001 /*
002 * Copyright (C) 2006 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
017 package com.google.common.reflect;
018
019 import static com.google.common.base.Preconditions.checkArgument;
020 import static com.google.common.base.Preconditions.checkNotNull;
021 import static com.google.common.base.Preconditions.checkState;
022
023 import com.google.common.annotations.Beta;
024 import com.google.common.annotations.VisibleForTesting;
025 import com.google.common.base.Predicate;
026 import com.google.common.collect.AbstractSequentialIterator;
027 import com.google.common.collect.ForwardingSet;
028 import com.google.common.collect.ImmutableList;
029 import com.google.common.collect.ImmutableMap;
030 import com.google.common.collect.ImmutableSet;
031 import com.google.common.collect.ImmutableSortedSet;
032 import com.google.common.collect.Iterables;
033 import com.google.common.collect.Iterators;
034 import com.google.common.collect.Maps;
035 import com.google.common.collect.Ordering;
036 import com.google.common.collect.Sets;
037
038 import java.io.Serializable;
039 import java.lang.reflect.GenericArrayType;
040 import java.lang.reflect.ParameterizedType;
041 import java.lang.reflect.Type;
042 import java.lang.reflect.TypeVariable;
043 import java.lang.reflect.WildcardType;
044 import java.util.Comparator;
045 import java.util.Map;
046 import java.util.Set;
047 import java.util.SortedSet;
048
049 import javax.annotation.Nullable;
050
051 /**
052 * A {@link Type} with generics.
053 *
054 * <p>Operations that are otherwise only available in {@link Class} are implemented to support
055 * {@code Type}, for instance {@link #isAssignableFrom}, {@link #isArray} and {@link
056 * #getGenericInterfaces} etc.
057 *
058 * <p>There are three ways to get a {@code TypeToken} instance: <ul>
059 * <li>Wrap a {@code Type} obtained via reflection. For example: {@code
060 * TypeToken.of(method.getGenericReturnType())}.
061 * <li>Capture a generic type with a (usually anonymous) subclass. For example: <pre> {@code
062 *
063 * new TypeToken<List<String>>() {}
064 * }</pre>
065 * Note that it's critical that the actual type argument is carried by a subclass.
066 * The following code is wrong because it only captures the {@code <T>} type variable
067 * of the {@code listType()} method signature; while {@code <String>} is lost in erasure:
068 * <pre> {@code
069 *
070 * class Util {
071 * static <T> TypeToken<List<T>> listType() {
072 * return new TypeToken<List<T>>() {};
073 * }
074 * }
075 *
076 * TypeToken<List<String>> stringListType = Util.<String>listType();
077 * }</pre>
078 * <li>Capture a generic type with a (usually anonymous) subclass and resolve it against
079 * a context class that knows what the type parameters are. For example: <pre> {@code
080 * abstract class IKnowMyType<T> {
081 * TypeToken<T> type = new TypeToken<T>(getClass()) {};
082 * }
083 * new IKnowMyType<String>() {}.type => String
084 * }</pre>
085 * </ul>
086 *
087 * <p>{@code TypeToken} is serializable when no type variable is contained in the type.
088 *
089 * <p>Note to Guice users: {@code} TypeToken is similar to Guice's {@code TypeLiteral} class,
090 * but with one important difference: it supports non-reified types such as {@code T},
091 * {@code List<T>} or even {@code List<? extends Number>}; while TypeLiteral does not.
092 * TypeToken is also serializable and offers numerous additional utility methods.
093 *
094 * @author Bob Lee
095 * @author Sven Mawson
096 * @author Ben Yu
097 * @since 12.0
098 */
099 @Beta
100 @SuppressWarnings("serial") // SimpleTypeToken is the serialized form.
101 public abstract class TypeToken<T> extends TypeCapture<T> implements Serializable {
102
103 private final Type runtimeType;
104
105 /** Resolver for resolving types with {@link #runtimeType} as context. */
106 private transient TypeResolver typeResolver;
107
108 /**
109 * Constructs a new type token of {@code T}.
110 *
111 * <p>Clients create an empty anonymous subclass. Doing so embeds the type
112 * parameter in the anonymous class's type hierarchy so we can reconstitute
113 * it at runtime despite erasure.
114 *
115 * <p>For example: <pre> {@code
116 *
117 * TypeToken<List<String>> t = new TypeToken<List<String>>() {};
118 * }</pre>
119 */
120 protected TypeToken() {
121 this.runtimeType = capture();
122 checkState(!(runtimeType instanceof TypeVariable<?>),
123 "Cannot construct a TypeToken for a type variable.\n" +
124 "You probably meant to call new TypeToken<%s>(getClass()) " +
125 "that can resolve the type variable for you.\n" +
126 "If you do need to create a TypeToken of a type variable, " +
127 "please use TypeToken.of() instead.", runtimeType);
128 }
129
130 /**
131 * Constructs a new type token of {@code T}. Free type variables are resolved against {@code
132 * declaringClass}.
