/*
 * Copyright 2002-2018 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,
 * 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.beans.ConstructorProperties;
import java.lang.reflect.Constructor;
import java.lang.reflect.Executable;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashSet;
import java.util.LinkedHashSet;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Set;

import org.apache.commons.logging.Log;

import org.springframework.beans.BeanMetadataElement;
import org.springframework.beans.BeanWrapper;
import org.springframework.beans.BeanWrapperImpl;
import org.springframework.beans.BeansException;
import org.springframework.beans.TypeConverter;
import org.springframework.beans.TypeMismatchException;
import org.springframework.beans.factory.BeanCreationException;
import org.springframework.beans.factory.BeanDefinitionStoreException;
import org.springframework.beans.factory.InjectionPoint;
import org.springframework.beans.factory.UnsatisfiedDependencyException;
import org.springframework.beans.factory.config.AutowireCapableBeanFactory;
import org.springframework.beans.factory.config.ConstructorArgumentValues;
import org.springframework.beans.factory.config.ConstructorArgumentValues.ValueHolder;
import org.springframework.beans.factory.config.DependencyDescriptor;
import org.springframework.core.GenericTypeResolver;
import org.springframework.core.MethodParameter;
import org.springframework.core.NamedThreadLocal;
import org.springframework.core.ParameterNameDiscoverer;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.util.ClassUtils;
import org.springframework.util.MethodInvoker;
import org.springframework.util.ObjectUtils;
import org.springframework.util.ReflectionUtils;
import org.springframework.util.StringUtils;

/**
 * Delegate for resolving constructors and factory methods.
 * Performs constructor resolution through argument matching.
 *
 * @author Juergen Hoeller
 * @author Rob Harrop
 * @author Mark Fisher
 * @author Costin Leau
 * @author Sebastien Deleuze
 * @since 2.0
 * @see #autowireConstructor
 * @see #instantiateUsingFactoryMethod
 * @see AbstractAutowireCapableBeanFactory
 */
class ConstructorResolver {

	private static final NamedThreadLocal<InjectionPoint> currentInjectionPoint =
			new NamedThreadLocal<>("Current injection point");

	private final AbstractAutowireCapableBeanFactory beanFactory;

	private final Log logger;


	/**
	 * Create a new ConstructorResolver for the given factory and instantiation strategy.
	 * @param beanFactory the BeanFactory to work with
	 */
	public ConstructorResolver(AbstractAutowireCapableBeanFactory beanFactory) {
		this.beanFactory = beanFactory;
		this.logger = beanFactory.getLogger();
	}


	/**
	 * "autowire constructor" (with constructor arguments by type) behavior.
	 * Also applied if explicit constructor argument values are specified,
	 * matching all remaining arguments with beans from the bean factory.
	 * <p>This corresponds to constructor injection: In this mode, a Spring
	 * bean factory is able to host components that expect constructor-based
	 * dependency resolution.
	 * @param beanName the name of the bean
	 * @param mbd the merged bean definition for the bean
	 * @param chosenCtors chosen candidate constructors (or {@code null} if none)
	 * @param explicitArgs argument values passed in programmatically via the getBean method,
	 * or {@code null} if none (-> use constructor argument values from bean definition)
	 * @return a BeanWrapper for the new instance
	 */
	public BeanWrapper autowireConstructor(String beanName, RootBeanDefinition mbd,
			@Nullable Constructor<?>[] chosenCtors, @Nullable Object[] explicitArgs) {

		BeanWrapperImpl bw = new BeanWrapperImpl();
		this.beanFactory.initBeanWrapper(bw);

		//当前bean被使用的构造器对象变量
		Constructor<?> constructorToUse = null;
		//封装构造器参数对象
		ArgumentsHolder argsHolderToUse = null;
		//构造器使用的参数对象
		Object[] argsToUse = null;

		/**
		 * 若通过getBean的方式传递进来的参数,我们直接不要去解析了直接可以确定选择哪个构造器
		 */
		if (explicitArgs != null) {
			//赋值给argsToUse
			argsToUse = explicitArgs;
		}
		else {
			/**
			 * 针对我们单实例的bean的时候，第一次都会走解析的流程，那么在这里加入缓存没有任何意思
			 * 那么我们多例的bean,每一次调用getBean的时候就会调用一次构造函数,那么缓存在这里就会起到很好的作用
			 * 因为解析构造函数 逻辑十分复杂很消耗性能
			 */
			Object[] argsToResolve = null;
			synchronized (mbd.constructorArgumentLock) {
				//从缓存中获取已经解析的构造方法
				constructorToUse = (Constructor<?>) mbd.resolvedConstructorOrFactoryMethod;
				if (constructorToUse != null && mbd.constructorArgumentsResolved) {
					// 从缓存中获取出解析出来构造器对应的参数
					argsToUse = mbd.resolvedConstructorArguments;
					if (argsToUse == null) {
						// 若 argsToUse 为空，则获取未解析的构造方法参数列表
						argsToResolve = mbd.preparedConstructorArguments;
					}
				}
			}
			// 缓存中存在,则解析存储在 BeanDefinition 中的参数
			// 如给定方法的构造函数 A(int ,int )，则通过此方法后就会把配置文件中的("1","1")转换为 (1,1)
			// 缓存中的值可能是原始值也有可能是最终值
			if (argsToResolve != null) {
				/**
				 * 在这里 也有可能解析循环依赖，但是在这里不能解决循环依赖，因为还没有到暴露早期对象
				 */
				argsToUse = resolvePreparedArguments(beanName, mbd, bw, constructorToUse, argsToResolve);
			}
		}

