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.FluentIterable;
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.Maps;
032 import com.google.common.collect.Ordering;
033
034 import java.io.Serializable;
035 import java.lang.reflect.GenericArrayType;
036 import java.lang.reflect.ParameterizedType;
037 import java.lang.reflect.Type;
038 import java.lang.reflect.TypeVariable;
039 import java.lang.reflect.WildcardType;
040 import java.util.Arrays;
041 import java.util.Comparator;
042 import java.util.Map;
043 import java.util.Set;
044
045 import javax.annotation.Nullable;
046
047 /**
048 * A {@link Type} with generics.
049 *
050 * <p>Operations that are otherwise only available in {@link Class} are implemented to support
051 * {@code Type}, for example {@link #isAssignableFrom}, {@link #isArray} and {@link
052 * #getComponentType}. It also provides additional utilities such as {@link #getTypes} and {@link
053 * #resolveType} etc.
054 *
055 * <p>There are three ways to get a {@code TypeToken} instance: <ul>
056 * <li>Wrap a {@code Type} obtained via reflection. For example: {@code
057 * TypeToken.of(method.getGenericReturnType())}.
058 * <li>Capture a generic type with a (usually anonymous) subclass. For example: <pre> {@code
059 *
060 * new TypeToken<List<String>>() {}
061 * }</pre>
062 * Note that it's critical that the actual type argument is carried by a subclass.
063 * The following code is wrong because it only captures the {@code <T>} type variable
064 * of the {@code listType()} method signature; while {@code <String>} is lost in erasure:
065 * <pre> {@code
066 *
067 * class Util {
068 * static <T> TypeToken<List<T>> listType() {
069 * return new TypeToken<List<T>>() {};
070 * }
071 * }
072 *
073 * TypeToken<List<String>> stringListType = Util.<String>listType();
074 * }</pre>
075 * <li>Capture a generic type with a (usually anonymous) subclass and resolve it against
076 * a context class that knows what the type parameters are. For example: <pre> {@code
077 * abstract class IKnowMyType<T> {
078 * TypeToken<T> type = new TypeToken<T>(getClass()) {};
079 * }
080 * new IKnowMyType<String>() {}.type => String
081 * }</pre>
082 * </ul>
083 *
084 * <p>{@code TypeToken} is serializable when no type variable is contained in the type.
085 *
086 * <p>Note to Guice users: {@code} TypeToken is similar to Guice's {@code TypeLiteral} class,
087 * but with one important difference: it supports non-reified types such as {@code T},
088 * {@code List<T>} or even {@code List<? extends Number>}; while TypeLiteral does not.
089 * TypeToken is also serializable and offers numerous additional utility methods.
090 *
091 * @author Bob Lee
092 * @author Sven Mawson
093 * @author Ben Yu
094 * @since 12.0
095 */
096 @Beta
097 @SuppressWarnings("serial") // SimpleTypeToken is the serialized form.
098 public abstract class TypeToken<T> extends TypeCapture<T> implements Serializable {
099
100 private final Type runtimeType;
101
102 /** Resolver for resolving types with {@link #runtimeType} as context. */
103 private transient TypeResolver typeResolver;
104
105 /**
106 * Constructs a new type token of {@code T}.
107 *
108 * <p>Clients create an empty anonymous subclass. Doing so embeds the type
109 * parameter in the anonymous class's type hierarchy so we can reconstitute
110 * it at runtime despite erasure.
111 *
112 * <p>For example: <pre> {@code
113 *
114 * TypeToken<List<String>> t = new TypeToken<List<String>>() {};
115 * }</pre>
116 */
117 protected TypeToken() {
118 this.runtimeType = capture();
119 checkState(!(runtimeType instanceof TypeVariable),
120 "Cannot construct a TypeToken for a type variable.\n" +
121 "You probably meant to call new TypeToken<%s>(getClass()) " +
122 "that can resolve the type variable for you.\n" +
123 "If you do need to create a TypeToken of a type variable, " +
124 "please use TypeToken.of() instead.", runtimeType);
125 }
126
127 /**
128 * Constructs a new type token of {@code T} while resolving free type variables in the context of
129 * {@code declaringClass}.
130 *
131 * <p>Clients create an empty anonymous subclass. Doing so embeds the type
132 * parameter in the anonymous class's type hierarchy so we can reconstitute
133 * it at runtime despite erasure.
134 *
135 * <p>For example: <pre> {@code
136 *
137 * abstract class IKnowMyType<T> {
138 * TypeToken<T> getMyType() {
139 * return new TypeToken<T>(getClass()) {};
140 * }
141 * }
142 *
143 * new IKnowMyType<String>() {}.getMyType() => String
144 * }</pre>
145 */
146 protected TypeToken(Class<?> declaringClass) {
147 Type captured = super.capture();
148 if (captured instanceof Class) {
149 this.runtimeType = captured;
150 } else {
151 this.runtimeType = of(declaringClass).resolveType(captured).runtimeType;
152 }
153 }
154
155 private TypeToken(Type type) {
156 this.runtimeType = checkNotNull(type);
157 }
158
159 /** Returns an instance of type token that wraps {@code type}. */
160 public static <T> TypeToken<T> of(Class<T> type) {
161 return new SimpleTypeToken<T>(type);
162 }
163
164 /** Returns an instance of type token that wraps {@code type}. */
165 public static TypeToken<?> of(Type type) {
166 return new SimpleTypeToken<Object>(type);
167 }
168
169 /**
170 * Returns the raw type of {@code T}. Formally speaking, if {@code T} is returned by
171 * {@link java.lang.reflect.Method#getGenericReturnType}, the raw type is what's returned by
172 * {@link java.lang.reflect.Method#getReturnType} of the same method object. Specifically:
173 * <ul>
174 * <li>If {@code T} is a {@code Class} itself, {@code T} itself is returned.
