$Gson$Types.java
/*
* Copyright (C) 2008 Google Inc.
*
* 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.gson.internal;
import static com.google.gson.internal.$Gson$Preconditions.checkArgument;
import static java.util.Objects.requireNonNull;
import java.io.Serializable;
import java.lang.reflect.Array;
import java.lang.reflect.GenericArrayType;
import java.lang.reflect.GenericDeclaration;
import java.lang.reflect.Modifier;
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.HashMap;
import java.util.Map;
import java.util.NoSuchElementException;
import java.util.Objects;
import java.util.Properties;
/**
* Static methods for working with types.
*
* @author Bob Lee
* @author Jesse Wilson
*/
public final class $Gson$Types {
static final Type[] EMPTY_TYPE_ARRAY = new Type[] {};
private $Gson$Types() {
throw new UnsupportedOperationException();
}
/**
* Returns a new parameterized type, applying {@code typeArguments} to {@code rawType} and
* enclosed by {@code ownerType}.
*
* @return a {@link java.io.Serializable serializable} parameterized type.
*/
public static ParameterizedType newParameterizedTypeWithOwner(
Type ownerType, Type rawType, Type... typeArguments) {
return new ParameterizedTypeImpl(ownerType, rawType, typeArguments);
}
/**
* Returns an array type whose elements are all instances of {@code componentType}.
*
* @return a {@link java.io.Serializable serializable} generic array type.
*/
public static GenericArrayType arrayOf(Type componentType) {
return new GenericArrayTypeImpl(componentType);
}
/**
* Returns a type that represents an unknown type that extends {@code bound}. For example, if
* {@code bound} is {@code CharSequence.class}, this returns {@code ? extends CharSequence}. If
* {@code bound} is {@code Object.class}, this returns {@code ?}, which is shorthand for {@code ?
* extends Object}.
*/
public static WildcardType subtypeOf(Type bound) {
Type[] upperBounds;
if (bound instanceof WildcardType) {
upperBounds = ((WildcardType) bound).getUpperBounds();
} else {
upperBounds = new Type[] {bound};
}
return new WildcardTypeImpl(upperBounds, EMPTY_TYPE_ARRAY);
}
/**
* Returns a type that represents an unknown supertype of {@code bound}. For example, if {@code
* bound} is {@code String.class}, this returns {@code ? super String}.
*/
public static WildcardType supertypeOf(Type bound) {
Type[] lowerBounds;
if (bound instanceof WildcardType) {
lowerBounds = ((WildcardType) bound).getLowerBounds();
} else {
lowerBounds = new Type[] {bound};
}
return new WildcardTypeImpl(new Type[] {Object.class}, lowerBounds);
}
/**
* Returns a type that is functionally equal but not necessarily equal according to {@link
* Object#equals(Object) Object.equals()}. The returned type is {@link java.io.Serializable}.
*/
public static Type canonicalize(Type type) {
if (type instanceof Class) {
Class<?> c = (Class<?>) type;
return c.isArray() ? new GenericArrayTypeImpl(canonicalize(c.getComponentType())) : c;
} else if (type instanceof ParameterizedType) {
ParameterizedType p = (ParameterizedType) type;
return new ParameterizedTypeImpl(
p.getOwnerType(), p.getRawType(), p.getActualTypeArguments());
} else if (type instanceof GenericArrayType) {
GenericArrayType g = (GenericArrayType) type;
return new GenericArrayTypeImpl(g.getGenericComponentType());
} else if (type instanceof WildcardType) {
WildcardType w = (WildcardType) type;
return new WildcardTypeImpl(w.getUpperBounds(), w.getLowerBounds());
} else {
// type is either serializable as-is or unsupported
return type;
}
}
public static Class<?> getRawType(Type type) {
if (type instanceof Class<?>) {
// type is a normal class.
return (Class<?>) type;
} else if (type instanceof ParameterizedType) {
ParameterizedType parameterizedType = (ParameterizedType) type;
// getRawType() returns Type instead of Class; that seems to be an API mistake,
// see https://bugs.openjdk.org/browse/JDK-8250659
Type rawType = parameterizedType.getRawType();
checkArgument(rawType instanceof Class);
return (Class<?>) rawType;
} else if (type instanceof GenericArrayType) {
Type componentType = ((GenericArrayType) type).getGenericComponentType();
return Array.newInstance(getRawType(componentType), 0).getClass();
} else if (type instanceof TypeVariable) {
// we could use the variable's bounds, but that won't work if there are multiple.
