目录
代码块1：applyMergedBeanDefinitionPostProcessors
代码块6：unsatisfiedNonSimpleProperties
代码块13：applyBeanPostProcessorsBeforeInitialization
代码块14：postProcessBeforeInitialization
代码块17：applyBeanPostProcessorsAfterInitialization
代码块18：registerDisposableBeanIfNecessary
代码块23：inferDestroyMethodIfNecessary
Spring IoC源码学习全系列
Spring IoC源码学习：ApplicationContext 刷新前的配置
Spring IoC源码学习：obtainFreshBeanFactory详解
Spring IoC源码学习：parseDefaultElement详解
Spring IoC源码学习：parseCustomElement详解
Spring IoC源码学习：context:component-scan节点详解
Spring IoC源码学习：invokeBeanFactoryPostProcessors详解
Spring IoC源码学习：registerBeanPostProcessors详解
Spring IoC源码学习：finishBeanFactoryInitialization详解
Spring IoC源码学习：createBean详解（上）
Spring IoC源码学习：createBean详解（下）
Spring IoC源码学习：finishRefresh详解
接着Spring IoC：createBean详解（上），我们继续解析创建 bean 实例的剩下内容。
首先，我们回到Spring IoC：createBean详解（上）中的代码块3，doCreateBean 方法。
protected Object doCreateBean(final String beanName, final RootBeanDefinition mbd, final Object[] args) throws BeanCreationException { // Instantiate the bean. // 1.新建Bean包装类 BeanWrapper instanceWrapper = null; if (mbd.isSingleton()) { // 2.如果是FactoryBean，则需要先移除未完成的FactoryBean实例的缓存 instanceWrapper = this.factoryBeanInstanceCache.remove(beanName); } if (instanceWrapper == null) { // 3.根据beanName、mbd、args，使用对应的策略创建Bean实例，并返回包装类BeanWrapper instanceWrapper = createBeanInstance(beanName, mbd, args); } // 4.拿到创建好的Bean实例 final Object bean = (instanceWrapper != null ? instanceWrapper.getWrappedInstance() : null); // 5.拿到Bean实例的类型 Class<?> beanType = (instanceWrapper != null ? instanceWrapper.getWrappedClass() : null); mbd.resolvedTargetType = beanType; // Allow post-processors to modify the merged bean definition. synchronized (mbd.postProcessingLock) { if (!mbd.postProcessed) { try { // 6.应用后置处理器MergedBeanDefinitionPostProcessor，允许修改MergedBeanDefinition， // Autowired注解正是通过此方法实现注入类型的预解析 applyMergedBeanDefinitionPostProcessors(mbd, beanType, beanName); } catch (Throwable ex) { throw new BeanCreationException(mbd.getResourceDescription(), beanName, "Post-processing of merged bean definition failed", ex); } mbd.postProcessed = true; } } // Eagerly cache singletons to be able to resolve circular references // even when triggered by lifecycle interfaces like BeanFactoryAware. // 7.判断是否需要提早曝光实例：单例 && 允许循环依赖 && 当前bean正在创建中 boolean earlySingletonExposure = (mbd.isSingleton() && this.allowCircularReferences && isSingletonCurrentlyInCreation(beanName)); if (earlySingletonExposure) { if (logger.isDebugEnabled()) { logger.debug("Eagerly caching bean '" + beanName + "' to allow for resolving potential circular references"); } // 8.提前曝光beanName的ObjectFactory，用于解决循环引用 addSingletonFactory(beanName, new ObjectFactory<Object>() { @Override public Object getObject() throws BeansException { // 8.1 应用后置处理器SmartInstantiationAwareBeanPostProcessor，允许返回指定bean的早期引用，若没有则直接返回bean return getEarlyBeanReference(beanName, mbd, bean); } }); } // Initialize the bean instance. 初始化bean实例。 Object exposedObject = bean; try { // 9.对bean进行属性填充；其中，可能存在依赖于其他bean的属性，则会递归初始化依赖的bean实例 populateBean(beanName, mbd, instanceWrapper); if (exposedObject != null) { // 10.对bean进行初始化 exposedObject = initializeBean(beanName, exposedObject, mbd); } } catch (Throwable ex) { if (ex instanceof BeanCreationException && beanName.equals(((BeanCreationException) ex).getBeanName())) { throw (BeanCreationException) ex; } else { throw new BeanCreationException( mbd.getResourceDescription(), beanName, "Initialization of bean failed", ex); } } if (earlySingletonExposure) { // 11.如果允许提前曝光实例，则进行循环依赖检查 Object earlySingletonReference = getSingleton(beanName, false); // 11.1 earlySingletonReference只有在当前解析的bean存在循环依赖的情况下才会不为空 if (earlySingletonReference != null) { if (exposedObject == bean) { // 11.2 如果exposedObject没有在initializeBean方法中被增强，则不影响之前的循环引用 exposedObject = earlySingletonReference; } else if (!this.allowRawInjectionDespiteWrapping && hasDependentBean(beanName)) { // 11.3 如果exposedObject在initializeBean方法中被增强 && 不允许在循环引用的情况下使用注入原始bean实例 // && 当前bean有被其他bean依赖 // 11.4 拿到依赖当前bean的所有bean的beanName数组 String[] dependentBeans = getDependentBeans(beanName); Set<String> actualDependentBeans = new LinkedHashSet<String>(dependentBeans.length); for (String dependentBean : dependentBeans) { // 11.5 尝试移除这些bean的实例，因为这些bean依赖的bean已经被增强了，他们依赖的bean相当于脏数据 if (!removeSingletonIfCreatedForTypeCheckOnly(dependentBean)) { // 11.6 移除失败的添加到 actualDependentBeans actualDependentBeans.add(dependentBean); } } if (!actualDependentBeans.isEmpty()) { // 11.7 如果存在移除失败的，则抛出异常，因为存在bean依赖了“脏数据” throw new BeanCurrentlyInCreationException(beanName, "Bean with name '" + beanName + "' has been injected into other beans [" + StringUtils.collectionToCommaDelimitedString(actualDependentBeans) + "] in its raw version as part of a circular reference, but has eventually been " + "wrapped. This means that said other beans do not use the final version of the " + "bean. This is often the result of over-eager type matching - consider using " + "'getBeanNamesOfType' with the 'allowEagerInit' flag turned off, for example."); } } } } // Register bean as disposable. try { // 12.注册用于销毁的bean，执行销毁操作的有三种：自定义destroy方法、DisposableBean接口、DestructionAwareBeanPostProcessor registerDisposableBeanIfNecessary(beanName, bean, mbd); } catch (BeanDefinitionValidationException ex) { throw new BeanCreationException( mbd.getResourceDescription(), beanName, "Invalid destruction signature", ex); } // 13.完成创建并返回 return exposedObject; }
