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:obtainFreshBeanFactory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
前言
接着 Spring IoC:createBean详解(上),我们继续解析创建 bean 实例的剩下内容。
正文
首先,我们回到 Spring IoC:createBean详解(上)中的代码块3,doCreateBean 方法。
doCreateBean
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。
代码块2:addSingletonFactory
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。
代码块3:getEarlyBeanReference
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;
}
代码块4:populateBean
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。
代码块5:autowireByName
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。
代码块7:isSimpleProperty
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);
// ...
}
代码块8:containsBean
@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)));
}
代码块9:autowireByType
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;
}
}
代码块10:applyPropertyValues
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);
}
}
代码块11:initializeBean
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。
代码块12:invokeAwareMethods
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。
代码块15:invokeInitMethods
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。
代码块16:invokeCustomInitMethod
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。
代码块19:requiresDestruction
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.DisposableBeanAdapter.hasDestroyMethod(bean, mbd):判断 bean 是否有 destroy 方法,见代码块20详解。
3.DisposableBeanAdapter.hasApplicableProcessors:是否存在适用于 bean 的 DestructionAwareBeanPostProcessor,见代码块21详解。
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。
代码块21:hasApplicableProcessors
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;
}
代码块22:DisposableBeanAdapter
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);
}
代码块24:filterPostProcessors
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;
}
总结
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。