/*
* Copyright 2002-2010 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.constretto.internal;
import java.lang.ref.Reference;
import java.lang.ref.WeakReference;
import java.lang.reflect.*;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import java.util.WeakHashMap;
/**
* Helper class for resolving generic types against type variables.
*
* <p>Mainly intended for usage within the framework, resolving method
* parameter types even when they are declared generically.
*
* @author Juergen Hoeller
* @author Rob Harrop
* @since 2.5.2
* @see GenericCollectionTypeResolver
*/
public abstract class GenericTypeResolver {
/** Cache from Class to TypeVariable Map */
private static final Map<Class, Reference<Map<TypeVariable, Type>>> typeVariableCache =
Collections.synchronizedMap(new WeakHashMap<Class, Reference<Map<TypeVariable, Type>>>());
/**
* Determine the target type for the given parameter specification.
* @param methodParam the method parameter specification
* @return the corresponding generic parameter type
*/
public static Type getTargetType(MethodParameter methodParam) {
if (methodParam.getConstructor() != null) {
return methodParam.getConstructor().getGenericParameterTypes()[methodParam.getParameterIndex()];
}
else {
if (methodParam.getParameterIndex() >= 0) {
return methodParam.getMethod().getGenericParameterTypes()[methodParam.getParameterIndex()];
}
else {
return methodParam.getMethod().getGenericReturnType();
}
}
}
private static Class[] doResolveTypeArguments(Class ownerClass, Class classToIntrospect, Class genericIfc) {
while (classToIntrospect != null) {
if (genericIfc.isInterface()) {
Type[] ifcs = classToIntrospect.getGenericInterfaces();
for (Type ifc : ifcs) {
Class[] result = doResolveTypeArguments(ownerClass, ifc, genericIfc);
if (result != null) {
return result;
}
}
}
else {
Class[] result = doResolveTypeArguments(
ownerClass, classToIntrospect.getGenericSuperclass(), genericIfc);
if (result != null) {
return result;
}
}
classToIntrospect = classToIntrospect.getSuperclass();
}
return null;
}
@SuppressWarnings("unchecked")
private static Class[] doResolveTypeArguments(Class ownerClass, Type ifc, Class genericIfc) {
if (ifc instanceof ParameterizedType) {
ParameterizedType paramIfc = (ParameterizedType) ifc;
Type rawType = paramIfc.getRawType();
if (genericIfc.equals(rawType)) {
Type[] typeArgs = paramIfc.getActualTypeArguments();
Class[] result = new Class[typeArgs.length];
for (int i = 0; i < typeArgs.length; i++) {
Type arg = typeArgs[i];
result[i] = extractClass(ownerClass, arg);
}
return result;
}
else if (genericIfc.isAssignableFrom((Class) rawType)) {
return doResolveTypeArguments(ownerClass, (Class) rawType, genericIfc);
}
}
else if (genericIfc.isAssignableFrom((Class) ifc)) {
return doResolveTypeArguments(ownerClass, (Class) ifc, genericIfc);
}
return null;
}
/**
* Extract a class instance from given Type.
*/
private static Class extractClass(Class ownerClass, Type arg) {
if (arg instanceof ParameterizedType) {
return extractClass(ownerClass, ((ParameterizedType) arg).getRawType());
}
else if (arg instanceof GenericArrayType) {
GenericArrayType gat = (GenericArrayType) arg;
Type gt = gat.getGenericComponentType();
Class<?> componentClass = extractClass(ownerClass, gt);
return Array.newInstance(componentClass, 0).getClass();
}
else if (arg instanceof TypeVariable) {
TypeVariable tv = (TypeVariable) arg;
arg = getTypeVariableMap(ownerClass).get(tv);
if (arg == null) {
arg = extractBoundForTypeVariable(tv);
}
else {
arg = extractClass(ownerClass, arg);
}
}
return (arg instanceof Class ? (Class) arg : Object.class);
}
/**
* Build a mapping of {@link java.lang.reflect.TypeVariable#getName TypeVariable names} to concrete
* {@link Class} for the specified {@link Class}. Searches all super types,
* enclosing types and interfaces.