3.根据 beanName、mbd、args，使用对应的策略创建 bean 实例，并返回包装类 BeanWrapper，见Spring IoC：createBean详解（上）中的代码块3。
6.应用后置处理器 MergedBeanDefinitionPostProcessor，允许修改MergedBeanDefinition，见代码块1详解。
8.提前曝光 beanName 的 ObjectFactory，用于解决循环引用，见代码块2详解。
8.1 应用后置处理器SmartInstantiationAwareBeanPostProcessor，允许返回指定 bean 的早期引用，见代码块3详解。
9.对 bean 进行属性填充；其中，可能存在依赖于其他bean 的属性，则会递归初始化依赖的 bean 实例，见代码块4详解。
10.对 bean 进行初始化，见代码块11详解。
11.1 earlySingletonReference 只有在当前解析的bean 存在循环依赖的情况下才会不为空。
因为如果不是循环依赖，只会在完全创建完 bean 实例才会添加到 singletonObjects 缓存。此时，我们正在创建 bean 的过程中，还没有完全创建完，singletonObjects缓存是肯定没有当前 beanName 的；而如果不存在循环引用，从 doGetBean 方法开始，getSingleton方法只会在最初 doGetBean 方法里调用一次，不存在循环引用，也就用不到提前曝光的ObjectFactory 来创建 bean 对象，从而 earlySingletonObjects 缓存肯定也是没有 beanName 的 bean 实例对象的，所以必然返回空。
12.注册用于销毁的 bean，执行销毁操作的有三种：自定义 destroy 方法、DisposableBean接口、DestructionAwareBeanPostProcessor，见代码块18详解。
代码块1：applyMergedBeanDefinitionPostProcessors
protected void applyMergedBeanDefinitionPostProcessors(RootBeanDefinition mbd, Class<?> beanType, String beanName) { // 1.获取BeanFactory中已注册的BeanPostProcessor for (BeanPostProcessor bp : getBeanPostProcessors()) { if (bp instanceof MergedBeanDefinitionPostProcessor) { // 2.调用MergedBeanDefinitionPostProcessor的postProcessMergedBeanDefinition方法， // 对指定bean的给定MergedBeanDefinition进行后置处理，@Autowire注解在这边对元数据进行预解析 MergedBeanDefinitionPostProcessor bdp = (MergedBeanDefinitionPostProcessor) bp; bdp.postProcessMergedBeanDefinition(mbd, beanType, beanName); } } }
调用MergedBeanDefinitionPostProcessor 的 postProcessMergedBeanDefinition 方法，对指定bean 的给定MergedBeanDefinition进行后置处理，@Autowire 注解在这边对元数据进行预解析，之后会单独介绍。
protected void addSingletonFactory(String beanName, ObjectFactory<?> singletonFactory) { Assert.notNull(singletonFactory, "Singleton factory must not be null"); synchronized (this.singletonObjects) { // 1.如果beanName不存在于singletonObjects缓存中 if (!this.singletonObjects.containsKey(beanName)) { // 2.将beanName和singletonFactory注册到singletonFactories缓存（beanName -> 该beanName的单例工厂） this.singletonFactories.put(beanName, singletonFactory); // 3.移除earlySingletonObjects缓存中的beanName（beanName -> beanName的早期单例对象） this.earlySingletonObjects.remove(beanName); // 4.将beanName注册到registeredSingletons缓存（已经注册的单例集合） this.registeredSingletons.add(beanName); } } }
在Spring IoC：finishBeanFactoryInitialization详解中的代码块7，我们通过提前曝光的 ObjectFactory 获得“不完整” 的 bean 实例，从而解决循环引用的问题，ObjectFactory 就是通过这边的 singletonObjects 缓存来进行曝光的。
protected Object getEarlyBeanReference(String beanName, RootBeanDefinition mbd, Object bean) { Object exposedObject = bean; // 1.如果bean不为空 && mbd不是合成 && 存在InstantiationAwareBeanPostProcessors if (bean != null && !mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) { for (BeanPostProcessor bp : getBeanPostProcessors()) { // 2.应用所有SmartInstantiationAwareBeanPostProcessor，调用getEarlyBeanReference方法 if (bp instanceof SmartInstantiationAwareBeanPostProcessor) { SmartInstantiationAwareBeanPostProcessor ibp = (SmartInstantiationAwareBeanPostProcessor) bp; // 3.允许SmartInstantiationAwareBeanPostProcessor返回指定bean的早期引用 exposedObject = ibp.getEarlyBeanReference(exposedObject, beanName); if (exposedObject == null) { return null; } } } } // 4.返回要作为bean引用公开的对象，如果没有SmartInstantiationAwareBeanPostProcessor修改，则返回的是入参的bean对象本身 return exposedObject; }
protected void populateBean(String beanName, RootBeanDefinition mbd, BeanWrapper bw) { // 1.返回此bean的属性值 PropertyValues pvs = mbd.getPropertyValues(); // 2.bw为空时的处理 if (bw == null) { if (!pvs.isEmpty()) { // 2.1 如果bw为空，属性不为空，抛异常，无法将属性值应用于null实例 throw new BeanCreationException( mbd.getResourceDescription(), beanName, "Cannot apply property values to null instance"); } else { // Skip property population phase for null instance. // 2.2 如果bw为空，属性也为空，则跳过 return; } } // Give any InstantiationAwareBeanPostProcessors the opportunity to modify the // state of the bean before properties are set. This can be used, for example, // to support styles of field injection. // 用于标识是否继续之后的属性填充 boolean continueWithPropertyPopulation = true; if (!mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) { // 3.1 如果mbd不是合成的 && 存在InstantiationAwareBeanPostProcessor，则遍历处理InstantiationAwareBeanPostProcessor for (BeanPostProcessor bp : getBeanPostProcessors()) { if (bp instanceof InstantiationAwareBeanPostProcessor) { InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp; // 3.2 在bean实例化后，属性填充之前被调用，允许修改bean的属性，如果返回false，则跳过之后的属性填充 if (!ibp.postProcessAfterInstantiation(bw.getWrappedInstance(), beanName)) { // 3.3 如果返回false，将continueWithPropertyPopulation赋值为false，代表要跳过之后的属性填充 continueWithPropertyPopulation = false; break; } } } } // 3.4 如果continueWithPropertyPopulation为false，则跳过之后的属性填充 if (!continueWithPropertyPopulation) { return; } // 4.