		//缓存中没有
		if (constructorToUse == null) {
			/**
			 * 该标志是否需要解析出构造函数  chosenCtors传入进来的不为空
			 * mbd.getResolvedAutowireMode() == AutowireCapableBeanFactory.AUTOWIRE_CONSTRUCTOR 注入模式为3
			 */
			boolean autowiring = (chosenCtors != null ||
					mbd.getResolvedAutowireMode() == AutowireCapableBeanFactory.AUTOWIRE_CONSTRUCTOR);
			ConstructorArgumentValues resolvedValues = null;

			int minNrOfArgs;
			//getBean传递进来的构造器参数不为空
			if (explicitArgs != null) {
				//把参数的长度赋值给minNrOfArgs
				minNrOfArgs = explicitArgs.length;
			}
			//getBean传递进来的构造器参数为空
			else {
				//在bean定义解析的时候，会把构造器参数vlaue的对象保存到bean定义的ConstructorArgumentValuesz中
				ConstructorArgumentValues cargs = mbd.getConstructorArgumentValues();
				resolvedValues = new ConstructorArgumentValues();
				//解析参数的个数
				minNrOfArgs = resolveConstructorArguments(beanName, mbd, bw, cargs, resolvedValues);
			}

			//上一个方法传入进来的构造函数
			Constructor<?>[] candidates = chosenCtors;
			//如果 chosenCtors 未传入,需要我们再次解析
			if (candidates == null) {
				//获取当前bean的构造函数
				Class<?> beanClass = mbd.getBeanClass();
				try {
					//通过class获取到bean的构造函数
					candidates = (mbd.isNonPublicAccessAllowed() ?
							beanClass.getDeclaredConstructors() : beanClass.getConstructors());
				}
				catch (Throwable ex) {
					throw new BeanCreationException(mbd.getResourceDescription(), beanName,
							"Resolution of declared constructors on bean Class [" + beanClass.getName() +
							"] from ClassLoader [" + beanClass.getClassLoader() + "] failed", ex);
				}
			}
			AutowireUtils.sortConstructors(candidates);
			int minTypeDiffWeight = Integer.MAX_VALUE;
			Set<Constructor<?>> ambiguousConstructors = null;
			LinkedList<UnsatisfiedDependencyException> causes = null;
			//循环我们构造函数
			for (Constructor<?> candidate : candidates) {
				//获取构造函数的参数类型集合
				Class<?>[] paramTypes = candidate.getParameterTypes();

				//?????在这里有疑问  代码进入到这里 constructorToUse 一定是为null才会进入到这里
				if (constructorToUse != null && argsToUse.length > paramTypes.length) {
					// Already found greedy constructor that can be satisfied ->
					// do not look any further, there are only less greedy constructors left.
					break;
				}
				//当前构造器参数的长度<bean定义中解析出来的参数的长度 ,那么当前构造器不匹配
				if (paramTypes.length < minNrOfArgs) {
					continue;
				}

				//当前循环的构造器参数的长度<bean定义中解析出来的参数的长度
				ArgumentsHolder argsHolder;

				//从bean定义中解析出来的构造函数参数不为null
				if (resolvedValues != null) {
					try {
						String[] paramNames = ConstructorPropertiesChecker.evaluate(candidate, paramTypes.length);
						if (paramNames == null) {
							// 获取构造函数、方法参数的探测器
							ParameterNameDiscoverer pnd = this.beanFactory.getParameterNameDiscoverer();
							if (pnd != null) {
								//通过探测器获取构造函数的参数名称
								paramNames = pnd.getParameterNames(candidate);
							}
						}
						// 根据构造函数和构造参数，创建参数持有者 ArgumentsHolder 对象
						argsHolder = createArgumentArray(beanName, mbd, resolvedValues, bw, paramTypes, paramNames,
								getUserDeclaredConstructor(candidate), autowiring);
					}
					catch (UnsatisfiedDependencyException ex) {
						// 若发生 UnsatisfiedDependencyException 异常，添加到 causes 中。
						if (logger.isTraceEnabled()) {
							logger.trace("Ignoring constructor [" + candidate + "] of bean '" + beanName + "': " + ex);
						}
						// Swallow and try next constructor.
						if (causes == null) {
							causes = new LinkedList<>();
						}
						causes.add(ex);
						continue;
					}
				}
				else {
					// Explicit arguments given -> arguments length must match exactly.
					// continue 构造函数没有参数
					if (paramTypes.length != explicitArgs.length) {
						continue;
					}
					// 根据 explicitArgs ，创建 ArgumentsHolder 对象
					argsHolder = new ArgumentsHolder(explicitArgs);
				}