133 *
134 * <p>Clients create an empty anonymous subclass. Doing so embeds the type
135 * parameter in the anonymous class's type hierarchy so we can reconstitute
136 * it at runtime despite erasure.
137 *
138 * <p>For example: <pre> {@code
139 *
140 * abstract class IKnowMyType<T> {
141 * TypeToken<T> getMyType() {
142 * return new TypeToken<T>(getClass()) {};
143 * }
144 * }
145 *
146 * new IKnowMyType<String>() {}.getMyType() => String
147 * }</pre>
148 */
149 protected TypeToken(Class<?> declaringClass) {
150 Type captured = super.capture();
151 if (captured instanceof Class) {
152 this.runtimeType = captured;
153 } else {
154 this.runtimeType = of(declaringClass).resolveType(captured).runtimeType;
155 }
156 }
157
158 private TypeToken(Type type) {
159 this.runtimeType = checkNotNull(type);
160 }
161
162 /** Returns an instance of type token that wraps {@code type}. */
163 public static <T> TypeToken<T> of(Class<T> type) {
164 return new SimpleTypeToken<T>(type);
165 }
166
167 /** Returns an instance of type token that wraps {@code type}. */
168 public static TypeToken<?> of(Type type) {
169 return new SimpleTypeToken<Object>(type);
170 }
171
172 /**
173 * Returns the raw type of {@code T}. Formally speaking, if {@code T} is returned by
174 * {@link java.lang.reflect.Method#getGenericReturnType}, the raw type is what's returned by
175 * {@link java.lang.reflect.Method#getReturnType} of the same method object. Specifically:
176 * <ul>
177 * <li>If {@code T} is a {@code Class} itself, {@code T} itself is returned.
178 * <li>If {@code T} is a {@link ParameterizedType}, the raw type of the parameterized type is
179 * returned.
180 * <li>If {@code T} is a {@link GenericArrayType}, the returned type is the corresponding array
181 * class. For example: {@code List<Integer>[] => List[]}.
182 * <li>If {@code T} is a type variable or a wildcard type, the raw type of the first upper bound
183 * is returned. For example: {@code <X extends Foo> => Foo}.
184 * </ul>
185 */
186 public final Class<? super T> getRawType() {
187 Class<?> rawType = getRawType(runtimeType);
188 @SuppressWarnings("unchecked") // raw type is |T|
189 Class<? super T> result = (Class<? super T>) rawType;
190 return result;
191 }
192
193 /** Returns the resolved type of the represented type token. */
194 public final Type getType() {
195 return runtimeType;
196 }
197
198 /**
199 * Returns a new {@code TypeToken} where type variables represented by {@code typeParam}
200 * are substituted by the {@code typeArg}. For example, it can be used to construct
201 * {@code Map<K, V>} for any {@code K} and {@code V} type: <pre> {@code
202 *
203 * static <K, V> TypeToken<Map<K, V>> mapOf(
204 * TypeToken<K> keyType, TypeToken<V> valueType) {
205 * return new TypeToken<Map<K, V>>() {}
206 * .where(new TypeParameter<K>() {}, keyType)
207 * .where(new TypeParameter<V>() {}, valueType);
208 * }
209 * }</pre>
210 *
211 * @param <X> The parameter type
212 * @param typeParam the parameter type variable
213 * @param typeArg the actual type to substitute
214 */
215 public final <X> TypeToken<T> where(TypeParameter<X> typeParam, TypeToken<X> typeArg) {
216 TypeResolver resolver = new TypeResolver()
217 .where(ImmutableMap.of(typeParam.typeVariable, typeArg.runtimeType));
218 // If there's any type error, we'd report now rather than later.
219 return new SimpleTypeToken<T>(resolver.resolve(runtimeType));
220 }
221
222 /**
223 * Returns a new {@code TypeToken} where type variables represented by {@code typeParam}
224 * are substituted by the {@code typeArg}. For example, it can be used to construct
225 * {@code Map<K, V>} for any {@code K} and {@code V} type: <pre> {@code
226 *
227 * static <K, V> TypeToken<Map<K, V>> mapOf(
228 * Class<K> keyType, Class<V> valueType) {
229 * return new TypeToken<Map<K, V>>() {}
230 * .where(new TypeParameter<K>() {}, keyType)
231 * .where(new TypeParameter<V>() {}, valueType);
232 * }
233 * }</pre>
234 *
235 * @param <X> The parameter type
236 * @param typeParam the parameter type variable
237 * @param typeArg the actual type to substitute
238 */
239 public final <X> TypeToken<T> where(TypeParameter<X> typeParam, Class<X> typeArg) {
240 return where(typeParam, of(typeArg));
241 }
242
243 /**
244 * Resolves the given {@code type} against the type context represented by this type.