175 * <li>If {@code T} is a {@link ParameterizedType}, the raw type of the parameterized type is
176 * returned.
177 * <li>If {@code T} is a {@link GenericArrayType}, the returned type is the corresponding array
178 * class. For example: {@code List<Integer>[] => List[]}.
179 * <li>If {@code T} is a type variable or a wildcard type, the raw type of the first upper bound
180 * is returned. For example: {@code <X extends Foo> => Foo}.
181 * </ul>
182 */
183 public final Class<? super T> getRawType() {
184 Class<?> rawType = getRawType(runtimeType);
185 @SuppressWarnings("unchecked") // raw type is |T|
186 Class<? super T> result = (Class<? super T>) rawType;
187 return result;
188 }
189
190 /**
191 * Returns the raw type of the class or parameterized type; if {@code T} is type variable or
192 * wildcard type, the raw types of all its upper bounds are returned.
193 */
194 private ImmutableSet<Class<? super T>> getImmediateRawTypes() {
195 // Cast from ImmutableSet<Class<?>> to ImmutableSet<Class<? super T>>
196 @SuppressWarnings({"unchecked", "rawtypes"})
197 ImmutableSet<Class<? super T>> result = (ImmutableSet) getRawTypes(runtimeType);
198 return result;
199 }
200
201 /** Returns the represented type. */
202 public final Type getType() {
203 return runtimeType;
204 }
205
206 /**
207 * Returns a new {@code TypeToken} where type variables represented by {@code typeParam}
208 * are substituted by {@code typeArg}. For example, it can be used to construct
209 * {@code Map<K, V>} for any {@code K} and {@code V} type: <pre> {@code
210 *
211 * static <K, V> TypeToken<Map<K, V>> mapOf(
212 * TypeToken<K> keyType, TypeToken<V> valueType) {
213 * return new TypeToken<Map<K, V>>() {}
214 * .where(new TypeParameter<K>() {}, keyType)
215 * .where(new TypeParameter<V>() {}, valueType);
216 * }
217 * }</pre>
218 *
219 * @param <X> The parameter type
220 * @param typeParam the parameter type variable
221 * @param typeArg the actual type to substitute
222 */
223 public final <X> TypeToken<T> where(TypeParameter<X> typeParam, TypeToken<X> typeArg) {
224 TypeResolver resolver = new TypeResolver()
225 .where(ImmutableMap.of(typeParam.typeVariable, typeArg.runtimeType));
226 // If there's any type error, we'd report now rather than later.
227 return new SimpleTypeToken<T>(resolver.resolveType(runtimeType));
228 }
229
230 /**
231 * Returns a new {@code TypeToken} where type variables represented by {@code typeParam}
232 * are substituted by {@code typeArg}. For example, it can be used to construct
233 * {@code Map<K, V>} for any {@code K} and {@code V} type: <pre> {@code
234 *
235 * static <K, V> TypeToken<Map<K, V>> mapOf(
236 * Class<K> keyType, Class<V> valueType) {
237 * return new TypeToken<Map<K, V>>() {}
238 * .where(new TypeParameter<K>() {}, keyType)
239 * .where(new TypeParameter<V>() {}, valueType);
240 * }
241 * }</pre>
242 *
243 * @param <X> The parameter type
244 * @param typeParam the parameter type variable
245 * @param typeArg the actual type to substitute
246 */
247 public final <X> TypeToken<T> where(TypeParameter<X> typeParam, Class<X> typeArg) {
248 return where(typeParam, of(typeArg));
249 }
250
251 /**
252 * Resolves the given {@code type} against the type context represented by this type.
253 * For example: <pre> {@code
254 *
255 * new TypeToken<List<String>>() {}.resolveType(
256 * List.class.getMethod("get", int.class).getGenericReturnType())
257 * => String.class
258 * }</pre>
259 */
260 public final TypeToken<?> resolveType(Type type) {
261 checkNotNull(type);
262 TypeResolver resolver = typeResolver;
263 if (resolver == null) {
264 resolver = (typeResolver = TypeResolver.accordingTo(runtimeType));
265 }
266 return of(resolver.resolveType(type));
267 }
268
269 private TypeToken<?> resolveSupertype(Type type) {
270 TypeToken<?> supertype = resolveType(type);
271 // super types' type mapping is a subset of type mapping of this type.
272 supertype.typeResolver = typeResolver;
273 return supertype;
274 }
275
276 /**
277 * Returns the generic superclass of this type or {@code null} if the type represents
278 * {@link Object} or an interface. This method is similar but different from {@link
279 * Class#getGenericSuperclass}. For example, {@code
280 * new TypeToken<StringArrayList>() {}.getGenericSuperclass()} will return {@code
281 * new TypeToken<ArrayList<String>>() {}}; while {@code
282 * StringArrayList.class.getGenericSuperclass()} will return {@code ArrayList<E>}, where {@code E}
283 * is the type variable declared by class {@code ArrayList}.
284 *
285 * <p>If this type is a type variable or wildcard, its first upper bound is examined and returned
286 * if the bound is a class or extends from a class. This means that the returned type could be a
287 * type variable too.
