01.一般的流程是，这里是从上一章的preInstantiateSingleton方法顺序过来的。
getBean() -> doGetBean() -> createBean() -> doCreateBean() -> createBeanInstance() -> populateBean() -> initializeBean()
02.getBean方法，一般就是调用doGetBean方法
@Override
public Object getBean(String name) throws BeansException {
return doGetBean(name, null, null, false);
}
03.doGetBean方法
protected <T> T doGetBean(
String name, @Nullable Class<T> requiredType, @Nullable Object[] args, boolean typeCheckOnly)
throws BeansException {
/**
* 提取对应的beanName，有人可能会认为此处直接使用即可，为什么还要进行转换呢，原因在于当bean对象实现FactoryBean接口之后就会变成&beanName，同时如果存在别名，也需要把别名进行转换*/
String beanName = transformedBeanName(name);
Object bean;
// Eagerly check singleton cache for manually registered singletons.
/**提前检查单例缓存中是否有手动注册的单例对象，跟循环依赖有关联*/
Object sharedInstance = getSingleton(beanName);
// 如果bean的单例对象找到了，且没有创建bean实例时要使用的参数
if (sharedInstance != null && args == null) {
if (logger.isTraceEnabled()) {
if (isSingletonCurrentlyInCreation(beanName)) {
logger.trace("Returning eagerly cached instance of singleton bean '" + beanName +
"' that is not fully initialized yet - a consequence of a circular reference");
}
else {
logger.trace("Returning cached instance of singleton bean '" + beanName + "'");
}
}
// 返回对象的实例，这句话的重点在于当你实现了FactoryBean接口的对象，需要获取具体的对象的时候就需要此方法来进行获取了
bean = getObjectForBeanInstance(sharedInstance, name, beanName, null);
}
else {
// Fail if we're already creating this bean instance:
// We're assumably within a circular reference.
// 当对象都是单例的时候会尝试解决循环依赖的问题，但是原型模式下如果存在循环依赖的情况，那么直接抛出异常
if (isPrototypeCurrentlyInCreation(beanName)) {
throw new BeanCurrentlyInCreationException(beanName);
}
// Check if bean definition exists in this factory.
// 如果bean定义不存在，就检查父工厂是否有
BeanFactory parentBeanFactory = getParentBeanFactory();
// 如果beanDefinitionMap中也就是在所有已经加载的类中不包含beanName，那么就尝试从父容器中获取
if (parentBeanFactory != null && !containsBeanDefinition(beanName)) {
// Not found -> check parent.
// 获取name对应的规范名称【全类名】，如果name前面有'&'，则会返回'&'+规范名称【全类名】
String nameToLookup = originalBeanName(name);
// 如果父工厂是AbstractBeanFactory的实例
if (parentBeanFactory instanceof AbstractBeanFactory) {
// 调用父工厂的doGetBean方法，就是该方法。【递归】
return ((AbstractBeanFactory) parentBeanFactory).doGetBean(
nameToLookup, requiredType, args, typeCheckOnly);
}
else if (args != null) {
// Delegation to parent with explicit args.
// 如果有创建bean实例时要使用的参数
// Delegation to parent with explicit args. 使用显示参数委派给父工厂
// 使用父工厂获取该bean对象,通bean全类名和创建bean实例时要使用的参数
return (T) parentBeanFactory.getBean(nameToLookup, args);
}
else if (requiredType != null) {
// No args -> delegate to standard getBean method.
// 没有创建bean实例时要使用的参数 -> 委托给标准的getBean方法。
// 使用父工厂获取该bean对象,通bean全类名和所需的bean类型
return parentBeanFactory.getBean(nameToLookup, requiredType);
}
else {
// 使用父工厂获取bean，通过bean全类名
return (T) parentBeanFactory.getBean(nameToLookup);
}
}
// 如果不是做类型检查，那么表示要创建bean，此处在集合中做一个记录
if (!typeCheckOnly) {
// 为beanName标记为已经创建（或将要创建）
markBeanAsCreated(beanName);
}
try {
// 此处做了BeanDefinition对象的转换，当我们从xml文件中加载beandefinition对象的时候，封装的对象是GenericBeanDefinition,
// 此处要做类型转换，如果是子类bean的话，会合并父类的相关属性
RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);
// 检查mbd的合法性，不合格会引发验证异常
checkMergedBeanDefinition(mbd, beanName, args);
// Guarantee initialization of beans that the current bean depends on.