解析自动装配模式为AUTOWIRE_BY_NAME和AUTOWIRE_BY_TYPE（现在几乎不用） if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_NAME || mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_TYPE) { MutablePropertyValues newPvs = new MutablePropertyValues(pvs); if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_NAME) { // 4.1 解析autowireByName的注入 autowireByName(beanName, mbd, bw, newPvs); } if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_TYPE) { // 4.2 解析autowireByType的注入 autowireByType(beanName, mbd, bw, newPvs); } pvs = newPvs; } // 5.BeanFactory是否注册过InstantiationAwareBeanPostProcessors boolean hasInstAwareBpps = hasInstantiationAwareBeanPostProcessors(); // 6.是否需要依赖检查 boolean needsDepCheck = (mbd.getDependencyCheck() != RootBeanDefinition.DEPENDENCY_CHECK_NONE); // 7.注册过InstantiationAwareBeanPostProcessors 或者 需要依赖检查 if (hasInstAwareBpps || needsDepCheck) { PropertyDescriptor[] filteredPds = filterPropertyDescriptorsForDependencyCheck(bw, mbd.allowCaching); if (hasInstAwareBpps) { // 7.1 应用后置处理器InstantiationAwareBeanPostProcessor for (BeanPostProcessor bp : getBeanPostProcessors()) { if (bp instanceof InstantiationAwareBeanPostProcessor) { InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp; // 7.1.1 应用后置处理器InstantiationAwareBeanPostProcessor的方法postProcessPropertyValues， // 进行属性填充前的再次处理。例子：现在最常用的@Autowire属性注入就是这边注入依赖的bean实例对象 pvs = ibp.postProcessPropertyValues(pvs, filteredPds, bw.getWrappedInstance(), beanName); if (pvs == null) { return; } } } } if (needsDepCheck) { // 7.2 依赖检查，对应depends-on属性 checkDependencies(beanName, mbd, filteredPds, pvs); } } // 8.将所有PropertyValues中的属性填充到bean中 applyPropertyValues(beanName, mbd, bw, pvs); }
4.1 解析 autowireByName 的注入，见代码块5详解。
4.2 解析 autowireByType 的注入，见代码块9详解。
7.1.1 应用后置处理器InstantiationAwareBeanPostProcessor 的方法 postProcessPropertyValues，进行属性填充前的再次处理。现在最常用的 @Autowire 属性注入就是这边注入依赖的 bean 实例对象，具体实现在 AutowiredAnnotationBeanPostProcessor，该内容会在之后介绍 @Autowire 的文章中单独介绍。
8.将所有 PropertyValues 中的属性填充到 bean 中，见代码块10详解。
protected void autowireByName( String beanName, AbstractBeanDefinition mbd, BeanWrapper bw, MutablePropertyValues pvs) { // 1.寻找bw中需要依赖注入的属性 String[] propertyNames = unsatisfiedNonSimpleProperties(mbd, bw); for (String propertyName : propertyNames) { // 2.校验是否存在beanName=propertyName的bean实例或者BeanDefinition if (containsBean(propertyName)) { // 3.获取propertyName的bean实例对象 Object bean = getBean(propertyName); // 4.将属性名和属性值添加到pvs pvs.add(propertyName, bean); // 5.注册依赖关系到缓存（beanName依赖propertyName） registerDependentBean(propertyName, beanName); if (logger.isDebugEnabled()) { logger.debug("Added autowiring by name from bean name '" + beanName + "' via property '" + propertyName + "' to bean named '" + propertyName + "'"); } } else { if (logger.isTraceEnabled()) { logger.trace("Not autowiring property '" + propertyName + "' of bean '" + beanName + "' by name: no matching bean found"); } } } }
1.寻找 bw 中需要依赖注入的属性，见代码块6详解。
2.校验是否存在 beanName = propertyName 的 bean 实例或者BeanDefinition，见代码块8详解。
5.注册依赖关系到缓存（beanName 依赖 propertyName），见Spring IoC：getBean详解中代码块7详解。
autowireByName 的使用例子
Spring 配置：
<!-- 8.autowireByName --> <bean id="fruit" class="com.joonwhee.open.demo.simple.Fruit" autowire="byName"> <property name="color" value="Red"/> </bean> <!-- id值跟Fruit里的属性名一致 --> <bean id="apple" class="com.joonwhee.open.demo.simple.Apple"/>
Fruit 对象：
public class Fruit { private Apple apple; private String color; public Apple getApple() { return apple; } public void setApple(Apple apple) { this.apple = apple; } public String getColor() { return color; } public void setColor(String color) { this.color = color; } }
代码块6：unsatisfiedNonSimpleProperties
protected String[] unsatisfiedNonSimpleProperties(AbstractBeanDefinition mbd, BeanWrapper bw) { Set<String> result = new TreeSet<String>(); // 1.拿到mdb的属性值 PropertyValues pvs = mbd.getPropertyValues(); // 2.拿到bw的PropertyDescriptors PropertyDescriptor[] pds = bw.getPropertyDescriptors(); // 3.遍历bw的PropertyDescriptors for (PropertyDescriptor pd : pds) { // 4.pd用于写入属性值的方法不为空 && pd不是从依赖性检查中排除的bean属性 && pd不包含在pvs里 // && pd的属性类型不是“简单”属性（基础类型、枚举、Number等） // 4.1 isSimpleProperty: 判断属性是不是“简单”属性 if (pd.getWriteMethod() != null && !isExcludedFromDependencyCheck(pd) && !pvs.contains(pd.getName()) && !BeanUtils.isSimpleProperty(pd.getPropertyType())) { // 4.2 符合条件，则添加pd的name到result中 result.add(pd.getName()); } } return StringUtils.toStringArray(result); }
4.1 isSimpleProperty：判断属性是不是 “简单”属性，见代码块7详解。
