autowireutils.java

来自「一个关于Spring框架的示例应用程序,简单使用,可以参考.」· Java 代码 · 共 97 行

/*
 * Copyright 2002-2004 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.beans.factory.support;

import java.lang.reflect.Constructor;
import java.lang.reflect.Modifier;
import java.util.Arrays;
import java.util.Comparator;

import org.springframework.beans.BeanUtils;

/**
 * Utility class that contains various methods useful for
 * the implementation of autowire-capable bean factories.
 * @author Juergen Hoeller
 * @since 1.1.2
 * @see AbstractAutowireCapableBeanFactory
 */
public abstract class AutowireUtils {

	/**
	 * Sort the given constructors, preferring public constructors and "greedy" ones
	 * with a maximum of arguments. The result will contain public constructors first,
	 * with decreasing number of arguments, then non-public constructors, again with
	 * decreasing number of arguments.
	 * @param constructors the constructor array to sort
	 */
	public static void sortConstructors(Constructor[] constructors) {
		Arrays.sort(constructors, new Comparator() {
			public int compare(Object o1, Object o2) {
				Constructor c1 = (Constructor) o1;
				Constructor c2 = (Constructor) o2;
				boolean p1 = Modifier.isPublic(c1.getModifiers());
				boolean p2 = Modifier.isPublic(c2.getModifiers());
				if (p1 != p2) {
					return (p1 ? -1 : 1);
				}
				int c1pl = c1.getParameterTypes().length;
				int c2pl = c2.getParameterTypes().length;
				return (new Integer(c1pl)).compareTo(new Integer(c2pl)) * -1;
			}
		});
	}

	/**
	 * Determine a weight that represents the class hierarchy difference between types and
	 * arguments. A direct match, i.e. type Integer -> arg of class Integer, does not increase
	 * the result - all direct matches means weight 0. A match between type Object and arg of
	 * class Integer would increase the weight by 2, due to the superclass 2 steps up in the
	 * hierarchy (i.e. Object) being the last one that still matches the required type Object.
	 * Type Number and class Integer would increase the weight by 1 accordingly, due to the
	 * superclass 1 step up the hierarchy (i.e. Number) still matching the required type Number.
	 * Therefore, with an arg of type Integer, a constructor (Integer) would be preferred to a
	 * constructor (Number) which would in turn be preferred to a constructor (Object).
	 * All argument weights get accumulated.
	 * @param argTypes the argument types to match
	 * @param args the arguments to match
	 * @return the accumulated weight for all arguments
	 */
	public static int getTypeDifferenceWeight(Class[] argTypes, Object[] args) {
		int result = 0;
		for (int i = 0; i < argTypes.length; i++) {
			if (!BeanUtils.isAssignable(argTypes[i], args[i])) {
				return Integer.MAX_VALUE;
			}
			if (args[i] != null) {
				Class superClass = args[i].getClass().getSuperclass();
				while (superClass != null) {
					if (argTypes[i].isAssignableFrom(superClass)) {
						result++;
						superClass = superClass.getSuperclass();
					}
					else {
						superClass = null;
					}
				}
			}
		}
		return result;
	}

}