				// isLenientConstructorResolution 判断解析构造函数的时候是否以宽松模式还是严格模式
				// 严格模式：解析构造函数时，必须所有的都需要匹配，否则抛出异常
				// 宽松模式：使用具有"最接近的模式"进行匹配
				// typeDiffWeight：类型差异权重
				int typeDiffWeight = (mbd.isLenientConstructorResolution() ?
						argsHolder.getTypeDifferenceWeight(paramTypes) : argsHolder.getAssignabilityWeight(paramTypes));
				// Choose this constructor if it represents the closest match.
				// 如果它代表着当前最接近的匹配则选择其作为构造函数
				if (typeDiffWeight < minTypeDiffWeight) {
					constructorToUse = candidate;
					argsHolderToUse = argsHolder;
					argsToUse = argsHolder.arguments;
					minTypeDiffWeight = typeDiffWeight;
					ambiguousConstructors = null;
				}
				else if (constructorToUse != null && typeDiffWeight == minTypeDiffWeight) {
					if (ambiguousConstructors == null) {
						ambiguousConstructors = new LinkedHashSet<>();
						ambiguousConstructors.add(constructorToUse);
					}
					ambiguousConstructors.add(candidate);
				}
			}

			// 没有可执行的工厂方法，抛出异常
			if (constructorToUse == null) {
				if (causes != null) {
					UnsatisfiedDependencyException ex = causes.removeLast();
					for (Exception cause : causes) {
						this.beanFactory.onSuppressedException(cause);
					}
					throw ex;
				}
				throw new BeanCreationException(mbd.getResourceDescription(), beanName,
						"Could not resolve matching constructor " +
						"(hint: specify index/type/name arguments for simple parameters to avoid type ambiguities)");
			}
			else if (ambiguousConstructors != null && !mbd.isLenientConstructorResolution()) {
				throw new BeanCreationException(mbd.getResourceDescription(), beanName,
						"Ambiguous constructor matches found in bean '" + beanName + "' " +
						"(hint: specify index/type/name arguments for simple parameters to avoid type ambiguities): " +
						ambiguousConstructors);
			}

			// 将解析的构造函数加入缓存
			if (explicitArgs == null) {
				argsHolderToUse.storeCache(mbd, constructorToUse);
			}
		}

		try {
			//获取实例化策略
			final InstantiationStrategy strategy = beanFactory.getInstantiationStrategy();
			Object beanInstance;

			if (System.getSecurityManager() != null) {
				final Constructor<?> ctorToUse = constructorToUse;
				final Object[] argumentsToUse = argsToUse;
				beanInstance = AccessController.doPrivileged((PrivilegedAction<Object>) () ->
						strategy.instantiate(mbd, beanName, beanFactory, ctorToUse, argumentsToUse),
						beanFactory.getAccessControlContext());
			}
			else {
				//通过反射调用构造函数
				beanInstance = strategy.instantiate(mbd, beanName, this.beanFactory, constructorToUse, argsToUse);
			}

			bw.setBeanInstance(beanInstance);
			return bw;
		}
		catch (Throwable ex) {
			throw new BeanCreationException(mbd.getResourceDescription(), beanName,
					"Bean instantiation via constructor failed", ex);
		}
	}

	/**
	 * Resolve the factory method in the specified bean definition, if possible.
	 * {@link RootBeanDefinition#getResolvedFactoryMethod()} can be checked for the result.
	 * @param mbd the bean definition to check
	 */
	public void resolveFactoryMethodIfPossible(RootBeanDefinition mbd) {
		Class<?> factoryClass;
		boolean isStatic;
		if (mbd.getFactoryBeanName() != null) {
			factoryClass = this.beanFactory.getType(mbd.getFactoryBeanName());
			isStatic = false;
		}
		else {
			factoryClass = mbd.getBeanClass();
			isStatic = true;
		}
		Assert.state(factoryClass != null, "Unresolvable factory class");
		factoryClass = ClassUtils.getUserClass(factoryClass);

		Method[] candidates = getCandidateMethods(factoryClass, mbd);
		Method uniqueCandidate = null;
		for (Method candidate : candidates) {
			if (Modifier.isStatic(candidate.getModifiers()) == isStatic && mbd.isFactoryMethod(candidate)) {
				if (uniqueCandidate == null) {
					uniqueCandidate = candidate;
				}
				else if (!Arrays.equals(uniqueCandidate.getParameterTypes(), candidate.getParameterTypes())) {
					uniqueCandidate = null;
					break;
				}
			}
		}
		synchronized (mbd.constructorArgumentLock) {
			mbd.resolvedConstructorOrFactoryMethod = uniqueCandidate;
		}
	}