288 */
289 @Nullable
290 final TypeToken<? super T> getGenericSuperclass() {
291 if (runtimeType instanceof TypeVariable) {
292 // First bound is always the super class, if one exists.
293 return boundAsSuperclass(((TypeVariable<?>) runtimeType).getBounds()[0]);
294 }
295 if (runtimeType instanceof WildcardType) {
296 // wildcard has one and only one upper bound.
297 return boundAsSuperclass(((WildcardType) runtimeType).getUpperBounds()[0]);
298 }
299 Type superclass = getRawType().getGenericSuperclass();
300 if (superclass == null) {
301 return null;
302 }
303 @SuppressWarnings("unchecked") // super class of T
304 TypeToken<? super T> superToken = (TypeToken<? super T>) resolveSupertype(superclass);
305 return superToken;
306 }
307
308 @Nullable private TypeToken<? super T> boundAsSuperclass(Type bound) {
309 TypeToken<?> token = of(bound);
310 if (token.getRawType().isInterface()) {
311 return null;
312 }
313 @SuppressWarnings("unchecked") // only upper bound of T is passed in.
314 TypeToken<? super T> superclass = (TypeToken<? super T>) token;
315 return superclass;
316 }
317
318 /**
319 * Returns the generic interfaces that this type directly {@code implements}. This method is
320 * similar but different from {@link Class#getGenericInterfaces()}. For example, {@code
321 * new TypeToken<List<String>>() {}.getGenericInterfaces()} will return a list that contains
322 * {@code new TypeToken<Iterable<String>>() {}}; while {@code List.class.getGenericInterfaces()}
323 * will return an array that contains {@code Iterable<T>}, where the {@code T} is the type
324 * variable declared by interface {@code Iterable}.
325 *
326 * <p>If this type is a type variable or wildcard, its upper bounds are examined and those that
327 * are either an interface or upper-bounded only by interfaces are returned. This means that the
328 * returned types could include type variables too.
329 */
330 final ImmutableList<TypeToken<? super T>> getGenericInterfaces() {
331 if (runtimeType instanceof TypeVariable) {
332 return boundsAsInterfaces(((TypeVariable<?>) runtimeType).getBounds());
333 }
334 if (runtimeType instanceof WildcardType) {
335 return boundsAsInterfaces(((WildcardType) runtimeType).getUpperBounds());
336 }
337 ImmutableList.Builder<TypeToken<? super T>> builder = ImmutableList.builder();
338 for (Type interfaceType : getRawType().getGenericInterfaces()) {
339 @SuppressWarnings("unchecked") // interface of T
340 TypeToken<? super T> resolvedInterface = (TypeToken<? super T>)
341 resolveSupertype(interfaceType);
342 builder.add(resolvedInterface);
343 }
344 return builder.build();
345 }
346
347 private ImmutableList<TypeToken<? super T>> boundsAsInterfaces(Type[] bounds) {
348 ImmutableList.Builder<TypeToken<? super T>> builder = ImmutableList.builder();
349 for (Type bound : bounds) {
350 @SuppressWarnings("unchecked") // upper bound of T
351 TypeToken<? super T> boundType = (TypeToken<? super T>) of(bound);
352 if (boundType.getRawType().isInterface()) {
353 builder.add(boundType);
354 }
355 }
356 return builder.build();
357 }
358
359 /**
360 * Returns the set of interfaces and classes that this type is or is a subtype of. The returned
361 * types are parameterized with proper type arguments.
362 *
363 * <p>Subtypes are always listed before supertypes. But the reverse is not true. A type isn't
364 * necessarily a subtype of all the types following. Order between types without subtype
365 * relationship is arbitrary and not guaranteed.
366 *
367 * <p>If this type is a type variable or wildcard, upper bounds that are themselves type variables
368 * aren't included (their super interfaces and superclasses are).
369 */
370 public final TypeSet getTypes() {
371 return new TypeSet();
372 }
373
374 /**
375 * Returns the generic form of {@code superclass}. For example, if this is
376 * {@code ArrayList<String>}, {@code Iterable<String>} is returned given the
377 * input {@code Iterable.class}.
378 */
379 public final TypeToken<? super T> getSupertype(Class<? super T> superclass) {
380 checkArgument(superclass.isAssignableFrom(getRawType()),
381 "%s is not a super class of %s", superclass, this);
382 if (runtimeType instanceof TypeVariable) {
383 return getSupertypeFromUpperBounds(superclass, ((TypeVariable<?>) runtimeType).getBounds());
384 }
385 if (runtimeType instanceof WildcardType) {
386 return getSupertypeFromUpperBounds(superclass, ((WildcardType) runtimeType).getUpperBounds());
387 }
388 if (superclass.isArray()) {
389 return getArraySupertype(superclass);
390 }
391 @SuppressWarnings("unchecked") // resolved supertype
392 TypeToken<? super T> supertype = (TypeToken<? super T>)
393 resolveSupertype(toGenericType(superclass).runtimeType);
394 return supertype;
395 }
396
397 /**
398 * Returns subtype of {@code this} with {@code subclass} as the raw class.
399 * For example, if this is {@code Iterable<String>} and {@code subclass} is {@code List},
400 * {@code List<String>} is returned.
