目录
- 1.1 单例模式的实例化
- 1.1.1 从缓存中获取
- 1.1.2 前置处理
- 1.1.3 获取Bean
- 1.1.4 后置处理
- 1.1.5 加入缓存
- 1.2 原型模式实例化
- 1.3 其他模式实例化
- 官网：Home
- 参考书籍：Spring源码深度解析-郝佳编著-微信读书
上一篇文章我们分析到不同的作用域创建Bean，但是我们没有详细来解释，让我们回到关键的代码片段
AbstractBeanFactory
// Create bean instance.
//创建单例Bean
if (mbd.isSingleton()) {
//这里使用了一个匿名内部类，创建Bean实例对象，并且注册给所依赖的对象
sharedInstance = getSingleton(beanName, () -> {
try {
//创建一个指定Bean实例对象，如果有父级继承，则合并子类和父类的定义
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.
//显式地从容器单例模式Bean缓存中清除实例对象
destroySingleton(beanName);
throw ex;
}
});
//获取给定Bean的实例对象
bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd);
}
//创建多例Bean
else if (mbd.isPrototype()) {
//原型模式(Prototype)是每次都会创建一个新的对象
Object prototypeInstance = null;
try {
//加载前置处理，默认的功能是注册当前创建的原型对象
beforePrototypeCreation(beanName);
//创建指定Bean对象实例
prototypeInstance = createBean(beanName, mbd, args);
}
finally {
//加载后置处理，默认的功能告诉IOC容器指定Bean的原型对象不再创建
afterPrototypeCreation(beanName);
}
//获取给定Bean的实例对象
bean = getObjectForBeanInstance(prototypeInstance, name, beanName, mbd);
}
//要创建的Bean既不是Singleton也不是Prototype
//如：request、session、application等生命周期
else {
String scopeName = mbd.getScope();
final Scope scope = this.scopes.get(scopeName);
//Bean定义资源中没有配置生命周期范围，则Bean定义不合法
if (scope == null) {
throw new IllegalStateException("No Scope registered for scope name '" + scopeName + "'");
}
try {
//这里又使用了一个匿名内部类，获取一个指定生命周期范围的实例
Object scopedInstance = scope.get(beanName, () -> {
//前置处理
beforePrototypeCreation(beanName);
try {
return createBean(beanName, mbd, args);
}
finally {
//后置处理
afterPrototypeCreation(beanName);
}
});
//获取给定Bean的实例对象
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);
}
}
这段代码的大体逻辑可以分为如下：
- singleton Bean实例化
- Prototype Bean实例化
- 其他类型 Bean 实例化(session,request等)
下面我们来具体看看呗，让我们回顾一下Spring的作用域吧
| Scope | 说明 |
|---|---|
| singleton | （默认情况下）为每个Spring IoC容器将单个Bean定义的Scope扩大到单个对象实例。 |
| prototype | 将单个Bean定义的Scope扩大到任何数量的对象实例。 |
| request | 将单个Bean定义的Scope扩大到单个HTTP请求的生命周期。也就是说，每个HTTP请求都有自己的Bean实例，该实例是在单个Bean定义的基础上创建的。只在Web感知的Spring ApplicationContext 的上下文中有效。 |
| session | 将单个Bean定义的Scope扩大到一个HTTP Session 的生命周期。只在Web感知的Spring ApplicationContext 的上下文中有效。 |
| application | 将单个Bean定义的 Scope 扩大到 ServletContext 的生命周期中。只在Web感知的Spring ApplicationContext 的上下文中有效。 |
| websocket | 将单个Bean定义的 Scope 扩大到 WebSocket 的生命周期。仅在具有Web感知的 Spring ApplicationContext 的上下文中有效。 |
1.1 单例模式的实例化
- 关键代码
AbstractBeanFactory
// Create bean instance.
//创建单例Bean
if (mbd.isSingleton()) {
//这里使用了一个匿名内部类，创建Bean实例对象，并且注册给所依赖的对象
sharedInstance = getSingleton(beanName, () -> {
try {
//创建一个指定Bean实例对象，如果有父级继承，则合并子类和父类的定义
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.
