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468 lines (399 loc) · 15.6 KB
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/**
* Copyright 2012-2020 The Feign 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 feign;
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.NoSuchElementException;
/**
* Static methods for working with types.
*
* @author Bob Lee
* @author Jesse Wilson
*/
public final class Types {
private static final Type[] EMPTY_TYPE_ARRAY = new Type[0];
private Types() {
// No instances.
}
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;
// I'm not exactly sure why getRawType() returns Type instead of Class. Neal isn't either but
// suspects some pathological case related to nested classes exists.
Type rawType = parameterizedType.getRawType();
if (!(rawType instanceof Class)) {
throw new IllegalArgumentException();
}
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) {
return getRawType(((WildcardType) type).getUpperBounds()[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);
}
}
/**
* Returns true if {@code a} and {@code b} are equal.
*/
static boolean equals(Type a, Type b) {
if (a == b) {
return true; // Also handles (a == null && b == null).
} else if (a instanceof Class) {
return a.equals(b); // Class already specifies equals().
} else if (a instanceof ParameterizedType) {
if (!(b instanceof ParameterizedType)) {
return false;
}
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 va.getGenericDeclaration() == vb.getGenericDeclaration()
&& va.getName().equals(vb.getName());
} else {
return false; // This isn't a type we support!
}
}
/**
* 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>}.
*/
static Type getGenericSupertype(Type context, Class<?> rawType, Class<?> toResolve) {
if (toResolve == rawType) {
return context;
}
// We skip searching through interfaces if unknown is an interface.
if (toResolve.isInterface()) {
Class<?>[] interfaces = rawType.getInterfaces();
for (int i = 0, length = interfaces.length; i < length; i++) {
if (interfaces[i] == toResolve) {
return rawType.getGenericInterfaces()[i];
} else if (toResolve.isAssignableFrom(interfaces[i])) {
return getGenericSupertype(rawType.getGenericInterfaces()[i], interfaces[i], toResolve);
}
}
}
// Check our supertypes.
if (!rawType.isInterface()) {
while (rawType != Object.class) {
Class<?> rawSupertype = rawType.getSuperclass();
if (rawSupertype == toResolve) {
return rawType.getGenericSuperclass();
} else if (toResolve.isAssignableFrom(rawSupertype)) {
return getGenericSupertype(rawType.getGenericSuperclass(), rawSupertype, toResolve);
}
rawType = rawSupertype;
}
}
// We can't resolve this further.
return toResolve;
}
private static int indexOf(Object[] array, Object toFind) {
for (int i = 0; i < array.length; i++) {
if (toFind.equals(array[i])) {
return i;
}
}
throw new NoSuchElementException();
}
private static boolean equal(Object a, Object b) {
return a == b || (a != null && a.equals(b));
}
private static int hashCodeOrZero(Object o) {
return o != null ? o.hashCode() : 0;
}
static String typeToString(Type type) {
return type instanceof Class ? ((Class<?>) type).getName() : type.toString();
}
/**
* 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.
*/
static Type getSupertype(Type context, Class<?> contextRawType, Class<?> supertype) {
if (!supertype.isAssignableFrom(contextRawType)) {
throw new IllegalArgumentException();
}
return resolve(context, contextRawType,
getGenericSupertype(context, contextRawType, supertype));
}
static Type resolve(Type context, Class<?> contextRawType, Type toResolve) {
// This implementation is made a little more complicated in an attempt to avoid object-creation.