401 */
402 public final TypeToken<? extends T> getSubtype(Class<?> subclass) {
403 checkArgument(!(runtimeType instanceof TypeVariable),
404 "Cannot get subtype of type variable <%s>", this);
405 if (runtimeType instanceof WildcardType) {
406 return getSubtypeFromLowerBounds(subclass, ((WildcardType) runtimeType).getLowerBounds());
407 }
408 checkArgument(getRawType().isAssignableFrom(subclass),
409 "%s isn't a subclass of %s", subclass, this);
410 // unwrap array type if necessary
411 if (isArray()) {
412 return getArraySubtype(subclass);
413 }
414 @SuppressWarnings("unchecked") // guarded by the isAssignableFrom() statement above
415 TypeToken<? extends T> subtype = (TypeToken<? extends T>)
416 of(resolveTypeArgsForSubclass(subclass));
417 return subtype;
418 }
419
420 /** Returns true if this type is assignable from the given {@code type}. */
421 public final boolean isAssignableFrom(TypeToken<?> type) {
422 return isAssignableFrom(type.runtimeType);
423 }
424
425 /** Check if this type is assignable from the given {@code type}. */
426 public final boolean isAssignableFrom(Type type) {
427 return isAssignable(checkNotNull(type), runtimeType);
428 }
429
430 /**
431 * Returns true if this type is known to be an array type, such as {@code int[]}, {@code T[]},
432 * {@code <? extends Map<String, Integer>[]>} etc.
433 */
434 public final boolean isArray() {
435 return getComponentType() != null;
436 }
437
438 /**
439 * Returns the array component type if this type represents an array ({@code int[]}, {@code T[]},
440 * {@code <? extends Map<String, Integer>[]>} etc.), or else {@code null} is returned.
441 */
442 @Nullable public final TypeToken<?> getComponentType() {
443 Type componentType = Types.getComponentType(runtimeType);
444 if (componentType == null) {
445 return null;
446 }
447 return of(componentType);
448 }
449
450 /**
451 * The set of interfaces and classes that {@code T} is or is a subtype of. {@link Object} is not
452 * included in the set if this type is an interface.
453 */
454 public class TypeSet extends ForwardingSet<TypeToken<? super T>> implements Serializable {
455
456 private transient ImmutableSet<TypeToken<? super T>> types;
457
458 TypeSet() {}
459
460 /** Returns the types that are interfaces implemented by this type. */
461 public TypeSet interfaces() {
462 return new InterfaceSet(this);
463 }
464
465 /** Returns the types that are classes. */
466 public TypeSet classes() {
467 return new ClassSet();
468 }
469
470 @Override protected Set<TypeToken<? super T>> delegate() {
471 ImmutableSet<TypeToken<? super T>> filteredTypes = types;
472 if (filteredTypes == null) {
473 // Java has no way to express ? super T when we parameterize TypeToken vs. Class.
474 @SuppressWarnings({"unchecked", "rawtypes"})
475 ImmutableList<TypeToken<? super T>> collectedTypes = (ImmutableList)
476 TypeCollector.FOR_GENERIC_TYPE.collectTypes(TypeToken.this);
477 return (types = FluentIterable.from(collectedTypes)
478 .filter(TypeFilter.IGNORE_TYPE_VARIABLE_OR_WILDCARD)
479 .toImmutableSet());
480 } else {
481 return filteredTypes;
482 }
483 }
484
485 /** Returns the raw types of the types in this set, in the same order. */
486 public Set<Class<? super T>> rawTypes() {
487 // Java has no way to express ? super T when we parameterize TypeToken vs. Class.
488 @SuppressWarnings({"unchecked", "rawtypes"})
489 ImmutableList<Class<? super T>> collectedTypes = (ImmutableList)
490 TypeCollector.FOR_RAW_TYPE.collectTypes(getImmediateRawTypes());
491 return ImmutableSet.copyOf(collectedTypes);
492 }
493
494 private static final long serialVersionUID = 0;
495 }
496
497 private final class InterfaceSet extends TypeSet {
498
499 private transient final TypeSet allTypes;
500 private transient ImmutableSet<TypeToken<? super T>> interfaces;
501
502 InterfaceSet(TypeSet allTypes) {
503 this.allTypes = allTypes;
504 }
505
506 @Override protected Set<TypeToken<? super T>> delegate() {
507 ImmutableSet<TypeToken<? super T>> result = interfaces;
508 if (result == null) {
509 return (interfaces = FluentIterable.from(allTypes)
510 .filter(TypeFilter.INTERFACE_ONLY)
511 .toImmutableSet());
512 } else {
513 return result;
514 }
515 }
516
517 @Override public TypeSet interfaces() {
518 return this;
519 }
520
521 @Override public Set<Class<? super T>> rawTypes() {
522 // Java has no way to express ? super T when we parameterize TypeToken vs. Class.