public static boolean isSimpleProperty(Class<?> clazz) { Assert.notNull(clazz, "Class must not be null"); // clazz是简单值类型 || （ clazz是数组 && clazz的组件类型为简单值类型） // getComponentType：返回数组的组件类型，例如: String[] 返回 String.class，如果是非数组，则返回null return isSimpleValueType(clazz) || (clazz.isArray() && isSimpleValueType(clazz.getComponentType())); } public static boolean isSimpleValueType(Class<?> clazz) { return (ClassUtils.isPrimitiveOrWrapper(clazz) || clazz.isEnum() || CharSequence.class.isAssignableFrom(clazz) || Number.class.isAssignableFrom(clazz) || Date.class.isAssignableFrom(clazz) || URI.class == clazz || URL.class == clazz || Locale.class == clazz || Class.class == clazz); } // ClassUtils.java public static boolean isPrimitiveOrWrapper(Class<?> clazz) { Assert.notNull(clazz, "Class must not be null"); // clazz为基础类型 或者 clazz是基础类型的封装类 return (clazz.isPrimitive() || isPrimitiveWrapper(clazz)); } public static boolean isPrimitiveWrapper(Class<?> clazz) { Assert.notNull(clazz, "Class must not be null"); // 检查clazz是否为8种基础类型的包装类 // primitiveWrapperTypeMap缓存包含8种基础类型和包装类的映射，例如：Integer.class -> int.class return primitiveWrapperTypeMap.containsKey(clazz); } static { primitiveWrapperTypeMap.put(Boolean.class, boolean.class); primitiveWrapperTypeMap.put(Byte.class, byte.class); primitiveWrapperTypeMap.put(Character.class, char.class); primitiveWrapperTypeMap.put(Double.class, double.class); primitiveWrapperTypeMap.put(Float.class, float.class); primitiveWrapperTypeMap.put(Integer.class, int.class); primitiveWrapperTypeMap.put(Long.class, long.class); primitiveWrapperTypeMap.put(Short.class, short.class); // ... }
@Override public boolean containsBean(String name) { // 1.将name转换为真正的beanName String beanName = transformedBeanName(name); // 2.检查singletonObjects缓存和beanDefinitionMap缓存中是否存在beanName if (containsSingleton(beanName) || containsBeanDefinition(beanName)) { // 3.name不带&前缀，或者是FactoryBean，则返回true return (!BeanFactoryUtils.isFactoryDereference(name) || isFactoryBean(name)); } // Not found -> check parent. // 4.没有找到则检查parentBeanFactory BeanFactory parentBeanFactory = getParentBeanFactory(); return (parentBeanFactory != null && parentBeanFactory.containsBean(originalBeanName(name))); }
protected void autowireByType( String beanName, AbstractBeanDefinition mbd, BeanWrapper bw, MutablePropertyValues pvs) { TypeConverter converter = getCustomTypeConverter(); if (converter == null) { converter = bw; } Set<String> autowiredBeanNames = new LinkedHashSet<String>(4); // 1.寻找bw中需要依赖注入的属性 String[] propertyNames = unsatisfiedNonSimpleProperties(mbd, bw); // 2.遍历所有需要依赖注入的属性 for (String propertyName : propertyNames) { try { PropertyDescriptor pd = bw.getPropertyDescriptor(propertyName); // Don't try autowiring by type for type Object: never makes sense, // even if it technically is a unsatisfied, non-simple property. if (Object.class != pd.getPropertyType()) { // 3.获取指定属性的set方法，封装成MethodParameter（必须有set方法才能通过属性来注入） MethodParameter methodParam = BeanUtils.getWriteMethodParameter(pd); // Do not allow eager init for type matching in case of a prioritized post-processor. boolean eager = !PriorityOrdered.class.isAssignableFrom(bw.getWrappedClass()); // 4.将MethodParameter的方法参数索引信息封装成DependencyDescriptor DependencyDescriptor desc = new AutowireByTypeDependencyDescriptor(methodParam, eager); // 5.解析当前属性所匹配的bean实例，并把解析到的bean实例的beanName存储在autowiredBeanNames中 Object autowiredArgument = resolveDependency(desc, beanName, autowiredBeanNames, converter); if (autowiredArgument != null) { // 6.如果找到了依赖的bean实例，将属性名和bean实例放到pvs中 pvs.add(propertyName, autowiredArgument); } for (String autowiredBeanName : autowiredBeanNames) { // 7.注册依赖关系，beanName依赖autowiredBeanName registerDependentBean(autowiredBeanName, beanName); if (logger.isDebugEnabled()) { logger.debug("Autowiring by type from bean name '" + beanName + "' via property '" + propertyName + "' to bean named '" + autowiredBeanName + "'"); } } autowiredBeanNames.clear(); } } catch (BeansException ex) { throw new UnsatisfiedDependencyException(mbd.getResourceDescription(), beanName, propertyName, ex); } } }
1.寻找 bw 中需要依赖注入的属性，见代码块6详解。
5.解析当前属性所匹配的 bean 实例，并把解析到的 bean 实例的beanName 存储在 autowiredBeanNames 中，见Spring IoC：createBean详解（上）中代码块9详解。
7.注册依赖关系，beanName 依赖 autowiredBeanName，见Spring IoC：getBean详解中代码块7详解。
autowireByType 的使用例子
Spring 配置：
<bean id="fruit" class="com.joonwhee.open.demo.simple.Fruit" autowire="byType"> <property name="color" value="Red"/> </bean> <!-- id值随便取，fruit中的apple属性通过类型匹配 --> <bean id="uselessName" class="com.joonwhee.open.demo.simple.Apple"/>
Fruit 对象：
public class Fruit { private Apple apple; private String color; public Apple getApple() { return apple; } public void setApple(Apple apple) { this.apple = apple; } public String getColor() { return color; } public void setColor(String color) { this.color = color; } }