// having a raw type that's more general than necessary is okay
return Object.class;
} else if (type instanceof WildcardType) {
Type[] bounds = ((WildcardType) type).getUpperBounds();
// Currently the JLS only permits one bound for wildcards so using first bound is safe
assert bounds.length == 1;
return getRawType(bounds[0]);
} else {
String className = type == null ? "null" : type.getClass().getName();
throw new IllegalArgumentException(
"Expected a Class, ParameterizedType, or GenericArrayType, but <"
+ type
+ "> is of type "
+ className);
}
}
private static boolean equal(Object a, Object b) {
return Objects.equals(a, b);
}
/** Returns true if {@code a} and {@code b} are equal. */
public static boolean equals(Type a, Type b) {
if (a == b) {
// also handles (a == null && b == null)
return true;
} else if (a instanceof Class) {
// Class already specifies equals().
return a.equals(b);
} else if (a instanceof ParameterizedType) {
if (!(b instanceof ParameterizedType)) {
return false;
}
// TODO: save a .clone() call
ParameterizedType pa = (ParameterizedType) a;
ParameterizedType pb = (ParameterizedType) b;
return equal(pa.getOwnerType(), pb.getOwnerType())
&& pa.getRawType().equals(pb.getRawType())
&& Arrays.equals(pa.getActualTypeArguments(), pb.getActualTypeArguments());
} else if (a instanceof GenericArrayType) {
if (!(b instanceof GenericArrayType)) {
return false;
}
GenericArrayType ga = (GenericArrayType) a;
GenericArrayType gb = (GenericArrayType) b;
return equals(ga.getGenericComponentType(), gb.getGenericComponentType());
} else if (a instanceof WildcardType) {
if (!(b instanceof WildcardType)) {
return false;
}
WildcardType wa = (WildcardType) a;
WildcardType wb = (WildcardType) b;
return Arrays.equals(wa.getUpperBounds(), wb.getUpperBounds())
&& Arrays.equals(wa.getLowerBounds(), wb.getLowerBounds());
} else if (a instanceof TypeVariable) {
if (!(b instanceof TypeVariable)) {
return false;
}
TypeVariable<?> va = (TypeVariable<?>) a;
TypeVariable<?> vb = (TypeVariable<?>) b;
return Objects.equals(va.getGenericDeclaration(), vb.getGenericDeclaration())
&& va.getName().equals(vb.getName());
} else {
// This isn't a type we support. Could be a generic array type, wildcard type, etc.
return false;
}
}
public static String typeToString(Type type) {
return type instanceof Class ? ((Class<?>) type).getName() : type.toString();
}
/**
* Returns the generic supertype for {@code supertype}. For example, given a class {@code
* IntegerSet}, the result for when supertype is {@code Set.class} is {@code Set<Integer>} and the
* result when the supertype is {@code Collection.class} is {@code Collection<Integer>}.
*/
private static Type getGenericSupertype(Type context, Class<?> rawType, Class<?> supertype) {
if (supertype == rawType) {
return context;
}
// we skip searching through interfaces if unknown is an interface
if (supertype.isInterface()) {
Class<?>[] interfaces = rawType.getInterfaces();
for (int i = 0, length = interfaces.length; i < length; i++) {
if (interfaces[i] == supertype) {
return rawType.getGenericInterfaces()[i];
} else if (supertype.isAssignableFrom(interfaces[i])) {
return getGenericSupertype(rawType.getGenericInterfaces()[i], interfaces[i], supertype);
}
}
}
// check our supertypes
if (!rawType.isInterface()) {
while (rawType != Object.class) {
Class<?> rawSupertype = rawType.getSuperclass();
if (rawSupertype == supertype) {
return rawType.getGenericSuperclass();
} else if (supertype.isAssignableFrom(rawSupertype)) {
return getGenericSupertype(rawType.getGenericSuperclass(), rawSupertype, supertype);
}
rawType = rawSupertype;
}
}
// we can't resolve this further
return supertype;
}
/**
* Returns the generic form of {@code supertype}. For example, if this is {@code
* ArrayList<String>}, this returns {@code Iterable<String>} given the input {@code
* Iterable.class}.
