScheduledThreadPoolExecutor.class); 330 setImplementation(Writer.class, StringWriter.class); 331 setImplementation(Runnable.class, Dummies.DummyRunnable.class); 332 setImplementation(ThreadFactory.class, Dummies.DummyThreadFactory.class); 333 setImplementation(Executor.class, Dummies.DummyExecutor.class); 334 } 335 336 @SuppressWarnings("unchecked") // it's a subtype map 337 @NullableDecl 338 private static <T> Class<? extends T> getImplementation(Class<T> type) { 339 return (Class<? extends T>) implementations.get(type); 340 } 341 342 private static final Logger logger = Logger.getLogger(ArbitraryInstances.class.getName()); 343 344 /** 345 * Returns an arbitrary instance for {@code type}, or {@code null} if no arbitrary instance can be 346 * determined. 347 */ 348 @NullableDecl 349 public static <T> T get(Class<T> type) { 350 T defaultValue = DEFAULTS.getInstance(type); 351 if (defaultValue != null) { 352 return defaultValue; 353 } 354 Class<? extends T> implementation = getImplementation(type); 355 if (implementation != null) { 356 return get(implementation); 357 } 358 if (type == Stream.class) { 359 return type.cast(Stream.empty()); 360 } 361 if (type.isEnum()) { 362 T[] enumConstants = type.getEnumConstants(); 363 return (enumConstants.length == 0) ? null : enumConstants[0]; 364 } 365 if (type.isArray()) { 366 return createEmptyArray(type); 367 } 368 T jvmDefault = Defaults.defaultValue(Primitives.unwrap(type)); 369 if (jvmDefault != null) { 370 return jvmDefault; 371 } 372 if (Modifier.isAbstract(type.getModifiers()) || !Modifier.isPublic(type.getModifiers())) { 373 return arbitraryConstantInstanceOrNull(type); 374 } 375 final Constructor<T> constructor; 376 try { 377 constructor = type.getConstructor(); 378 } catch (NoSuchMethodException e) { 379 return arbitraryConstantInstanceOrNull(type); 380 } 381 constructor.setAccessible(true); // accessibility check is too slow 382 try { 383 return constructor.newInstance(); 384 } catch (InstantiationException | IllegalAccessException impossible) { 385 throw new AssertionError(impossible); 386 } catch (InvocationTargetException e) { 387 logger.log(Level.WARNING, "Exception while invoking default constructor.", e.getCause()); 388 return arbitraryConstantInstanceOrNull(type); 389 } 390 } 391 392 @NullableDecl 393 private static <T> T arbitraryConstantInstanceOrNull(Class<T> type) { 394 Field[] fields = type.getDeclaredFields(); 395 Arrays.sort(fields, BY_FIELD_NAME); 396 for (Field field : fields) { 397 if (Modifier.isPublic(field.getModifiers()) 398 && Modifier.isStatic(field.getModifiers()) 399 && Modifier.isFinal(field.getModifiers())) { 400 if (field.getGenericType() == field.getType() && type.isAssignableFrom(field.getType())) { 401 field.setAccessible(true); 402 try { 403 T constant = type.cast(field.get(null)); 404 if (constant != null) { 405 return constant; 406 } 407 } catch (IllegalAccessException impossible) { 408 throw new AssertionError(impossible); 409 } 410 } 411 } 412 } 413 return null; 414 } 415 416 private static <T> T createEmptyArray(Class<T> arrayType) { 417 return arrayType.cast(Array.newInstance(arrayType.getComponentType(), 0)); 418 } 419 420 // Internal implementations of some classes, with public default constructor that get() needs. 421 private static final class Dummies { 422 423 public static final class InMemoryPrintStream extends PrintStream { 424 public InMemoryPrintStream() { 425 super(new ByteArrayOutputStream()); 426 } 427 } 428 429 public static final class InMemoryPrintWriter extends PrintWriter { 430 public InMemoryPrintWriter() { 431 super(new StringWriter()); 432 } 433 } 434 435 public static final class DeterministicRandom extends Random { 436 public DeterministicRandom() { 437 super(0); 438 } 439 } 440 441 public static final class DummyScheduledThreadPoolExecutor extends ScheduledThreadPoolExecutor { 442 public DummyScheduledThreadPoolExecutor() { 443 super(1); 444 } 445 } 446 447 public static final class DummyCountDownLatch extends CountDownLatch { 448 public DummyCountDownLatch() { 449 super(0); 450 } 451 } 452 453 public static final class DummyRunnable implements Runnable, Serializable { 454 @Override 455 public void run() {} 456 } 457 458 public static final class DummyThreadFactory implements ThreadFactory, Serializable { 459 @Override 460 public Thread newThread(Runnable r) { 461 return new Thread(r); 462 } 463 } 464 465 public static final class DummyExecutor implements Executor, Serializable { 466 @Override 467 public void execute(Runnable command) {} 468 } 469 } 470 471 private static final class NullByteSink extends ByteSink implements Serializable { 472 private static final NullByteSink INSTANCE = new NullByteSink(); 473 474 @Override 475 public OutputStream openStream() { 476 return ByteStreams.nullOutputStream(); 477 } 478 } 479 480 // Compare by toString() to satisfy 2 properties: 481 // 1. compareTo(null) should throw NullPointerException 482 // 2. the order is deterministic and easy to understand, for debugging purpose. 483 private static final class ByToString implements Comparable<Object>, Serializable { 484 private static final ByToString INSTANCE = new ByToString(); 485 486 @Override 487 public int compareTo(Object o) { 488 return toString().compareTo(o.toString()); 489 } 490 491 @Override 492 public String toString() { 493 return "BY_TO_STRING"; 494 } 495 496 private Object readResolve() { 497 return INSTANCE; 498 } 499 } 500 501 // Always equal is a valid total ordering. And it works for any Object. 502 private static final class AlwaysEqual extends Ordering<Object> implements Serializable { 503 private static final AlwaysEqual INSTANCE = new AlwaysEqual(); 504 505 @Override 506 public int compare(Object o1, Object o2) { 507 return 0; 508 } 509 510 @Override 511 public String toString() { 512 return "ALWAYS_EQUAL"; 513 } 514 515 private Object readResolve() { 516 return INSTANCE; 517 } 518 } 519 520 private ArbitraryInstances() {} 521}