protected void applyPropertyValues(String beanName, BeanDefinition mbd, BeanWrapper bw, PropertyValues pvs) { if (pvs == null || pvs.isEmpty()) { return; } MutablePropertyValues mpvs = null; List<PropertyValue> original; if (System.getSecurityManager() != null) { if (bw instanceof BeanWrapperImpl) { ((BeanWrapperImpl) bw).setSecurityContext(getAccessControlContext()); } } // 1.获取属性值列表 if (pvs instanceof MutablePropertyValues) { mpvs = (MutablePropertyValues) pvs; // 1.1 如果mpvs中的值已经被转换为对应的类型，那么可以直接设置到BeanWrapper中 if (mpvs.isConverted()) { // Shortcut: use the pre-converted values as-is. try { bw.setPropertyValues(mpvs); return; } catch (BeansException ex) { throw new BeanCreationException( mbd.getResourceDescription(), beanName, "Error setting property values", ex); } } original = mpvs.getPropertyValueList(); } else { // 1.2 如果pvs并不是使用MutablePropertyValues封装的类型，那么直接使用原始的属性获取方法 original = Arrays.asList(pvs.getPropertyValues()); } TypeConverter converter = getCustomTypeConverter(); if (converter == null) { converter = bw; } // 2.1 获取对应的解析器 BeanDefinitionValueResolver valueResolver = new BeanDefinitionValueResolver(this, beanName, mbd, converter); // Create a deep copy, resolving any references for values. // 2.2 创建深层拷贝副本，用于存放解析后的属性值 List<PropertyValue> deepCopy = new ArrayList<PropertyValue>(original.size()); boolean resolveNecessary = false; // 3.遍历属性，将属性转换为对应类的对应属性的类型 for (PropertyValue pv : original) { if (pv.isConverted()) { // 3.1 如果pv已经包含转换的值，则直接添加到deepCopy deepCopy.add(pv); } else { // 3.2 否则，进行转换 // 3.2.1 拿到pv的原始属性名和属性值 String propertyName = pv.getName(); Object originalValue = pv.getValue(); // 3.2.2 使用解析器解析原始属性值 Object resolvedValue = valueResolver.resolveValueIfNecessary(pv, originalValue); Object convertedValue = resolvedValue; // 3.2.3 判断该属性是否可转换 boolean convertible = bw.isWritableProperty(propertyName) && !PropertyAccessorUtils.isNestedOrIndexedProperty(propertyName); if (convertible) { // 3.2.4 如果可转换，则转换指定目标属性的给定值 convertedValue = convertForProperty(resolvedValue, propertyName, bw, converter); } // Possibly store converted value in merged bean definition, // in order to avoid re-conversion for every created bean instance. // 3.2.5 在合并的BeanDefinition中存储转换后的值，以避免为每个创建的bean实例重新转换 if (resolvedValue == originalValue) { if (convertible) { pv.setConvertedValue(convertedValue); } deepCopy.add(pv); } else if (convertible && originalValue instanceof TypedStringValue && !((TypedStringValue) originalValue).isDynamic() && !(convertedValue instanceof Collection || ObjectUtils.isArray(convertedValue))) { pv.setConvertedValue(convertedValue); deepCopy.add(pv); } else { resolveNecessary = true; deepCopy.add(new PropertyValue(pv, convertedValue)); } } } if (mpvs != null && !resolveNecessary) { mpvs.setConverted(); } // Set our (possibly massaged) deep copy. try { // 4.设置bean的属性值为deepCopy bw.setPropertyValues(new MutablePropertyValues(deepCopy)); } catch (BeansException ex) { throw new BeanCreationException( mbd.getResourceDescription(), beanName, "Error setting property values", ex); } }
protected Object initializeBean(final String beanName, final Object bean, RootBeanDefinition mbd) { // 1.激活Aware方法 if (System.getSecurityManager() != null) { AccessController.doPrivileged(new PrivilegedAction<Object>() { @Override public Object run() { invokeAwareMethods(beanName, bean); return null; } }, getAccessControlContext()); } else { invokeAwareMethods(beanName, bean); } Object wrappedBean = bean; if (mbd == null || !mbd.isSynthetic()) { // 2.在初始化前应用BeanPostProcessor的postProcessBeforeInitialization方法，允许对bean实例进行包装 wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName); } try { // 3.调用初始化方法 invokeInitMethods(beanName, wrappedBean, mbd); } catch (Throwable ex) { throw new BeanCreationException( (mbd != null ? mbd.getResourceDescription() : null), beanName, "Invocation of init method failed", ex); } if (mbd == null || !mbd.isSynthetic()) { // 4.在初始化后应用BeanPostProcessor的postProcessAfterInitialization方法，允许对bean实例进行包装 wrappedBean = applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName); } // 5.返回wrappedBean return wrappedBean; }
1.激活 Aware方法，见代码块12详解。
2.在初始化前应用后置处理器 BeanPostProcessor 的 postProcessBeforeInitialization 方法，允许对bean 实例进行包装，见代码块13详解。
3.调用初始化方法，见代码块15详解。
4.在初始化后应用后置处理器 BeanPostProcessor 的 postProcessAfterInitialization 方法，允许对bean 实例进行包装，见代码块17详解。
private void invokeAwareMethods(final String beanName, final Object bean) { if (bean instanceof Aware) { // BeanNameAware: 实现此接口的类想要拿到beanName，因此我们在这边赋值给它 if (bean instanceof BeanNameAware) { ((BeanNameAware) bean).setBeanName(beanName); } // BeanClassLoaderAware：实现此接口的类想要拿到beanClassLoader，因此我们在这边赋值给它 if (bean instanceof BeanClassLoaderAware) { ((BeanClassLoaderAware) bean).setBeanClassLoader(getBeanClassLoader()); } // BeanFactoryAware: 实现此接口的类想要拿到 BeanFactory，因此我们在这边赋值给它 if (bean instanceof BeanFactoryAware) { ((BeanFactoryAware) bean).setBeanFactory(AbstractAutowireCapableBeanFactory.this); } } }