245 * For example: <pre> {@code
246 *
247 * new TypeToken<List<String>>() {}.resolveType(
248 * List.class.getMethod("get", int.class).getGenericReturnType())
249 * => String.class
250 * }</pre>
251 */
252 public final TypeToken<?> resolveType(Type type) {
253 checkNotNull(type);
254 TypeResolver resolver = typeResolver;
255 if (resolver == null) {
256 resolver = (typeResolver = TypeResolver.accordingTo(runtimeType));
257 }
258 return of(resolver.resolve(type));
259 }
260
261 private TypeToken<?> resolveSupertype(Type type) {
262 TypeToken<?> supertype = resolveType(type);
263 // super types' type mapping is a subset of type mapping of this type.
264 supertype.typeResolver = typeResolver;
265 return supertype;
266 }
267
268 /**
269 * Returns the generic superclass of this type or {@code null} if the type represents
270 * {@link Object} or an interface. This method is similar but different from {@link
271 * Class#getGenericSuperclass}. For example, {@code
272 * new TypeToken<StringArrayList>() {}.getGenericSuperclass()} will return {@code
273 * new TypeToken<ArrayList<String>>() {}}; while {@code
274 * StringArrayList.class.getGenericSuperclass()} will return {@code ArrayList<E>}, where {@code E}
275 * is the type variable declared by class {@code ArrayList}.
276 *
277 * <p>If this type is a type variable or wildcard, its first upper bound is examined and returned
278 * if the bound is a class or extends from a class. This means that the returned type could be a
279 * type variable too.
280 */
281 @Nullable
282 final TypeToken<? super T> getGenericSuperclass() {
283 if (runtimeType instanceof TypeVariable) {
284 // First bound is always the super class, if one exists.
285 return boundAsSuperclass(((TypeVariable<?>) runtimeType).getBounds()[0]);
286 }
287 if (runtimeType instanceof WildcardType) {
288 // wildcard has one and only one upper bound.
289 return boundAsSuperclass(((WildcardType) runtimeType).getUpperBounds()[0]);
290 }
291 Type superclass = getRawType().getGenericSuperclass();
292 if (superclass == null) {
293 return null;
294 }
295 @SuppressWarnings("unchecked") // super class of T
296 TypeToken<? super T> superToken = (TypeToken<? super T>) resolveSupertype(superclass);
297 return superToken;
298 }
299
300 @Nullable private TypeToken<? super T> boundAsSuperclass(Type bound) {
301 TypeToken<?> token = of(bound);
302 if (token.getRawType().isInterface()) {
303 return null;
304 }
305 @SuppressWarnings("unchecked") // only upper bound of T is passed in.
306 TypeToken<? super T> superclass = (TypeToken<? super T>) token;
307 return superclass;
308 }
309
310 /**
311 * Returns the generic interfaces that this type directly {@code implements}. This method is
312 * similar but different from {@link Class#getGenericInterfaces()}. For example, {@code
313 * new TypeToken<List<String>>() {}.getGenericInterfaces()} will return a list that contains
314 * {@code new TypeToken<Iterable<String>>() {}}; while {@code List.class.getGenericInterfaces()}
315 * will return an array that contains {@code Iterable<T>}, where the {@code T} is the type
316 * variable declared by interface {@code Iterable}.
317 *
318 * <p>If this type is a type variable or wildcard, its upper bounds are examined and those that
319 * are either an interface or upper-bounded only by interfaces are returned. This means that the
320 * returned types could include type variables too.
321 */
322 final ImmutableList<TypeToken<? super T>> getGenericInterfaces() {
323 if (runtimeType instanceof TypeVariable) {
324 return boundsAsInterfaces(((TypeVariable<?>) runtimeType).getBounds());
325 }
326 if (runtimeType instanceof WildcardType) {
327 return boundsAsInterfaces(((WildcardType) runtimeType).getUpperBounds());
328 }
329 ImmutableList.Builder<TypeToken<? super T>> builder = ImmutableList.builder();
330 for (Type interfaceType : getRawType().getGenericInterfaces()) {
331 @SuppressWarnings("unchecked") // interface of T
332 TypeToken<? super T> resolvedInterface = (TypeToken<? super T>)
333 resolveSupertype(interfaceType);
334 builder.add(resolvedInterface);
335 }
336 return builder.build();
337 }
338
339 private ImmutableList<TypeToken<? super T>> boundsAsInterfaces(Type[] bounds) {
340 ImmutableList.Builder<TypeToken<? super T>> builder = ImmutableList.builder();
341 for (Type bound : bounds) {
342 @SuppressWarnings("unchecked") // upper bound of T
343 TypeToken<? super T> boundType = (TypeToken<? super T>) of(bound);
344 if (boundType.getRawType().isInterface()) {
345 builder.add(boundType);
346 }
347 }
348 return builder.build();
349 }
350
351 /**
352 * Returns the set of interfaces and classes that this type is or is a subtype of. The returned
353 * types are parameterized with proper type arguments.