	/**
	 * Retrieve all candidate methods for the given class, considering
	 * the {@link RootBeanDefinition#isNonPublicAccessAllowed()} flag.
	 * Called as the starting point for factory method determination.
	 */
	private Method[] getCandidateMethods(Class<?> factoryClass, RootBeanDefinition mbd) {
		if (System.getSecurityManager() != null) {
			return AccessController.doPrivileged((PrivilegedAction<Method[]>) () ->
					(mbd.isNonPublicAccessAllowed() ?
						ReflectionUtils.getAllDeclaredMethods(factoryClass) : factoryClass.getMethods()));
		}
		else {
			return (mbd.isNonPublicAccessAllowed() ?
					ReflectionUtils.getAllDeclaredMethods(factoryClass) : factoryClass.getMethods());
		}
	}

	/**
	 * Instantiate the bean using a named factory method. The method may be static, if the
	 * bean definition parameter specifies a class, rather than a "factory-bean", or
	 * an instance variable on a factory object itself configured using Dependency Injection.
	 * <p>Implementation requires iterating over the static or instance methods with the
	 * name specified in the RootBeanDefinition (the method may be overloaded) and trying
	 * to match with the parameters. We don't have the types attached to constructor args,
	 * so trial and error is the only way to go here. The explicitArgs array may contain
	 * argument values passed in programmatically via the corresponding getBean method.
	 * @param beanName the name of the bean
	 * @param mbd the merged bean definition for the bean
	 * @param explicitArgs argument values passed in programmatically via the getBean
	 * method, or {@code null} if none (-> use constructor argument values from bean definition)
	 * @return a BeanWrapper for the new instance
	 */
	public BeanWrapper instantiateUsingFactoryMethod(
			String beanName, RootBeanDefinition mbd, @Nullable Object[] explicitArgs) {

		BeanWrapperImpl bw = new BeanWrapperImpl();
		this.beanFactory.initBeanWrapper(bw);

		Object factoryBean;
		Class<?> factoryClass;
		boolean isStatic;

		String factoryBeanName = mbd.getFactoryBeanName();
		if (factoryBeanName != null) {
			if (factoryBeanName.equals(beanName)) {
				throw new BeanDefinitionStoreException(mbd.getResourceDescription(), beanName,
						"factory-bean reference points back to the same bean definition");
			}
			factoryBean = this.beanFactory.getBean(factoryBeanName);
			if (mbd.isSingleton() && this.beanFactory.containsSingleton(beanName)) {
				throw new ImplicitlyAppearedSingletonException();
			}
			factoryClass = factoryBean.getClass();
			isStatic = false;
		}
		else {
			// It's a static factory method on the bean class.
			if (!mbd.hasBeanClass()) {
				throw new BeanDefinitionStoreException(mbd.getResourceDescription(), beanName,
						"bean definition declares neither a bean class nor a factory-bean reference");
			}
			factoryBean = null;
			factoryClass = mbd.getBeanClass();
			isStatic = true;
		}

		Method factoryMethodToUse = null;
		ArgumentsHolder argsHolderToUse = null;
		Object[] argsToUse = null;

		if (explicitArgs != null) {
			argsToUse = explicitArgs;
		}
		else {
			Object[] argsToResolve = null;
			synchronized (mbd.constructorArgumentLock) {
				factoryMethodToUse = (Method) mbd.resolvedConstructorOrFactoryMethod;
				if (factoryMethodToUse != null && mbd.constructorArgumentsResolved) {
					// Found a cached factory method...
					argsToUse = mbd.resolvedConstructorArguments;
					if (argsToUse == null) {
						argsToResolve = mbd.preparedConstructorArguments;
					}
				}
			}
			if (argsToResolve != null) {
				argsToUse = resolvePreparedArguments(beanName, mbd, bw, factoryMethodToUse, argsToResolve);
			}
		}

		if (factoryMethodToUse == null || argsToUse == null) {
			// Need to determine the factory method...
			// Try all methods with this name to see if they match the given arguments.
			factoryClass = ClassUtils.getUserClass(factoryClass);

			Method[] rawCandidates = getCandidateMethods(factoryClass, mbd);
			List<Method> candidateList = new ArrayList<>();
			for (Method candidate : rawCandidates) {
				if (Modifier.isStatic(candidate.getModifiers()) == isStatic && mbd.isFactoryMethod(candidate)) {
					candidateList.add(candidate);
				}
			}
			Method[] candidates = candidateList.toArray(new Method[0]);
			AutowireUtils.sortFactoryMethods(candidates);

			ConstructorArgumentValues resolvedValues = null;
			boolean autowiring = (mbd.getResolvedAutowireMode() == AutowireCapableBeanFactory.AUTOWIRE_CONSTRUCTOR);
			int minTypeDiffWeight = Integer.MAX_VALUE;
			Set<Method> ambiguousFactoryMethods = null;

			int minNrOfArgs;
			if (explicitArgs != null) {
				minNrOfArgs = explicitArgs.length;
			}
			else {
				// We don't have arguments passed in programmatically, so we need to resolve the
				// arguments specified in the constructor arguments held in the bean definition.
				if (mbd.hasConstructorArgumentValues()) {
					ConstructorArgumentValues cargs = mbd.getConstructorArgumentValues();
					resolvedValues = new ConstructorArgumentValues();
					minNrOfArgs = resolveConstructorArguments(beanName, mbd, bw, cargs, resolvedValues);
				}
				else {
					minNrOfArgs = 0;
				}
			}

