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