*
* @param supertype a superclass of, or interface implemented by, this.
*/
private static Type getSupertype(Type context, Class<?> contextRawType, Class<?> supertype) {
if (context instanceof WildcardType) {
// Wildcards are useless for resolving supertypes. As the upper bound has the same raw type,
// use it instead
Type[] bounds = ((WildcardType) context).getUpperBounds();
// Currently the JLS only permits one bound for wildcards so using first bound is safe
assert bounds.length == 1;
context = bounds[0];
}
checkArgument(supertype.isAssignableFrom(contextRawType));
return resolve(
context,
contextRawType,
$Gson$Types.getGenericSupertype(context, contextRawType, supertype));
}
/**
* Returns the component type of this array type.
*
* @throws ClassCastException if this type is not an array.
*/
public static Type getArrayComponentType(Type array) {
return array instanceof GenericArrayType
? ((GenericArrayType) array).getGenericComponentType()
: ((Class<?>) array).getComponentType();
}
/**
* Returns the element type of this collection type.
*
* @throws IllegalArgumentException if this type is not a collection.
*/
public static Type getCollectionElementType(Type context, Class<?> contextRawType) {
Type collectionType = getSupertype(context, contextRawType, Collection.class);
if (collectionType instanceof ParameterizedType) {
return ((ParameterizedType) collectionType).getActualTypeArguments()[0];
}
return Object.class;
}
/**
* Returns a two element array containing this map's key and value types in positions 0 and 1
* respectively.
*/
public static Type[] getMapKeyAndValueTypes(Type context, Class<?> contextRawType) {
/*
* Work around a problem with the declaration of java.util.Properties. That
* class should extend Hashtable<String, String>, but it's declared to
* extend Hashtable<Object, Object>.
*/
if (context == Properties.class) {
return new Type[] {String.class, String.class}; // TODO: test subclasses of Properties!
}
Type mapType = getSupertype(context, contextRawType, Map.class);
// TODO: strip wildcards?
if (mapType instanceof ParameterizedType) {
ParameterizedType mapParameterizedType = (ParameterizedType) mapType;
return mapParameterizedType.getActualTypeArguments();
}
return new Type[] {Object.class, Object.class};
}
public static Type resolve(Type context, Class<?> contextRawType, Type toResolve) {
return resolve(context, contextRawType, toResolve, new HashMap<TypeVariable<?>, Type>());
}
private static Type resolve(
Type context,
Class<?> contextRawType,
Type toResolve,
Map<TypeVariable<?>, Type> visitedTypeVariables) {
// this implementation is made a little more complicated in an attempt to avoid object-creation
TypeVariable<?> resolving = null;
while (true) {
if (toResolve instanceof TypeVariable) {
TypeVariable<?> typeVariable = (TypeVariable<?>) toResolve;
Type previouslyResolved = visitedTypeVariables.get(typeVariable);
if (previouslyResolved != null) {
// cannot reduce due to infinite recursion
return (previouslyResolved == Void.TYPE) ? toResolve : previouslyResolved;
}
// Insert a placeholder to mark the fact that we are in the process of resolving this type
visitedTypeVariables.put(typeVariable, Void.TYPE);
if (resolving == null) {
resolving = typeVariable;
}
toResolve = resolveTypeVariable(context, contextRawType, typeVariable);
if (toResolve == typeVariable) {
break;
}
} else if (toResolve instanceof Class && ((Class<?>) toResolve).isArray()) {
Class<?> original = (Class<?>) toResolve;
Type componentType = original.getComponentType();
Type newComponentType =
resolve(context, contextRawType, componentType, visitedTypeVariables);
toResolve = equal(componentType, newComponentType) ? original : arrayOf(newComponentType);
break;
} else if (toResolve instanceof GenericArrayType) {
GenericArrayType original = (GenericArrayType) toResolve;
Type componentType = original.getGenericComponentType();
Type newComponentType =