			LinkedList<UnsatisfiedDependencyException> causes = null;

			for (Method candidate : candidates) {
				Class<?>[] paramTypes = candidate.getParameterTypes();

				if (paramTypes.length >= minNrOfArgs) {
					ArgumentsHolder argsHolder;

					if (explicitArgs != null) {
						// Explicit arguments given -> arguments length must match exactly.
						if (paramTypes.length != explicitArgs.length) {
							continue;
						}
						argsHolder = new ArgumentsHolder(explicitArgs);
					}
					else {
						// Resolved constructor arguments: type conversion and/or autowiring necessary.
						try {
							String[] paramNames = null;
							ParameterNameDiscoverer pnd = this.beanFactory.getParameterNameDiscoverer();
							if (pnd != null) {
								paramNames = pnd.getParameterNames(candidate);
							}
							argsHolder = createArgumentArray(
									beanName, mbd, resolvedValues, bw, paramTypes, paramNames, candidate, autowiring);
						}
						catch (UnsatisfiedDependencyException ex) {
							if (logger.isTraceEnabled()) {
								logger.trace("Ignoring factory method [" + candidate + "] of bean '" + beanName + "': " + ex);
							}
							// Swallow and try next overloaded factory method.
							if (causes == null) {
								causes = new LinkedList<>();
							}
							causes.add(ex);
							continue;
						}
					}

					int typeDiffWeight = (mbd.isLenientConstructorResolution() ?
							argsHolder.getTypeDifferenceWeight(paramTypes) : argsHolder.getAssignabilityWeight(paramTypes));
					// Choose this factory method if it represents the closest match.
					if (typeDiffWeight < minTypeDiffWeight) {
						factoryMethodToUse = candidate;
						argsHolderToUse = argsHolder;
						argsToUse = argsHolder.arguments;
						minTypeDiffWeight = typeDiffWeight;
						ambiguousFactoryMethods = null;
					}
					// Find out about ambiguity: In case of the same type difference weight
					// for methods with the same number of parameters, collect such candidates
					// and eventually raise an ambiguity exception.
					// However, only perform that check in non-lenient constructor resolution mode,
					// and explicitly ignore overridden methods (with the same parameter signature).
					else if (factoryMethodToUse != null && typeDiffWeight == minTypeDiffWeight &&
							!mbd.isLenientConstructorResolution() &&
							paramTypes.length == factoryMethodToUse.getParameterCount() &&
							!Arrays.equals(paramTypes, factoryMethodToUse.getParameterTypes())) {
						if (ambiguousFactoryMethods == null) {
							ambiguousFactoryMethods = new LinkedHashSet<>();
							ambiguousFactoryMethods.add(factoryMethodToUse);
						}
						ambiguousFactoryMethods.add(candidate);
					}
				}
			}

			if (factoryMethodToUse == null) {
				if (causes != null) {
					UnsatisfiedDependencyException ex = causes.removeLast();
					for (Exception cause : causes) {
						this.beanFactory.onSuppressedException(cause);
					}
					throw ex;
				}
				List<String> argTypes = new ArrayList<>(minNrOfArgs);
				if (explicitArgs != null) {
					for (Object arg : explicitArgs) {
						argTypes.add(arg != null ? arg.getClass().getSimpleName() : "null");
					}
				}
				else if (resolvedValues != null) {
					Set<ValueHolder> valueHolders = new LinkedHashSet<>(resolvedValues.getArgumentCount());
					valueHolders.addAll(resolvedValues.getIndexedArgumentValues().values());
					valueHolders.addAll(resolvedValues.getGenericArgumentValues());
					for (ValueHolder value : valueHolders) {
						String argType = (value.getType() != null ? ClassUtils.getShortName(value.getType()) :
								(value.getValue() != null ? value.getValue().getClass().getSimpleName() : "null"));
						argTypes.add(argType);
					}
				}
				String argDesc = StringUtils.collectionToCommaDelimitedString(argTypes);
				throw new BeanCreationException(mbd.getResourceDescription(), beanName,
						"No matching factory method found: " +
						(mbd.getFactoryBeanName() != null ?
							"factory bean '" + mbd.getFactoryBeanName() + "'; " : "") +
						"factory method '" + mbd.getFactoryMethodName() + "(" + argDesc + ")'. " +
						"Check that a method with the specified name " +
						(minNrOfArgs > 0 ? "and arguments " : "") +
						"exists and that it is " +
						(isStatic ? "static" : "non-static") + ".");
			}
			else if (void.class == factoryMethodToUse.getReturnType()) {
				throw new BeanCreationException(mbd.getResourceDescription(), beanName,
						"Invalid factory method '" + mbd.getFactoryMethodName() +
						"': needs to have a non-void return type!");
			}
			else if (ambiguousFactoryMethods != null) {
				throw new BeanCreationException(mbd.getResourceDescription(), beanName,
						"Ambiguous factory method matches found in bean '" + beanName + "' " +
						"(hint: specify index/type/name arguments for simple parameters to avoid type ambiguities): " +
						ambiguousFactoryMethods);
			}