354 *
355 * <p>Subtypes are always listed before supertypes. But the reverse is not true. A type isn't
356 * necessarily a subtype of all the types following. Order between types without subtype
357 * relationship is arbitrary and not guaranteed.
358 *
359 * <p>If this type is a type variable or wildcard, upper bounds that are themselves type variables
360 * aren't included (their super interfaces and superclasses are).
361 */
362 public final TypeSet getTypes() {
363 return new TypeSet();
364 }
365
366 /**
367 * Returns the generic form of {@code superclass}. For example, if this is
368 * {@code ArrayList<String>}, {@code Iterable<String>} is returned given the
369 * input {@code Iterable.class}.
370 */
371 public final TypeToken<? super T> getSupertype(Class<? super T> superclass) {
372 checkArgument(superclass.isAssignableFrom(getRawType()),
373 "%s is not a super class of %s", superclass, this);
374 if (runtimeType instanceof TypeVariable) {
375 return getSupertypeFromUpperBounds(superclass, ((TypeVariable<?>) runtimeType).getBounds());
376 }
377 if (runtimeType instanceof WildcardType) {
378 return getSupertypeFromUpperBounds(superclass, ((WildcardType) runtimeType).getUpperBounds());
379 }
380 if (superclass.isArray()) {
381 return getArraySupertype(superclass);
382 }
383 @SuppressWarnings("unchecked") // resolved supertype
384 TypeToken<? super T> supertype = (TypeToken<? super T>)
385 resolveSupertype(toGenericType(superclass).runtimeType);
386 return supertype;
387 }
388
389 /**
390 * Returns subtype of {@code this} with {@code subclass} as the raw class.
391 * For example, if this is {@code Iterable<String>} and {@code subclass} is {@code List},
392 * {@code List<String>} is returned.
393 */
394 public final TypeToken<? extends T> getSubtype(Class<?> subclass) {
395 checkArgument(!(runtimeType instanceof TypeVariable),
396 "Cannot get subtype of type variable <%s>", this);
397 if (runtimeType instanceof WildcardType) {
398 return getSubtypeFromLowerBounds(subclass, ((WildcardType) runtimeType).getLowerBounds());
399 }
400 checkArgument(getRawType().isAssignableFrom(subclass),
401 "%s isn't a subclass of %s", subclass, this);
402 // unwrap array type if necessary
403 if (isArray()) {
404 return getArraySubtype(subclass);
405 }
406 @SuppressWarnings("unchecked") // guarded by the isAssignableFrom() statement above
407 TypeToken<? extends T> subtype = (TypeToken<? extends T>)
408 of(resolveTypeArgsForSubclass(subclass));
409 return subtype;
410 }
411
412 /** Returns true if this type is assignable from the given {@code type}. */
413 public final boolean isAssignableFrom(TypeToken<?> type) {
414 return isAssignableFrom(type.runtimeType);
415 }
416
417 /** Check if this type is assignable from the given {@code type}. */
418 public final boolean isAssignableFrom(Type type) {
419 return isAssignable(checkNotNull(type), runtimeType);
420 }
421
422 /** Returns true if this type is known to be an array type. */
423 public final boolean isArray() {
424 return getComponentType() != null;
425 }
426
427 /**
428 * Returns the Type representing the component type of an array. If this type does not represent
429 * an array type this method returns null.
430 */
431 @Nullable public final TypeToken<?> getComponentType() {
432 Type componentType = Types.getComponentType(runtimeType);
433 if (componentType == null) {
434 return null;
435 }
436 return of(componentType);
437 }
438
439 /**
440 * The set of interfaces and classes that {@code T} is or is a subtype of. {@link Object} is not
441 * included in the set if this type is an interface.