// 如果存在依赖的bean的话，那么则优先实例化依赖的bean
String[] dependsOn = mbd.getDependsOn();
if (dependsOn != null) {
// 如果存在依赖，则需要递归实例化依赖的bean
for (String dep : dependsOn) {
// 如果beanName已注册依赖于dependentBeanName的关系
if (isDependent(beanName, dep)) {
throw new BeanCreationException(mbd.getResourceDescription(), beanName,
"Circular depends-on relationship between '" + beanName + "' and '" + dep + "'");
}
// 注册各个bean的依赖关系，方便进行销毁
registerDependentBean(dep, beanName);
try {
// 递归优先实例化被依赖的Bean
getBean(dep);
}
// 捕捉为找到BeanDefinition异常：'beanName'依赖于缺少的bean'dep'
catch (NoSuchBeanDefinitionException ex) {
throw new BeanCreationException(mbd.getResourceDescription(), beanName,
"'" + beanName + "' depends on missing bean '" + dep + "'", ex);
}
}
}
// Create bean instance.
// 创建bean的实例对象
if (mbd.isSingleton()) {
// 返回以beanName的(原始)单例对象，如果尚未注册，则使用singletonFactory创建并注册一个对象:
sharedInstance = getSingleton(beanName, () -> {
try {
// 为给定的合并后BeanDefinition(和参数)创建一个bean实例
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.
// 显示地从单例缓存中删除实例：它可能是由创建过程急切地放在那里，以允许循环引用解析。还要删除
// 接收到该Bean临时引用的任何Bean
// 销毁给定的bean。如果找到相应的一次性Bean实例，则委托给destoryBean
destroySingleton(beanName);
// 重新抛出ex
throw ex;
}
});
// 从beanInstance中获取公开的Bean对象，主要处理beanInstance是FactoryBean对象的情况，如果不是
// FactoryBean会直接返回beanInstance实例
bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd);
}
// 原型模式的bean对象创建
else if (mbd.isPrototype()) {
// It's a prototype -> create a new instance.
// 它是一个原型 -> 创建一个新实例
// 定义prototype实例
Object prototypeInstance = null;
try {
// 创建Prototype对象前的准备工作，默认实现将beanName添加到prototypesCurrentlyInCreation中
beforePrototypeCreation(beanName);
// 为mbd(和参数)创建一个bean实例
prototypeInstance = createBean(beanName, mbd, args);
}
finally {
// 创建完prototype实例后的回调，默认是将beanName从prototypesCurrentlyInCreation移除
afterPrototypeCreation(beanName);
}
// 从beanInstance中获取公开的Bean对象，主要处理beanInstance是FactoryBean对象的情况，如果不是
// FactoryBean会直接返回beanInstance实例
bean = getObjectForBeanInstance(prototypeInstance, name, beanName, mbd);
}
else {
// 指定的scope上实例化bean
String scopeName = mbd.getScope();
if (!StringUtils.hasLength(scopeName)) {
throw new IllegalStateException("No scope name defined for bean ´" + beanName + "'");
}
// 从scopes中获取scopeName对于的Scope对象
Scope scope = this.scopes.get(scopeName);
// 如果scope为null
if (scope == null) {
// 抛出非法状态异常：没有名为'scopeName'的scope注册
throw new IllegalStateException("No Scope registered for scope name '" + scopeName + "'");
}
try {
// 从scope中获取beanName对应的实例对象
Object scopedInstance = scope.get(beanName, () -> {
// 创建Prototype对象前的准备工作，默认实现 将beanName添加到prototypesCurrentlyInCreation中
beforePrototypeCreation(beanName);
try {
// 为mbd(和参数)创建一个bean实例
return createBean(beanName, mbd, args);
}
finally {
// 创建完prototype实例后的回调，默认是将beanName从prototypesCurrentlyInCreation移除
afterPrototypeCreation(beanName);
}
});
// 从beanInstance中获取公开的Bean对象，主要处理beanInstance是FactoryBean对象的情况，如果不是
// FactoryBean会直接返回beanInstance实例
bean = getObjectForBeanInstance(scopedInstance, name, beanName, mbd);
}
catch (IllegalStateException ex) {
// 捕捉非法状态异常
// 抛出Bean创建异常：作用域 'scopeName' 对于当前线程是不活动的；如果您打算从单个实例引用它，请考虑为此
// beanDefinition一个作用域代理
throw new BeanCreationException(beanName,
"Scope '" + scopeName + "' is not active for the current thread; consider " +
"defining a scoped proxy for this bean if you intend to refer to it from a singleton",
ex);
}
}
}
catch (BeansException ex) {
// 捕捉获取Bean对象抛出的Bean异常
// 在Bean创建失败后，对缓存的元数据执行适当的清理
cleanupAfterBeanCreationFailure(beanName);
// 重新抛出ex
throw ex;
}
}
// Check if required type matches the type of the actual bean instance.