如果对 Spring 比较熟悉的同学应该知道，以 Aware 为结尾的类都是一些扩展接口，用于提供给开发者获取到 BeanFactory 中的一些属性或对象。
代码块13：applyBeanPostProcessorsBeforeInitialization
@Override public Object applyBeanPostProcessorsBeforeInitialization(Object existingBean, String beanName) throws BeansException { Object result = existingBean; // 1.遍历所有注册的BeanPostProcessor实现类，调用postProcessBeforeInitialization方法 for (BeanPostProcessor beanProcessor : getBeanPostProcessors()) { // 2.在bean初始化方法执行前，调用postProcessBeforeInitialization方法 result = beanProcessor.postProcessBeforeInitialization(result, beanName); if (result == null) { return result; } } return result; }
在 bean初始化前，调用所有 BeanPostProcessors 的postProcessBeforeInitialization 方法，这个在很早之前就说过了。这边提一个比较重要的实现类：ApplicationContextAwareProcessor，见代码块14详解。
代码块14：postProcessBeforeInitialization
@Override public Object postProcessBeforeInitialization(final Object bean, String beanName) throws BeansException { AccessControlContext acc = null; if (System.getSecurityManager() != null && (bean instanceof EnvironmentAware || bean instanceof EmbeddedValueResolverAware || bean instanceof ResourceLoaderAware || bean instanceof ApplicationEventPublisherAware || bean instanceof MessageSourceAware || bean instanceof ApplicationContextAware)) { acc = this.applicationContext.getBeanFactory().getAccessControlContext(); } if (acc != null) { AccessController.doPrivileged(new PrivilegedAction<Object>() { @Override public Object run() { invokeAwareInterfaces(bean); return null; } }, acc); } else { // 调用Aware接口 invokeAwareInterfaces(bean); } return bean; } private void invokeAwareInterfaces(Object bean) { if (bean instanceof Aware) { if (bean instanceof EnvironmentAware) { ((EnvironmentAware) bean).setEnvironment(this.applicationContext.getEnvironment()); } if (bean instanceof EmbeddedValueResolverAware) { ((EmbeddedValueResolverAware) bean).setEmbeddedValueResolver(this.embeddedValueResolver); } if (bean instanceof ResourceLoaderAware) { ((ResourceLoaderAware) bean).setResourceLoader(this.applicationContext); } if (bean instanceof ApplicationEventPublisherAware) { ((ApplicationEventPublisherAware) bean).setApplicationEventPublisher(this.applicationContext); } if (bean instanceof MessageSourceAware) { ((MessageSourceAware) bean).setMessageSource(this.applicationContext); } // ApplicationContextAware：实现此接口的类想要拿到ApplicationContext，因此我们在这边赋值给它 if (bean instanceof ApplicationContextAware) { ((ApplicationContextAware) bean).setApplicationContext(this.applicationContext); } } }
我们经常通过实现 ApplicationContextAware 接口来拿到 ApplicationContext，我们之所以能拿到 ApplicationContext，就是在这边被赋值的。
protected void invokeInitMethods(String beanName, final Object bean, RootBeanDefinition mbd) throws Throwable { // 1.首先检查bean是否实现了InitializingBean接口，如果是的话调用afterPropertiesSet方法 boolean isInitializingBean = (bean instanceof InitializingBean); if (isInitializingBean && (mbd == null || !mbd.isExternallyManagedInitMethod("afterPropertiesSet"))) { if (logger.isDebugEnabled()) { logger.debug("Invoking afterPropertiesSet() on bean with name '" + beanName + "'"); } // 2.调用afterPropertiesSet方法 if (System.getSecurityManager() != null) { try { AccessController.doPrivileged(new PrivilegedExceptionAction<Object>() { @Override public Object run() throws Exception { ((InitializingBean) bean).afterPropertiesSet(); return null; } }, getAccessControlContext()); } catch (PrivilegedActionException pae) { throw pae.getException(); } } else { ((InitializingBean) bean).afterPropertiesSet(); } } if (mbd != null) { String initMethodName = mbd.getInitMethodName(); if (initMethodName != null && !(isInitializingBean && "afterPropertiesSet".equals(initMethodName)) && !mbd.isExternallyManagedInitMethod(initMethodName)) { // 3.调用自定义初始化方法 invokeCustomInitMethod(beanName, bean, mbd); } } }
2.调用自定义初始化方法，见代码块16详解。
protected void invokeCustomInitMethod(String beanName, final Object bean, RootBeanDefinition mbd) throws Throwable { // 1.拿到初始化方法的方法名 String initMethodName = mbd.getInitMethodName(); // 2.根据方法名拿到方法 final Method initMethod = (mbd.isNonPublicAccessAllowed() ? BeanUtils.findMethod(bean.getClass(), initMethodName) : ClassUtils.getMethodIfAvailable(bean.getClass(), initMethodName)); if (initMethod == null) { // 3.如果不存在initMethodName对应的方法，并且是强制执行初始化方法(默认为强制), 则抛出异常 if (mbd.isEnforceInitMethod()) { throw new BeanDefinitionValidationException("Couldn't find an init method named '" + initMethodName + "' on bean with name '" + beanName + "'"); } else { // 如果设置了非强制，找不到则直接返回 if (logger.isDebugEnabled()) { logger.debug("No default init method named '" + initMethodName + "' found on bean with name '" + beanName + "'"); } // Ignore non-existent default lifecycle methods. return; } } if (logger.isDebugEnabled()) { logger.debug("Invoking init method '" + initMethodName + "' on bean with name '" + beanName + "'"); } // 4.