public Object getBean(String name) throws BeansException {return this.doGetBean(name, (Class)null, (Object[])null, false);}

protected <T> T doGetBean(String name, Class<T> requiredType, final Object[] args, boolean typeCheckOnly) throws BeansException {final String beanName = this.transformedBeanName(name);Object sharedInstance = this.getSingleton(beanName);Object bean;if (sharedInstance != null && args == null) {if (this.logger.isDebugEnabled()) {if (this.isSingletonCurrentlyInCreation(beanName)) {this.logger.debug("Returning eagerly cached instance of singleton bean '" + beanName + "' that is not fully initialized yet - a consequence of a circular reference");} else {this.logger.debug("Returning cached instance of singleton bean '" + beanName + "'");}}bean = this.getObjectForBeanInstance(sharedInstance, name, beanName, (RootBeanDefinition)null);} else {if (this.isPrototypeCurrentlyInCreation(beanName)) {throw new BeanCurrentlyInCreationException(beanName);}BeanFactory parentBeanFactory = this.getParentBeanFactory();if (parentBeanFactory != null && !this.containsBeanDefinition(beanName)) {String nameToLookup = this.originalBeanName(name);if (args != null) {return parentBeanFactory.getBean(nameToLookup, args);}return parentBeanFactory.getBean(nameToLookup, requiredType);}if (!typeCheckOnly) {this.markBeanAsCreated(beanName);}try {final RootBeanDefinition mbd = this.getMergedLocalBeanDefinition(beanName);this.checkMergedBeanDefinition(mbd, beanName, args);String[] dependsOn = mbd.getDependsOn();String[] var11;if (dependsOn != null) {var11 = dependsOn;int var12 = dependsOn.length;for(int var13 = 0; var13 < var12; ++var13) {String dependsOnBean = var11[var13];if (this.isDependent(beanName, dependsOnBean)) {throw new BeanCreationException(mbd.getResourceDescription(), beanName, "Circular depends-on relationship between '" + beanName + "' and '" + dependsOnBean + "'");}this.registerDependentBean(dependsOnBean, beanName);this.getBean(dependsOnBean);}}if (mbd.isSingleton()) {sharedInstance = this.getSingleton(beanName, new ObjectFactory<Object>() {public Object getObject() throws BeansException {try {return AbstractBeanFactory.this.createBean(beanName, mbd, args);} catch (BeansException var2) {AbstractBeanFactory.this.destroySingleton(beanName);throw var2;}}});bean = this.getObjectForBeanInstance(sharedInstance, name, beanName, mbd);} else if (mbd.isPrototype()) {var11 = null;Object prototypeInstance;try {this.beforePrototypeCreation(beanName);prototypeInstance = this.createBean(beanName, mbd, args);} finally {this.afterPrototypeCreation(beanName);}bean = this.getObjectForBeanInstance(prototypeInstance, name, beanName, mbd);} else {String scopeName = mbd.getScope();Scope scope = (Scope)this.scopes.get(scopeName);if (scope == null) {throw new IllegalStateException("No Scope registered for scope '" + scopeName + "'");}try {Object scopedInstance = scope.get(beanName, new ObjectFactory<Object>() {public Object getObject() throws BeansException {AbstractBeanFactory.this.beforePrototypeCreation(beanName);Object var1;try {var1 = AbstractBeanFactory.this.createBean(beanName, mbd, args);} finally {AbstractBeanFactory.this.afterPrototypeCreation(beanName);}return var1;}});bean = this.getObjectForBeanInstance(scopedInstance, name, beanName, mbd);} catch (IllegalStateException var21) {throw new BeanCreationException(beanName, "Scope '" + scopeName + "' is not active for the current thread; " + "consider defining a scoped proxy for this bean if you intend to refer to it from a singleton", var21);}}} catch (BeansException var23) {this.cleanupAfterBeanCreationFailure(beanName);throw var23;}}if (requiredType != null && bean != null && !requiredType.isAssignableFrom(bean.getClass())) {try {return this.getTypeConverter().convertIfNecessary(bean, requiredType);} catch (TypeMismatchException var22) {if (this.logger.isDebugEnabled()) {this.logger.debug("Failed to convert bean '" + name + "' to required type [" + ClassUtils.getQualifiedName(requiredType) + "]", var22);}throw new BeanNotOfRequiredTypeException(name, requiredType, bean.getClass());}} else {return bean;}}

protected String transformedBeanName(String name) {return this.canonicalName(BeanFactoryUtils.transformedBeanName(name));}

public static String transformedBeanName(String name) {Assert.notNull(name, "'name' must not be null");String beanName;for(beanName = name; beanName.startsWith("&"); beanName = beanName.substring("&".length())) {}return beanName;}

public String canonicalName(String name) {String canonicalName = name;String resolvedName;do {resolvedName = (String)this.aliasMap.get(canonicalName);if (resolvedName != null) {canonicalName = resolvedName;}} while(resolvedName != null);return canonicalName;}

