spring ReflectiveConstructorResolver 源码

  • 2022-08-08
  • 浏览 (128)

spring ReflectiveConstructorResolver 代码


 * Copyright 2002-2021 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
 *      https://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,
 * See the License for the specific language governing permissions and
 * limitations under the License.

package org.springframework.expression.spel.support;

import java.lang.reflect.Constructor;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Comparator;
import java.util.List;

import org.springframework.core.MethodParameter;
import org.springframework.core.convert.TypeDescriptor;
import org.springframework.expression.AccessException;
import org.springframework.expression.ConstructorExecutor;
import org.springframework.expression.ConstructorResolver;
import org.springframework.expression.EvaluationContext;
import org.springframework.expression.EvaluationException;
import org.springframework.expression.TypeConverter;
import org.springframework.lang.Nullable;

 * A constructor resolver that uses reflection to locate the constructor that should be invoked.
 * @author Andy Clement
 * @author Juergen Hoeller
 * @since 3.0
public class ReflectiveConstructorResolver implements ConstructorResolver {

	 * Locate a constructor on the type. There are three kinds of match that might occur:
	 * <ol>
	 * <li>An exact match where the types of the arguments match the types of the constructor
	 * <li>An in-exact match where the types we are looking for are subtypes of those defined on the constructor
	 * <li>A match where we are able to convert the arguments into those expected by the constructor, according to the
	 * registered type converter.
	 * </ol>
	public ConstructorExecutor resolve(EvaluationContext context, String typeName, List<TypeDescriptor> argumentTypes)
			throws AccessException {

		try {
			TypeConverter typeConverter = context.getTypeConverter();
			Class<?> type = context.getTypeLocator().findType(typeName);
			Constructor<?>[] ctors = type.getConstructors();

			Arrays.sort(ctors, Comparator.comparingInt(Constructor::getParameterCount));

			Constructor<?> closeMatch = null;
			Constructor<?> matchRequiringConversion = null;

			for (Constructor<?> ctor : ctors) {
				int paramCount = ctor.getParameterCount();
				List<TypeDescriptor> paramDescriptors = new ArrayList<>(paramCount);
				for (int i = 0; i < paramCount; i++) {
					paramDescriptors.add(new TypeDescriptor(new MethodParameter(ctor, i)));
				ReflectionHelper.ArgumentsMatchInfo matchInfo = null;
				if (ctor.isVarArgs() && argumentTypes.size() >= paramCount - 1) {
					// *sigh* complicated
					// Basically.. we have to have all parameters match up until the varargs one, then the rest of what is
					// being provided should be
					// the same type whilst the final argument to the method must be an array of that (oh, how easy...not) -
					// or the final parameter
					// we are supplied does match exactly (it is an array already).
					matchInfo = ReflectionHelper.compareArgumentsVarargs(paramDescriptors, argumentTypes, typeConverter);
				else if (paramCount == argumentTypes.size()) {
					// worth a closer look
					matchInfo = ReflectionHelper.compareArguments(paramDescriptors, argumentTypes, typeConverter);
				if (matchInfo != null) {
					if (matchInfo.isExactMatch()) {
						return new ReflectiveConstructorExecutor(ctor);
					else if (matchInfo.isCloseMatch()) {
						closeMatch = ctor;
					else if (matchInfo.isMatchRequiringConversion()) {
						matchRequiringConversion = ctor;

			if (closeMatch != null) {
				return new ReflectiveConstructorExecutor(closeMatch);
			else if (matchRequiringConversion != null) {
				return new ReflectiveConstructorExecutor(matchRequiringConversion);
			else {
				return null;
		catch (EvaluationException ex) {
			throw new AccessException("Failed to resolve constructor", ex);



spring 源码目录


spring BooleanTypedValue 源码

spring DataBindingMethodResolver 源码

spring DataBindingPropertyAccessor 源码

spring ReflectionHelper 源码

spring ReflectiveConstructorExecutor 源码

spring ReflectiveMethodExecutor 源码

spring ReflectiveMethodResolver 源码

spring ReflectivePropertyAccessor 源码

spring SimpleEvaluationContext 源码

spring StandardEvaluationContext 源码

0  赞