调用初始化方法 if (System.getSecurityManager() != null) { AccessController.doPrivileged(new PrivilegedExceptionAction<Object>() { @Override public Object run() throws Exception { ReflectionUtils.makeAccessible(initMethod); return null; } }); try { AccessController.doPrivileged(new PrivilegedExceptionAction<Object>() { @Override public Object run() throws Exception { initMethod.invoke(bean); return null; } }, getAccessControlContext()); } catch (PrivilegedActionException pae) { InvocationTargetException ex = (InvocationTargetException) pae.getException(); throw ex.getTargetException(); } } else { try { ReflectionUtils.makeAccessible(initMethod); initMethod.invoke(bean); } catch (InvocationTargetException ex) { throw ex.getTargetException(); } } }
代码块17：applyBeanPostProcessorsAfterInitialization
@Override public Object applyBeanPostProcessorsAfterInitialization(Object existingBean, String beanName) throws BeansException { Object result = existingBean; // 1.遍历所有注册的BeanPostProcessor实现类，调用postProcessAfterInitialization方法 for (BeanPostProcessor beanProcessor : getBeanPostProcessors()) { // 2.在bean初始化方法执行后，调用postProcessAfterInitialization方法 result = beanProcessor.postProcessAfterInitialization(result, beanName); if (result == null) { return result; } } return result; }
代码块18：registerDisposableBeanIfNecessary
protected void registerDisposableBeanIfNecessary(String beanName, Object bean, RootBeanDefinition mbd) { AccessControlContext acc = (System.getSecurityManager() != null ? getAccessControlContext() : null); // 1.mbd的scope不是prototype && 给定的bean需要在关闭时销毁 if (!mbd.isPrototype() && requiresDestruction(bean, mbd)) { if (mbd.isSingleton()) { // 2.单例模式下注册用于销毁的bean到disposableBeans缓存，执行给定bean的所有销毁工作： // DestructionAwareBeanPostProcessors，DisposableBean接口，自定义销毁方法 // 2.1 DisposableBeanAdapter：使用DisposableBeanAdapter来封装用于销毁的bean registerDisposableBean(beanName, new DisposableBeanAdapter(bean, beanName, mbd, getBeanPostProcessors(), acc)); } else { // 3.自定义scope处理 // A bean with a custom scope... Scope scope = this.scopes.get(mbd.getScope()); if (scope == null) { throw new IllegalStateException("No Scope registered for scope name '" + mbd.getScope() + "'"); } scope.registerDestructionCallback(beanName, new DisposableBeanAdapter(bean, beanName, mbd, getBeanPostProcessors(), acc)); } } }
1.requiresDestruction(bean, mbd)：判断给定的 bean 是否需要在关闭时销毁，见代码块19详解。
2.1 使用 DisposableBeanAdapter 来封装用于销毁的 bean，见代码块22详解。
protected boolean requiresDestruction(Object bean, RootBeanDefinition mbd) { // 1.DisposableBeanAdapter.hasDestroyMethod(bean, mbd)：判断bean是否有destroy方法 // 2.hasDestructionAwareBeanPostProcessors()：判断当前BeanFactory是否注册过DestructionAwareBeanPostProcessor // 3.DisposableBeanAdapter.hasApplicableProcessors：是否存在适用于bean的DestructionAwareBeanPostProcessor return (bean != null && (DisposableBeanAdapter.hasDestroyMethod(bean, mbd) || (hasDestructionAwareBeanPostProcessors() && DisposableBeanAdapter.hasApplicableProcessors(bean, getBeanPostProcessors())))); }
1.如果 bean 实现了 DisposableBean 接口或bean 是 AutoCloseable 实例，则返回 true，因为这两个接口都有关闭的方法。
代码块20：hasDestroyMethod
public static boolean hasDestroyMethod(Object bean, RootBeanDefinition beanDefinition) { if (bean instanceof DisposableBean || closeableInterface.isInstance(bean)) { // 1.如果bean实现了DisposableBean接口 或者 bean是AutoCloseable实例，则返回true return true; } // 2.拿到bean自定义的destroy方法名 String destroyMethodName = beanDefinition.getDestroyMethodName(); if (AbstractBeanDefinition.INFER_METHOD.equals(destroyMethodName)) { // 3.如果自定义的destroy方法名为“(inferred)”（该名字代表需要我们自己去推测destroy的方法名）， // 则检查该bean是否存在方法名为“close”或“shutdown”的方法，如果存在，则返回true return (ClassUtils.hasMethod(bean.getClass(), CLOSE_METHOD_NAME) || ClassUtils.hasMethod(bean.getClass(), SHUTDOWN_METHOD_NAME)); } // 4.如果destroyMethodName不为空，则返回true return StringUtils.hasLength(destroyMethodName); }
1.如果 bean 实现了 DisposableBean 接口或 bean 是 AutoCloseable 实例，则返回 true，因为这两个接口都有关闭的方法。
public static boolean hasApplicableProcessors(Object bean, List<BeanPostProcessor> postProcessors) { if (!CollectionUtils.isEmpty(postProcessors)) { // 1.遍历所有的BeanPostProcessor for (BeanPostProcessor processor : postProcessors) { // 2.如果processor是DestructionAwareBeanPostProcessor if (processor instanceof DestructionAwareBeanPostProcessor) { DestructionAwareBeanPostProcessor dabpp = (DestructionAwareBeanPostProcessor) processor; try { if (dabpp.requiresDestruction(bean)) { // 3.如果给定的bean实例需要通过此后处理器进行销毁，则返回true return true; } } catch (AbstractMethodError err) { // A pre-4.3 third-party DestructionAwareBeanPostProcessor... // As of 5.0, we can let requiresDestruction be a Java 8 default method which returns true. return true; } } } } return false; }