while (true) {
if (toResolve instanceof TypeVariable) {
TypeVariable<?> typeVariable = (TypeVariable<?>) toResolve;
toResolve = resolveTypeVariable(context, contextRawType, typeVariable);
if (toResolve == typeVariable) {
return toResolve;
}
} else if (toResolve instanceof Class && ((Class<?>) toResolve).isArray()) {
Class<?> original = (Class<?>) toResolve;
Type componentType = original.getComponentType();
Type newComponentType = resolve(context, contextRawType, componentType);
return componentType == newComponentType ? original
: new GenericArrayTypeImpl(
newComponentType);
} else if (toResolve instanceof GenericArrayType) {
GenericArrayType original = (GenericArrayType) toResolve;
Type componentType = original.getGenericComponentType();
Type newComponentType = resolve(context, contextRawType, componentType);
return componentType == newComponentType ? original
: new GenericArrayTypeImpl(
newComponentType);
} else if (toResolve instanceof ParameterizedType) {
ParameterizedType original = (ParameterizedType) toResolve;
Type ownerType = original.getOwnerType();
Type newOwnerType = resolve(context, contextRawType, ownerType);
boolean changed = newOwnerType != ownerType;
Type[] args = original.getActualTypeArguments();
for (int t = 0, length = args.length; t < length; t++) {
Type resolvedTypeArgument = resolve(context, contextRawType, args[t]);
if (resolvedTypeArgument != args[t]) {
if (!changed) {
args = args.clone();
changed = true;
}
args[t] = resolvedTypeArgument;
}
}
return changed
? new ParameterizedTypeImpl(newOwnerType, original.getRawType(), args)
: original;
} 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]);
if (lowerBound != originalLowerBound[0]) {
return new WildcardTypeImpl(new Type[] {Object.class}, new Type[] {lowerBound});
}
} else if (originalUpperBound.length == 1) {
Type upperBound = resolve(context, contextRawType, originalUpperBound[0]);
if (upperBound != originalUpperBound[0]) {
return new WildcardTypeImpl(new Type[] {upperBound}, EMPTY_TYPE_ARRAY);
}
}
return original;
} else {
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;
}
/**
* 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;
}
private static void checkNotPrimitive(Type type) {
if (type instanceof Class<?> && ((Class<?>) type).isPrimitive()) {
throw new IllegalArgumentException();
}
}
static final class ParameterizedTypeImpl implements ParameterizedType {
private final Type ownerType;
private final Type rawType;
private final Type[] typeArguments;
ParameterizedTypeImpl(Type ownerType, Type rawType, Type... typeArguments) {
// Require an owner type if the raw type needs it.
if (rawType instanceof Class<?>
&& (ownerType == null) != (((Class<?>) rawType).getEnclosingClass() == null)) {
throw new IllegalArgumentException();
}
this.ownerType = ownerType;
this.rawType = rawType;
this.typeArguments = typeArguments.clone();
for (Type typeArgument : this.typeArguments) {
if (typeArgument == null) {
throw new NullPointerException();
}
checkNotPrimitive(typeArgument);
}
}
public Type[] getActualTypeArguments() {
return typeArguments.clone();
}
public Type getRawType() {
return rawType;
}
public Type getOwnerType() {
return ownerType;
}
@Override
public boolean equals(Object other) {
return other instanceof ParameterizedType && Types.equals(this, (ParameterizedType) other);
}
@Override
public int hashCode() {
return Arrays.hashCode(typeArguments) ^ rawType.hashCode() ^ hashCodeOrZero(ownerType);
}
@Override
public String toString() {
StringBuilder result = new StringBuilder(30 * (typeArguments.length + 1));
result.append(typeToString(rawType));
if (typeArguments.length == 0) {
return result.toString();
}
result.append("<").append(typeToString(typeArguments[0]));
for (int i = 1; i < typeArguments.length; i++) {
result.append(", ").append(typeToString(typeArguments[i]));
}
return result.append(">").toString();
}
}
private static final class GenericArrayTypeImpl implements GenericArrayType {
private final Type componentType;
GenericArrayTypeImpl(Type componentType) {
this.componentType = componentType;
}
public Type getGenericComponentType() {
return componentType;
}
@Override
public boolean equals(Object o) {
return o instanceof GenericArrayType
&& Types.equals(this, (GenericArrayType) o);
}
@Override
public int hashCode() {
return componentType.hashCode();
}
@Override
public String toString() {
return typeToString(componentType) + "[]";
}
}
/**
* The WildcardType interface supports multiple upper bounds and multiple lower bounds. We only
* support what the Java 6 language needs - at most one bound. If a lower bound is set, the upper
* bound must be Object.class.
*/
static final class WildcardTypeImpl implements WildcardType {
private final Type upperBound;
private final Type lowerBound;
WildcardTypeImpl(Type[] upperBounds, Type[] lowerBounds) {
if (lowerBounds.length > 1) {
throw new IllegalArgumentException();
}
if (upperBounds.length != 1) {
throw new IllegalArgumentException();
}
if (lowerBounds.length == 1) {
if (lowerBounds[0] == null) {
throw new NullPointerException();
}
checkNotPrimitive(lowerBounds[0]);
if (upperBounds[0] != Object.class) {
throw new IllegalArgumentException();
}
this.lowerBound = lowerBounds[0];
this.upperBound = Object.class;
} else {
if (upperBounds[0] == null) {
throw new NullPointerException();
}
checkNotPrimitive(upperBounds[0]);
this.lowerBound = null;
this.upperBound = upperBounds[0];
}
}
public Type[] getUpperBounds() {
return new Type[] {upperBound};
}
public Type[] getLowerBounds() {
return lowerBound != null ? new Type[] {lowerBound} : EMPTY_TYPE_ARRAY;
}
@Override
public boolean equals(Object other) {
return other instanceof WildcardType && 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);
}
if (upperBound == Object.class) {
return "?";
}
return "? extends " + typeToString(upperBound);
}
}
}