/*
* 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.core;
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.Collection;
import java.util.Map;
/**
* Helper class for determining element types of collections and maps.
*
* <p>Mainly intended for usage within the framework, determining the
* target type of values to be added to a collection or map
* (to be able to attempt type conversion if appropriate).
*
* @author Juergen Hoeller
* @since 2.0
*/
public abstract class GenericCollectionTypeResolver {
/**
* Determine the generic element type of the given Collection class
* (if it declares one through a generic superclass or generic interface).
* @param collectionClass the collection class to introspect
* @return the generic type, or <code>null</code> if none
*/
public static Class<?> getCollectionType(Class<? extends Collection> collectionClass) {
return extractTypeFromClass(collectionClass, Collection.class, 0);
}
/**
* Determine the generic key type of the given Map class
* (if it declares one through a generic superclass or generic interface).
* @param mapClass the map class to introspect
* @return the generic type, or <code>null</code> if none
*/
public static Class<?> getMapKeyType(Class<? extends Map> mapClass) {
return extractTypeFromClass(mapClass, Map.class, 0);
}
/**
* Determine the generic value type of the given Map class
* (if it declares one through a generic superclass or generic interface).
* @param mapClass the map class to introspect
* @return the generic type, or <code>null</code> if none
*/
public static Class<?> getMapValueType(Class<? extends Map> mapClass) {
return extractTypeFromClass(mapClass, Map.class, 1);
}
/**
* Determine the generic element type of the given Collection field.
* @param collectionField the collection field to introspect
* @return the generic type, or <code>null</code> if none
*/
public static Class<?> getCollectionFieldType(Field collectionField) {
return getGenericFieldType(collectionField, Collection.class, 0, 1);
}
/**
* Determine the generic element type of the given Collection field.
* @param collectionField the collection field to introspect
* @param nestingLevel the nesting level of the target type
* (typically 1; e.g. in case of a List of Lists, 1 would indicate the
* nested List, whereas 2 would indicate the element of the nested List)
* @return the generic type, or <code>null</code> if none
*/
public static Class<?> getCollectionFieldType(Field collectionField, int nestingLevel) {
return getGenericFieldType(collectionField, Collection.class, 0, nestingLevel);
}
/**
* Determine the generic key type of the given Map field.
* @param mapField the map field to introspect
* @return the generic type, or <code>null</code> if none
*/
public static Class<?> getMapKeyFieldType(Field mapField) {
return getGenericFieldType(mapField, Map.class, 0, 1);
}
/**
* Determine the generic key type of the given Map field.
* @param mapField the map field to introspect
* @param nestingLevel the nesting level of the target type
* (typically 1; e.g. in case of a List of Lists, 1 would indicate the
* nested List, whereas 2 would indicate the element of the nested List)
* @return the generic type, or <code>null</code> if none
*/
public static Class<?> getMapKeyFieldType(Field mapField, int nestingLevel) {
return getGenericFieldType(mapField, Map.class, 0, nestingLevel);
}
/**
* Determine the generic value type of the given Map field.
* @param mapField the map field to introspect
* @return the generic type, or <code>null</code> if none
*/
public static Class<?> getMapValueFieldType(Field mapField) {
return getGenericFieldType(mapField, Map.class, 1, 1);
}
/**
* Determine the generic value type of the given Map field.
* @param mapField the map field to introspect
* @param nestingLevel the nesting level of the target type
* (typically 1; e.g. in case of a List of Lists, 1 would indicate the
* nested List, whereas 2 would indicate the element of the nested List)
* @return the generic type, or <code>null</code> if none
*/
public static Class<?> getMapValueFieldType(Field mapField, int nestingLevel) {
return getGenericFieldType(mapField, Map.class, 1, nestingLevel);
}
/**
* Determine the generic element type of the given Collection parameter.
* @param methodParam the method parameter specification
* @return the generic type, or <code>null</code> if none
*/
public static Class<?> getCollectionParameterType(MethodParameter methodParam) {
return getGenericParameterType(methodParam, Collection.class, 0);
}
/**
* Determine the generic key type of the given Map parameter.
* @param methodParam the method parameter specification
* @return the generic type, or <code>null</code> if none
*/
public static Class<?> getMapKeyParameterType(MethodParameter methodParam) {
return getGenericParameterType(methodParam, Map.class, 0);
}
/**
* Determine the generic value type of the given Map parameter.
* @param methodParam the method parameter specification
* @return the generic type, or <code>null</code> if none
*/
public static Class<?> getMapValueParameterType(MethodParameter methodParam) {
return getGenericParameterType(methodParam, Map.class, 1);
}
/**
* Determine the generic element type of the given Collection return type.
* @param method the method to check the return type for
* @return the generic type, or <code>null</code> if none
*/
public static Class<?> getCollectionReturnType(Method method) {
return getGenericReturnType(method, Collection.class, 0, 1);
}
/**
* Determine the generic element type of the given Collection return type.