public DisposableBeanAdapter(Object bean, String beanName, RootBeanDefinition beanDefinition, List<BeanPostProcessor> postProcessors, AccessControlContext acc) { Assert.notNull(bean, "Disposable bean must not be null"); this.bean = bean; this.beanName = beanName; // 1.判断bean是否需要调用DisposableBean的destroy方法 this.invokeDisposableBean = (this.bean instanceof DisposableBean && !beanDefinition.isExternallyManagedDestroyMethod("destroy")); this.nonPublicAccessAllowed = beanDefinition.isNonPublicAccessAllowed(); this.acc = acc; // 2.拿到自定义的destroy方法名 String destroyMethodName = inferDestroyMethodIfNecessary(bean, beanDefinition); if (destroyMethodName != null && !(this.invokeDisposableBean && "destroy".equals(destroyMethodName)) && !beanDefinition.isExternallyManagedDestroyMethod(destroyMethodName)) { this.destroyMethodName = destroyMethodName; // 3.拿到自定义的destroy方法，赋值给this.destroyMethod this.destroyMethod = determineDestroyMethod(); if (this.destroyMethod == null) { if (beanDefinition.isEnforceDestroyMethod()) { // 4.如果destroy方法名为空，并且enforceDestroyMethod为true，则抛出异常 throw new BeanDefinitionValidationException("Couldn't find a destroy method named '" + destroyMethodName + "' on bean with name '" + beanName + "'"); } } else { // 5.拿到destroy方法的参数类型数组 Class<?>[] paramTypes = this.destroyMethod.getParameterTypes(); if (paramTypes.length > 1) { // 6.如果destroy方法的参数大于1个，则抛出异常 throw new BeanDefinitionValidationException("Method '" + destroyMethodName + "' of bean '" + beanName + "' has more than one parameter - not supported as destroy method"); } else if (paramTypes.length == 1 && boolean.class != paramTypes[0]) { // 7.如果destroy方法的参数为1个，并且该参数的类型不为boolean，则抛出异常 throw new BeanDefinitionValidationException("Method '" + destroyMethodName + "' of bean '" + beanName + "' has a non-boolean parameter - not supported as destroy method"); } } } // 8.查找DestructionAwareBeanPostProcessors，并赋值给this.beanPostProcessors this.beanPostProcessors = filterPostProcessors(postProcessors, bean); }
2.拿到自定义的 destroy 方法名，见代码块23详解。
8.查找 DestructionAwareBeanPostProcessors，并赋值给beanPostProcessors，见代码块24详解。
代码块23：inferDestroyMethodIfNecessary
private String inferDestroyMethodIfNecessary(Object bean, RootBeanDefinition beanDefinition) { // 1.拿到beanDefinition的destroy方法名 String destroyMethodName = beanDefinition.getDestroyMethodName(); // 2.如果destroy方法名为“(inferred)”|| destroyMethodName为null，并且bean是AutoCloseable实例 if (AbstractBeanDefinition.INFER_METHOD.equals(destroyMethodName) || (destroyMethodName == null && closeableInterface.isInstance(bean))) { // Only perform destroy method inference or Closeable detection // in case of the bean not explicitly implementing DisposableBean // 3.如果bean没有实现DisposableBean接口，则尝试推测destroy方法的名字 if (!(bean instanceof DisposableBean)) { try { // 4.尝试在bean中寻找方法名为close的方法作为destroy方法 return bean.getClass().getMethod(CLOSE_METHOD_NAME).getName(); } catch (NoSuchMethodException ex) { try { // 5.尝试在bean中寻找方法名为close的方法作为shutdown方法 return bean.getClass().getMethod(SHUTDOWN_METHOD_NAME).getName(); } catch (NoSuchMethodException ex2) { // no candidate destroy method found } } } // 6.如果没有找到，则返回null return null; } return (StringUtils.hasLength(destroyMethodName) ? destroyMethodName : null); }
private List<DestructionAwareBeanPostProcessor> filterPostProcessors(List<BeanPostProcessor> processors, Object bean) { List<DestructionAwareBeanPostProcessor> filteredPostProcessors = null; if (!CollectionUtils.isEmpty(processors)) { filteredPostProcessors = new ArrayList<DestructionAwareBeanPostProcessor>(processors.size()); // 1.遍历所有的BeanPostProcessor for (BeanPostProcessor processor : processors) { // 2.如果processor是DestructionAwareBeanPostProcessor if (processor instanceof DestructionAwareBeanPostProcessor) { DestructionAwareBeanPostProcessor dabpp = (DestructionAwareBeanPostProcessor) processor; try { if (dabpp.requiresDestruction(bean)) { // 3.如果给定的bean实例需要通过此后处理器进行销毁，则添加到filteredPostProcessors filteredPostProcessors.add(dabpp); } } catch (AbstractMethodError err) { // A pre-4.3 third-party DestructionAwareBeanPostProcessor... // As of 5.0, we can let requiresDestruction be a Java 8 default method which returns true. filteredPostProcessors.add(dabpp); } } } } return filteredPostProcessors; }
至此，finishBeanFactoryInitialization 方法解析完毕，我们通过Spring IoC：finishBeanFactoryInitialization详解、Spring IoC：getBean详解、Spring IoC：createBean详解（上）和本文共四篇文章来介绍 finishBeanFactoryInitialization 方法。在 finishBeanFactoryInitialization 方法中，我们主要做了以下操作：
· 将之前解析的 BeanDefinition 进一步处理，将有父 BeanDefinition 的进行合并，获得 MergedBeanDefinition
· 尝试从缓存获取 bean 实例
· 处理特殊的 bean —— FactoryBean 的创建
· 创建 bean 实例
· 循环引用的处理
· bean 实例属性填充
· bean 实例的初始化
· BeanPostProcessor 的各种扩展应用
finishBeanFactoryInitialization 方法解析的结束，也标志着 Spring IoC 整个构建过程中，重要的内容基本都已经解析完毕。由于工程较为浩大，因此整个系列的文章中，肯定会有各种各样的问题：理解错误的、用词不一致的（有时候用 “BeanDefinition”，有时候用 “bean 定义”）、漏掉的等等，后续如果有时间，可能会在抽空完善一下，尽量减少出现的问题，也欢迎各位同学指正文章中的错误。
另外，本系列文章到目前为止都是单纯的解析 Spring IoC 的源码，之后可能会再补充一些重要的内容，例如：本文提到要写的@Autowire 注解的依赖注入过程、Spring IoC 中的核心类的介绍等。
