constructorresolver.java

来自「spring framework 2.5.4源代码」· Java 代码 · 共 648 行 · 第 1/2 页

/*
 * Copyright 2002-2008 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.Method;
import java.lang.reflect.Modifier;
import java.util.HashSet;
import java.util.Iterator;
import java.util.LinkedHashSet;
import java.util.Map;
import java.util.Set;

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.UnsatisfiedDependencyException;
import org.springframework.beans.factory.config.AutowireCapableBeanFactory;
import org.springframework.beans.factory.config.ConstructorArgumentValues;
import org.springframework.beans.factory.config.DependencyDescriptor;
import org.springframework.beans.factory.config.TypedStringValue;
import org.springframework.core.GenericTypeResolver;
import org.springframework.core.JdkVersion;
import org.springframework.core.MethodParameter;
import org.springframework.util.MethodInvoker;
import org.springframework.util.ObjectUtils;
import org.springframework.util.ReflectionUtils;

/**
 * Helper class for resolving constructors and factory methods.
 * Performs constructor resolution through argument matching.
 *
 * <p>Operates on an {@link AbstractBeanFactory} and an {@link InstantiationStrategy}.
 * Used by {@link AbstractAutowireCapableBeanFactory}.
 *
 * @author Juergen Hoeller
 * @author Rob Harrop
 * @author Mark Fisher
 * @since 2.0
 * @see #autowireConstructor
 * @see #instantiateUsingFactoryMethod
 * @see AbstractAutowireCapableBeanFactory
 */
class ConstructorResolver {

	private final AbstractBeanFactory beanFactory;

	private final AutowireCapableBeanFactory autowireFactory;

	private final InstantiationStrategy instantiationStrategy;

	private final TypeConverter typeConverter;


	/**
	 * Create a new ConstructorResolver for the given factory and instantiation strategy.
	 * @param beanFactory the BeanFactory to work with
	 * @param autowireFactory the BeanFactory as AutowireCapableBeanFactory
	 * @param instantiationStrategy the instantiate strategy for creating bean instances
	 * @param typeConverter the TypeConverter to use (or <code>null</code> for using the default)
	 */
	public ConstructorResolver(AbstractBeanFactory beanFactory, AutowireCapableBeanFactory autowireFactory,
			InstantiationStrategy instantiationStrategy, TypeConverter typeConverter) {

		this.beanFactory = beanFactory;
		this.autowireFactory = autowireFactory;
		this.instantiationStrategy = instantiationStrategy;
		this.typeConverter = typeConverter;
	}


	/**
	 * "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</code> if none)
	 * @param explicitArgs argument values passed in programmatically via the getBean method,
	 * or <code>null</code> if none (-> use constructor argument values from bean definition)
	 * @return a BeanWrapper for the new instance
	 */
	protected BeanWrapper autowireConstructor(
			String beanName, RootBeanDefinition mbd, Constructor[] chosenCtors, Object[] explicitArgs) {

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

		Constructor constructorToUse = null;
		Object[] argsToUse = null;

		if (explicitArgs != null) {
			argsToUse = explicitArgs;
		}
		else {
			constructorToUse = (Constructor) mbd.resolvedConstructorOrFactoryMethod;
			if (constructorToUse != null) {
				// Found a cached constructor...
				argsToUse = mbd.resolvedConstructorArguments;
				if (argsToUse == null) {
					Class[] paramTypes = constructorToUse.getParameterTypes();
					Object[] argsToResolve = mbd.preparedConstructorArguments;
					TypeConverter converter = (this.typeConverter != null ? this.typeConverter : bw);
					BeanDefinitionValueResolver valueResolver =
							new BeanDefinitionValueResolver(this.beanFactory, beanName, mbd, converter);
					argsToUse = new Object[argsToResolve.length];
					for (int i = 0; i < argsToResolve.length; i++) {
						Object argValue = argsToResolve[i];
						MethodParameter methodParam = new MethodParameter(constructorToUse, i);
						if (JdkVersion.isAtLeastJava15()) {
							GenericTypeResolver.resolveParameterType(methodParam, constructorToUse.getDeclaringClass());
						}
						if (argValue instanceof AutowiredArgumentMarker) {
							argValue = resolveAutowiredArgument(methodParam, beanName, null, converter);
						}
						else if (argValue instanceof BeanMetadataElement) {
							argValue = valueResolver.resolveValueIfNecessary("constructor argument", argValue);
						}
						argsToUse[i] = converter.convertIfNecessary(argValue, paramTypes[i], methodParam);
					}
				}
			}
		}

		if (constructorToUse == null) {
			// Need to resolve the constructor.
			boolean autowiring = (chosenCtors != null ||
					mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_CONSTRUCTOR);
			ConstructorArgumentValues resolvedValues = null;

			int minNrOfArgs = 0;
			if (explicitArgs != null) {
				minNrOfArgs = explicitArgs.length;
			}
			else {
				ConstructorArgumentValues cargs = mbd.getConstructorArgumentValues();
				resolvedValues = new ConstructorArgumentValues();
				minNrOfArgs = resolveConstructorArguments(beanName, mbd, bw, cargs, resolvedValues);
			}

