/*
* Copyright (C) 2011 The Guava Authors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.common.reflect;
import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.collect.Iterables.transform;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Function;
import com.google.common.base.Joiner;
import com.google.common.base.Objects;
import com.google.common.base.Predicates;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.Iterables;
import java.io.Serializable;
import java.lang.reflect.Array;
import java.lang.reflect.GenericArrayType;
import java.lang.reflect.GenericDeclaration;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.lang.reflect.TypeVariable;
import java.lang.reflect.WildcardType;
import java.util.Arrays;
import java.util.Collection;
import java.util.concurrent.atomic.AtomicReference;
import javax.annotation.Nullable;
/**
* Utilities for working with {@link Type}.
*
* @author Ben Yu
*/
final class Types {
/** Class#toString without the "class " and "interface " prefixes */
private static final Function<Type, String> TYPE_TO_STRING =
new Function<Type, String>() {
@Override public String apply(Type from) {
return Types.toString(from);
}
};
private static final Joiner COMMA_JOINER = Joiner.on(", ").useForNull("null");
/** Returns the array type of {@code componentType}. */
static Type newArrayType(Type componentType) {
if (componentType instanceof WildcardType) {
WildcardType wildcard = (WildcardType) componentType;
Type[] lowerBounds = wildcard.getLowerBounds();
checkArgument(lowerBounds.length <= 1, "Wildcard cannot have more than one lower bounds.");
if (lowerBounds.length == 1) {
return supertypeOf(newArrayType(lowerBounds[0]));
} else {
Type[] upperBounds = wildcard.getUpperBounds();
checkArgument(upperBounds.length == 1, "Wildcard should have only one upper bound.");
return subtypeOf(newArrayType(upperBounds[0]));
}
}
return JavaVersion.CURRENT.newArrayType(componentType);
}
/**
* Returns a type where {@code rawType} is parameterized by
* {@code arguments} and is owned by {@code ownerType}.
*/
static ParameterizedType newParameterizedTypeWithOwner(
@Nullable Type ownerType, Class<?> rawType, Type... arguments) {
if (ownerType == null) {
return newParameterizedType(rawType, arguments);
}
// ParameterizedTypeImpl constructor already checks, but we want to throw NPE before IAE
checkNotNull(arguments);
checkArgument(rawType.getEnclosingClass() != null, "Owner type for unenclosed %s", rawType);
return new ParameterizedTypeImpl(ownerType, rawType, arguments);
}
/**
* Returns a type where {@code rawType} is parameterized by
* {@code arguments}.
*/
static ParameterizedType newParameterizedType(Class<?> rawType, Type... arguments) {
return new ParameterizedTypeImpl(
ClassOwnership.JVM_BEHAVIOR.getOwnerType(rawType), rawType, arguments);
}
/** Decides what owner type to use for constructing {@link ParameterizedType} from a raw class. */
private enum ClassOwnership {
OWNED_BY_ENCLOSING_CLASS {
@Nullable
@Override
Class<?> getOwnerType(Class<?> rawType) {
return rawType.getEnclosingClass();
}
},
LOCAL_CLASS_HAS_NO_OWNER {
@Nullable
@Override
Class<?> getOwnerType(Class<?> rawType) {
if (rawType.isLocalClass()) {
return null;
} else {
return rawType.getEnclosingClass();
}
}
};
@Nullable abstract Class<?> getOwnerType(Class<?> rawType);
static final ClassOwnership JVM_BEHAVIOR = detectJvmBehavior();
private static ClassOwnership detectJvmBehavior() {
class LocalClass<T> {}
Class<?> subclass = new LocalClass<String>() {}.getClass();
ParameterizedType parameterizedType = (ParameterizedType)
subclass.getGenericSuperclass();
for (ClassOwnership behavior : ClassOwnership.values()) {
if (behavior.getOwnerType(LocalClass.class) == parameterizedType.getOwnerType()) {
return behavior;
}
}
throw new AssertionError();
}
}
/**
* Returns a new {@link TypeVariable} that belongs to {@code declaration} with
* {@code name} and {@code bounds}.
*/
static <D extends GenericDeclaration> TypeVariable<D> newArtificialTypeVariable(
D declaration, String name, Type... bounds) {
return new TypeVariableImpl<D>(
declaration,
name,
(bounds.length == 0)
? new Type[] { Object.class }
: bounds);
}
/** Returns a new {@link WildcardType} with {@code upperBound}. */
@VisibleForTesting static WildcardType subtypeOf(Type upperBound) {
return new WildcardTypeImpl(new Type[0], new Type[] { upperBound });
}
/** Returns a new {@link WildcardType} with {@code lowerBound}. */
@VisibleForTesting static WildcardType supertypeOf(Type lowerBound) {
return new WildcardTypeImpl(new Type[] { lowerBound }, new Type[] { Object.class });
}
/**
* Returns human readable string representation of {@code type}.
* <ul>
* <li> For array type {@code Foo[]}, {@code "com.mypackage.Foo[]"} are
* returned.
* <li> For any class, {@code theClass.getName()} are returned.
