defaultsingletonbeanregistry.java

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/*
 * 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.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.LinkedHashMap;
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.apache.commons.logging.LogFactory;

import org.springframework.beans.factory.BeanCreationException;
import org.springframework.beans.factory.BeanCreationNotAllowedException;
import org.springframework.beans.factory.BeanCurrentlyInCreationException;
import org.springframework.beans.factory.DisposableBean;
import org.springframework.beans.factory.ObjectFactory;
import org.springframework.beans.factory.config.SingletonBeanRegistry;
import org.springframework.core.CollectionFactory;
import org.springframework.core.SimpleAliasRegistry;
import org.springframework.util.Assert;
import org.springframework.util.StringUtils;

/**
 * Generic registry for shared bean instances, implementing the
 * {@link org.springframework.beans.factory.config.SingletonBeanRegistry}.
 * Allows for registering singleton instances that should be shared
 * for all callers of the registry, to be obtained via bean name.
 *
 * <p>Also supports registration of
 * {@link org.springframework.beans.factory.DisposableBean} instances,
 * (which might or might not correspond to registered singletons),
 * to be destroyed on shutdown of the registry. Dependencies between
 * beans can be registered to enforce an appropriate shutdown order.
 *
 * <p>This class mainly serves as base class for
 * {@link org.springframework.beans.factory.BeanFactory} implementations,
 * factoring out the common management of singleton bean instances. Note that
 * the {@link org.springframework.beans.factory.config.ConfigurableBeanFactory}
 * interface extends the {@link SingletonBeanRegistry} interface.
 *
 * <p>Note that this class assumes neither a bean definition concept
 * nor a specific creation process for bean instances, in contrast to
 * {@link AbstractBeanFactory} and {@link DefaultListableBeanFactory}
 * (which inherit from it). Can alternatively also be used as a nested
 * helper to delegate to.
 *
 * @author Juergen Hoeller
 * @since 2.0
 * @see #registerSingleton
 * @see #registerDisposableBean
 * @see org.springframework.beans.factory.DisposableBean
 * @see org.springframework.beans.factory.config.ConfigurableBeanFactory
 */
public class DefaultSingletonBeanRegistry extends SimpleAliasRegistry implements SingletonBeanRegistry {

	/**
	 * Internal marker for a null singleton object:
	 * used as marker value for concurrent Maps (which don't support null values).
	 */
	protected static final Object NULL_OBJECT = new Object();


	/** Logger available to subclasses */
	protected final Log logger = LogFactory.getLog(getClass());

	/** Cache of singleton objects: bean name --> bean instance */
	private final Map singletonObjects = CollectionFactory.createConcurrentMapIfPossible(16);

	/** Cache of singleton factories: bean name --> ObjectFactory */
	private final Map singletonFactories = new HashMap();

	/** Cache of early singleton objects: bean name --> bean instance */
	private final Map earlySingletonObjects = new HashMap();

	/** Set of registered singletons, containing the bean names in registration order */
	private final Set registeredSingletons = new LinkedHashSet(16);

	/** Names of beans that are currently in creation */
	private final Set singletonsCurrentlyInCreation = Collections.synchronizedSet(new HashSet());

	/** List of suppressed Exceptions, available for associating related causes */
	private List suppressedExceptions;

	/** Flag that indicates whether we're currently within destroySingletons */
	private boolean singletonsCurrentlyInDestruction = false;

	/** Disposable bean instances: bean name --> disposable instance */
	private final Map disposableBeans = new LinkedHashMap(16);

	/** Map between dependent bean names: bean name --> Set of dependent bean names */
	private final Map dependentBeanMap = CollectionFactory.createConcurrentMapIfPossible(16);

	/** Map between depending bean names: bean name --> Set of bean names for the bean's dependencies */
	private final Map dependenciesForBeanMap = CollectionFactory.createConcurrentMapIfPossible(16);


	public void registerSingleton(String beanName, Object singletonObject) throws IllegalStateException {
		Assert.notNull(beanName, "'beanName' must not be null");
		synchronized (this.singletonObjects) {
			Object oldObject = this.singletonObjects.get(beanName);
			if (oldObject != null) {
				throw new IllegalStateException("Could not register object [" + singletonObject +
						"] under bean name '" + beanName + "': there is already object [" + oldObject + "] bound");
			}
			addSingleton(beanName, singletonObject);
		}
	}