//显式地从容器单例模式Bean缓存中清除实例对象
destroySingleton(beanName);
throw ex;
}
});
//获取给定Bean的实例对象
bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd);
}
我们可以看到他的关键代码在于getSingleton方法，下面我们来看看这个方法
DefaultSingletonBeanRegistry
public Object getSingleton(String beanName, ObjectFactory<?> singletonFactory) {
Assert.notNull(beanName, "Bean name must not be null");
//全局加锁
synchronized (this.singletonObjects) {
// 从缓存中获取单例bean
// 因为 singleton 模式其实就是复用已经创建的 bean 所以这步骤必须检查
Object singletonObject = this.singletonObjects.get(beanName);
if (singletonObject == null) {
//是否正在销毁该bean
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 + "'");
}
// 加载前置处理
beforeSingletonCreation(beanName);
boolean newSingleton = false;
boolean recordSuppressedExceptions = (this.suppressedExceptions == null);
if (recordSuppressedExceptions) {
this.suppressedExceptions = new LinkedHashSet<>();
}
try {
// 初始化 bean
// 这个过程其实是调用 createBean() 方法
singletonObject = singletonFactory.getObject();
newSingleton = true;
}
catch (IllegalStateException ex) {
// Has the singleton object implicitly appeared in the meantime ->
// if yes, proceed with it since the exception indicates that state.
singletonObject = this.singletonObjects.get(beanName);
if (singletonObject == null) {
throw ex;
}
}
catch (BeanCreationException ex) {
if (recordSuppressedExceptions) {
for (Exception suppressedException : this.suppressedExceptions) {
ex.addRelatedCause(suppressedException);
}
}
throw ex;
}
finally {
if (recordSuppressedExceptions) {
this.suppressedExceptions = null;
}
//后置处理
afterSingletonCreation(beanName);
}
if (newSingleton) {
//加入缓存中
addSingleton(beanName, singletonObject);
}
}
return singletonObject;
}
}
它的大体流程可以分为几步：
- 尝试从缓存中获取单例Bean，如果已经加载了则直接返回，否则开始加载过程
- 加载前置处理
- 获取Bean实例
- 后置处理
- 加入缓存
1.1.1 从缓存中获取
DefaultSingletonBeanRegistry
// 单例缓存对象
private final Map<String, Object> singletonObjects = new ConcurrentHashMap<>(256);
这里的逻辑与上一篇的文章的从缓存中获取Bean差不多，这就不多概述了，我们来到下一环节，前置处理
1.1.2 前置处理
beforeSingletonCreation(beanName)是个标记方法，
// 用于添加标志，当前 bean 正处于创建中
protected void beforeSingletonCreation(String beanName) {
if (!this.inCreationCheckExclusions.contains(beanName) && !this.singletonsCurrentlyInCreation.add(beanName)) {
//添加失败，抛出异常
throw new BeanCurrentlyInCreationException(beanName);
}
}
把 beanName 添加到 singletonsCurrentlyInCreationmap中，用来表示该单例bean正在创建，如果添加失败，抛出异常。
1.1.3 获取Bean
通过createBean(beanName)方法返回的 singletonFactory 获取Bean。
try {
singletonObject = singletonFactory.getObject();
newSingleton = true;
}
catch (IllegalStateException ex) {
// Has the singleton object implicitly appeared in the meantime ->
// if yes, proceed with it since the exception indicates that state.
