/*
* 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.springframework.util;
import java.lang.reflect.GenericArrayType;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.lang.reflect.WildcardType;
import org.springframework.util.ClassUtils;
/**
* Utility to work with Java 5 generic type parameters.
* Mainly for internal use within the framework.
*
* @author Ramnivas Laddad
* @author Juergen Hoeller
* @author Chris Beams
* @since 2.0.7
*/
public abstract class TypeUtils {
/**
* Check if the right-hand side type may be assigned to the left-hand side
* type following the Java generics rules.
* @param lhsType the target type
* @param rhsType the value type that should be assigned to the target type
* @return true if rhs is assignable to lhs
*/
public static boolean isAssignable(Type lhsType, Type rhsType) {
Assert.notNull(lhsType, "Left-hand side type must not be null");
Assert.notNull(rhsType, "Right-hand side type must not be null");
// all types are assignable to themselves and to class Object
if (lhsType.equals(rhsType) || lhsType.equals(Object.class)) {
return true;
}
if (lhsType instanceof Class<?>) {
Class<?> lhsClass = (Class<?>) lhsType;
// just comparing two classes
if (rhsType instanceof Class<?>) {
return ClassUtils.isAssignable(lhsClass, (Class<?>) rhsType);
}
if (rhsType instanceof ParameterizedType) {
Type rhsRaw = ((ParameterizedType) rhsType).getRawType();
// a parameterized type is always assignable to its raw class type
if (rhsRaw instanceof Class<?>) {
return ClassUtils.isAssignable(lhsClass, (Class<?>) rhsRaw);
}
}
else if (lhsClass.isArray() && rhsType instanceof GenericArrayType) {
Type rhsComponent = ((GenericArrayType) rhsType).getGenericComponentType();
return isAssignable(lhsClass.getComponentType(), rhsComponent);
}
}
// parameterized types are only assignable to other parameterized types and class types
if (lhsType instanceof ParameterizedType) {
if (rhsType instanceof Class<?>) {
Type lhsRaw = ((ParameterizedType) lhsType).getRawType();
if (lhsRaw instanceof Class<?>) {
return ClassUtils.isAssignable((Class<?>) lhsRaw, (Class<?>) rhsType);
}
}
else if (rhsType instanceof ParameterizedType) {
return isAssignable((ParameterizedType) lhsType, (ParameterizedType) rhsType);
}
}
if (lhsType instanceof GenericArrayType) {
Type lhsComponent = ((GenericArrayType) lhsType).getGenericComponentType();
if (rhsType instanceof Class<?>) {
Class<?> rhsClass = (Class<?>) rhsType;
if (rhsClass.isArray()) {
return isAssignable(lhsComponent, rhsClass.getComponentType());
}
}
else if (rhsType instanceof GenericArrayType) {
Type rhsComponent = ((GenericArrayType) rhsType).getGenericComponentType();
return isAssignable(lhsComponent, rhsComponent);
}
}
if (lhsType instanceof WildcardType) {
return isAssignable((WildcardType) lhsType, rhsType);
}
return false;
}
private static boolean isAssignable(ParameterizedType lhsType, ParameterizedType rhsType) {
if (lhsType.equals(rhsType)) {
return true;
}
Type[] lhsTypeArguments = lhsType.getActualTypeArguments();
Type[] rhsTypeArguments = rhsType.getActualTypeArguments();
if (lhsTypeArguments.length != rhsTypeArguments.length) {
return false;
}
for (int size = lhsTypeArguments.length, i = 0; i < size; ++i) {
Type lhsArg = lhsTypeArguments[i];
Type rhsArg = rhsTypeArguments[i];
if (!lhsArg.equals(rhsArg) &&
!(lhsArg instanceof WildcardType && isAssignable((WildcardType) lhsArg, rhsArg))) {
return false;
}
}
return true;
}
private static boolean isAssignable(WildcardType lhsType, Type rhsType) {
Type[] lUpperBounds = lhsType.getUpperBounds();
// supply the implicit upper bound if none are specified
if (lUpperBounds.length == 0) {
lUpperBounds = new Type[] { Object.class };
}
Type[] lLowerBounds = lhsType.getLowerBounds();
// supply the implicit lower bound if none are specified
if (lLowerBounds.length == 0) {
lLowerBounds = new Type[] { null };
}
if (rhsType instanceof WildcardType) {
// both the upper and lower bounds of the right-hand side must be
// completely enclosed in the upper and lower bounds of the left-
// hand side.
WildcardType rhsWcType = (WildcardType) rhsType;
Type[] rUpperBounds = rhsWcType.getUpperBounds();
if (rUpperBounds.length == 0) {
rUpperBounds = new Type[] { Object.class };
}
Type[] rLowerBounds = rhsWcType.getLowerBounds();
if (rLowerBounds.length == 0) {
rLowerBounds = new Type[] { null };
}
for (Type lBound : lUpperBounds) {
for (Type rBound : rUpperBounds) {
if (!isAssignableBound(lBound, rBound)) {
return false;
}
}
for (Type rBound : rLowerBounds) {
if (!isAssignableBound(lBound, rBound)) {
return false;
}
}
}
for (Type lBound : lLowerBounds) {
for (Type rBound : rUpperBounds) {
if (!isAssignableBound(rBound, lBound)) {
return false;
}
}
for (Type rBound : rLowerBounds) {
if (!isAssignableBound(rBound, lBound)) {
return false;
}
}
}
}
else {
for (Type lBound : lUpperBounds) {
if (!isAssignableBound(lBound, rhsType)) {
return false;
}
}
for (Type lBound : lLowerBounds) {
if (!isAssignableBound(rhsType, lBound)) {
return false;
}
}
}
return true;
}
public static boolean isAssignableBound(Type lhsType, Type rhsType) {
if (rhsType == null) {
return true;
}
if (lhsType == null) {
return false;
}
return isAssignable(lhsType, rhsType);
}
}