TypeParameterResolver.java
/*
* Copyright 2009-2021 the original author or 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 org.apache.ibatis.reflection;
import java.lang.reflect.Array;
import java.lang.reflect.Field;
import java.lang.reflect.GenericArrayType;
import java.lang.reflect.Method;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.lang.reflect.TypeVariable;
import java.lang.reflect.WildcardType;
import java.util.Arrays;
/**
* @author Iwao AVE!
*/
public class TypeParameterResolver {
/**
* Resolve field type.
*
* @param field
* the field
* @param srcType
* the src type
* @return The field type as {@link Type}. If it has type parameters in the declaration,<br>
* they will be resolved to the actual runtime {@link Type}s.
*/
public static Type resolveFieldType(Field field, Type srcType) {
Type fieldType = field.getGenericType();
Class<?> declaringClass = field.getDeclaringClass();
return resolveType(fieldType, srcType, declaringClass);
}
/**
* Resolve return type.
*
* @param method
* the method
* @param srcType
* the src type
* @return The return type of the method as {@link Type}. If it has type parameters in the declaration,<br>
* they will be resolved to the actual runtime {@link Type}s.
*/
public static Type resolveReturnType(Method method, Type srcType) {
Type returnType = method.getGenericReturnType();
Class<?> declaringClass = method.getDeclaringClass();
return resolveType(returnType, srcType, declaringClass);
}
/**
* Resolve param types.
*
* @param method
* the method
* @param srcType
* the src type
* @return The parameter types of the method as an array of {@link Type}s. If they have type parameters in the
* declaration,<br>
* they will be resolved to the actual runtime {@link Type}s.
*/
public static Type[] resolveParamTypes(Method method, Type srcType) {
Type[] paramTypes = method.getGenericParameterTypes();
Class<?> declaringClass = method.getDeclaringClass();
Type[] result = new Type[paramTypes.length];
for (int i = 0; i < paramTypes.length; i++) {
result[i] = resolveType(paramTypes[i], srcType, declaringClass);
}
return result;
}
private static Type resolveType(Type type, Type srcType, Class<?> declaringClass) {
if (type instanceof TypeVariable) {
return resolveTypeVar((TypeVariable<?>) type, srcType, declaringClass);
} else if (type instanceof ParameterizedType) {
return resolveParameterizedType((ParameterizedType) type, srcType, declaringClass);
} else if (type instanceof GenericArrayType) {
return resolveGenericArrayType((GenericArrayType) type, srcType, declaringClass);
} else {
return type;
}
}
private static Type resolveGenericArrayType(GenericArrayType genericArrayType, Type srcType, Class<?> declaringClass) {
Type componentType = genericArrayType.getGenericComponentType();
Type resolvedComponentType = null;
if (componentType instanceof TypeVariable) {
resolvedComponentType = resolveTypeVar((TypeVariable<?>) componentType, srcType, declaringClass);
} else if (componentType instanceof GenericArrayType) {
resolvedComponentType = resolveGenericArrayType((GenericArrayType) componentType, srcType, declaringClass);
} else if (componentType instanceof ParameterizedType) {
resolvedComponentType = resolveParameterizedType((ParameterizedType) componentType, srcType, declaringClass);
}
if (resolvedComponentType instanceof Class) {
return Array.newInstance((Class<?>) resolvedComponentType, 0).getClass();
} else {
return new GenericArrayTypeImpl(resolvedComponentType);
}
}
private static ParameterizedType resolveParameterizedType(ParameterizedType parameterizedType, Type srcType, Class<?> declaringClass) {
Class<?> rawType = (Class<?>) parameterizedType.getRawType();
Type[] typeArgs = parameterizedType.getActualTypeArguments();
Type[] args = new Type[typeArgs.length];
for (int i = 0; i < typeArgs.length; i++) {
if (typeArgs[i] instanceof TypeVariable) {
args[i] = resolveTypeVar((TypeVariable<?>) typeArgs[i], srcType, declaringClass);
} else if (typeArgs[i] instanceof ParameterizedType) {
args[i] = resolveParameterizedType((ParameterizedType) typeArgs[i], srcType, declaringClass);
} else if (typeArgs[i] instanceof WildcardType) {
args[i] = resolveWildcardType((WildcardType) typeArgs[i], srcType, declaringClass);
} else {
args[i] = typeArgs[i];
}
}
return new ParameterizedTypeImpl(rawType, null, args);
}
private static Type resolveWildcardType(WildcardType wildcardType, Type srcType, Class<?> declaringClass) {
Type[] lowerBounds = resolveWildcardTypeBounds(wildcardType.getLowerBounds(), srcType, declaringClass);
Type[] upperBounds = resolveWildcardTypeBounds(wildcardType.getUpperBounds(), srcType, declaringClass);
return new WildcardTypeImpl(lowerBounds, upperBounds);
}
private static Type[] resolveWildcardTypeBounds(Type[] bounds, Type srcType, Class<?> declaringClass) {
Type[] result = new Type[bounds.length];
