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/*
 * Copyright 2002-2005 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.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.springframework.beans.BeanWrapper;
import org.springframework.beans.BeansException;
import org.springframework.beans.TypeMismatchException;
import org.springframework.beans.factory.BeanCreationException;
import org.springframework.beans.factory.config.BeanDefinition;
import org.springframework.beans.factory.config.BeanDefinitionHolder;
import org.springframework.beans.factory.config.RuntimeBeanReference;
import org.springframework.beans.factory.config.TypedStringValue;
import org.springframework.core.CollectionFactory;

/**
 * Helper class for use by BeanFactory implementations,
 * resolving values contained in BeanDefinition objects
 * into the actual values applied to th target bean instance.
 *
 * 

Works on an AbstractBeanFactory and a plain BeanDefinition object. * Used by AbstractAutowireCapableBeanFactory. * * @author Juergen Hoeller * @since 1.2 * @see AbstractAutowireCapableBeanFactory */ public class BeanDefinitionValueResolver { protected final Log logger = LogFactory.getLog(getClass()); private final AbstractBeanFactory beanFactory; private final String beanName; private final BeanDefinition beanDefinition; /** * Create a new BeanDefinitionValueResolver for the given BeanFactory * and BeanDefinition. * @param beanFactory the BeanFactory to resolve against * @param beanName the name of the bean that we work on * @param beanDefinition the BeanDefinition of the bean that we work on */ public BeanDefinitionValueResolver( AbstractBeanFactory beanFactory, String beanName, BeanDefinition beanDefinition) { this.beanName = beanName; this.beanDefinition = beanDefinition; this.beanFactory = beanFactory; } /** * Given a PropertyValue, return a value, resolving any references to other * beans in the factory if necessary. The value could be: *

  • A BeanDefinition, which leads to the creation of a corresponding * new bean instance. Singleton flags and names of such "inner beans" * are always ignored: Inner beans are anonymous prototypes. *
  • A RuntimeBeanReference, which must be resolved. *
  • A ManagedList. This is a special collection that may contain * RuntimeBeanReferences or Collections that will need to be resolved. *
  • A ManagedSet. May also contain RuntimeBeanReferences or * Collections that will need to be resolved. *
  • A ManagedMap. In this case the value may be a RuntimeBeanReference * or Collection that will need to be resolved. *
  • An ordinary object or null, in which case it's left alone. */ public Object resolveValueIfNecessary(String argName, Object value) throws BeansException { // We must check each value to see whether it requires a runtime reference // to another bean to be resolved. if (value instanceof BeanDefinitionHolder) { // Resolve BeanDefinitionHolder: contains BeanDefinition with name and aliases. BeanDefinitionHolder bdHolder = (BeanDefinitionHolder) value; return resolveInnerBeanDefinition(bdHolder.getBeanName(), bdHolder.getBeanDefinition()); } else if (value instanceof BeanDefinition) { // Resolve plain BeanDefinition, without contained name: use dummy name. BeanDefinition bd = (BeanDefinition) value; return resolveInnerBeanDefinition("(inner bean)", bd); } else if (value instanceof RuntimeBeanReference) { RuntimeBeanReference ref = (RuntimeBeanReference) value; return resolveReference(argName, ref); } else if (value instanceof ManagedList) { // May need to resolve contained runtime references. return resolveManagedList(argName, (List) value); } else if (value instanceof ManagedSet) { // May need to resolve contained runtime references. return resolveManagedSet(argName, (Set) value); } else if (value instanceof ManagedMap) { // May need to resolve contained runtime references. return resolveManagedMap(argName, (Map) value); } else if (value instanceof TypedStringValue) { // Convert value to target type here. TypedStringValue typedStringValue = (TypedStringValue) value; try { return this.beanFactory.doTypeConversionIfNecessary( typedStringValue.getValue(), typedStringValue.getTargetType()); } catch (TypeMismatchException ex) { // Improve the message by showing the context. throw new BeanCreationException( this.beanDefinition.getResourceDescription(), this.beanName, "Error converting typed String value for " + argName, ex); } } else { // no need to resolve value return value; } } /** * Resolve an inner bean definition. */ private Object resolveInnerBeanDefinition(String innerBeanName, BeanDefinition innerBd) throws BeansException { if (logger.isDebugEnabled()) { logger.debug("Resolving inner bean definition '" + innerBeanName + "' of bean '" + this.beanName + "'"); } RootBeanDefinition mergedInnerBd = this.beanFactory.getMergedBeanDefinition(innerBeanName, innerBd); Object innerBean = this.beanFactory.createBean(innerBeanName, mergedInnerBd, null); if (mergedInnerBd.isSingleton()) { this.beanFactory.registerDependentBean(innerBeanName, this.beanName); } return this.beanFactory.getObjectForSharedInstance(innerBeanName, innerBean); } /** * Resolve a reference to another bean in the factory. */ private Object resolveReference(String argName, RuntimeBeanReference ref) throws BeansException { if (logger.isDebugEnabled()) { logger.debug("Resolving reference from property '" + argName + "' in bean '" + this.beanName + "' to bean '" + ref.getBeanName() + "'"); } try { if (ref.isToParent()) { if (this.beanFactory.getParentBeanFactory() == null) { throw new BeanCreationException( this.beanDefinition.getResourceDescription(), this.beanName, "Can't resolve reference to bean '" + ref.getBeanName() + "' in parent factory: no parent factory available"); } return this.beanFactory.getParentBeanFactory().getBean(ref.getBeanName()); } else { if (this.beanDefinition.isSingleton()) { this.beanFactory.registerDependentBean(ref.getBeanName(), this.beanName); } return this.beanFactory.getBean(ref.getBeanName()); } } catch (BeansException ex) { throw new BeanCreationException( this.beanDefinition.getResourceDescription(), this.beanName, "Can't resolve reference to bean '" + ref.getBeanName() + "' while setting property '" + argName + "'", ex); } } /** * For each element in the ManagedList, resolve reference if necessary. */ private List resolveManagedList(String argName, List ml) throws BeansException { List resolved = new ArrayList(ml.size()); for (int i = 0; i < ml.size(); i++) { resolved.add( resolveValueIfNecessary( argName + BeanWrapper.PROPERTY_KEY_PREFIX + i + BeanWrapper.PROPERTY_KEY_SUFFIX, ml.get(i))); } return resolved; } /** * For each element in the ManagedList, resolve reference if necessary. */ private Set resolveManagedSet(String argName, Set ms) throws BeansException { Set resolved = CollectionFactory.createLinkedSetIfPossible(ms.size()); int i = 0; for (Iterator it = ms.iterator(); it.hasNext();) { resolved.add( resolveValueIfNecessary( argName + BeanWrapper.PROPERTY_KEY_PREFIX + i + BeanWrapper.PROPERTY_KEY_SUFFIX, it.next())); i++; } return resolved; } /** * For each element in the ManagedMap, resolve reference if necessary. */ private Map resolveManagedMap(String argName, Map mm) throws BeansException { Map resolved = CollectionFactory.createLinkedMapIfPossible(mm.size()); Iterator it = mm.entrySet().iterator(); while (it.hasNext()) { Map.Entry entry = (Map.Entry) it.next(); resolved.put( resolveValueIfNecessary(argName, entry.getKey()), resolveValueIfNecessary( argName + BeanWrapper.PROPERTY_KEY_PREFIX + entry.getKey() + BeanWrapper.PROPERTY_KEY_SUFFIX, entry.getValue())); } return resolved; } }




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