* <p>If the specified nesting level is higher than 1, the element type of
* a nested Collection/Map will be analyzed.
* @param method the method to check the return type for
* @param nestingLevel the nesting level of the target type
* (typically 1; e.g. in case of a List of Lists, 1 would indicate the
* nested List, whereas 2 would indicate the element of the nested List)
* @return the generic type, or <code>null</code> if none
*/
public static Class<?> getCollectionReturnType(Method method, int nestingLevel) {
return getGenericReturnType(method, Collection.class, 0, nestingLevel);
}
/**
* Determine the generic key type of the given Map return type.
* @param method the method to check the return type for
* @return the generic type, or <code>null</code> if none
*/
public static Class<?> getMapKeyReturnType(Method method) {
return getGenericReturnType(method, Map.class, 0, 1);
}
/**
* Determine the generic key type of the given Map return type.
* @param method the method to check the return type for
* @param nestingLevel the nesting level of the target type
* (typically 1; e.g. in case of a List of Lists, 1 would indicate the
* nested List, whereas 2 would indicate the element of the nested List)
* @return the generic type, or <code>null</code> if none
*/
public static Class<?> getMapKeyReturnType(Method method, int nestingLevel) {
return getGenericReturnType(method, Map.class, 0, nestingLevel);
}
/**
* Determine the generic value type of the given Map return type.
* @param method the method to check the return type for
* @return the generic type, or <code>null</code> if none
*/
public static Class<?> getMapValueReturnType(Method method) {
return getGenericReturnType(method, Map.class, 1, 1);
}
/**
* Determine the generic value type of the given Map return type.
* @param method the method to check the return type for
* @param nestingLevel the nesting level of the target type
* (typically 1; e.g. in case of a List of Lists, 1 would indicate the
* nested List, whereas 2 would indicate the element of the nested List)
* @return the generic type, or <code>null</code> if none
*/
public static Class<?> getMapValueReturnType(Method method, int nestingLevel) {
return getGenericReturnType(method, Map.class, 1, nestingLevel);
}
/**
* Extract the generic parameter type from the given method or constructor.
* @param methodParam the method parameter specification
* @param source the source class/interface defining the generic parameter types
* @param typeIndex the index of the type (e.g. 0 for Collections,
* 0 for Map keys, 1 for Map values)
* @return the generic type, or <code>null</code> if none
*/
private static Class<?> getGenericParameterType(MethodParameter methodParam, Class<?> source, int typeIndex) {
return extractType(methodParam, GenericTypeResolver.getTargetType(methodParam),
source, typeIndex, methodParam.getNestingLevel(), 1);
}
/**
* Extract the generic type from the given field.
* @param field the field to check the type for
* @param source the source class/interface defining the generic parameter types
* @param typeIndex the index of the type (e.g. 0 for Collections,
* 0 for Map keys, 1 for Map values)
* @param nestingLevel the nesting level of the target type
* @return the generic type, or <code>null</code> if none
*/
private static Class<?> getGenericFieldType(Field field, Class<?> source, int typeIndex, int nestingLevel) {
return extractType(null, field.getGenericType(), source, typeIndex, nestingLevel, 1);
}
/**
* Extract the generic return type from the given method.
* @param method the method to check the return type for
* @param source the source class/interface defining the generic parameter types
* @param typeIndex the index of the type (e.g. 0 for Collections,
* 0 for Map keys, 1 for Map values)
* @param nestingLevel the nesting level of the target type
* @return the generic type, or <code>null</code> if none
*/
private static Class<?> getGenericReturnType(Method method, Class<?> source, int typeIndex, int nestingLevel) {
return extractType(null, method.getGenericReturnType(), source, typeIndex, nestingLevel, 1);
}
/**
* Extract the generic type from the given Type object.
* @param methodParam the method parameter specification
* @param type the Type to check
* @param source the source collection/map Class that we check
* @param typeIndex the index of the actual type argument
* @param nestingLevel the nesting level of the target type
* @param currentLevel the current nested level
* @return the generic type as Class, or <code>null</code> if none
*/
private static Class<?> extractType(
MethodParameter methodParam, Type type, Class<?> source, int typeIndex, int nestingLevel, int currentLevel) {
Type resolvedType = type;
if (type instanceof TypeVariable && methodParam != null && methodParam.typeVariableMap != null) {
Type mappedType = methodParam.typeVariableMap.get((TypeVariable) type);
if (mappedType != null) {
resolvedType = mappedType;
}
}
if (resolvedType instanceof ParameterizedType) {
return extractTypeFromParameterizedType(
methodParam, (ParameterizedType) resolvedType, source, typeIndex, nestingLevel, currentLevel);
}
else if (resolvedType instanceof Class) {
return extractTypeFromClass(methodParam, (Class) resolvedType, source, typeIndex, nestingLevel, currentLevel);
}
else {
return null;
}
}
/**
* Extract the generic type from the given ParameterizedType object.