	/**
	 * Add the given singleton object to the singleton cache of this factory.
	 * <p>To be called for eager registration of singletons.
	 * @param beanName the name of the bean
	 * @param singletonObject the singleton object
	 */
	protected void addSingleton(String beanName, Object singletonObject) {
		synchronized (this.singletonObjects) {
			this.singletonObjects.put(beanName, (singletonObject != null ? singletonObject : NULL_OBJECT));
			this.singletonFactories.remove(beanName);
			this.earlySingletonObjects.remove(beanName);
			this.registeredSingletons.add(beanName);
		}
	}

	/**
	 * Add the given singleton factory for building the specified singleton
	 * if necessary.
	 * <p>To be called for eager registration of singletons, e.g. to be able to
	 * resolve circular references.
	 * @param beanName the name of the bean
	 * @param singletonFactory the factory for the singleton object
	 */
	protected void addSingletonFactory(String beanName, ObjectFactory singletonFactory) {
		Assert.notNull(singletonFactory, "Singleton factory must not be null");
		synchronized (this.singletonObjects) {
			if (!this.singletonObjects.containsKey(beanName)) {
				this.singletonFactories.put(beanName, singletonFactory);
				this.earlySingletonObjects.remove(beanName);
				this.registeredSingletons.add(beanName);
			}
		}
	}

	public Object getSingleton(String beanName) {
		return getSingleton(beanName, true);
	}

	/**
	 * Return the (raw) singleton object registered under the given name.
	 * <p>Checks already instantiated singletons and also allows for an early
	 * reference to a currently created singleton (resolving a circular reference).
	 * @param beanName the name of the bean to look for
	 * @param allowEarlyReference whether early references should be created or not
	 * @return the registered singleton object, or <code>null</code> if none found
	 */
	protected Object getSingleton(String beanName, boolean allowEarlyReference) {
		Object singletonObject = this.singletonObjects.get(beanName);
		if (singletonObject == null) {
			synchronized (this.singletonObjects) {
				singletonObject = this.earlySingletonObjects.get(beanName);
				if (singletonObject == null && allowEarlyReference) {
					ObjectFactory singletonFactory = (ObjectFactory) this.singletonFactories.remove(beanName);
					if (singletonFactory != null) {
						singletonObject = singletonFactory.getObject();
						this.earlySingletonObjects.put(beanName, singletonObject);
					}
				}
			}
		}
		return (singletonObject != NULL_OBJECT ? singletonObject : null);
	}

	/**
	 * Return the (raw) singleton object registered under the given name,
	 * creating and registering a new one if none registered yet.
	 * @param beanName the name of the bean
	 * @param singletonFactory the ObjectFactory to lazily create the singleton
	 * with, if necessary
	 * @return the registered singleton object
	 */
	public Object getSingleton(String beanName, ObjectFactory singletonFactory) {
		Assert.notNull(beanName, "'beanName' must not be null");
		synchronized (this.singletonObjects) {
			Object singletonObject = this.singletonObjects.get(beanName);
			if (singletonObject == null) {
				if (this.singletonsCurrentlyInDestruction) {
					throw new BeanCreationNotAllowedException(beanName,
							"Singleton bean creation not allowed while the singletons of this factory are in destruction " +
							"(Do not request a bean from a BeanFactory in a destroy method implementation!)");
				}
				if (logger.isDebugEnabled()) {
					logger.debug("Creating shared instance of singleton bean '" + beanName + "'");
				}
				beforeSingletonCreation(beanName);
				boolean recordSuppressedExceptions = (this.suppressedExceptions == null);
				if (recordSuppressedExceptions) {
					this.suppressedExceptions = new LinkedList();
				}
				try {
					singletonObject = singletonFactory.getObject();
				}
				catch (BeanCreationException ex) {
					for (Iterator it = this.suppressedExceptions.iterator(); it.hasNext();) {
						ex.addRelatedCause((Exception) it.next());
					}
					throw ex;
				}
				finally {
					if (recordSuppressedExceptions) {
						this.suppressedExceptions = null;
					}
					afterSingletonCreation(beanName);
				}
				addSingleton(beanName, singletonObject);
			}
			return (singletonObject != NULL_OBJECT ? singletonObject : null);
		}