			if (explicitArgs == null && argsHolderToUse != null) {
				argsHolderToUse.storeCache(mbd, factoryMethodToUse);
			}
		}

		try {
			Object beanInstance;

			if (System.getSecurityManager() != null) {
				final Object fb = factoryBean;
				final Method factoryMethod = factoryMethodToUse;
				final Object[] args = argsToUse;
				beanInstance = AccessController.doPrivileged((PrivilegedAction<Object>) () ->
						beanFactory.getInstantiationStrategy().instantiate(mbd, beanName, beanFactory, fb, factoryMethod, args),
						beanFactory.getAccessControlContext());
			}
			else {
				beanInstance = this.beanFactory.getInstantiationStrategy().instantiate(
						mbd, beanName, this.beanFactory, factoryBean, factoryMethodToUse, argsToUse);
			}

			bw.setBeanInstance(beanInstance);
			return bw;
		}
		catch (Throwable ex) {
			throw new BeanCreationException(mbd.getResourceDescription(), beanName,
					"Bean instantiation via factory method failed", ex);
		}
	}

	/**
	 * Resolve the constructor arguments for this bean into the resolvedValues object.
	 * This may involve looking up other beans.
	 * <p>This method is also used for handling invocations of static factory methods.
	 */
	private int resolveConstructorArguments(String beanName, RootBeanDefinition mbd, BeanWrapper bw,
			ConstructorArgumentValues cargs, ConstructorArgumentValues resolvedValues) {

		TypeConverter customConverter = this.beanFactory.getCustomTypeConverter();
		TypeConverter converter = (customConverter != null ? customConverter : bw);
		BeanDefinitionValueResolver valueResolver =
				new BeanDefinitionValueResolver(this.beanFactory, beanName, mbd, converter);

		int minNrOfArgs = cargs.getArgumentCount();

		for (Map.Entry<Integer, ConstructorArgumentValues.ValueHolder> entry : cargs.getIndexedArgumentValues().entrySet()) {
			int index = entry.getKey();
			if (index < 0) {
				throw new BeanCreationException(mbd.getResourceDescription(), beanName,
						"Invalid constructor argument index: " + index);
			}
			if (index > minNrOfArgs) {
				minNrOfArgs = index + 1;
			}
			ConstructorArgumentValues.ValueHolder valueHolder = entry.getValue();
			if (valueHolder.isConverted()) {
				resolvedValues.addIndexedArgumentValue(index, valueHolder);
			}
			else {
				Object resolvedValue =
						valueResolver.resolveValueIfNecessary("constructor argument", valueHolder.getValue());
				ConstructorArgumentValues.ValueHolder resolvedValueHolder =
						new ConstructorArgumentValues.ValueHolder(resolvedValue, valueHolder.getType(), valueHolder.getName());
				resolvedValueHolder.setSource(valueHolder);
				resolvedValues.addIndexedArgumentValue(index, resolvedValueHolder);
			}
		}

		for (ConstructorArgumentValues.ValueHolder valueHolder : cargs.getGenericArgumentValues()) {
			if (valueHolder.isConverted()) {
				resolvedValues.addGenericArgumentValue(valueHolder);
			}
			else {
				Object resolvedValue =
						valueResolver.resolveValueIfNecessary("constructor argument", valueHolder.getValue());
				ConstructorArgumentValues.ValueHolder resolvedValueHolder = new ConstructorArgumentValues.ValueHolder(
						resolvedValue, valueHolder.getType(), valueHolder.getName());
				resolvedValueHolder.setSource(valueHolder);
				resolvedValues.addGenericArgumentValue(resolvedValueHolder);
			}
		}

		return minNrOfArgs;
	}

	/**
	 * Create an array of arguments to invoke a constructor or factory method,
	 * given the resolved constructor argument values.
	 */
	private ArgumentsHolder createArgumentArray(
			String beanName, RootBeanDefinition mbd, @Nullable ConstructorArgumentValues resolvedValues,
			BeanWrapper bw, Class<?>[] paramTypes, @Nullable String[] paramNames, Executable executable,
			boolean autowiring) throws UnsatisfiedDependencyException {

		TypeConverter customConverter = this.beanFactory.getCustomTypeConverter();
		TypeConverter converter = (customConverter != null ? customConverter : bw);

		ArgumentsHolder args = new ArgumentsHolder(paramTypes.length);
		Set<ConstructorArgumentValues.ValueHolder> usedValueHolders = new HashSet<>(paramTypes.length);
		Set<String> autowiredBeanNames = new LinkedHashSet<>(4);

