Spring之单例Bean的创建

final String beanName = transformedBeanName(name); Object bean; // Eagerly check singleton cache for manually registered singletons. Object sharedInstance = getSingleton(beanName); if (sharedInstance != null && args == null) { if (eEnabled()) { if (isSingletonCurrentlyInCreation(beanName)) { ("Returning eagerly cached instance of singleton bean '" + beanName + "' that is not fully initialized yet - a consequence of a circular reference"); } else { ("Returning cached instance of singleton bean '" + beanName + "'"); } } bean = getObjectForBeanInstance(sharedInstance, name, beanName, null); } else { // Fail if we're already creating this bean instance: // We're assumably within a circular reference. if (isPrototypeCurrentlyInCreation(beanName)) { throw new BeanCurrentlyInCreationException(beanName); } // Check if bean definition exists in this factory. BeanFactory parentBeanFactory = getParentBeanFactory(); if (parentBeanFactory != null && !containsBeanDefinition(beanName)) { // Not found -> check parent. String nameToLookup = originalBeanName(name); if (parentBeanFactory instanceof AbstractBeanFactory) { return ((AbstractBeanFactory) parentBeanFactory).doGetBean( nameToLookup, requiredType, args, typeCheckOnly); } else if (args != null) { // Delegation to parent with explicit args. return (T) n(nameToLookup, args); } else if (requiredType != null) { // No args -> delegate to standard getBean method. return n(nameToLookup, requiredType); } else { return (T) n(nameToLookup); } } if (!typeCheckOnly) { markBeanAsCreated(beanName); } try { final RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName); checkMergedBeanDefinition(mbd, beanName, args); // Guarantee initialization of beans that the current bean depends on. String[] dependsOn = endsOn(); if (dependsOn != null) { for (String dep : dependsOn) { if (isDependent(beanName, dep)) { throw new BeanCreationException(ourceDescription(), beanName, "Circular depends-on relationship between '" + beanName + "' and '" + dep + "'"); } registerDependentBean(dep, beanName); try { getBean(dep);

getBean(dep); } catch (NoSuchBeanDefinitionException ex) { throw new BeanCreationException(ourceDescription(), beanName, "'" + beanName + "' depends on missing bean '" + dep + "'", ex); } } } // Create bean instance. if (leton()) { 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); } else if (otype()) { // It's a prototype -> create a new instance. Object prototypeInstance = null; try { beforePrototypeCreation(beanName); prototypeInstance = createBean(beanName, mbd, args); } finally { afterPrototypeCreation(beanName); } bean = getObjectForBeanInstance(prototypeInstance, name, beanName, mbd); } else { String scopeName = pe(); final Scope scope = (scopeName); if (scope == null) { throw new IllegalStateException("No Scope registered for scope name '" + scopeName + "'"); } try { Object scopedInstance = (beanName, () -> { beforePrototypeCreation(beanName); try { return createBean(beanName, mbd, args); } finally { afterPrototypeCreation(beanName); } }); bean = getObjectForBeanInstance(scopedInstance, name, beanName, mbd); } catch (IllegalStateException ex) { 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", ex); } } } catch (BeansException ex) {

@Overrideprotected Object createBean(String beanName, RootBeanDefinition mbd, @Nullable Object[] args) throws BeanCreationException { if (eEnabled()) { ("Creating instance of bean '" + beanName + "'"); } RootBeanDefinition mbdToUse = mbd; // Make sure bean class is actually resolved 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 && !nClass() && nClassName() != null) { mbdToUse = new RootBeanDefinition(mbd); nClass(resolvedClass); } // Prepare method overrides. try { eMethodOverrides(); } catch (BeanDefinitionValidationException ex) { throw new BeanDefinitionStoreException(ourceDescription(), 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(ourceDescription(), beanName, "BeanPostProcessor before instantiation of bean failed", ex); } try { Object beanInstance = doCreateBean(beanName, mbdToUse, args); if (eEnabled()) { ("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( ourceDescription(), beanName, "Unexpected exception during bean creation", ex); }}

// to support styles of field injection. if (!hetic() && hasInstantiationAwareBeanPostProcessors()) { for (BeanPostProcessor bp : getBeanPostProcessors()) { if (bp instanceof InstantiationAwareBeanPostProcessor) { InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp; if (!ocessAfterInstantiation(ppedInstance(), beanName)) { return; } } } } PropertyValues pvs = (pertyValues() ? pertyValues() : null); int resolvedAutowireMode = olvedAutowireMode(); if (resolvedAutowireMode == AUTOWIRE_BY_NAME || resolvedAutowireMode == AUTOWIRE_BY_TYPE) { MutablePropertyValues newPvs = new MutablePropertyValues(pvs); // Add property values based on autowire by name if applicable. if (resolvedAutowireMode == AUTOWIRE_BY_NAME) { autowireByName(beanName, mbd, bw, newPvs); } // Add property values based on autowire by type if applicable. if (resolvedAutowireMode == AUTOWIRE_BY_TYPE) { autowireByType(beanName, mbd, bw, newPvs); } pvs = newPvs; } boolean hasInstAwareBpps = hasInstantiationAwareBeanPostProcessors(); boolean needsDepCheck = (endencyCheck() != ENCY_CHECK_NONE); PropertyDescriptor[] filteredPds = null; if (hasInstAwareBpps) { if (pvs == null) { pvs = pertyValues(); } for (BeanPostProcessor bp : getBeanPostProcessors()) { if (bp instanceof InstantiationAwareBeanPostProcessor) { InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp; PropertyValues pvsToUse = ocessProperties(pvs, ppedInstance(), beanName); if (pvsToUse == null) { if (filteredPds == null) { filteredPds = filterPropertyDescriptorsForDependencyCheck(bw, aching); } pvsToUse = ocessPropertyValues(pvs, filteredPds, ppedInstance(), beanName); if (pvsToUse == null) { return; } } pvs = pvsToUse; } } } if (needsDepCheck) { if (filteredPds == null) { filteredPds = filterPropertyDescriptorsForDependencyCheck(bw, aching); } checkDependencies(beanName, mbd, filteredPds, pvs); } if (pvs != null) { applyPropertyValues(beanName, mbd, bw, pvs); }}