singletonObject = this.singletonObjects.get(beanName);
if (singletonObject == null) {
throw ex;
}
}
catch (BeanCreationException ex) {
if (recordSuppressedExceptions) {
for (Exception suppressedException : this.suppressedExceptions) {
ex.addRelatedCause(suppressedException);
}
}
throw ex;
}
我们来详细看看createBean方法，首先这个方法是一个接口
AbstractBeanFactory
protected abstract Object createBean(String beanName, RootBeanDefinition mbd, @Nullable Object[] args)
throws BeanCreationException;
该方法定义在 AbstractBeanFactory 中。其含义是根据给定的 BeanDefinition 和 args实例化一个 bean 对象，如果该 BeanDefinition 存在父类，则该 BeanDefinition 已经合并了父类的属性。所有 Bean 实例的创建都会委托给该方法实现。
AbstractAutowireCapableBeanFactory
protected Object createBean(String beanName, RootBeanDefinition mbd, @Nullable Object[] args)
throws BeanCreationException {
if (logger.isDebugEnabled()) {
logger.debug("Creating instance of bean '" + beanName + "'");
}
RootBeanDefinition mbdToUse = mbd;
// 确保此时的 bean 已经被解析了
// 如果获取的class 属性不为null，则克隆该 BeanDefinition
// 主要是因为该动态解析的 class 无法保存到到共享的 BeanDefinition
Class<?> resolvedClass = resolveBeanClass(mbd, beanName);
if (resolvedClass != null && !mbd.hasBeanClass() && mbd.getBeanClassName() != null) {
mbdToUse = new RootBeanDefinition(mbd);
mbdToUse.setBeanClass(resolvedClass);
}
try {
// 验证和准备覆盖方法
mbdToUse.prepareMethodOverrides();
}
catch (BeanDefinitionValidationException ex) {
throw new BeanDefinitionStoreException(mbdToUse.getResourceDescription(),
beanName, "Validation of method overrides failed", ex);
}
try {
// 给 BeanPostProcessors 一个机会用来返回一个代理类而不是真正的类实例
// AOP 的功能就是基于这个地方
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 {
// 执行真正创建 bean 的过程
Object beanInstance = doCreateBean(beanName, mbdToUse, args);
if (logger.isDebugEnabled()) {
logger.debug("Finished creating instance of bean '" + beanName + "'");
}
return beanInstance;
}
catch (BeanCreationException | ImplicitlyAppearedSingletonException ex) {
throw ex;
}
catch (Throwable ex) {
throw new BeanCreationException(
mbdToUse.getResourceDescription(), beanName, "Unexpected exception during bean creation", ex);
}
}
大体总结以上步骤：
- 根据设置的class属性或者根据className来解析Class。
Class<?> resolvedClass = resolveBeanClass(mbd, beanName)
主要是获取bean的class，并设置到BeanDefinition中，通过类加载器来加载到对应的Class类
- 对override属性进行标记及验证。很多读者可能会不知道这个方法的作用，因为在Spring的配置里面根本就没有诸如override-method之类的配置，那么这个方法到底是干什么用的呢？其实在Spring中确实没有override-method这样的配置，但是如果读过前面的部分，可能会有所发现，在Spring配置中是存在lookup-method和replace-method的，而这两个配置的加载其实就是将配置统一存放在BeanDefinition中的methodOverrides属性里，而这个函数的操作其实也就是针对于这两个配置的，那么当bean实例化的时候，如果检测到了methodOverrides属性不为空，则动态的为当前bean生成代理并使用相应的拦截器对bean做处理
// Prepare method overrides.
try {
// 准备方法重写
mbdToUse.prepareMethodOverrides();
}
catch (BeanDefinitionValidationException ex) {
throw new BeanDefinitionStoreException(mbdToUse.getResourceDescription(),
beanName, "Validation of method overrides failed", ex);
}
public void prepareMethodOverrides() throws BeanDefinitionValidationException {
// Check that lookup methods exists.
//检测是否存在方法注入,并循环预处理方法注入
// Check that lookup methods exist and determine their overloaded status.
if (hasMethodOverrides()) {
getMethodOverrides().getOverrides().forEach(this::prepareMethodOverride);
}
}
protected void prepareMethodOverride(MethodOverride mo) throws BeanDefinitionValidationException {
// 统计注入的方法个数
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() + "]");
}
// 如果为1,则将注入方法标记为未重载
// 注意:当有多个重载方法时,为了确定调用哪个具体的方法,Spring对重载方法的参数解析是很复杂的
// 所以,如果注入方法没有被重载这里就将其标记,省去了对方法参数的解析过程,直接调用即可
else if (count == 1) {
// Mark override as not overloaded, to avoid the overhead of arg type checking.
mo.setOverloaded(false);
}
}
- 应用初始化前的后处理器，解析指定bean是否存在初始化前的短路操作。
在真正调用doCreate方法创建bean的实例前使用了这样一个方法resolveBeforeInstantiation (beanName, mbd)对BeanDefinigiton中的属性做些前置处理。
当然，无论其中是否有相应的逻辑实现我们都可以理解，因为真正逻辑实现前后留有处理函数也是可扩展的一种体现，但是，这并不是最重要的，在函数中还提供了一个短路判断，这才是最为关键的部分
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);
}
protected Object resolveBeforeInstantiation(String beanName, RootBeanDefinition mbd) {
Object bean = null;
//如果尚未被解析
if (!Boolean.FALSE.equals(mbd.beforeInstantiationResolved)) {
// Make sure bean class is actually resolved at this point.
