/*
* 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.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 Set 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 containing bean names: bean name --> Set of bean names that the bean contains */
private final Map containedBeanMap = CollectionFactory.createConcurrentMapIfPossible(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.get(beanName);
if (singletonFactory != null) {
singletonObject = singletonFactory.getObject();
this.earlySingletonObjects.put(beanName, singletonObject);
this.singletonFactories.remove(beanName);
}
}
}
}
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 LinkedHashSet();
}
try {
singletonObject = singletonFactory.getObject();
}
catch (BeanCreationException ex) {
if (recordSuppressedExceptions) {
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);
}
}
/**
* Register an Exception that happened to get suppressed during the creation of a
* singleton bean instance, e.g. a temporary circular reference resolution problem.
* @param ex the Exception to register
*/
protected void onSuppressedException(Exception ex) {
synchronized (this.singletonObjects) {
if (this.suppressedExceptions != null) {
this.suppressedExceptions.add(ex);
}
}
}
/**
* Remove the bean with the given name from the singleton cache of this factory,
* to be able to clean up eager registration of a singleton if creation failed.
* @param beanName the name of the bean
* @see #getSingletonMutex()
*/
protected void removeSingleton(String beanName) {
synchronized (this.singletonObjects) {
this.singletonObjects.remove(beanName);
this.singletonFactories.remove(beanName);
this.earlySingletonObjects.remove(beanName);
this.registeredSingletons.remove(beanName);
}
}
public boolean containsSingleton(String beanName) {
return (this.singletonObjects.containsKey(beanName));
}
public String[] getSingletonNames() {
synchronized (this.singletonObjects) {
return StringUtils.toStringArray(this.registeredSingletons);
}
}
public int getSingletonCount() {
synchronized (this.singletonObjects) {
return this.registeredSingletons.size();
}
}
/**
* Callback before singleton creation.
* <p>Default implementation register the singleton as currently in creation.
* @param beanName the name of the singleton about to be created
* @see #isSingletonCurrentlyInCreation
*/
protected void beforeSingletonCreation(String beanName) {
if (!this.singletonsCurrentlyInCreation.add(beanName)) {
throw new BeanCurrentlyInCreationException(beanName);
}
}
/**
* Callback after singleton creation.
* <p>Default implementation marks the singleton as not in creation anymore.
* @param beanName the name of the singleton that has been created
* @see #isSingletonCurrentlyInCreation
*/
protected void afterSingletonCreation(String beanName) {
if (!this.singletonsCurrentlyInCreation.remove(beanName)) {
throw new IllegalStateException("Singleton '" + beanName + "' isn't currently in creation");
}
}
/**
* Return whether the specified singleton bean is currently in creation
* (within the entire factory).
* @param beanName the name of the bean
*/
public final boolean isSingletonCurrentlyInCreation(String beanName) {
return this.singletonsCurrentlyInCreation.contains(beanName);
}
/**
* Add the given bean to the list of disposable beans in this registry.
* Disposable beans usually correspond to registered singletons,
* matching the bean name but potentially being a different instance
* (for example, a DisposableBean adapter for a singleton that does not
* naturally implement Spring's DisposableBean interface).
* @param beanName the name of the bean
* @param bean the bean instance
*/
public void registerDisposableBean(String beanName, DisposableBean bean) {
synchronized (this.disposableBeans) {
this.disposableBeans.put(beanName, bean);
}
}
/**
* Register a containment relationship between two beans,
* e.g. between an inner bean and its containing outer bean.
* <p>Also registers the containing bean as dependent on the contained bean
* in terms of destruction order.
* @param containedBeanName the name of the contained (inner) bean
* @param containingBeanName the name of the containing (outer) bean
* @see #registerDependentBean
*/
public void registerContainedBean(String containedBeanName, String containingBeanName) {
synchronized (this.containedBeanMap) {
Set containedBeans = (Set) this.containedBeanMap.get(containingBeanName);
if (containedBeans == null) {
containedBeans = new LinkedHashSet(8);
this.containedBeanMap.put(containingBeanName, containedBeans);
}
containedBeans.add(containedBeanName);
}
registerDependentBean(containedBeanName, containingBeanName);
}
/**
* Register a dependent bean for the given bean,
* to be destroyed before the given bean is destroyed.
* @param beanName the name of the bean
* @param dependentBeanName the name of the dependent bean
*/
public void registerDependentBean(String beanName, String dependentBeanName) {
synchronized (this.dependentBeanMap) {
Set dependentBeans = (Set) this.dependentBeanMap.get(beanName);
if (dependentBeans == null) {
dependentBeans = new LinkedHashSet(8);
this.dependentBeanMap.put(beanName, dependentBeans);
}
dependentBeans.add(dependentBeanName);
}
synchronized (this.dependenciesForBeanMap) {
Set dependenciesForBean = (Set) this.dependenciesForBeanMap.get(dependentBeanName);
if (dependenciesForBean == null) {
dependenciesForBean = new LinkedHashSet(8);
this.dependenciesForBeanMap.put(dependentBeanName, dependenciesForBean);
}
dependenciesForBean.add(beanName);
}
}
/**
* Determine whether a dependent bean has been registered for the given name.
