/*
* Copyright (C) 2008 Google Inc.
*
* 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 com.google.gson;
import java.lang.reflect.Array;
import java.lang.reflect.GenericArrayType;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.lang.reflect.WildcardType;
/**
* Utility class containing some methods for obtaining information on types.
*
* @author Inderjeet Singh
* @author Joel Leitch
*/
final class TypeUtils {
/**
* Returns the actual type matching up with the first type variable.
* So, for a {@code typeInfo} instance defined as:
* <pre>
* class Foo<A, B> {
* }
* Type fooType = new TypeToken<Foo<Integer, String>>() {}.getType();
* </pre>
* <code>TypeUtils.getActualTypeForFirstTypeVariable(fooType)</code> will return Integer.class.
*/
static Type getActualTypeForFirstTypeVariable(Type type) {
if (type instanceof Class<?>) {
return Object.class;
} else if (type instanceof ParameterizedType) {
return ((ParameterizedType)type).getActualTypeArguments()[0];
} else if (type instanceof GenericArrayType) {
return getActualTypeForFirstTypeVariable(((GenericArrayType)type).getGenericComponentType());
} else {
throw new IllegalArgumentException("Type \'" + type + "\' is not a Class, "
+ "ParameterizedType, or GenericArrayType. Can't extract class.");
}
}
static boolean isArray(Type type) {
if (type instanceof Class<?>) {
return ((Class<?>)type).isArray();
} else if (type instanceof GenericArrayType) {
return true;
} else {
return false;
}
}
/**
* This method returns the actual raw class associated with the specified type.
*/
static Class<?> toRawClass(Type type) {
if (type instanceof Class<?>) {
return (Class<?>) type;
} else if (type instanceof ParameterizedType) {
ParameterizedType actualType = (ParameterizedType)type;
return toRawClass(actualType.getRawType());
} else if (type instanceof GenericArrayType) {
GenericArrayType actualType = (GenericArrayType) type;
Class<?> rawClass = toRawClass(actualType.getGenericComponentType());
return wrapWithArray(rawClass);
} else if (type instanceof WildcardType) {
WildcardType castedType = (WildcardType) type;
return toRawClass(castedType.getUpperBounds()[0]);
} else {
throw new IllegalArgumentException("Type \'" + type + "\' is not a Class, "
+ "ParameterizedType, or GenericArrayType. Can't extract class.");
}
}
static Class<?> wrapWithArray(Class<?> rawClass) {
return Array.newInstance(rawClass, 0).getClass();
}
private TypeUtils() {
// Class with just some static utility methods, should not be instantiated
}
}