@Override@Nullablepublic 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*/@Nullableprotected 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;}

    /** 获取给定bean实例的对象，要么bean实例本身，要么当它是一个FactroyBean时，它创建出来的对象**/protected Object getObjectForBeanInstance(Object beanInstance, String name, String beanName, @Nullable RootBeanDefinition mbd) {// 如果指定的name是&开头即工厂相关的，但又不是FactoryBean类型，则抛出异常，类型验证不通过if (BeanFactoryUtils.isFactoryDereference(name)) {if (beanInstance instanceof NullBean) {return beanInstance;}if (!(beanInstance instanceof FactoryBean)) {throw new BeanIsNotAFactoryException(beanName, beanInstance.getClass());}}
// 现在我们有个这个bean实例，但是这个bean实例可能是普通bean也可能是FactoryBean，如果是FactoryBean，那么我们使用它来获取工厂实例，如果调用者需要的是FactoryBean本身，那么beanName参数需要带"&"if (!(beanInstance instanceof FactoryBean) || BeanFactoryUtils.isFactoryDereference(name)) {return beanInstance;}// 到这里就明确是一个FactoryBean，因为如果不是上边已经返回了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.if (mbd == null && containsBeanDefinition(beanName)) {mbd = getMergedLocalBeanDefinition(beanName);}boolean synthetic = (mbd != null && mbd.isSynthetic());object = getObjectFromFactoryBean(factory, beanName, !synthetic);}return object;}

     /**  获得从给定的FactoryBean获取出来的对象*/protected Object getObjectFromFactoryBean(FactoryBean<?> factory, String beanName, boolean shouldPostProcess) {if (factory.isSingleton() && containsSingleton(beanName)) {synchronized (getSingletonMutex()) {Object object = this.factoryBeanObjectCache.get(beanName);if (object == null) {object = doGetObjectFromFactoryBean(factory, beanName);// Only post-process and store if not put there already during getObject() call above// (e.g. because of circular reference processing triggered by custom getBean calls)Object alreadyThere = this.factoryBeanObjectCache.get(beanName);if (alreadyThere != null) {object = alreadyThere;}else {if (shouldPostProcess) {if (isSingletonCurrentlyInCreation(beanName)) {// Temporarily return non-post-processed object, not storing it yet..return object;}beforeSingletonCreation(beanName);try {object = postProcessObjectFromFactoryBean(object, beanName);}catch (Throwable ex) {throw new BeanCreationException(beanName,"Post-processing of FactoryBean's singleton object failed", ex);}finally {afterSingletonCreation(beanName);}}if (containsSingleton(beanName)) {this.factoryBeanObjectCache.put(beanName, object);}}}return object;}}else {Object object = doGetObjectFromFactoryBean(factory, beanName);if (shouldPostProcess) {try {object = postProcessObjectFromFactoryBean(object, beanName);}catch (Throwable ex) {throw new BeanCreationException(beanName, "Post-processing of FactoryBean's object failed", ex);}}return object;}}

private Object doGetObjectFromFactoryBean(final FactoryBean<?> factory, final String beanName)throws BeanCreationException {Object object;try {if (System.getSecurityManager() != null) {AccessControlContext acc = getAccessControlContext();try {object = AccessController.doPrivileged((PrivilegedExceptionAction<Object>) factory::getObject, acc);}catch (PrivilegedActionException pae) {throw pae.getException();}}else {object = factory.getObject();}}catch (FactoryBeanNotInitializedException ex) {throw new BeanCurrentlyInCreationException(beanName, ex.toString());}catch (Throwable ex) {throw new BeanCreationException(beanName, "FactoryBean threw exception on object creation", ex);}// Do not accept a null value for a FactoryBean that's not fully// initialized yet: Many FactoryBeans just return null then.if (object == null) {if (isSingletonCurrentlyInCreation(beanName)) {throw new BeanCurrentlyInCreationException(beanName, "FactoryBean which is currently in creation returned null from getObject");}object = new NullBean();}return object;}

// Create bean instance.if (mbd.isSingleton()) {sharedInstance = getSingleton(beanName, () -> {try {return createBean(beanName, mbd, args);}catch (BeansException ex) {// Explicitly remove instance from singleton cache: It might have been put there// eagerly by the creation process, to allow for circular reference resolution.// Also remove any beans that received a temporary reference to the bean.
                            destroySingleton(beanName);throw ex;}});bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd);}