* @param beanName the name of the bean to check
*/
protected boolean hasDependentBean(String beanName) {
return this.dependentBeanMap.containsKey(beanName);
}
/**
* Return the names of all beans which depend on the specified bean, if any.
* @param beanName the name of the bean
* @return the array of dependent bean names, or an empty array if none
*/
public String[] getDependentBeans(String beanName) {
Set dependentBeans = (Set) this.dependentBeanMap.get(beanName);
if (dependentBeans == null) {
return new String[0];
}
return (String[]) dependentBeans.toArray(new String[dependentBeans.size()]);
}
/**
* Return the names of all beans that the specified bean depends on, if any.
* @param beanName the name of the bean
* @return the array of names of beans which the bean depends on,
* or an empty array if none
*/
public String[] getDependenciesForBean(String beanName) {
Set dependenciesForBean = (Set) this.dependenciesForBeanMap.get(beanName);
if (dependenciesForBean == null) {
return new String[0];
}
return (String[]) dependenciesForBean.toArray(new String[dependenciesForBean.size()]);
}
public void destroySingletons() {
if (logger.isInfoEnabled()) {
logger.info("Destroying singletons in " + this);
}
synchronized (this.singletonObjects) {
this.singletonsCurrentlyInDestruction = true;
}
synchronized (this.disposableBeans) {
String[] disposableBeanNames = StringUtils.toStringArray(this.disposableBeans.keySet());
for (int i = disposableBeanNames.length - 1; i >= 0; i--) {
destroySingleton(disposableBeanNames[i]);
}
}
this.containedBeanMap.clear();
this.dependentBeanMap.clear();
this.dependenciesForBeanMap.clear();
synchronized (this.singletonObjects) {
this.singletonObjects.clear();
this.singletonFactories.clear();
this.earlySingletonObjects.clear();
this.registeredSingletons.clear();
this.singletonsCurrentlyInDestruction = false;
}
}
/**
* Destroy the given bean. Delegates to <code>destroyBean</code>
* if a corresponding disposable bean instance is found.
* @param beanName the name of the bean
* @see #destroyBean
*/
public void destroySingleton(String beanName) {
// Remove a registered singleton of the given name, if any.
removeSingleton(beanName);
// Destroy the corresponding DisposableBean instance.
DisposableBean disposableBean = null;
synchronized (this.disposableBeans) {
disposableBean = (DisposableBean) this.disposableBeans.remove(beanName);
}
destroyBean(beanName, disposableBean);
}
/**
* Destroy the given bean. Must destroy beans that depend on the given
* bean before the bean itself. Should not throw any exceptions.
* @param beanName the name of the bean
* @param bean the bean instance to destroy
*/
protected void destroyBean(String beanName, DisposableBean bean) {
// Trigger destruction of dependent beans first...
Set dependencies = (Set) this.dependentBeanMap.remove(beanName);
if (dependencies != null) {
if (logger.isDebugEnabled()) {
logger.debug("Retrieved dependent beans for bean '" + beanName + "': " + dependencies);
}
for (Iterator it = dependencies.iterator(); it.hasNext();) {
String dependentBeanName = (String) it.next();
destroySingleton(dependentBeanName);
}
}
// Actually destroy the bean now...
if (bean != null) {
try {
bean.destroy();
}
catch (Throwable ex) {
logger.error("Destroy method on bean with name '" + beanName + "' threw an exception", ex);
}
}
// Trigger destruction of contained beans...
Set containedBeans = (Set) this.containedBeanMap.remove(beanName);
if (containedBeans != null) {
for (Iterator it = containedBeans.iterator(); it.hasNext();) {
String containedBeanName = (String) it.next();
destroySingleton(containedBeanName);
}
}
// Remove destroyed bean from other beans' dependencies.
synchronized (this.dependentBeanMap) {
for (Iterator it = this.dependentBeanMap.entrySet().iterator(); it.hasNext();) {
Map.Entry entry = (Map.Entry) it.next();
Set dependenciesToClean = (Set) entry.getValue();
dependenciesToClean.remove(beanName);
if (dependenciesToClean.isEmpty()) {
it.remove();
}
}
}
// Remove destroyed bean's prepared dependency information.
this.dependenciesForBeanMap.remove(beanName);
}
/**
* Expose the singleton mutex to subclasses.
* <p>Subclasses should synchronize on the given Object if they perform
* any sort of extended singleton creation phase. In particular, subclasses
* should <i>not</i> have their own mutexes involved in singleton creation,
* to avoid the potential for deadlocks in lazy-init situations.
*/
protected final Object getSingletonMutex() {
return this.singletonObjects;
}
}