Spring 源码分析--bean的加载详细分析
Posted 否定之否定
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一：缓存中获取单例bean
前面已经提到过，单例在Spring的同一个容器内只会被创建一次，后续再获取bean直接从单例缓存中获取，当然这里也只是尝试加载，首先尝试从缓存中加载，然后再次尝试从singletonFactories中加载。因为在创建单例bean的时候会存在依赖注入的情况，而在创建依赖的时候为了避免循环依赖，Spring创建bean的原则是不等bean创建完成就会将创建bean的ObjectFactory提早曝光加入到缓存中，一旦下一个bean创建时需要依赖上个bean,则直接使用ObjectFactory。
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<String, Object> singletonObjects = new ConcurrentHashMap<String, Object>(256); /** Cache of singleton factories: bean name --> ObjectFactory */ private final Map<String, ObjectFactory<?>> singletonFactories = new HashMap<String, ObjectFactory<?>>(16); /** Cache of early singleton objects: bean name --> bean instance */ private final Map<String, Object> earlySingletonObjects = new HashMap<String, Object>(16); /** Set of registered singletons, containing the bean names in registration order */ private final Set<String> registeredSingletons = new LinkedHashSet<String>(256); /** Names of beans that are currently in creation */ private final Set<String> singletonsCurrentlyInCreation = Collections.newSetFromMap(new ConcurrentHashMap<String, Boolean>(16)); /** Names of beans currently excluded from in creation checks */ private final Set<String> inCreationCheckExclusions = Collections.newSetFromMap(new ConcurrentHashMap<String, Boolean>(16)); /** List of suppressed Exceptions, available for associating related causes */ private Set<Exception> suppressedExceptions; /** Flag that indicates whether we\'re currently within destroySingletons */ private boolean singletonsCurrentlyInDestruction = false; /** Disposable bean instances: bean name --> disposable instance */ private final Map<String, Object> disposableBeans = new LinkedHashMap<String, Object>(); /** Map between containing bean names: bean name --> Set of bean names that the bean contains */ private final Map<String, Set<String>> containedBeanMap = new ConcurrentHashMap<String, Set<String>>(16); /** Map between dependent bean names: bean name --> Set of dependent bean names */ private final Map<String, Set<String>> dependentBeanMap = new ConcurrentHashMap<String, Set<String>>(64); /** Map between depending bean names: bean name --> Set of bean names for the bean\'s dependencies */ private final Map<String, Set<String>> dependenciesForBeanMap = new ConcurrentHashMap<String, Set<String>>(64); @Override 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); } } } @Override 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} if none found */ protected Object getSingleton(String beanName, boolean allowEarlyReference) { Object singletonObject = this.singletonObjects.get(beanName); if (singletonObject == null && isSingletonCurrentlyInCreation(beanName)) { synchronized (this.singletonObjects) { singletonObject = this.earlySingletonObjects.get(beanName); if (singletonObject == null && allowEarlyReference) { ObjectFactory<?> singletonFactory = 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 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 newSingleton = false; boolean recordSuppressedExceptions = (this.suppressedExceptions == null); if (recordSuppressedExceptions) { this.suppressedExceptions = new LinkedHashSet<Exception>(); } try { singletonObject = singletonFactory.getObject(); newSingleton = true; } catch (IllegalStateException ex) { // Has the singleton object implicitly appeared in the meantime -> // if yes, proceed with it since the exception indicates that state. singletonObject = this.singletonObjects.get(beanName); if (singletonObject == null) { throw ex; } } catch (BeanCreationException ex) { if (recordSuppressedExceptions) { for (Exception suppressedException : this.suppressedExceptions) { ex.addRelatedCause(suppressedException); } } throw ex; } finally { if (recordSuppressedExceptions) { this.suppressedExceptions = null; } afterSingletonCreation(beanName); } if (newSingleton) { 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); } } @Override public boolean containsSingleton(String beanName) { return this.singletonObjects.containsKey(beanName); } @Override public String[] getSingletonNames() { synchronized (this.singletonObjects) { return StringUtils.toStringArray(this.registeredSingletons); } } @Override public int getSingletonCount() { synchronized (this.singletonObjects) { return this.registeredSingletons.size(); } } public void setCurrentlyInCreation(String beanName, boolean inCreation) { Assert.notNull(beanName, "Bean name must not be null"); if (!inCreation) { this.inCreationCheckExclusions.add(beanName); } else { this.inCreationCheckExclusions.remove(beanName); } } public boolean isCurrentlyInCreation(String beanName) { Assert.notNull(beanName, "Bean name must not be null"); return (!this.inCreationCheckExclusions.contains(beanName) && isActuallyInCreation(beanName)); } protected boolean isActuallyInCreation(String beanName) { return isSingletonCurrentlyInCreation(beanName); } /** * Return whether the specified singleton bean is currently in creation * (within the entire factory). * @param beanName the name of the bean */ public boolean isSingletonCurrentlyInCreation(String beanName) { return this.singletonsCurrentlyInCreation.contains(beanName); } /** * Callback before singleton creation. * <p>The 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.inCreationCheckExclusions.contains(beanName) && !this.singletonsCurrentlyInCreation.add(beanName)) { throw new BeanCurrentlyInCreationException(beanName); } } /** * Callback after singleton creation. * <p>The 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.inCreationCheckExclusions.contains(beanName) && !this.singletonsCurrentlyInCreation.remove(beanName)) { throw new IllegalStateException("Singleton \'" + beanName + "\' isn\'t currently in creation"); } } /** * Add the given bean to the list of disposable beans in this registry. * <p>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) { // A quick check for an existing entry upfront, avoiding synchronization... Set<String> containedBeans = this.containedBeanMap.get(containingBeanName); if (containedBeans != null && containedBeans.contains(containedBeanName)) { return; } // No entry yet -> fully synchronized manipulation of the containedBeans Set synchronized (this.containedBeanMap) { containedBeans = this.containedBeanMap.get(containingBeanName); if (containedBeans == null) { containedBeans = new LinkedHashSet<String>(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) { // A quick check for an existing entry upfront, avoiding synchronization... String canonicalName = canonicalName(beanName); Set<String> dependentBeans = this.dependentBeanMap.get(canonicalName); if (dependentBeans != null && dependentBeans.contains(dependentBeanName)) { return; } // No entry yet -> fully synchronized manipulation of the dependentBeans Set synchronized (this.dependentBeanMap) { dependentBeans = this.dependentBeanMap.get(canonicalName); if (dependentBeans == null) { dependentBeans = new LinkedHashSet<String>(8); this.dependentBeanMap.put(canonicalName, dependentBeans); } dependentBeans.add(dependentBeanName); } synchronized (this.dependenciesForBeanMap) { Set<String> dependenciesForBean = this.dependenciesForBeanMap.get(dependentBeanName); if (dependenciesForBean == null) { dependenciesForBean = new LinkedHashSet<String>(8); this.dependenciesForBeanMap.put(dependentBeanName, dependenciesForBean); } dependenciesForBean.add(canonicalName); } } /** * Determine whether the specified dependent bean has been registered as * dependent on the given bean or on any of its transitive dependencies. * @param beanName the name of the bean to check * @param dependentBeanName the name of the dependent bean * @since 4.0 */ protected boolean isDependent(String beanName, String dependentBeanName) { return isDependent(beanName, dependentBeanName, null); } private boolean isDependent(String beanName, String dependentBeanName, Set<String> alreadySeen) { if (alreadySeen != null && alreadySeen.contains(beanName)) { return false; } String canonicalName = canonicalName(beanName); Set<String> dependentBeans = this.dependentBeanMap.get(canonicalName); if (dependentBeans == null) { return false; } if (dependentBeans.contains(dependentBeanName)) { return true; } for (String transitiveDependency : dependentBeans) { if (alreadySeen == null) { alreadySeen = new HashSet<String>(); } alreadySeen.add(beanName); if (isDependent(transitiveDependency, dependentBeanName, alreadySeen)) { return true; } } return false; } /** * 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<String> dependentBeans = this.dependentBeanMap.get(beanName); if (dependentBeans == null) { return new String[0]; } return StringUtils.toStringArray(dependentBeans); } /** * 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<String> dependenciesForBean = this.dependenciesForBeanMap.get(beanName); if (dependenciesForBean == null) { return new String[0]; } return dependenciesForBean.toArray(new String[dependenciesForBean.size()]); } public void destroySingletons() { if (logger.isDebugEnabled()) { logger.debug("Destroying singletons in " + this); } synchronized (this.singletonObjects) { this.singletonsCurrentlyInDestruction = true; } String[] disposableBeanNames; synchronized (this.disposableBeans) { 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} * 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; 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<String> dependencies = this.dependentBeanMap.remove(beanName); if (dependencies != null) { if (logger.isDebugEnabled()) { logger.debug("Retrieved dependent beans for bean \'" + beanName + "\': " + dependencies); } for (String dependentBeanName : dependencies) { 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<String> containedBeans = this.containedBeanMap.remove(beanName); if (containedBeans != null) { for (String containedBeanName : containedBeans) { destroySingleton(containedBeanName); } } // Remove destroyed bean from other beans\' dependencies. synchronized (this.dependentBeanMap) { for (Iterator<Map.Entry<String, Set<String>>> it = this.dependentBeanMap.entrySet().iterator(); it.hasNext();) { Map.Entry<String, Set<String>> entry = it.next(); Set<String> dependenciesToClean = entry.getValue(); dependenciesToClean.remove(beanName); if (dependenciesToClean.isEmpty()) { it.remove(); } } } // Remove destroyed bean\'s prepared dependency information. this.dependenciesForBeanMap.remove(beanName); } /** * Exposes the singleton mutex to subclasses and external collaborators. * <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. */ public final Object getSingletonMutex() { return this.singletonObjects; } }
二：从bean的实例中获取对象
在getBean方法中，getObjectForBeanInstance是个高频率使用的方法，无论是从缓存中获得bean还是根据不同的scope加载bean。总之，我们得到的bean的实例后要做的第一步就是调用这个方法来检测一下正确性，其实就是永恒检测当前bean是否是FactoryBean类型的bean，如果是，那么需要调用该bean对应的FactoryBean实例中的getObject()作为返回值。
无论是从缓存中获取到的bean还是通过不同scope策略加载的bean都只是最原始的bean状态，并不一定是我们最终想要的bean。
（2.1）getObjectForBeanInstance
public abstract class AbstractBeanFactory extends FactoryBeanRegistrySupport implements ConfigurableBeanFactory { /** * Get the object for the given bean instance, either the bean * instance itself or its created object in case of a FactoryBean. * @param beanInstance the shared bean instance * @param name name that may include factory dereference prefix * @param beanName the canonical bean name * @param mbd the merged bean definition * @return the object to expose for the bean */ protected Object getObjectForBeanInstance( Object beanInstance, String name, String beanName, RootBeanDefinition mbd) { // Don\'t let calling code try to dereference the factory if the bean isn\'t a factory. if (BeanFactoryUtils.isFactoryDereference(name) && !(beanInstance instanceof FactoryBean)) { throw new BeanIsNotAFactoryException(transformedBeanName(name), beanInstance.getClass()); } // Now we have the bean instance, which may be a normal bean or a FactoryBean. // If it\'s a FactoryBean, we use it to create a bean instance, unless the // caller actually wants a reference to the factory. if (!(beanInstance instanceof FactoryBean) || BeanFactoryUtils.isFactoryDereference(name)) { return beanInstance; } Object object = null; if (mbd == null) { object = getCachedObjectForFactoryBean(beanName); } if (object == null) { // Return bean instance from factory. FactoryBean<?> factory = (FactoryBean<?>) beanInstance; // Caches object obtained from FactoryBean if it is a singleton. Spring 源码分析--bean的加载整体分析