for (int i = 0; i < bounds.length; i++) {
if (bounds[i] instanceof TypeVariable) {
result[i] = resolveTypeVar((TypeVariable<?>) bounds[i], srcType, declaringClass);
} else if (bounds[i] instanceof ParameterizedType) {
result[i] = resolveParameterizedType((ParameterizedType) bounds[i], srcType, declaringClass);
} else if (bounds[i] instanceof WildcardType) {
result[i] = resolveWildcardType((WildcardType) bounds[i], srcType, declaringClass);
} else {
result[i] = bounds[i];
}
}
return result;
}
private static Type resolveTypeVar(TypeVariable<?> typeVar, Type srcType, Class<?> declaringClass) {
Type result;
Class<?> clazz;
if (srcType instanceof Class) {
clazz = (Class<?>) srcType;
} else if (srcType instanceof ParameterizedType) {
ParameterizedType parameterizedType = (ParameterizedType) srcType;
clazz = (Class<?>) parameterizedType.getRawType();
} else {
throw new IllegalArgumentException("The 2nd arg must be Class or ParameterizedType, but was: " + srcType.getClass());
}
if (clazz == declaringClass) {
Type[] bounds = typeVar.getBounds();
if (bounds.length > 0) {
return bounds[0];
}
return Object.class;
}
Type superclass = clazz.getGenericSuperclass();
result = scanSuperTypes(typeVar, srcType, declaringClass, clazz, superclass);
if (result != null) {
return result;
}
Type[] superInterfaces = clazz.getGenericInterfaces();
for (Type superInterface : superInterfaces) {
result = scanSuperTypes(typeVar, srcType, declaringClass, clazz, superInterface);
if (result != null) {
return result;
}
}
return Object.class;
}
private static Type scanSuperTypes(TypeVariable<?> typeVar, Type srcType, Class<?> declaringClass, Class<?> clazz, Type superclass) {
if (superclass instanceof ParameterizedType) {
ParameterizedType parentAsType = (ParameterizedType) superclass;
Class<?> parentAsClass = (Class<?>) parentAsType.getRawType();
TypeVariable<?>[] parentTypeVars = parentAsClass.getTypeParameters();
if (srcType instanceof ParameterizedType) {
parentAsType = translateParentTypeVars((ParameterizedType) srcType, clazz, parentAsType);
}
if (declaringClass == parentAsClass) {
for (int i = 0; i < parentTypeVars.length; i++) {
if (typeVar.equals(parentTypeVars[i])) {
return parentAsType.getActualTypeArguments()[i];
}
}
}
if (declaringClass.isAssignableFrom(parentAsClass)) {
return resolveTypeVar(typeVar, parentAsType, declaringClass);
}
} else if (superclass instanceof Class && declaringClass.isAssignableFrom((Class<?>) superclass)) {
return resolveTypeVar(typeVar, superclass, declaringClass);
}
return null;
}
private static ParameterizedType translateParentTypeVars(ParameterizedType srcType, Class<?> srcClass, ParameterizedType parentType) {
Type[] parentTypeArgs = parentType.getActualTypeArguments();
Type[] srcTypeArgs = srcType.getActualTypeArguments();
TypeVariable<?>[] srcTypeVars = srcClass.getTypeParameters();
Type[] newParentArgs = new Type[parentTypeArgs.length];
boolean noChange = true;
for (int i = 0; i < parentTypeArgs.length; i++) {
if (parentTypeArgs[i] instanceof TypeVariable) {
for (int j = 0; j < srcTypeVars.length; j++) {
if (srcTypeVars[j].equals(parentTypeArgs[i])) {
noChange = false;
newParentArgs[i] = srcTypeArgs[j];
}
}
} else {
newParentArgs[i] = parentTypeArgs[i];
}
}
return noChange ? parentType : new ParameterizedTypeImpl((Class<?>)parentType.getRawType(), null, newParentArgs);
}
private TypeParameterResolver() {
super();
}
static class ParameterizedTypeImpl implements ParameterizedType {
private Class<?> rawType;
private Type ownerType;
private Type[] actualTypeArguments;
public ParameterizedTypeImpl(Class<?> rawType, Type ownerType, Type[] actualTypeArguments) {
super();
this.rawType = rawType;
this.ownerType = ownerType;
this.actualTypeArguments = actualTypeArguments;
}
@Override
public Type[] getActualTypeArguments() {
return actualTypeArguments;
}
@Override
public Type getOwnerType() {
return ownerType;
}
@Override
public Type getRawType() {
return rawType;
}
@Override
public String toString() {
return "ParameterizedTypeImpl [rawType=" + rawType + ", ownerType=" + ownerType + ", actualTypeArguments=" + Arrays.toString(actualTypeArguments) + "]";
}
}
static class WildcardTypeImpl implements WildcardType {
private Type[] lowerBounds;
private Type[] upperBounds;
WildcardTypeImpl(Type[] lowerBounds, Type[] upperBounds) {
super();
this.lowerBounds = lowerBounds;
this.upperBounds = upperBounds;
}
@Override
public Type[] getLowerBounds() {
return lowerBounds;
}
@Override
public Type[] getUpperBounds() {
return upperBounds;
}
}
static class GenericArrayTypeImpl implements GenericArrayType {
private Type genericComponentType;
GenericArrayTypeImpl(Type genericComponentType) {
super();
this.genericComponentType = genericComponentType;
}
@Override
public Type getGenericComponentType() {
return genericComponentType;
}
}
}