442 */
443 public class TypeSet extends ForwardingSet<TypeToken<? super T>> implements Serializable {
444
445 private transient ImmutableSet<TypeToken<? super T>> types;
446
447 TypeSet() {}
448
449 /** Returns the types that are interfaces implemented by this type. */
450 public TypeSet interfaces() {
451 return new InterfaceSet(this);
452 }
453
454 /** Returns the types that are classes. */
455 public TypeSet classes() {
456 return new ClassSet();
457 }
458
459 @Override protected Set<TypeToken<? super T>> delegate() {
460 ImmutableSet<TypeToken<? super T>> filteredTypes = types;
461 if (filteredTypes == null) {
462 return (types = ImmutableSet.copyOf(
463 Sets.filter(findAllTypes(), TypeFilter.IGNORE_TYPE_VARIABLE_OR_WILDCARD)));
464 } else {
465 return filteredTypes;
466 }
467 }
468
469 /** Returns the raw types of the types in this set, in the same order. */
470 public final Set<Class<? super T>> rawTypes() {
471 ImmutableSet.Builder<Class<? super T>> builder = ImmutableSet.builder();
472 for (TypeToken<? super T> type : this) {
473 builder.add(type.getRawType());
474 }
475 return builder.build();
476 }
477
478 private static final long serialVersionUID = 0;
479 }
480
481 private final class InterfaceSet extends TypeSet {
482
483 private transient final ImmutableSet<TypeToken<? super T>> interfaces;
484
485 InterfaceSet(Iterable<TypeToken<? super T>> allTypes) {
486 this.interfaces = ImmutableSet.copyOf(Iterables.filter(allTypes, TypeFilter.INTERFACE_ONLY));
487 }
488
489 @Override protected Set<TypeToken<? super T>> delegate() {
490 return interfaces;
491 }
492
493 @Override public TypeSet interfaces() {
494 return this;
495 }
496
497 @Override public TypeSet classes() {
498 throw new UnsupportedOperationException("interfaces().classes() not supported.");
499 }
500
501 private Object readResolve() {
502 return getTypes().interfaces();
503 }
504
505 private static final long serialVersionUID = 0;
506 }
507
508 private final class ClassSet extends TypeSet {
509
510 private transient final ImmutableSet<TypeToken<? super T>> classes = ImmutableSet.copyOf(
511 Iterators.filter(new AbstractSequentialIterator<TypeToken<? super T>>(
512 getRawType().isInterface() ? null : TypeToken.this) {
513 @Override protected TypeToken<? super T> computeNext(TypeToken<? super T> previous) {
514 return previous.getGenericSuperclass();
515 }
516 }, TypeFilter.IGNORE_TYPE_VARIABLE_OR_WILDCARD));
517
518 @Override protected Set<TypeToken<? super T>> delegate() {
519 return classes;
520 }
521
522 @Override public TypeSet classes() {
523 return this;
524 }
525
526 @Override public TypeSet interfaces() {
527 throw new UnsupportedOperationException("classes().interfaces() not supported.");
528 }
529
530 private Object readResolve() {
531 return getTypes().classes();
532 }
533
534 private static final long serialVersionUID = 0;
535 }
536
537 private SortedSet<TypeToken<? super T>> findAllTypes() {
538 // type -> order number. 1 for Object, 2 for anything directly below, so on so forth.
539 Map<TypeToken<? super T>, Integer> map = Maps.newHashMap();
540 collectTypes(map);
541 return sortKeysByValue(map, Ordering.natural().reverse());
542 }
543
544 /** Collects all types to map, and returns the total depth from T up to Object. */
545 private int collectTypes(Map<? super TypeToken<? super T>, Integer> map) {
546 Integer existing = map.get(this);
547 if (existing != null) {
548 // short circuit: if set contains type it already contains its supertypes
549 return existing;
550 }
551 int aboveMe = getRawType().isInterface()
552 ? 1 // interfaces should be listed before Object
553 : 0;
554 for (TypeToken<? super T> interfaceType : getGenericInterfaces()) {
555 aboveMe = Math.max(aboveMe, interfaceType.collectTypes(map));
556 }
557 TypeToken<? super T> superclass = getGenericSuperclass();
558 if (superclass != null) {
559 aboveMe = Math.max(aboveMe, superclass.collectTypes(map));
560 }
561 // TODO(benyu): should we include Object for interface?
562 // Also, CharSequence[] and Object[] for String[]?
563 map.put(this, aboveMe + 1);
564 return aboveMe + 1;
565 }
566
567 private enum TypeFilter implements Predicate<TypeToken<?>> {
568
569 IGNORE_TYPE_VARIABLE_OR_WILDCARD {
570 @Override public boolean apply(TypeToken<?> type) {
571 return !(type.runtimeType instanceof TypeVariable
572 || type.runtimeType instanceof WildcardType);
573 }
574 },
575 INTERFACE_ONLY {
576 @Override public boolean apply(TypeToken<?> type) {
577 return type.getRawType().isInterface();
578 }
579 }
580 }
581
582 /**
583 * Returns true if {@code o} is another {@code TypeToken} that represents the same {@link Type}
584 * at runtime.