    /*** 返回beanName注册过的单例对象，如果没有，那么创建并注册该beanName的实例*/public Object getSingleton(String beanName, ObjectFactory<?> singletonFactory) {Assert.notNull(beanName, "Bean name must not be null");synchronized (this.singletonObjects) {Object singletonObject = this.singletonObjects.get(beanName);  // 1if (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); // 2boolean newSingleton = false;boolean recordSuppressedExceptions = (this.suppressedExceptions == null);if (recordSuppressedExceptions) {this.suppressedExceptions = new LinkedHashSet<>();}try {singletonObject = singletonFactory.getObject(); // 3newSingleton = 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); // 4}if (newSingleton) {addSingleton(beanName, singletonObject);}}return 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); // 放入缓存this.singletonFactories.remove(beanName);this.earlySingletonObjects.remove(beanName);this.registeredSingletons.add(beanName);}}

                    sharedInstance = getSingleton(beanName, () -> { // 这里是jdk8引入的函数是写法，这里其实就是ObjectFactroy的一个匿名类实现try {return createBean(beanName, mbd, args);}catch (BeansException ex) {// Explicitly remove instance from singleton cache: It might have been put there// eagerly by the creation process, to allow for circular reference resolution.// Also remove any beans that received a temporary reference to the bean.
                            destroySingleton(beanName);throw ex;}});

/*** Central method of this class: creates a bean instance,* populates the bean instance, applies post-processors, etc.* @see #doCreateBean*/@Overrideprotected Object createBean(String beanName, RootBeanDefinition mbd, @Nullable Object[] args)throws BeanCreationException {if (logger.isTraceEnabled()) {logger.trace("Creating instance of bean '" + beanName + "'");}RootBeanDefinition mbdToUse = mbd;// Make sure bean class is actually resolv1ed at this point, and// clone the bean definition in case of a dynamically resolved Class// which cannot be stored in the shared merged bean definition.Class<?> resolvedClass = resolveBeanClass(mbd, beanName);if (resolvedClass != null && !mbd.hasBeanClass() && mbd.getBeanClassName() != null) {mbdToUse = new RootBeanDefinition(mbd);mbdToUse.setBeanClass(resolvedClass);}// Prepare method overrides.try {mbdToUse.prepareMethodOverrides();}catch (BeanDefinitionValidationException ex) {throw new BeanDefinitionStoreException(mbdToUse.getResourceDescription(),beanName, "Validation of method overrides failed", ex);}try {// Give BeanPostProcessors a chance to return a proxy instead of the target bean instance.Object bean = resolveBeforeInstantiation(beanName, mbdToUse);if (bean != null) {return bean;}}catch (Throwable ex) {throw new BeanCreationException(mbdToUse.getResourceDescription(), beanName,"BeanPostProcessor before instantiation of bean failed", ex);}try {Object beanInstance = doCreateBean(beanName, mbdToUse, args);if (logger.isTraceEnabled()) {logger.trace("Finished creating instance of bean '" + beanName + "'");}return beanInstance;}catch (BeanCreationException | ImplicitlyAppearedSingletonException ex) {// A previously detected exception with proper bean creation context already,// or illegal singleton state to be communicated up to DefaultSingletonBeanRegistry.throw ex;}catch (Throwable ex) {throw new BeanCreationException(mbdToUse.getResourceDescription(), beanName, "Unexpected exception during bean creation", ex);}}

/*** Validate and prepare the method overrides defined for this bean.* Checks for existence of a method with the specified name.* @throws BeanDefinitionValidationException in case of validation failure*/public void prepareMethodOverrides() throws BeanDefinitionValidationException {// Check that lookup methods exists.if (hasMethodOverrides()) {Set<MethodOverride> overrides = getMethodOverrides().getOverrides();synchronized (overrides) {for (MethodOverride mo : overrides) {prepareMethodOverride(mo);}}}}/*** Validate and prepare the given method override.* Checks for existence of a method with the specified name,* marking it as not overloaded if none found.* @param mo the MethodOverride object to validate* @throws BeanDefinitionValidationException in case of validation failure*/protected void prepareMethodOverride(MethodOverride mo) throws BeanDefinitionValidationException {int count = ClassUtils.getMethodCountForName(getBeanClass(), mo.getMethodName());if (count == 0) {throw new BeanDefinitionValidationException("Invalid method override: no method with name '" + mo.getMethodName() +"' on class [" + getBeanClassName() + "]");}else if (count == 1) {// Mark override as not overloaded, to avoid the overhead of arg type checking.mo.setOverloaded(false);}}