			// Take specified constructors, if any.
			Constructor[] candidates =
					(chosenCtors != null ? chosenCtors : mbd.getBeanClass().getDeclaredConstructors());
			AutowireUtils.sortConstructors(candidates);
			int minTypeDiffWeight = Integer.MAX_VALUE;

			for (int i = 0; i < candidates.length; i++) {
				Constructor candidate = candidates[i];
				Class[] paramTypes = candidate.getParameterTypes();

				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;
				}
				if (paramTypes.length < minNrOfArgs) {
					throw new BeanCreationException(mbd.getResourceDescription(), beanName,
							minNrOfArgs + " constructor arguments specified but no matching constructor found in bean '" +
							beanName + "' " +
							"(hint: specify index and/or type arguments for simple parameters to avoid type ambiguities)");
				}

				ArgumentsHolder args = null;

				if (resolvedValues != null) {
					// Try to resolve arguments for current constructor.
					try {
						args = createArgumentArray(
								beanName, mbd, resolvedValues, bw, paramTypes, candidate, autowiring);
					}
					catch (UnsatisfiedDependencyException ex) {
						if (this.beanFactory.logger.isTraceEnabled()) {
							this.beanFactory.logger.trace(
									"Ignoring constructor [" + candidate + "] of bean '" + beanName + "': " + ex);
						}
						if (i == candidates.length - 1 && constructorToUse == null) {
							throw ex;
						}
						else {
							// Swallow and try next constructor.
							this.beanFactory.onSuppressedException(ex);
							continue;
						}
					}
				}

				else {
					// Explicit arguments given -> arguments length must match exactly.
					if (paramTypes.length != explicitArgs.length) {
						continue;
					}
					args = new ArgumentsHolder(explicitArgs);
				}

				int typeDiffWeight = args.getTypeDifferenceWeight(paramTypes);
				// Choose this constructor if it represents the closest match.
				if (typeDiffWeight < minTypeDiffWeight) {
					constructorToUse = candidate;
					argsToUse = args.arguments;
					minTypeDiffWeight = typeDiffWeight;
				}
			}

			if (constructorToUse == null) {
				throw new BeanCreationException(
						mbd.getResourceDescription(), beanName, "Could not resolve matching constructor");
			}

			if (explicitArgs == null) {
				mbd.resolvedConstructorOrFactoryMethod = constructorToUse;
			}
		}

		try {
			Object beanInstance = this.instantiationStrategy.instantiate(
					mbd, beanName, this.beanFactory, constructorToUse, argsToUse);
			bw.setWrappedInstance(beanInstance);
			return bw;
		}
		catch (Throwable ex) {
			throw new BeanCreationException(mbd.getResourceDescription(), beanName, "Instantiation of bean failed", ex);
		}
	}

	/**
	 * 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</code> if none (-> use constructor argument values from bean definition)
	 * @return a BeanWrapper for the new instance
	 */
	public BeanWrapper instantiateUsingFactoryMethod(String beanName, RootBeanDefinition mbd, Object[] explicitArgs) {
		BeanWrapperImpl bw = new BeanWrapperImpl();
		this.beanFactory.initBeanWrapper(bw);

		Class factoryClass = null;
		Object factoryBean = null;
		boolean isStatic = true;

		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 (factoryBean == null) {
				throw new BeanCreationException(mbd.getResourceDescription(), beanName,
						"factory-bean '" + factoryBeanName + "' returned null");
			}
			factoryClass = factoryBean.getClass();
			isStatic = false;
		}
		else {
			// It's a static factory method on the bean class.
			factoryClass = mbd.getBeanClass();
		}

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

		if (explicitArgs != null) {
			argsToUse = explicitArgs;
		}
		else {
			factoryMethodToUse = (Method) mbd.resolvedConstructorOrFactoryMethod;
			if (factoryMethodToUse != null) {
				// Found a cached factory method...
				argsToUse = mbd.resolvedConstructorArguments;
				if (argsToUse == null) {
					Class[] paramTypes = factoryMethodToUse.getParameterTypes();
					Object[] argsToResolve = mbd.preparedConstructorArguments;
					TypeConverter converter = (this.typeConverter != null ? this.typeConverter : bw);
					BeanDefinitionValueResolver valueResolver =
							new BeanDefinitionValueResolver(this.beanFactory, beanName, mbd, converter);
					argsToUse = new Object[argsToResolve.length];
					for (int i = 0; i < argsToResolve.length; i++) {
						Object argValue = argsToResolve[i];
						MethodParameter methodParam = new MethodParameter(factoryMethodToUse, i);
						if (JdkVersion.isAtLeastJava15()) {
							GenericTypeResolver.resolveParameterType(methodParam, factoryClass);
						}
						if (argValue instanceof AutowiredArgumentMarker) {
							argValue = resolveAutowiredArgument(methodParam, beanName, null, converter);
						}
						else if (argValue instanceof BeanMetadataElement) {
							argValue = valueResolver.resolveValueIfNecessary("factory method argument", argValue);
						}
						argsToUse[i] = converter.convertIfNecessary(argValue, paramTypes[i], methodParam);
					}
				}
			}
		}