523 @SuppressWarnings({"unchecked", "rawtypes"})
524 ImmutableList<Class<? super T>> collectedTypes = (ImmutableList)
525 TypeCollector.FOR_RAW_TYPE.collectTypes(getImmediateRawTypes());
526 return FluentIterable.from(collectedTypes)
527 .filter(new Predicate<Class<?>>() {
528 @Override public boolean apply(Class<?> type) {
529 return type.isInterface();
530 }
531 })
532 .toImmutableSet();
533 }
534
535 @Override public TypeSet classes() {
536 throw new UnsupportedOperationException("interfaces().classes() not supported.");
537 }
538
539 private Object readResolve() {
540 return getTypes().interfaces();
541 }
542
543 private static final long serialVersionUID = 0;
544 }
545
546 private final class ClassSet extends TypeSet {
547
548 private transient ImmutableSet<TypeToken<? super T>> classes;
549
550 @Override protected Set<TypeToken<? super T>> delegate() {
551 ImmutableSet<TypeToken<? super T>> result = classes;
552 if (result == null) {
553 @SuppressWarnings({"unchecked", "rawtypes"})
554 ImmutableList<TypeToken<? super T>> collectedTypes = (ImmutableList)
555 TypeCollector.FOR_GENERIC_TYPE.classesOnly().collectTypes(TypeToken.this);
556 return (classes = FluentIterable.from(collectedTypes)
557 .filter(TypeFilter.IGNORE_TYPE_VARIABLE_OR_WILDCARD)
558 .toImmutableSet());
559 } else {
560 return result;
561 }
562 }
563
564 @Override public TypeSet classes() {
565 return this;
566 }
567
568 @Override public Set<Class<? super T>> rawTypes() {
569 // Java has no way to express ? super T when we parameterize TypeToken vs. Class.
570 @SuppressWarnings({"unchecked", "rawtypes"})
571 ImmutableList<Class<? super T>> collectedTypes = (ImmutableList)
572 TypeCollector.FOR_RAW_TYPE.classesOnly().collectTypes(getImmediateRawTypes());
573 return ImmutableSet.copyOf(collectedTypes);
574 }
575
576 @Override public TypeSet interfaces() {
577 throw new UnsupportedOperationException("classes().interfaces() not supported.");
578 }
579
580 private Object readResolve() {
581 return getTypes().classes();
582 }
583
584 private static final long serialVersionUID = 0;
585 }
586
587 private enum TypeFilter implements Predicate<TypeToken<?>> {
588
589 IGNORE_TYPE_VARIABLE_OR_WILDCARD {
590 @Override public boolean apply(TypeToken<?> type) {
591 return !(type.runtimeType instanceof TypeVariable
592 || type.runtimeType instanceof WildcardType);
593 }
594 },
595 INTERFACE_ONLY {
596 @Override public boolean apply(TypeToken<?> type) {
597 return type.getRawType().isInterface();
598 }
599 }
600 }
601
602 /**
603 * Returns true if {@code o} is another {@code TypeToken} that represents the same {@link Type}.
604 */
605 @Override public boolean equals(@Nullable Object o) {
606 if (o instanceof TypeToken) {
607 TypeToken<?> that = (TypeToken<?>) o;
608 return runtimeType.equals(that.runtimeType);
609 }
610 return false;
611 }
612
613 @Override public int hashCode() {
614 return runtimeType.hashCode();
615 }
616
617 @Override public String toString() {
618 return Types.toString(runtimeType);
619 }
620
621 /** Implemented to support serialization of subclasses. */
622 protected Object writeReplace() {
623 // TypeResolver just transforms the type to our own impls that are Serializable
624 // except TypeVariable.
625 return of(new TypeResolver().resolveType(runtimeType));
626 }
627
628 /**
629 * Ensures that this type token doesn't contain type variables, which can cause unchecked type
630 * errors for callers like {@link TypeToInstanceMap}.
631 */
632 final TypeToken<T> rejectTypeVariables() {
633 checkArgument(!Types.containsTypeVariable(runtimeType),
634 "%s contains a type variable and is not safe for the operation");
635 return this;
636 }
637
638 private static boolean isAssignable(Type from, Type to) {
639 if (to.equals(from)) {
640 return true;
641 }
642 if (to instanceof WildcardType) {
643 return isAssignableToWildcardType(from, (WildcardType) to);
644 }
645 // if "from" is type variable, it's assignable if any of its "extends"
646 // bounds is assignable to "to".
647 if (from instanceof TypeVariable) {
648 return isAssignableFromAny(((TypeVariable<?>) from).getBounds(), to);
649 }
650 // if "from" is wildcard, it'a assignable to "to" if any of its "extends"
651 // bounds is assignable to "to".
652 if (from instanceof WildcardType) {
653 return isAssignableFromAny(((WildcardType) from).getUpperBounds(), to);
654 }
655 if (from instanceof GenericArrayType) {
656 return isAssignableFromGenericArrayType((GenericArrayType) from, to);
657 }
658 // Proceed to regular Type assignability check
659 if (to instanceof Class) {
660 return isAssignableToClass(from, (Class<?>) to);
661 } else if (to instanceof ParameterizedType) {
662 return isAssignableToParameterizedType(from, (ParameterizedType) to);
663 } else if (to instanceof GenericArrayType) {
664 return isAssignableToGenericArrayType(from, (GenericArrayType) to);
665 } else { // to instanceof TypeVariable
666 return false;
667 }
668 }
669
670 private static boolean isAssignableFromAny(Type[] fromTypes, Type to) {
671 for (Type from : fromTypes) {
672 if (isAssignable(from, to)) {
673 return true;
674 }
675 }
676 return false;
677 }
678
679 private static boolean isAssignableToClass(Type from, Class<?> to) {
680 return to.isAssignableFrom(getRawType(from));
681 }
682
683 private static boolean isAssignableToWildcardType(
684 Type from, WildcardType to) {
685 // if "to" is <? extends Foo>, "from" can be:
686 // Foo, SubFoo, <? extends Foo>, <? extends SubFoo>, <T extends Foo> or
687 // <T extends SubFoo>.
688 // if "to" is <? super Foo>, "from" can be:
689 // Foo, SuperFoo, <? super Foo> or <? super SuperFoo>.