		for (int paramIndex = 0; paramIndex < paramTypes.length; paramIndex++) {
			Class<?> paramType = paramTypes[paramIndex];
			String paramName = (paramNames != null ? paramNames[paramIndex] : "");
			// Try to find matching constructor argument value, either indexed or generic.
			ConstructorArgumentValues.ValueHolder valueHolder = null;
			if (resolvedValues != null) {
				valueHolder = resolvedValues.getArgumentValue(paramIndex, paramType, paramName, usedValueHolders);
				// If we couldn't find a direct match and are not supposed to autowire,
				// let's try the next generic, untyped argument value as fallback:
				// it could match after type conversion (for example, String -> int).
				if (valueHolder == null && (!autowiring || paramTypes.length == resolvedValues.getArgumentCount())) {
					valueHolder = resolvedValues.getGenericArgumentValue(null, null, usedValueHolders);
				}
			}
			if (valueHolder != null) {
				// We found a potential match - let's give it a try.
				// Do not consider the same value definition multiple times!
				usedValueHolders.add(valueHolder);
				Object originalValue = valueHolder.getValue();
				Object convertedValue;
				if (valueHolder.isConverted()) {
					convertedValue = valueHolder.getConvertedValue();
					args.preparedArguments[paramIndex] = convertedValue;
				}
				else {
					MethodParameter methodParam = MethodParameter.forExecutable(executable, paramIndex);
					try {
						convertedValue = converter.convertIfNecessary(originalValue, paramType, methodParam);
					}
					catch (TypeMismatchException ex) {
						throw new UnsatisfiedDependencyException(
								mbd.getResourceDescription(), beanName, new InjectionPoint(methodParam),
								"Could not convert argument value of type [" +
										ObjectUtils.nullSafeClassName(valueHolder.getValue()) +
										"] to required type [" + paramType.getName() + "]: " + ex.getMessage());
					}
					Object sourceHolder = valueHolder.getSource();
					if (sourceHolder instanceof ConstructorArgumentValues.ValueHolder) {
						Object sourceValue = ((ConstructorArgumentValues.ValueHolder) sourceHolder).getValue();
						args.resolveNecessary = true;
						args.preparedArguments[paramIndex] = sourceValue;
					}
				}
				args.arguments[paramIndex] = convertedValue;
				args.rawArguments[paramIndex] = originalValue;
			}
			else {
				MethodParameter methodParam = MethodParameter.forExecutable(executable, paramIndex);
				// No explicit match found: we're either supposed to autowire or
				// have to fail creating an argument array for the given constructor.
				if (!autowiring) {
					throw new UnsatisfiedDependencyException(
							mbd.getResourceDescription(), beanName, new InjectionPoint(methodParam),
							"Ambiguous argument values for parameter of type [" + paramType.getName() +
							"] - did you specify the correct bean references as arguments?");
				}
				try {
					Object autowiredArgument =
							resolveAutowiredArgument(methodParam, beanName, autowiredBeanNames, converter);
					args.rawArguments[paramIndex] = autowiredArgument;
					args.arguments[paramIndex] = autowiredArgument;
					args.preparedArguments[paramIndex] = new AutowiredArgumentMarker();
					args.resolveNecessary = true;
				}
				catch (BeansException ex) {
					throw new UnsatisfiedDependencyException(
							mbd.getResourceDescription(), beanName, new InjectionPoint(methodParam), ex);
				}
			}
		}

		for (String autowiredBeanName : autowiredBeanNames) {
			this.beanFactory.registerDependentBean(autowiredBeanName, beanName);
			if (logger.isDebugEnabled()) {
				logger.debug("Autowiring by type from bean name '" + beanName +
						"' via " + (executable instanceof Constructor ? "constructor" : "factory method") +
						" to bean named '" + autowiredBeanName + "'");
			}
		}

		return args;
	}

	/**
	 * Resolve the prepared arguments stored in the given bean definition.
	 */
	private Object[] resolvePreparedArguments(
			String beanName, RootBeanDefinition mbd, BeanWrapper bw, Executable executable, Object[] argsToResolve) {
		//获取到我们自定义的类型转化器
		TypeConverter customConverter = this.beanFactory.getCustomTypeConverter();
		TypeConverter converter = (customConverter != null ? customConverter : bw);
		//获取我们的bean定义值解析器
		BeanDefinitionValueResolver valueResolver =
				new BeanDefinitionValueResolver(this.beanFactory, beanName, mbd, converter);
		//获取我们构造函数的参数对象
		Class<?>[] paramTypes = executable.getParameterTypes();

		Object[] resolvedArgs = new Object[argsToResolve.length];
		//循环我们的构造函数参数对象
		for (int argIndex = 0; argIndex < argsToResolve.length; argIndex++) {
			//获取参数对象
			Object argValue = argsToResolve[argIndex];
			MethodParameter methodParam = MethodParameter.forExecutable(executable, argIndex);
			GenericTypeResolver.resolveParameterType(methodParam, executable.getDeclaringClass());
			if (argValue instanceof AutowiredArgumentMarker) {
				argValue = resolveAutowiredArgument(methodParam, beanName, null, converter);
			}
			else if (argValue instanceof BeanMetadataElement) {
				argValue = valueResolver.resolveValueIfNecessary("constructor argument", argValue);
			}
			else if (argValue instanceof String) {
				argValue = this.beanFactory.evaluateBeanDefinitionString((String) argValue, mbd);
			}
			Class<?> paramType = paramTypes[argIndex];
			try {
				resolvedArgs[argIndex] = converter.convertIfNecessary(argValue, paramType, methodParam);
			}
			catch (TypeMismatchException ex) {
				throw new UnsatisfiedDependencyException(
						mbd.getResourceDescription(), beanName, new InjectionPoint(methodParam),
						"Could not convert argument value of type [" + ObjectUtils.nullSafeClassName(argValue) +
						"] to required type [" + paramType.getName() + "]: " + ex.getMessage());
			}
		}
		return resolvedArgs;
	}