if (mbd.hasBeanClass() && !mbd.isSynthetic() && hasInstantiationAware
BeanPostProcessors()) {
//
bean = applyBeanPostProcessorsBeforeInstantiation(mbd.getBeanClass(),
beanName);
if (bean != null) {
bean = applyBeanPostProcessorsAfterInitialization(bean, beanName);
}
}
mbd.beforeInstantiationResolved = (bean != null);
}
return bean;
}
- 当经过前置处理后返回的结果如果不为空，那么会直接略过后续的Bean的创建而直接返回结果。这一特性虽然很容易被忽略，但是却起着至关重要的作用，我们熟知的AOP功能就是基于这里的判断的。
- 这个方法核心就在于 applyBeanPostProcessorsBeforeInstantiation() 和 applyBeanPostProcessorsAfterInitialization() 两个方法，before 为实例化前的后处理器应用，after 为实例化后的后处理器应用，后面详细介绍
- 创建bean
try {
// 真正的创建Bean方法
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);
}
//真正创建Bean的方法
protected Object doCreateBean(final String beanName, final RootBeanDefinition mbd, final @Nullable Object[] args)
throws BeanCreationException {
// Instantiate the bean.
//BeanWrapper是对Bean的包装，其接口中所定义的功能很简单包括设置获取被包装的对象，获取被包装bean的属性描述器
BeanWrapper instanceWrapper = null;
if (mbd.isSingleton()) {
//单例模式，删除factoryBean缓存
instanceWrapper = this.factoryBeanInstanceCache.remove(beanName);
}
if (instanceWrapper == null) {
//使用合适的实例化策略来创建Bean：工厂方法、构造函数自动注入、简单初始化
instanceWrapper = createBeanInstance(beanName, mbd, args);
}
//从包装类中获取实例化的Bean
final Object bean = instanceWrapper.getWrappedInstance();
//获取实例化对象的类型
Class<?> beanType = instanceWrapper.getWrappedClass();
if (beanType != NullBean.class) {
mbd.resolvedTargetType = beanType;
}
// Allow post-processors to modify the merged bean definition.
//检查是否有后置处理
synchronized (mbd.postProcessingLock) {
if (!mbd.postProcessed) {
try {
//调用PostProcessor后置处理器，修改 BeanDefinition
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.
// 解决单例模式的循环依赖
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");
}
//这里是一个匿名内部类，为了防止循环引用，尽早持有对象的引用
addSingletonFactory(beanName, () -> getEarlyBeanReference(beanName, mbd, bean));
}
// Initialize the bean instance.
//Bean对象的初始化，依赖注入在此触发
//这个exposedObject在初始化完成之后返回作为依赖注入完成后的Bean
Object exposedObject = bean;
try {
//将Bean实例对象封装，并且Bean定义中配置的属性值赋值给实例对象
populateBean(beanName, mbd, instanceWrapper);
//初始化Bean对象
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) {
//获取指定名称的已注册的单例模式Bean对象
Object earlySingletonReference = getSingleton(beanName, false);
if (earlySingletonReference != null) {
//根据名称获取的已注册的Bean和正在实例化的Bean是同一个
if (exposedObject == bean) {
//当前实例化的Bean初始化完成
exposedObject = earlySingletonReference;
}
//当前Bean依赖其他Bean，并且当发生循环引用时不允许新创建实例对象
else if (!this.allowRawInjectionDespiteWrapping && hasDependentBean(beanName)) {
String[] dependentBeans = getDependentBeans(beanName);
Set<String> actualDependentBeans = new LinkedHashSet<>(dependentBeans.length);
//获取当前Bean所依赖的其他Bean
for (String dependentBean : dependentBeans) {
//对依赖Bean进行类型检查
if (!removeSingletonIfCreatedForTypeCheckOnly(dependentBean)) {
actualDependentBeans.add(dependentBean);
}
}
if (!actualDependentBeans.isEmpty()) {
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.
