Spring Framework example source code file (TypeUtils.java)

This example Spring Framework source code file (TypeUtils.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Spring Framework tags/keywords

class, class, left-hand, parameterizedtype, parameterizedtype, reflection, right-hand, type, type, typeutils, wildcardtype, wildcardtype

The Spring Framework TypeUtils.java source code

/*
 * Copyright 2002-2007 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.ParameterizedType;
import java.lang.reflect.Type;
import java.lang.reflect.WildcardType;

/**
 * Utility to work with Java 5 generic type parameters.
 * Mainly for internal use within the framework.
 *
 * @author Ramnivas Laddad
 * @author Juergen Hoeller
 * @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");
		if (lhsType.equals(rhsType)) {
			return true;
		}
		if (lhsType instanceof Class && rhsType instanceof Class) {
			return ClassUtils.isAssignable((Class) lhsType, (Class) rhsType);
		}
		if (lhsType instanceof ParameterizedType && rhsType instanceof ParameterizedType) {
			return isAssignable((ParameterizedType) lhsType, (ParameterizedType) rhsType);
		}
		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[] upperBounds = lhsType.getUpperBounds();
		Type[] lowerBounds = lhsType.getLowerBounds();
		for (int size = upperBounds.length, i = 0; i < size; ++i) {
			if (!isAssignable(upperBounds[i], rhsType)) {
				return false;
			}
		}
		for (int size = lowerBounds.length, i = 0; i < size; ++i) {
			if (!isAssignable(rhsType, lowerBounds[i])) {
				return false;
			}
		}
		return true;
	}

}