resolve(context, contextRawType, componentType, visitedTypeVariables);
toResolve = equal(componentType, newComponentType) ? original : arrayOf(newComponentType);
break;
} else if (toResolve instanceof ParameterizedType) {
ParameterizedType original = (ParameterizedType) toResolve;
Type ownerType = original.getOwnerType();
Type newOwnerType = resolve(context, contextRawType, ownerType, visitedTypeVariables);
boolean changed = !equal(newOwnerType, ownerType);
Type[] args = original.getActualTypeArguments();
for (int t = 0, length = args.length; t < length; t++) {
Type resolvedTypeArgument =
resolve(context, contextRawType, args[t], visitedTypeVariables);
if (!equal(resolvedTypeArgument, args[t])) {
if (!changed) {
args = args.clone();
changed = true;
}
args[t] = resolvedTypeArgument;
}
}
toResolve =
changed
? newParameterizedTypeWithOwner(newOwnerType, original.getRawType(), args)
: original;
break;
} else if (toResolve instanceof WildcardType) {
WildcardType original = (WildcardType) toResolve;
Type[] originalLowerBound = original.getLowerBounds();
Type[] originalUpperBound = original.getUpperBounds();
if (originalLowerBound.length == 1) {
Type lowerBound =
resolve(context, contextRawType, originalLowerBound[0], visitedTypeVariables);
if (lowerBound != originalLowerBound[0]) {
toResolve = supertypeOf(lowerBound);
break;
}
} else if (originalUpperBound.length == 1) {
Type upperBound =
resolve(context, contextRawType, originalUpperBound[0], visitedTypeVariables);
if (upperBound != originalUpperBound[0]) {
toResolve = subtypeOf(upperBound);
break;
}
}
toResolve = original;
break;
} else {
break;
}
}
// ensure that any in-process resolution gets updated with the final result
if (resolving != null) {
visitedTypeVariables.put(resolving, toResolve);
}
return toResolve;
}
private static Type resolveTypeVariable(
Type context, Class<?> contextRawType, TypeVariable<?> unknown) {
Class<?> declaredByRaw = declaringClassOf(unknown);
// we can't reduce this further
if (declaredByRaw == null) {
return unknown;
}
Type declaredBy = getGenericSupertype(context, contextRawType, declaredByRaw);
if (declaredBy instanceof ParameterizedType) {
int index = indexOf(declaredByRaw.getTypeParameters(), unknown);
return ((ParameterizedType) declaredBy).getActualTypeArguments()[index];
}
return unknown;
}
private static int indexOf(Object[] array, Object toFind) {
for (int i = 0, length = array.length; i < length; i++) {
if (toFind.equals(array[i])) {
return i;
}
}
throw new NoSuchElementException();
}
/**
* Returns the declaring class of {@code typeVariable}, or {@code null} if it was not declared by
* a class.
*/
private static Class<?> declaringClassOf(TypeVariable<?> typeVariable) {
GenericDeclaration genericDeclaration = typeVariable.getGenericDeclaration();
return genericDeclaration instanceof Class ? (Class<?>) genericDeclaration : null;
}
static void checkNotPrimitive(Type type) {
checkArgument(!(type instanceof Class<?>) || !((Class<?>) type).isPrimitive());
}
/**
* Whether an {@linkplain ParameterizedType#getOwnerType() owner type} must be specified when
* constructing a {@link ParameterizedType} for {@code rawType}.
*
* <p>Note that this method might not require an owner type for all cases where Java reflection
* would create parameterized types with owner type.
*/
public static boolean requiresOwnerType(Type rawType) {
if (rawType instanceof Class<?>) {
Class<?> rawTypeAsClass = (Class<?>) rawType;
return !Modifier.isStatic(rawTypeAsClass.getModifiers())
&& rawTypeAsClass.getDeclaringClass() != null;
}
return false;
}
// Here and below we put @SuppressWarnings("serial") on fields of type `Type`. Recent Java
// compilers complain that the declared type is not Serializable. But in this context we go out of
// our way to ensure that the Type in question is either Class (which is serializable) or one of
// the nested Type implementations here (which are also serializable).