* <li> For all other types, {@code type.toString()} are returned.
* </ul>
*/
static String toString(Type type) {
return (type instanceof Class)
? ((Class<?>) type).getName()
: type.toString();
}
@Nullable static Type getComponentType(Type type) {
checkNotNull(type);
final AtomicReference<Type> result = new AtomicReference<Type>();
new TypeVisitor() {
@Override void visitTypeVariable(TypeVariable<?> t) {
result.set(subtypeOfComponentType(t.getBounds()));
}
@Override void visitWildcardType(WildcardType t) {
result.set(subtypeOfComponentType(t.getUpperBounds()));
}
@Override void visitGenericArrayType(GenericArrayType t) {
result.set(t.getGenericComponentType());
}
@Override void visitClass(Class<?> t) {
result.set(t.getComponentType());
}
}.visit(type);
return result.get();
}
/**
* Returns {@code ? extends X} if any of {@code bounds} is a subtype of {@code X[]}; or null
* otherwise.
*/
@Nullable private static Type subtypeOfComponentType(Type[] bounds) {
for (Type bound : bounds) {
Type componentType = getComponentType(bound);
if (componentType != null) {
// Only the first bound can be a class or array.
// Bounds after the first can only be interfaces.
if (componentType instanceof Class) {
Class<?> componentClass = (Class<?>) componentType;
if (componentClass.isPrimitive()) {
return componentClass;
}
}
return subtypeOf(componentType);
}
}
return null;
}
private static final class GenericArrayTypeImpl
implements GenericArrayType, Serializable {
private final Type componentType;
GenericArrayTypeImpl(Type componentType) {
this.componentType = JavaVersion.CURRENT.usedInGenericType(componentType);
}
@Override public Type getGenericComponentType() {
return componentType;
}
@Override public String toString() {
return Types.toString(componentType) + "[]";
}
@Override public int hashCode() {
return componentType.hashCode();
}
@Override public boolean equals(Object obj) {
if (obj instanceof GenericArrayType) {
GenericArrayType that = (GenericArrayType) obj;
return Objects.equal(
getGenericComponentType(), that.getGenericComponentType());
}
return false;
}
private static final long serialVersionUID = 0;
}
private static final class ParameterizedTypeImpl
implements ParameterizedType, Serializable {
private final Type ownerType;
private final ImmutableList<Type> argumentsList;
private final Class<?> rawType;
ParameterizedTypeImpl(
@Nullable Type ownerType, Class<?> rawType, Type[] typeArguments) {
checkNotNull(rawType);
checkArgument(typeArguments.length == rawType.getTypeParameters().length);
disallowPrimitiveType(typeArguments, "type parameter");
this.ownerType = ownerType;
this.rawType = rawType;
this.argumentsList = JavaVersion.CURRENT.usedInGenericType(typeArguments);
}
@Override public Type[] getActualTypeArguments() {
return toArray(argumentsList);
}
@Override public Type getRawType() {
return rawType;
}
@Override public Type getOwnerType() {
return ownerType;
}
@Override public String toString() {
StringBuilder builder = new StringBuilder();
if (ownerType != null) {
builder.append(Types.toString(ownerType)).append('.');
}
builder.append(rawType.getName())
.append('<')
.append(COMMA_JOINER.join(transform(argumentsList, TYPE_TO_STRING)))
.append('>');
return builder.toString();
}
@Override public int hashCode() {
return (ownerType == null ? 0 : ownerType.hashCode())
^ argumentsList.hashCode() ^ rawType.hashCode();
}
@Override public boolean equals(Object other) {
if (!(other instanceof ParameterizedType)) {
return false;
}
ParameterizedType that = (ParameterizedType) other;
return getRawType().equals(that.getRawType())
&& Objects.equal(getOwnerType(), that.getOwnerType())
&& Arrays.equals(
getActualTypeArguments(), that.getActualTypeArguments());
}
private static final long serialVersionUID = 0;
}
private static final class TypeVariableImpl<D extends GenericDeclaration>
implements TypeVariable<D> {
private final D genericDeclaration;
private final String name;
private final ImmutableList<Type> bounds;
TypeVariableImpl(D genericDeclaration, String name, Type[] bounds) {
disallowPrimitiveType(bounds, "bound for type variable");
this.genericDeclaration = checkNotNull(genericDeclaration);
this.name = checkNotNull(name);
this.bounds = ImmutableList.copyOf(bounds);
}
@Override public Type[] getBounds() {
return toArray(bounds);
}
@Override public D getGenericDeclaration() {
return genericDeclaration;
}
@Override public String getName() {
return name;
}
@Override public String toString() {
return name;
}
@Override public int hashCode() {
return genericDeclaration.hashCode() ^ name.hashCode();
}
@Override public boolean equals(Object obj) {
if (NativeTypeVariableEquals.NATIVE_TYPE_VARIABLE_ONLY) {
// equal only to our TypeVariable implementation with identical bounds
if (obj instanceof TypeVariableImpl) {