585 */
586 @Override public boolean equals(@Nullable Object o) {
587 if (o instanceof TypeToken) {
588 TypeToken<?> that = (TypeToken<?>) o;
589 return runtimeType.equals(that.runtimeType);
590 }
591 return false;
592 }
593
594 @Override public int hashCode() {
595 return runtimeType.hashCode();
596 }
597
598 @Override public String toString() {
599 return Types.toString(runtimeType);
600 }
601
602 protected Object writeReplace() {
603 // TypeResolver just transforms the type to our own impls that are Serializable
604 // except TypeVariable.
605 return of(new TypeResolver().resolve(runtimeType));
606 }
607
608 private static boolean isAssignable(Type from, Type to) {
609 if (to.equals(from)) {
610 return true;
611 }
612 if (to instanceof WildcardType) {
613 return isAssignableToWildcardType(from, (WildcardType) to);
614 }
615 // if "from" is type variable, it's assignable if any of its "extends"
616 // bounds is assignable to "to".
617 if (from instanceof TypeVariable) {
618 return isAssignableFromAny(((TypeVariable<?>) from).getBounds(), to);
619 }
620 // if "from" is wildcard, it'a assignable to "to" if any of its "extends"
621 // bounds is assignable to "to".
622 if (from instanceof WildcardType) {
623 return isAssignableFromAny(((WildcardType) from).getUpperBounds(), to);
624 }
625 if (from instanceof GenericArrayType) {
626 return isAssignableFromGenericArrayType((GenericArrayType) from, to);
627 }
628 // Proceed to regular Type assignability check
629 if (to instanceof Class) {
630 return isAssignableToClass(from, (Class<?>) to);
631 } else if (to instanceof ParameterizedType) {
632 return isAssignableToParameterizedType(from, (ParameterizedType) to);
633 } else if (to instanceof GenericArrayType) {
634 return isAssignableToGenericArrayType(from, (GenericArrayType) to);
635 } else { // to instanceof TypeVariable
636 return false;
637 }
638 }
639
640 private static boolean isAssignableFromAny(Type[] fromTypes, Type to) {
641 for (Type from : fromTypes) {
642 if (isAssignable(from, to)) {
643 return true;
644 }
645 }
646 return false;
647 }
648
649 private static boolean isAssignableToClass(Type from, Class<?> to) {
650 return to.isAssignableFrom(getRawType(from));
651 }
652
653 private static boolean isAssignableToWildcardType(
654 Type from, WildcardType to) {
655 // if "to" is <? extends Foo>, "from" can be:
656 // Foo, SubFoo, <? extends Foo>, <? extends SubFoo>, <T extends Foo> or
657 // <T extends SubFoo>.
658 // if "to" is <? super Foo>, "from" can be:
659 // Foo, SuperFoo, <? super Foo> or <? super SuperFoo>.
660 return isAssignable(from, supertypeBound(to)) && isAssignableBySubtypeBound(from, to);
661 }
662
663 private static boolean isAssignableBySubtypeBound(Type from, WildcardType to) {
664 Type toSubtypeBound = subtypeBound(to);
665 if (toSubtypeBound == null) {
666 return true;
667 }
668 Type fromSubtypeBound = subtypeBound(from);
669 if (fromSubtypeBound == null) {
670 return false;
671 }
672 return isAssignable(toSubtypeBound, fromSubtypeBound);
673 }
674
675 private static boolean isAssignableToParameterizedType(Type from, ParameterizedType to) {
676 Class<?> matchedClass = getRawType(to);
677 if (!matchedClass.isAssignableFrom(getRawType(from))) {
678 return false;
679 }
680 Type[] typeParams = matchedClass.getTypeParameters();
681 Type[] toTypeArgs = to.getActualTypeArguments();
682 TypeToken<?> fromTypeToken = of(from);
683 for (int i = 0; i < typeParams.length; i++) {
684 // If "to" is "List<? extends CharSequence>"
685 // and "from" is StringArrayList,
686 // First step is to figure out StringArrayList "is-a" List<E> and <E> is
687 // String.
688 // typeParams[0] is E and fromTypeToken.get(typeParams[0]) will resolve to
689 // String.
690 // String is then matched against <? extends CharSequence>.