private static final class ParameterizedTypeImpl implements ParameterizedType, Serializable {
@SuppressWarnings("serial")
private final Type ownerType;
@SuppressWarnings("serial")
private final Type rawType;
@SuppressWarnings("serial")
private final Type[] typeArguments;
public ParameterizedTypeImpl(Type ownerType, Type rawType, Type... typeArguments) {
// TODO: Should this enforce that rawType is a Class? See JDK implementation of
// the ParameterizedType interface and https://bugs.openjdk.org/browse/JDK-8250659
requireNonNull(rawType);
if (ownerType == null && requiresOwnerType(rawType)) {
throw new IllegalArgumentException("Must specify owner type for " + rawType);
}
this.ownerType = ownerType == null ? null : canonicalize(ownerType);
this.rawType = canonicalize(rawType);
this.typeArguments = typeArguments.clone();
for (int t = 0, length = this.typeArguments.length; t < length; t++) {
requireNonNull(this.typeArguments[t]);
checkNotPrimitive(this.typeArguments[t]);
this.typeArguments[t] = canonicalize(this.typeArguments[t]);
}
}
@Override
public Type[] getActualTypeArguments() {
return typeArguments.clone();
}
@Override
public Type getRawType() {
return rawType;
}
@Override
public Type getOwnerType() {
return ownerType;
}
@Override
public boolean equals(Object other) {
return other instanceof ParameterizedType
&& $Gson$Types.equals(this, (ParameterizedType) other);
}
private static int hashCodeOrZero(Object o) {
return o != null ? o.hashCode() : 0;
}
@Override
public int hashCode() {
return Arrays.hashCode(typeArguments) ^ rawType.hashCode() ^ hashCodeOrZero(ownerType);
}
@Override
public String toString() {
int length = typeArguments.length;
if (length == 0) {
return typeToString(rawType);
}
StringBuilder stringBuilder = new StringBuilder(30 * (length + 1));
stringBuilder
.append(typeToString(rawType))
.append("<")
.append(typeToString(typeArguments[0]));
for (int i = 1; i < length; i++) {
stringBuilder.append(", ").append(typeToString(typeArguments[i]));
}
return stringBuilder.append(">").toString();
}
private static final long serialVersionUID = 0;
}
private static final class GenericArrayTypeImpl implements GenericArrayType, Serializable {
@SuppressWarnings("serial")
private final Type componentType;
public GenericArrayTypeImpl(Type componentType) {
requireNonNull(componentType);
this.componentType = canonicalize(componentType);
}
@Override
public Type getGenericComponentType() {
return componentType;
}
@Override
public boolean equals(Object o) {
return o instanceof GenericArrayType && $Gson$Types.equals(this, (GenericArrayType) o);
}
@Override
public int hashCode() {
return componentType.hashCode();
}
@Override
public String toString() {
return typeToString(componentType) + "[]";
}
private static final long serialVersionUID = 0;
}
/**
* The WildcardType interface supports multiple upper bounds and multiple lower bounds. We only
* support what the target Java version supports - at most one bound, see also
* https://bugs.openjdk.java.net/browse/JDK-8250660. If a lower bound is set, the upper bound must
* be Object.class.
*/
private static final class WildcardTypeImpl implements WildcardType, Serializable {
@SuppressWarnings("serial")
private final Type upperBound;
@SuppressWarnings("serial")
private final Type lowerBound;
public WildcardTypeImpl(Type[] upperBounds, Type[] lowerBounds) {
checkArgument(lowerBounds.length <= 1);
checkArgument(upperBounds.length == 1);
if (lowerBounds.length == 1) {
requireNonNull(lowerBounds[0]);
checkNotPrimitive(lowerBounds[0]);
checkArgument(upperBounds[0] == Object.class);
this.lowerBound = canonicalize(lowerBounds[0]);
this.upperBound = Object.class;
} else {
requireNonNull(upperBounds[0]);
checkNotPrimitive(upperBounds[0]);
this.lowerBound = null;
this.upperBound = canonicalize(upperBounds[0]);
}
}
@Override
public Type[] getUpperBounds() {
return new Type[] {upperBound};
}
@Override
public Type[] getLowerBounds() {
return lowerBound != null ? new Type[] {lowerBound} : EMPTY_TYPE_ARRAY;
}
@Override
public boolean equals(Object other) {
return other instanceof WildcardType && $Gson$Types.equals(this, (WildcardType) other);
}
@Override
public int hashCode() {
// this equals Arrays.hashCode(getLowerBounds()) ^ Arrays.hashCode(getUpperBounds());
return (lowerBound != null ? 31 + lowerBound.hashCode() : 1) ^ (31 + upperBound.hashCode());
}
@Override
public String toString() {
if (lowerBound != null) {
return "? super " + typeToString(lowerBound);
} else if (upperBound == Object.class) {
return "?";
} else {
return "? extends " + typeToString(upperBound);
}
}
private static final long serialVersionUID = 0;
}
}