690 return isAssignable(from, supertypeBound(to)) && isAssignableBySubtypeBound(from, to);
691 }
692
693 private static boolean isAssignableBySubtypeBound(Type from, WildcardType to) {
694 Type toSubtypeBound = subtypeBound(to);
695 if (toSubtypeBound == null) {
696 return true;
697 }
698 Type fromSubtypeBound = subtypeBound(from);
699 if (fromSubtypeBound == null) {
700 return false;
701 }
702 return isAssignable(toSubtypeBound, fromSubtypeBound);
703 }
704
705 private static boolean isAssignableToParameterizedType(Type from, ParameterizedType to) {
706 Class<?> matchedClass = getRawType(to);
707 if (!matchedClass.isAssignableFrom(getRawType(from))) {
708 return false;
709 }
710 Type[] typeParams = matchedClass.getTypeParameters();
711 Type[] toTypeArgs = to.getActualTypeArguments();
712 TypeToken<?> fromTypeToken = of(from);
713 for (int i = 0; i < typeParams.length; i++) {
714 // If "to" is "List<? extends CharSequence>"
715 // and "from" is StringArrayList,
716 // First step is to figure out StringArrayList "is-a" List<E> and <E> is
717 // String.
718 // typeParams[0] is E and fromTypeToken.get(typeParams[0]) will resolve to
719 // String.
720 // String is then matched against <? extends CharSequence>.
721 Type fromTypeArg = fromTypeToken.resolveType(typeParams[i]).runtimeType;
722 if (!matchTypeArgument(fromTypeArg, toTypeArgs[i])) {
723 return false;
724 }
725 }
726 return true;
727 }
728
729 private static boolean isAssignableToGenericArrayType(Type from, GenericArrayType to) {
730 if (from instanceof Class) {
731 Class<?> fromClass = (Class<?>) from;
732 if (!fromClass.isArray()) {
733 return false;
734 }
735 return isAssignable(fromClass.getComponentType(), to.getGenericComponentType());
736 } else if (from instanceof GenericArrayType) {
737 GenericArrayType fromArrayType = (GenericArrayType) from;
738 return isAssignable(fromArrayType.getGenericComponentType(), to.getGenericComponentType());
739 } else {
740 return false;
741 }
742 }
743
744 private static boolean isAssignableFromGenericArrayType(GenericArrayType from, Type to) {
745 if (to instanceof Class) {
746 Class<?> toClass = (Class<?>) to;
747 if (!toClass.isArray()) {
748 return toClass == Object.class; // any T[] is assignable to Object
749 }
750 return isAssignable(from.getGenericComponentType(), toClass.getComponentType());
751 } else if (to instanceof GenericArrayType) {
752 GenericArrayType toArrayType = (GenericArrayType) to;
753 return isAssignable(from.getGenericComponentType(), toArrayType.getGenericComponentType());
754 } else {
755 return false;
756 }
757 }
758
759 private static boolean matchTypeArgument(Type from, Type to) {
760 if (from.equals(to)) {
761 return true;
762 }
763 if (to instanceof WildcardType) {
764 return isAssignableToWildcardType(from, (WildcardType) to);
765 }
766 return false;
767 }
768
769 private static Type supertypeBound(Type type) {
770 if (type instanceof WildcardType) {
771 return supertypeBound((WildcardType) type);
772 }
773 return type;
774 }
775
776 private static Type supertypeBound(WildcardType type) {
777 Type[] upperBounds = type.getUpperBounds();
778 if (upperBounds.length == 1) {
779 return supertypeBound(upperBounds[0]);
780 } else if (upperBounds.length == 0) {
781 return Object.class;
782 } else {
783 throw new AssertionError(
784 "There should be at most one upper bound for wildcard type: " + type);
785 }
786 }
787
788 @Nullable private static Type subtypeBound(Type type) {
789 if (type instanceof WildcardType) {
790 return subtypeBound((WildcardType) type);
791 } else {
792 return type;
793 }
794 }
795
796 @Nullable private static Type subtypeBound(WildcardType type) {
797 Type[] lowerBounds = type.getLowerBounds();
798 if (lowerBounds.length == 1) {
799 return subtypeBound(lowerBounds[0]);
800 } else if (lowerBounds.length == 0) {
801 return null;
802 } else {
803 throw new AssertionError(
804 "Wildcard should have at most one lower bound: " + type);
805 }
806 }
807
808 @VisibleForTesting static Class<?> getRawType(Type type) {
809 // For wildcard or type variable, the first bound determines the runtime type.
810 return getRawTypes(type).iterator().next();
811 }
812
813 @VisibleForTesting static ImmutableSet<Class<?>> getRawTypes(Type type) {
814 if (type instanceof Class) {
815 return ImmutableSet.<Class<?>>of((Class<?>) type);
816 } else if (type instanceof ParameterizedType) {
817 ParameterizedType parameterizedType = (ParameterizedType) type;
818 // JDK implementation declares getRawType() to return Class<?>
819 return ImmutableSet.<Class<?>>of((Class<?>) parameterizedType.getRawType());
820 } else if (type instanceof GenericArrayType) {
821 GenericArrayType genericArrayType = (GenericArrayType) type;
822 return ImmutableSet.<Class<?>>of(Types.getArrayClass(
823 getRawType(genericArrayType.getGenericComponentType())));
824 } else if (type instanceof TypeVariable) {
825 return getRawTypes(((TypeVariable<?>) type).getBounds());
826 } else if (type instanceof WildcardType) {
827 return getRawTypes(((WildcardType) type).getUpperBounds());
828 } else {
829 throw new AssertionError(type + " unsupported");
830 }
831 }
832
833 private static ImmutableSet<Class<?>> getRawTypes(Type[] types) {
834 ImmutableSet.Builder<Class<?>> builder = ImmutableSet.builder();
835 for (Type type : types) {
836 builder.addAll(getRawTypes(type));
837 }
838 return builder.build();
839 }
840
841 /**
842 * Returns the type token representing the generic type declaration of {@code cls}. For example:
843 * {@code TypeToken.getGenericType(Iterable.class)} returns {@code Iterable<T>}.