691 Type fromTypeArg = fromTypeToken.resolveType(typeParams[i]).runtimeType;
692 if (!matchTypeArgument(fromTypeArg, toTypeArgs[i])) {
693 return false;
694 }
695 }
696 return true;
697 }
698
699 private static boolean isAssignableToGenericArrayType(Type from, GenericArrayType to) {
700 if (from instanceof Class) {
701 Class<?> fromClass = (Class<?>) from;
702 if (!fromClass.isArray()) {
703 return false;
704 }
705 return isAssignable(fromClass.getComponentType(), to.getGenericComponentType());
706 } else if (from instanceof GenericArrayType) {
707 GenericArrayType fromArrayType = (GenericArrayType) from;
708 return isAssignable(fromArrayType.getGenericComponentType(), to.getGenericComponentType());
709 } else {
710 return false;
711 }
712 }
713
714 private static boolean isAssignableFromGenericArrayType(GenericArrayType from, Type to) {
715 if (to instanceof Class) {
716 Class<?> toClass = (Class<?>) to;
717 if (!toClass.isArray()) {
718 return toClass == Object.class; // any T[] is assignable to Object
719 }
720 return isAssignable(from.getGenericComponentType(), toClass.getComponentType());
721 } else if (to instanceof GenericArrayType) {
722 GenericArrayType toArrayType = (GenericArrayType) to;
723 return isAssignable(from.getGenericComponentType(), toArrayType.getGenericComponentType());
724 } else {
725 return false;
726 }
727 }
728
729 private static boolean matchTypeArgument(Type from, Type to) {
730 if (from.equals(to)) {
731 return true;
732 }
733 if (to instanceof WildcardType) {
734 return isAssignableToWildcardType(from, (WildcardType) to);
735 }
736 return false;
737 }
738
739 private static Type supertypeBound(Type type) {
740 if (type instanceof WildcardType) {
741 return supertypeBound((WildcardType) type);
742 }
743 return type;
744 }
745
746 private static Type supertypeBound(WildcardType type) {
747 Type[] upperBounds = type.getUpperBounds();
748 if (upperBounds.length == 1) {
749 return supertypeBound(upperBounds[0]);
750 } else if (upperBounds.length == 0) {
751 return Object.class;
752 } else {
753 throw new AssertionError(
754 "There should be at most one upper bound for wildcard type: " + type);
755 }
756 }
757
758 @Nullable private static Type subtypeBound(Type type) {
759 if (type instanceof WildcardType) {
760 return subtypeBound((WildcardType) type);
761 } else {
762 return type;
763 }
764 }
765
766 @Nullable private static Type subtypeBound(WildcardType type) {
767 Type[] lowerBounds = type.getLowerBounds();
768 if (lowerBounds.length == 1) {
769 return subtypeBound(lowerBounds[0]);
770 } else if (lowerBounds.length == 0) {
771 return null;
772 } else {
773 throw new AssertionError(
774 "Wildcard should have at most one lower bound: " + type);
775 }
776 }
777
778 @VisibleForTesting static Class<?> getRawType(Type type) {
779 if (type instanceof Class) {
780 return (Class<?>) type;
781 } else if (type instanceof ParameterizedType) {
782 ParameterizedType parameterizedType = (ParameterizedType) type;
783 // JDK implementation declares getRawType() to return Class<?>
784 return (Class<?>) parameterizedType.getRawType();
785 } else if (type instanceof GenericArrayType) {
786 GenericArrayType genericArrayType = (GenericArrayType) type;
787 return Types.getArrayClass(getRawType(genericArrayType.getGenericComponentType()));
788 } else if (type instanceof TypeVariable) {
789 // First bound is always the "primary" bound that determines the runtime signature.
790 return getRawType(((TypeVariable<?>) type).getBounds()[0]);
791 } else if (type instanceof WildcardType) {
792 // Wildcard can have one and only one upper bound.
793 return getRawType(((WildcardType) type).getUpperBounds()[0]);
794 } else {
795 throw new AssertionError(type + " unsupported");
796 }
797 }
798
799 /**
800 * Returns the type token representing the generic type declaration of {@code cls}. For example:
801 * {@code TypeToken.getGenericType(Iterable.class)} returns {@code Iterable<T>}.
802 *
803 * <p>If {@code cls} isn't parameterized and isn't a generic array, the type token of the class is
804 * returned.
805 */
806 @VisibleForTesting static <T> TypeToken<? extends T> toGenericType(Class<T> cls) {
807 if (cls.isArray()) {
808 Type arrayOfGenericType = Types.newArrayType(
809 // If we are passed with int[].class, don't turn it to GenericArrayType
810 toGenericType(cls.getComponentType()).runtimeType);
811 @SuppressWarnings("unchecked") // array is covariant
812 TypeToken<? extends T> result = (TypeToken<? extends T>) of(arrayOfGenericType);
813 return result;
814 }
815 TypeVariable<Class<T>>[] typeParams = cls.getTypeParameters();
816 if (typeParams.length > 0) {
817 @SuppressWarnings("unchecked") // Like, it's Iterable<T> for Iterable.class
818 TypeToken<? extends T> type = (TypeToken<? extends T>)
819 of(Types.newParameterizedType(cls, typeParams));
820 return type;
821 } else {
822 return of(cls);
823 }
824 }
825
826 private TypeToken<? super T> getSupertypeFromUpperBounds(
827 Class<? super T> supertype, Type[] upperBounds) {
828 for (Type upperBound : upperBounds) {
829 @SuppressWarnings("unchecked") // T's upperbound is <? super T>.