TypeVariableImpl<?> that = (TypeVariableImpl<?>) obj;
return name.equals(that.getName())
&& genericDeclaration.equals(that.getGenericDeclaration())
&& bounds.equals(that.bounds);
}
return false;
} else {
// equal to any TypeVariable implementation regardless of bounds
if (obj instanceof TypeVariable) {
TypeVariable<?> that = (TypeVariable<?>) obj;
return name.equals(that.getName())
&& genericDeclaration.equals(that.getGenericDeclaration());
}
return false;
}
}
}
static final class WildcardTypeImpl implements WildcardType, Serializable {
private final ImmutableList<Type> lowerBounds;
private final ImmutableList<Type> upperBounds;
WildcardTypeImpl(Type[] lowerBounds, Type[] upperBounds) {
disallowPrimitiveType(lowerBounds, "lower bound for wildcard");
disallowPrimitiveType(upperBounds, "upper bound for wildcard");
this.lowerBounds = JavaVersion.CURRENT.usedInGenericType(lowerBounds);
this.upperBounds = JavaVersion.CURRENT.usedInGenericType(upperBounds);
}
@Override public Type[] getLowerBounds() {
return toArray(lowerBounds);
}
@Override public Type[] getUpperBounds() {
return toArray(upperBounds);
}
@Override public boolean equals(Object obj) {
if (obj instanceof WildcardType) {
WildcardType that = (WildcardType) obj;
return lowerBounds.equals(Arrays.asList(that.getLowerBounds()))
&& upperBounds.equals(Arrays.asList(that.getUpperBounds()));
}
return false;
}
@Override public int hashCode() {
return lowerBounds.hashCode() ^ upperBounds.hashCode();
}
@Override public String toString() {
StringBuilder builder = new StringBuilder("?");
for (Type lowerBound : lowerBounds) {
builder.append(" super ").append(Types.toString(lowerBound));
}
for (Type upperBound : filterUpperBounds(upperBounds)) {
builder.append(" extends ").append(Types.toString(upperBound));
}
return builder.toString();
}
private static final long serialVersionUID = 0;
}
private static Type[] toArray(Collection<Type> types) {
return types.toArray(new Type[types.size()]);
}
private static Iterable<Type> filterUpperBounds(Iterable<Type> bounds) {
return Iterables.filter(
bounds, Predicates.not(Predicates.<Type>equalTo(Object.class)));
}
private static void disallowPrimitiveType(Type[] types, String usedAs) {
for (Type type : types) {
if (type instanceof Class) {
Class<?> cls = (Class<?>) type;
checkArgument(!cls.isPrimitive(),
"Primitive type '%s' used as %s", cls, usedAs);
}
}
}
/** Returns the {@code Class} object of arrays with {@code componentType}. */
static Class<?> getArrayClass(Class<?> componentType) {
// TODO(user): This is not the most efficient way to handle generic
// arrays, but is there another way to extract the array class in a
// non-hacky way (i.e. using String value class names- "[L...")?
return Array.newInstance(componentType, 0).getClass();
}
// TODO(benyu): Once we are on Java 7, delete this abstraction
enum JavaVersion {
JAVA6 {
@Override GenericArrayType newArrayType(Type componentType) {
return new GenericArrayTypeImpl(componentType);
}
@Override Type usedInGenericType(Type type) {
checkNotNull(type);
if (type instanceof Class) {
Class<?> cls = (Class<?>) type;
if (cls.isArray()) {
return new GenericArrayTypeImpl(cls.getComponentType());
}
}
return type;
}
},
JAVA7 {
@Override Type newArrayType(Type componentType) {
if (componentType instanceof Class) {
return getArrayClass((Class<?>) componentType);
} else {
return new GenericArrayTypeImpl(componentType);
}
}
@Override Type usedInGenericType(Type type) {
return checkNotNull(type);
}
}
;
static final JavaVersion CURRENT =
(new TypeCapture<int[]>() {}.capture() instanceof Class)
? JAVA7 : JAVA6;
abstract Type newArrayType(Type componentType);
abstract Type usedInGenericType(Type type);
final ImmutableList<Type> usedInGenericType(Type[] types) {
ImmutableList.Builder<Type> builder = ImmutableList.builder();
for (Type type : types) {
builder.add(usedInGenericType(type));
}
return builder.build();
}
}
/**
* Per https://code.google.com/p/guava-libraries/issues/detail?id=1635,
* In JDK 1.7.0_51-b13, TypeVariableImpl.equals() is changed to no longer be equal to custom
* TypeVariable implementations. As a result, we need to make sure our TypeVariable implementation
* respects symmetry.
* Moreover, we don't want to reconstruct a native type variable <A> using our implementation
* unless some of its bounds have changed in resolution. This avoids creating unequal TypeVariable
* implementation unnecessarily. When the bounds do change, however, it's fine for the synthetic
* TypeVariable to be unequal to any native TypeVariable anyway.
*/
static final class NativeTypeVariableEquals<X> {
static final boolean NATIVE_TYPE_VARIABLE_ONLY =
!NativeTypeVariableEquals.class.getTypeParameters()[0].equals(
newArtificialTypeVariable(NativeTypeVariableEquals.class, "X"));
}
private Types() {}
}