844 *
845 * <p>If {@code cls} isn't parameterized and isn't a generic array, the type token of the class is
846 * returned.
847 */
848 @VisibleForTesting static <T> TypeToken<? extends T> toGenericType(Class<T> cls) {
849 if (cls.isArray()) {
850 Type arrayOfGenericType = Types.newArrayType(
851 // If we are passed with int[].class, don't turn it to GenericArrayType
852 toGenericType(cls.getComponentType()).runtimeType);
853 @SuppressWarnings("unchecked") // array is covariant
854 TypeToken<? extends T> result = (TypeToken<? extends T>) of(arrayOfGenericType);
855 return result;
856 }
857 TypeVariable<Class<T>>[] typeParams = cls.getTypeParameters();
858 if (typeParams.length > 0) {
859 @SuppressWarnings("unchecked") // Like, it's Iterable<T> for Iterable.class
860 TypeToken<? extends T> type = (TypeToken<? extends T>)
861 of(Types.newParameterizedType(cls, typeParams));
862 return type;
863 } else {
864 return of(cls);
865 }
866 }
867
868 private TypeToken<? super T> getSupertypeFromUpperBounds(
869 Class<? super T> supertype, Type[] upperBounds) {
870 for (Type upperBound : upperBounds) {
871 @SuppressWarnings("unchecked") // T's upperbound is <? super T>.
872 TypeToken<? super T> bound = (TypeToken<? super T>) of(upperBound);
873 if (of(supertype).isAssignableFrom(bound)) {
874 @SuppressWarnings({"rawtypes", "unchecked"}) // guarded by the isAssignableFrom check.
875 TypeToken<? super T> result = bound.getSupertype((Class) supertype);
876 return result;
877 }
878 }
879 throw new IllegalArgumentException(supertype + " isn't a super type of " + this);
880 }
881
882 private TypeToken<? extends T> getSubtypeFromLowerBounds(Class<?> subclass, Type[] lowerBounds) {
883 for (Type lowerBound : lowerBounds) {
884 @SuppressWarnings("unchecked") // T's lower bound is <? extends T>
885 TypeToken<? extends T> bound = (TypeToken<? extends T>) of(lowerBound);
886 // Java supports only one lowerbound anyway.
887 return bound.getSubtype(subclass);
888 }
889 throw new IllegalArgumentException(subclass + " isn't a subclass of " + this);
890 }
891
892 private TypeToken<? super T> getArraySupertype(Class<? super T> supertype) {
893 // with component type, we have lost generic type information
894 // Use raw type so that compiler allows us to call getSupertype()
895 @SuppressWarnings("rawtypes")
896 TypeToken componentType = checkNotNull(getComponentType(),
897 "%s isn't a super type of %s", supertype, this);
898 // array is covariant. component type is super type, so is the array type.
899 @SuppressWarnings("unchecked") // going from raw type back to generics
900 TypeToken<?> componentSupertype = componentType.getSupertype(supertype.getComponentType());
901 @SuppressWarnings("unchecked") // component type is super type, so is array type.
902 TypeToken<? super T> result = (TypeToken<? super T>)
903 // If we are passed with int[].class, don't turn it to GenericArrayType
904 of(newArrayClassOrGenericArrayType(componentSupertype.runtimeType));
905 return result;
906 }
907
908 private TypeToken<? extends T> getArraySubtype(Class<?> subclass) {
909 // array is covariant. component type is subtype, so is the array type.
910 TypeToken<?> componentSubtype = getComponentType()
911 .getSubtype(subclass.getComponentType());
912 @SuppressWarnings("unchecked") // component type is subtype, so is array type.
913 TypeToken<? extends T> result = (TypeToken<? extends T>)
914 // If we are passed with int[].class, don't turn it to GenericArrayType
915 of(newArrayClassOrGenericArrayType(componentSubtype.runtimeType));
916 return result;
917 }
918
919 private Type resolveTypeArgsForSubclass(Class<?> subclass) {
920 if (runtimeType instanceof Class) {
921 // no resolution needed
922 return subclass;
923 }
924 // class Base<A, B> {}
925 // class Sub<X, Y> extends Base<X, Y> {}
926 // Base<String, Integer>.subtype(Sub.class):
927
928 // Sub<X, Y>.getSupertype(Base.class) => Base<X, Y>
929 // => X=String, Y=Integer
930 // => Sub<X, Y>=Sub<String, Integer>
931 TypeToken<?> genericSubtype = toGenericType(subclass);
932 @SuppressWarnings({"rawtypes", "unchecked"}) // subclass isn't <? extends T>
933 Type supertypeWithArgsFromSubtype = genericSubtype
934 .getSupertype((Class) getRawType())
935 .runtimeType;
936 return new TypeResolver().where(supertypeWithArgsFromSubtype, runtimeType)
937 .resolveType(genericSubtype.runtimeType);
938 }
939
940 /**
941 * Creates an array class if {@code componentType} is a class, or else, a
942 * {@link GenericArrayType}. This is what Java7 does for generic array type
943 * parameters.