830 TypeToken<? super T> bound = (TypeToken<? super T>) of(upperBound);
831 if (of(supertype).isAssignableFrom(bound)) {
832 @SuppressWarnings({"rawtypes", "unchecked"}) // guarded by the isAssignableFrom check.
833 TypeToken<? super T> result = bound.getSupertype((Class) supertype);
834 return result;
835 }
836 }
837 throw new IllegalArgumentException(supertype + " isn't a super type of " + this);
838 }
839
840 private TypeToken<? extends T> getSubtypeFromLowerBounds(Class<?> subclass, Type[] lowerBounds) {
841 for (Type lowerBound : lowerBounds) {
842 @SuppressWarnings("unchecked") // T's lower bound is <? extends T>
843 TypeToken<? extends T> bound = (TypeToken<? extends T>) of(lowerBound);
844 // Java supports only one lowerbound anyway.
845 return bound.getSubtype(subclass);
846 }
847 throw new IllegalArgumentException(subclass + " isn't a subclass of " + this);
848 }
849
850 private TypeToken<? super T> getArraySupertype(Class<? super T> supertype) {
851 // with component type, we have lost generic type information
852 // Use raw type so that compiler allows us to call getSupertype()
853 @SuppressWarnings("rawtypes")
854 TypeToken componentType = checkNotNull(getComponentType(),
855 "%s isn't a super type of %s", supertype, this);
856 // array is covariant. component type is super type, so is the array type.
857 @SuppressWarnings("unchecked") // going from raw type back to generics
858 TypeToken<?> componentSupertype = componentType.getSupertype(supertype.getComponentType());
859 @SuppressWarnings("unchecked") // component type is super type, so is array type.
860 TypeToken<? super T> result = (TypeToken<? super T>)
861 // If we are passed with int[].class, don't turn it to GenericArrayType
862 of(newArrayClassOrGenericArrayType(componentSupertype.runtimeType));
863 return result;
864 }
865
866 private TypeToken<? extends T> getArraySubtype(Class<?> subclass) {
867 // array is covariant. component type is subtype, so is the array type.
868 TypeToken<?> componentSubtype = getComponentType()
869 .getSubtype(subclass.getComponentType());
870 @SuppressWarnings("unchecked") // component type is subtype, so is array type.
871 TypeToken<? extends T> result = (TypeToken<? extends T>)
872 // If we are passed with int[].class, don't turn it to GenericArrayType
873 of(newArrayClassOrGenericArrayType(componentSubtype.runtimeType));
874 return result;
875 }
876
877 private Type resolveTypeArgsForSubclass(Class<?> subclass) {
878 if (runtimeType instanceof Class) {
879 // no resolution needed
880 return subclass;
881 }
882 // class Base<A, B> {}
883 // class Sub<X, Y> extends Base<X, Y> {}
884 // Base<String, Integer>.subtype(Sub.class):
885
886 // Sub<X, Y>.getSupertype(Base.class) => Base<X, Y>
887 // => X=String, Y=Integer
888 // => Sub<X, Y>=Sub<String, Integer>
889 TypeToken<?> genericSubtype = toGenericType(subclass);
890 @SuppressWarnings({"rawtypes", "unchecked"}) // subclass isn't <? extends T>
891 Type supertypeWithArgsFromSubtype = genericSubtype
892 .getSupertype((Class) getRawType())
893 .runtimeType;
894 return new TypeResolver().where(supertypeWithArgsFromSubtype, runtimeType)
895 .resolve(genericSubtype.runtimeType);
896 }
897
898 /**
899 * Creates an array class if {@code componentType} is a class, or else, a
900 * {@link GenericArrayType}. This is what Java7 does for generic array type
901 * parameters.
902 */
903 private static Type newArrayClassOrGenericArrayType(Type componentType) {
904 return Types.JavaVersion.JAVA7.newArrayType(componentType);
905 }
906
907 private static <K, V> ImmutableSortedSet<K> sortKeysByValue(
908 final Map<K, V> map, final Comparator<? super V> valueComparator) {
909 Comparator<K> keyComparator = new Comparator<K>() {
910 @Override public int compare(K left, K right) {
911 return valueComparator.compare(map.get(left), map.get(right));
912 }
913 };
914 return ImmutableSortedSet.copyOf(keyComparator, map.keySet());
915 }
916
917 private static final class SimpleTypeToken<T> extends TypeToken<T> {
918
919 SimpleTypeToken(Type type) {
920 super(type);
921 }
922
923 private static final long serialVersionUID = 0;
924 }
925 }