//注册完成依赖注入的Bean
try {
registerDisposableBeanIfNecessary(beanName, bean, mbd);
}
catch (BeanDefinitionValidationException ex) {
throw new BeanCreationException(
mbd.getResourceDescription(), beanName, "Invalid destruction signature", ex);
}
return exposedObject;
}
我们来总结一下上面函数的大体步骤：
- 如果是单例则需要首先清除缓存
- 实例化bean，将BeanDefinition转换为BeanWrapper
- MergedBeanDefinitionPostProcessor的应用
- 依赖处理
- 属性填充，将所有属性填充至bean的实例中
- 循环依赖检查
- 注册DisposableBean
- 完成创建并返回
由于这是一个十分复杂的过程，而且涉及到循环依赖的问题，后面文章详细来解释
1.1.4 后置处理
afterSingletonCreation(beanName)同样是个表示方法
DefaultSingletonBeanRegistry
// 用于移除标记，当前 Bean 不处于创建中
protected void afterSingletonCreation(String beanName) {
if (!this.inCreationCheckExclusions.contains(beanName) && !this.singletonsCurrentlyInCreation.remove(beanName)) {
//移除失败，抛出异常
throw new IllegalStateException("Singleton '" + beanName + "' isn't currently in creation");
}
}
创建Bean之后移除创建标示。前置处理和后置处理的这个创建标示，会在调用isSingletonCurrentlyInCreation(String beanName)时用到，该方法用来判断当前bean是否已经在创建中。
1.1.5 加入缓存
DefaultSingletonBeanRegistry
if (newSingleton) {
addSingleton(beanName, singletonObject);
}
protected void addSingleton(String beanName, Object singletonObject) {
synchronized (this.singletonObjects) {
this.singletonObjects.put(beanName, singletonObject);
this.singletonFactories.remove(beanName);
this.earlySingletonObjects.remove(beanName);
this.registeredSingletons.add(beanName);
}
}
- 【put】singletonObjects 属性，单例 bean 的缓存。
- 【remove】singletonFactories 属性，单例 bean Factory 的缓存。
- 【remove】earlySingletonObjects 属性，“早期”创建的单例 bean 的缓存。
- 【add】registeredSingletons 属性，已经注册的单例缓存。
1.2 原型模式实例化
AbstractBeanFactory
//创建多例Bean
else if (mbd.isPrototype()) {
// It's a prototype -> create a new instance.
//原型模式(Prototype)是每次都会创建一个新的对象
Object prototypeInstance = null;
try {
//加载前置处理，默认的功能是注册当前创建的原型对象
beforePrototypeCreation(beanName);
//创建指定Bean对象实例
prototypeInstance = createBean(beanName, mbd, args);
}
finally {
//加载后置处理，默认的功能告诉IOC容器指定Bean的原型对象不再创建
afterPrototypeCreation(beanName);
}
//获取给定Bean的实例对象
bean = getObjectForBeanInstance(prototypeInstance, name, beanName, mbd);
}
原型模式很简单，直接创建一个新的实例就好了，不再从缓存中去获取，beforePrototypeCreation(beanName)前置处理，将当前bean标记为正在创建的原型，afterPrototypeCreation(beanName)后置处理，取消当前bean的正在创建标示。而getObjectForBeanInstance方法参考上一篇文章的详细解释
1.3 其他模式实例化
AbstractBeanFactory
//要创建的Bean既不是Singleton也不是Prototype
//如：request、session、application等生命周期
else {
String scopeName = mbd.getScope();
final Scope scope = this.scopes.get(scopeName);
//Bean定义资源中没有配置生命周期范围，则Bean定义不合法
if (scope == null) {
throw new IllegalStateException("No Scope registered for scope name '" + scopeName + "'");
}
try {
//这里又使用了一个匿名内部类，获取一个指定生命周期范围的实例
Object scopedInstance = scope.get(beanName, () -> {
//前置处理
beforePrototypeCreation(beanName);
try {
return createBean(beanName, mbd, args);
}
finally {
//后置处理
afterPrototypeCreation(beanName);
}
});
//获取给定Bean的实例对象
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);
}
}
核心流程和原型模式一样，只不过获取 bean 实例是由 scope.get() 实现，我们可以发现这个作用域的调用的主要方法：
- getObjectForBeanInstance（）
- afterPrototypeCreation（）
- createBean（）