	protected Constructor<?> getUserDeclaredConstructor(Constructor<?> constructor) {
		Class<?> declaringClass = constructor.getDeclaringClass();
		Class<?> userClass = ClassUtils.getUserClass(declaringClass);
		if (userClass != declaringClass) {
			try {
				return userClass.getDeclaredConstructor(constructor.getParameterTypes());
			}
			catch (NoSuchMethodException ex) {
				// No equivalent constructor on user class (superclass)...
				// Let's proceed with the given constructor as we usually would.
			}
		}
		return constructor;
	}

	/**
	 * Template method for resolving the specified argument which is supposed to be autowired.
	 */
	@Nullable
	protected Object resolveAutowiredArgument(MethodParameter param, String beanName,
			@Nullable Set<String> autowiredBeanNames, TypeConverter typeConverter) {

		if (InjectionPoint.class.isAssignableFrom(param.getParameterType())) {
			InjectionPoint injectionPoint = currentInjectionPoint.get();
			if (injectionPoint == null) {
				throw new IllegalStateException("No current InjectionPoint available for " + param);
			}
			return injectionPoint;
		}
		return this.beanFactory.resolveDependency(
				new DependencyDescriptor(param, true), beanName, autowiredBeanNames, typeConverter);
	}

	static InjectionPoint setCurrentInjectionPoint(@Nullable InjectionPoint injectionPoint) {
		InjectionPoint old = currentInjectionPoint.get();
		if (injectionPoint != null) {
			currentInjectionPoint.set(injectionPoint);
		}
		else {
			currentInjectionPoint.remove();
		}
		return old;
	}


	/**
	 * Private inner class for holding argument combinations.
	 */
	private static class ArgumentsHolder {

		public final Object[] rawArguments;

		public final Object[] arguments;

		public final Object[] preparedArguments;

		public boolean resolveNecessary = false;

		public ArgumentsHolder(int size) {
			this.rawArguments = new Object[size];
			this.arguments = new Object[size];
			this.preparedArguments = new Object[size];
		}

		public ArgumentsHolder(Object[] args) {
			this.rawArguments = args;
			this.arguments = args;
			this.preparedArguments = args;
		}

		public int getTypeDifferenceWeight(Class<?>[] paramTypes) {
			// If valid arguments found, determine type difference weight.
			// Try type difference weight on both the converted arguments and
			// the raw arguments. If the raw weight is better, use it.
			// Decrease raw weight by 1024 to prefer it over equal converted weight.
			int typeDiffWeight = MethodInvoker.getTypeDifferenceWeight(paramTypes, this.arguments);
			int rawTypeDiffWeight = MethodInvoker.getTypeDifferenceWeight(paramTypes, this.rawArguments) - 1024;
			return (rawTypeDiffWeight < typeDiffWeight ? rawTypeDiffWeight : typeDiffWeight);
		}

		public int getAssignabilityWeight(Class<?>[] paramTypes) {
			for (int i = 0; i < paramTypes.length; i++) {
				if (!ClassUtils.isAssignableValue(paramTypes[i], this.arguments[i])) {
					return Integer.MAX_VALUE;
				}
			}
			for (int i = 0; i < paramTypes.length; i++) {
				if (!ClassUtils.isAssignableValue(paramTypes[i], this.rawArguments[i])) {
					return Integer.MAX_VALUE - 512;
				}
			}
			return Integer.MAX_VALUE - 1024;
		}

		public void storeCache(RootBeanDefinition mbd, Executable constructorOrFactoryMethod) {
			synchronized (mbd.constructorArgumentLock) {
				mbd.resolvedConstructorOrFactoryMethod = constructorOrFactoryMethod;
				mbd.constructorArgumentsResolved = true;
				if (this.resolveNecessary) {
					mbd.preparedConstructorArguments = this.preparedArguments;
				}
				else {
					mbd.resolvedConstructorArguments = this.arguments;
				}
			}
		}
	}


	/**
	 * Marker for autowired arguments in a cached argument array.
 	 */
	private static class AutowiredArgumentMarker {
	}


	/**
	 * Delegate for checking Java 6's {@link ConstructorProperties} annotation.
	 */
	private static class ConstructorPropertiesChecker {

		@Nullable
		public static String[] evaluate(Constructor<?> candidate, int paramCount) {
			ConstructorProperties cp = candidate.getAnnotation(ConstructorProperties.class);
			if (cp != null) {
				String[] names = cp.value();
				if (names.length != paramCount) {
					throw new IllegalStateException("Constructor annotated with @ConstructorProperties but not " +
							"corresponding to actual number of parameters (" + paramCount + "): " + candidate);
				}
				return names;
			}
			else {
				return null;
			}
		}
	}

}