*/
static Map<TypeVariable, Type> getTypeVariableMap(Class clazz) {
Reference<Map<TypeVariable, Type>> ref = typeVariableCache.get(clazz);
Map<TypeVariable, Type> typeVariableMap = (ref != null ? ref.get() : null);
if (typeVariableMap == null) {
typeVariableMap = new HashMap<TypeVariable, Type>();
// interfaces
extractTypeVariablesFromGenericInterfaces(clazz.getGenericInterfaces(), typeVariableMap);
// super class
Type genericType = clazz.getGenericSuperclass();
Class type = clazz.getSuperclass();
while (type != null && !Object.class.equals(type)) {
if (genericType instanceof ParameterizedType) {
ParameterizedType pt = (ParameterizedType) genericType;
populateTypeMapFromParameterizedType(pt, typeVariableMap);
}
extractTypeVariablesFromGenericInterfaces(type.getGenericInterfaces(), typeVariableMap);
genericType = type.getGenericSuperclass();
type = type.getSuperclass();
}
// enclosing class
type = clazz;
while (type.isMemberClass()) {
genericType = type.getGenericSuperclass();
if (genericType instanceof ParameterizedType) {
ParameterizedType pt = (ParameterizedType) genericType;
populateTypeMapFromParameterizedType(pt, typeVariableMap);
}
type = type.getEnclosingClass();
}
typeVariableCache.put(clazz, new WeakReference<Map<TypeVariable, Type>>(typeVariableMap));
}
return typeVariableMap;
}
/**
* Extracts the bound <code>Type</code> for a given {@link java.lang.reflect.TypeVariable}.
*/
static Type extractBoundForTypeVariable(TypeVariable typeVariable) {
Type[] bounds = typeVariable.getBounds();
if (bounds.length == 0) {
return Object.class;
}
Type bound = bounds[0];
if (bound instanceof TypeVariable) {
bound = extractBoundForTypeVariable((TypeVariable) bound);
}
return bound;
}
private static void extractTypeVariablesFromGenericInterfaces(Type[] genericInterfaces, Map<TypeVariable, Type> typeVariableMap) {
for (Type genericInterface : genericInterfaces) {
if (genericInterface instanceof ParameterizedType) {
ParameterizedType pt = (ParameterizedType) genericInterface;
populateTypeMapFromParameterizedType(pt, typeVariableMap);
if (pt.getRawType() instanceof Class) {
extractTypeVariablesFromGenericInterfaces(
((Class) pt.getRawType()).getGenericInterfaces(), typeVariableMap);
}
}
else if (genericInterface instanceof Class) {
extractTypeVariablesFromGenericInterfaces(
((Class) genericInterface).getGenericInterfaces(), typeVariableMap);
}
}
}
/**
* Read the {@link java.lang.reflect.TypeVariable TypeVariables} from the supplied {@link java.lang.reflect.ParameterizedType}
* and add mappings corresponding to the {@link java.lang.reflect.TypeVariable#getName TypeVariable name} ->
* concrete type to the supplied {@link java.util.Map}.
* <p>Consider this case:
* <pre class="code>
* public interface Foo<S, T> {
* ..
* }
*
* public class FooImpl implements Foo<String, Integer> {
* ..
* }</pre>
* For '<code>FooImpl</code>' the following mappings would be added to the {@link java.util.Map}:
* {S=java.lang.String, T=java.lang.Integer}.
*/
private static void populateTypeMapFromParameterizedType(ParameterizedType type, Map<TypeVariable, Type> typeVariableMap) {
if (type.getRawType() instanceof Class) {
Type[] actualTypeArguments = type.getActualTypeArguments();
TypeVariable[] typeVariables = ((Class) type.getRawType()).getTypeParameters();
for (int i = 0; i < actualTypeArguments.length; i++) {
Type actualTypeArgument = actualTypeArguments[i];
TypeVariable variable = typeVariables[i];
if (actualTypeArgument instanceof Class) {
typeVariableMap.put(variable, actualTypeArgument);
}
else if (actualTypeArgument instanceof GenericArrayType) {
typeVariableMap.put(variable, actualTypeArgument);
}
else if (actualTypeArgument instanceof ParameterizedType) {
typeVariableMap.put(variable, actualTypeArgument);
}
else if (actualTypeArgument instanceof TypeVariable) {
// We have a type that is parameterized at instantiation time
// the nearest match on the bridge method will be the bounded type.
TypeVariable typeVariableArgument = (TypeVariable) actualTypeArgument;
Type resolvedType = typeVariableMap.get(typeVariableArgument);
if (resolvedType == null) {
resolvedType = extractBoundForTypeVariable(typeVariableArgument);
}
typeVariableMap.put(variable, resolvedType);
}
}
}
}
}