944 */
945 private static Type newArrayClassOrGenericArrayType(Type componentType) {
946 return Types.JavaVersion.JAVA7.newArrayType(componentType);
947 }
948
949 private static final class SimpleTypeToken<T> extends TypeToken<T> {
950
951 SimpleTypeToken(Type type) {
952 super(type);
953 }
954
955 private static final long serialVersionUID = 0;
956 }
957
958 /**
959 * Collects parent types from a sub type.
960 *
961 * @param <K> The type "kind". Either a TypeToken, or Class.
962 */
963 private abstract static class TypeCollector<K> {
964
965 static final TypeCollector<TypeToken<?>> FOR_GENERIC_TYPE =
966 new TypeCollector<TypeToken<?>>() {
967 @Override Class<?> getRawType(TypeToken<?> type) {
968 return type.getRawType();
969 }
970
971 @Override Iterable<? extends TypeToken<?>> getInterfaces(TypeToken<?> type) {
972 return type.getGenericInterfaces();
973 }
974
975 @Nullable
976 @Override TypeToken<?> getSuperclass(TypeToken<?> type) {
977 return type.getGenericSuperclass();
978 }
979 };
980
981 static final TypeCollector<Class<?>> FOR_RAW_TYPE =
982 new TypeCollector<Class<?>>() {
983 @Override Class<?> getRawType(Class<?> type) {
984 return type;
985 }
986
987 @Override Iterable<? extends Class<?>> getInterfaces(Class<?> type) {
988 return Arrays.asList(type.getInterfaces());
989 }
990
991 @Nullable
992 @Override Class<?> getSuperclass(Class<?> type) {
993 return type.getSuperclass();
994 }
995 };
996
997 /** For just classes, we don't have to traverse interfaces. */
998 final TypeCollector<K> classesOnly() {
999 return new ForwardingTypeCollector<K>(this) {
1000 @Override Iterable<? extends K> getInterfaces(K type) {
1001 return ImmutableSet.of();
1002 }
1003 @Override ImmutableList<K> collectTypes(Iterable<? extends K> types) {
1004 ImmutableList.Builder<K> builder = ImmutableList.builder();
1005 for (K type : types) {
1006 if (!getRawType(type).isInterface()) {
1007 builder.add(type);
1008 }
1009 }
1010 return super.collectTypes(builder.build());
1011 }
1012 };
1013 }
1014
1015 final ImmutableList<K> collectTypes(K type) {
1016 return collectTypes(ImmutableList.of(type));
1017 }
1018
1019 ImmutableList<K> collectTypes(Iterable<? extends K> types) {
1020 // type -> order number. 1 for Object, 2 for anything directly below, so on so forth.
1021 Map<K, Integer> map = Maps.newHashMap();
1022 for (K type : types) {
1023 collectTypes(type, map);
1024 }
1025 return sortKeysByValue(map, Ordering.natural().reverse());
1026 }
1027
1028 /** Collects all types to map, and returns the total depth from T up to Object. */
1029 private int collectTypes(K type, Map<? super K, Integer> map) {
1030 Integer existing = map.get(this);
1031 if (existing != null) {
1032 // short circuit: if set contains type it already contains its supertypes
1033 return existing;
1034 }
1035 int aboveMe = getRawType(type).isInterface()
1036 ? 1 // interfaces should be listed before Object
1037 : 0;
1038 for (K interfaceType : getInterfaces(type)) {
1039 aboveMe = Math.max(aboveMe, collectTypes(interfaceType, map));
1040 }
1041 K superclass = getSuperclass(type);
1042 if (superclass != null) {
1043 aboveMe = Math.max(aboveMe, collectTypes(superclass, map));
1044 }
1045 // TODO(benyu): should we include Object for interface?
1046 // Also, CharSequence[] and Object[] for String[]?
1047 map.put(type, aboveMe + 1);
1048 return aboveMe + 1;
1049 }
1050
1051 private static <K, V> ImmutableList<K> sortKeysByValue(
1052 final Map<K, V> map, final Comparator<? super V> valueComparator) {
1053 Ordering<K> keyOrdering = new Ordering<K>() {
1054 @Override public int compare(K left, K right) {
1055 return valueComparator.compare(map.get(left), map.get(right));
1056 }
1057 };
1058 return keyOrdering.immutableSortedCopy(map.keySet());
1059 }
1060
1061 abstract Class<?> getRawType(K type);
1062 abstract Iterable<? extends K> getInterfaces(K type);
1063 @Nullable abstract K getSuperclass(K type);
1064
1065 private static class ForwardingTypeCollector<K> extends TypeCollector<K> {
1066
1067 private final TypeCollector<K> delegate;
1068
1069 ForwardingTypeCollector(TypeCollector<K> delegate) {
1070 this.delegate = delegate;
1071 }
1072
1073 @Override Class<?> getRawType(K type) {
1074 return delegate.getRawType(type);
1075 }
1076
1077 @Override Iterable<? extends K> getInterfaces(K type) {
1078 return delegate.getInterfaces(type);
1079 }
1080
1081 @Override K getSuperclass(K type) {
1082 return delegate.getSuperclass(type);
1083 }
1084 }
1085 }
1086 }