* @param methodParam the method parameter specification
* @param ptype the ParameterizedType to check
* @param source the expected raw source type (can be <code>null</code>)
* @param typeIndex the index of the actual type argument
* @param nestingLevel the nesting level of the target type
* @param currentLevel the current nested level
* @return the generic type as Class, or <code>null</code> if none
*/
private static Class<?> extractTypeFromParameterizedType(MethodParameter methodParam,
ParameterizedType ptype, Class<?> source, int typeIndex, int nestingLevel, int currentLevel) {
if (!(ptype.getRawType() instanceof Class)) {
return null;
}
Class rawType = (Class) ptype.getRawType();
Type[] paramTypes = ptype.getActualTypeArguments();
if (nestingLevel - currentLevel > 0) {
int nextLevel = currentLevel + 1;
Integer currentTypeIndex = (methodParam != null ? methodParam.getTypeIndexForLevel(nextLevel) : null);
// Default is last parameter type: Collection element or Map value.
int indexToUse = (currentTypeIndex != null ? currentTypeIndex : paramTypes.length - 1);
Type paramType = paramTypes[indexToUse];
return extractType(methodParam, paramType, source, typeIndex, nestingLevel, nextLevel);
}
if (source != null && !source.isAssignableFrom(rawType)) {
return null;
}
Class fromSuperclassOrInterface =
extractTypeFromClass(methodParam, rawType, source, typeIndex, nestingLevel, currentLevel);
if (fromSuperclassOrInterface != null) {
return fromSuperclassOrInterface;
}
if (paramTypes == null || typeIndex >= paramTypes.length) {
return null;
}
Type paramType = paramTypes[typeIndex];
if (paramType instanceof TypeVariable && methodParam != null && methodParam.typeVariableMap != null) {
Type mappedType = methodParam.typeVariableMap.get((TypeVariable) paramType);
if (mappedType != null) {
paramType = mappedType;
}
}
if (paramType instanceof WildcardType) {
WildcardType wildcardType = (WildcardType) paramType;
Type[] upperBounds = wildcardType.getUpperBounds();
if (upperBounds != null && upperBounds.length > 0 && !Object.class.equals(upperBounds[0])) {
paramType = upperBounds[0];
}
else {
Type[] lowerBounds = wildcardType.getLowerBounds();
if (lowerBounds != null && lowerBounds.length > 0 && !Object.class.equals(lowerBounds[0])) {
paramType = lowerBounds[0];
}
}
}
if (paramType instanceof ParameterizedType) {
paramType = ((ParameterizedType) paramType).getRawType();
}
if (paramType instanceof GenericArrayType) {
// A generic array type... Let's turn it into a straight array type if possible.
Type compType = ((GenericArrayType) paramType).getGenericComponentType();
if (compType instanceof Class) {
return Array.newInstance((Class) compType, 0).getClass();
}
}
else if (paramType instanceof Class) {
// We finally got a straight Class...
return (Class) paramType;
}
return null;
}
/**
* Extract the generic type from the given Class object.
* @param clazz the Class to check
* @param source the expected raw source type (can be <code>null</code>)
* @param typeIndex the index of the actual type argument
* @return the generic type as Class, or <code>null</code> if none
*/
private static Class<?> extractTypeFromClass(Class<?> clazz, Class<?> source, int typeIndex) {
return extractTypeFromClass(null, clazz, source, typeIndex, 1, 1);
}
/**
* Extract the generic type from the given Class object.
* @param methodParam the method parameter specification
* @param clazz the Class to check
* @param source the expected raw source type (can be <code>null</code>)
* @param typeIndex the index of the actual type argument
* @param nestingLevel the nesting level of the target type
* @param currentLevel the current nested level
* @return the generic type as Class, or <code>null</code> if none
*/
private static Class<?> extractTypeFromClass(
MethodParameter methodParam, Class<?> clazz, Class<?> source, int typeIndex, int nestingLevel, int currentLevel) {
if (clazz.getName().startsWith("java.util.")) {
return null;
}
if (clazz.getSuperclass() != null && isIntrospectionCandidate(clazz.getSuperclass())) {
return extractType(methodParam, clazz.getGenericSuperclass(), source, typeIndex, nestingLevel, currentLevel);
}
Type[] ifcs = clazz.getGenericInterfaces();
if (ifcs != null) {
for (Type ifc : ifcs) {
Type rawType = ifc;
if (ifc instanceof ParameterizedType) {
rawType = ((ParameterizedType) ifc).getRawType();
}
if (rawType instanceof Class && isIntrospectionCandidate((Class) rawType)) {
return extractType(methodParam, ifc, source, typeIndex, nestingLevel, currentLevel);
}
}
}
return null;
}
/**
* Determine whether the given class is a potential candidate
* that defines generic collection or map types.
* @param clazz the class to check
* @return whether the given class is assignable to Collection or Map
*/
private static boolean isIntrospectionCandidate(Class clazz) {
return (Collection.class.isAssignableFrom(clazz) || Map.class.isAssignableFrom(clazz));
}
}
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