// 检查requiredType是否与实际Bean实例的类型匹配
// 如果requiredType不为null&&bean不是requiredType的实例
if (requiredType != null && !requiredType.isInstance(bean)) {
try {
// 获取此BeanFactory使用的类型转换器，将bean转换为requiredType
T convertedBean = getTypeConverter().convertIfNecessary(bean, requiredType);
// 如果convertedBean为null
if (convertedBean == null) {
// 抛出Bean不是必要类型的异常
throw new BeanNotOfRequiredTypeException(name, requiredType, bean.getClass());
}
// 返回convertedBean
return convertedBean;
}
catch (TypeMismatchException ex) {
if (logger.isTraceEnabled()) {
logger.trace("Failed to convert bean '" + name + "' to required type '" +
ClassUtils.getQualifiedName(requiredType) + "'", ex);
}
throw new BeanNotOfRequiredTypeException(name, requiredType, bean.getClass());
}
}
// 将bean返回出去
return (T) bean;
}
详细说明：doGetBean
03.这一段：上一章详细说过，就是害怕出现别名
// name有可能是 &xxx 或者 xxx，如果name是&xxx，那么beanName就是xxx
// name有可能传入进来的是别名，那么beanName就是id
String beanName = transformedBeanName(name);
Object beanInstance;
04.这一段：getSingleton从缓存中获取单例，上一章写过三级缓存
// Eagerly check singleton cache for manually registered singletons.
Object sharedInstance = getSingleton(beanName);
if (sharedInstance != null && args == null) {
if (logger.isTraceEnabled()) {
if (isSingletonCurrentlyInCreation(beanName)) {
logger.trace("Returning eagerly cached instance of singleton bean '" + beanName +
"' that is not fully initialized yet - a consequence of a circular reference");
}
else {
logger.trace("Returning cached instance of singleton bean '" + beanName + "'");
}
}
// 如果sharedInstance是FactoryBean，那么就调用getObject()返回对象
beanInstance = getObjectForBeanInstance(sharedInstance, name, beanName, null);
}
其中的getObjectForBeanInstance方法：为了防止传入的是FactoryBean类，那么要用这个FactoryBean类重写的方法getObject方法来获取真正的对象
protected Object getObjectForBeanInstance(
Object beanInstance, String name, String beanName, @Nullable RootBeanDefinition mbd) {
// Don't let calling code try to dereference the factory if the bean isn't a factory.
// 如果参数name是&xxx，那么就直接返回单例池中的对象 Bean的name如果以“&”开头，说明是想获得FactoryBean本身
if (BeanFactoryUtils.isFactoryDereference(name)) {
if (beanInstance instanceof NullBean) {
return beanInstance;
}
if (!(beanInstance instanceof FactoryBean)) {
//没有实现FactoryBean接口
throw new BeanIsNotAFactoryException(beanName, beanInstance.getClass());
}
if (mbd != null) {
//实现FactoryBean接口 将RootBeanDefinition 中的isFactoryBean 设置为true
mbd.isFactoryBean = true;
}
return beanInstance;
}
// 现在拥有了一个新的 BeanInstance, 这个实例可能是常规 Bean 也有可能是 FactoryBean<?>
// 如果是 FactoryBean<?> 则使用它创建实例, 但如果是开发者想要直接获取工厂实例而不是工厂的 getObject()
// 方法对应的实例, 那么传入的 BeanName 应该加入前缀 '&'
// 单例池中的对象不是FactoryBean，则直接返回
if (!(beanInstance instanceof FactoryBean)) {
return beanInstance;
}
//此时参数的name是factoryBean的name，但是没有以&开头，就代表要用getObject
Object object = null;
if (mbd != null) {
mbd.isFactoryBean = true;
}
else {
// 从factoryBeanObjectCache中直接拿对象
object = getCachedObjectForFactoryBean(beanName);
}
// 此时factoryBeanObjectCache中没有这个对象
// 激活 FactoryBean<?> 的 getObject() 方法
if (object == null) {
// Return bean instance from factory.
// 这里已经明确知道 beanInstance 一定是 FactoryBean<?> 类型
FactoryBean<?> factory = (FactoryBean<?>) beanInstance;
// Caches object obtained from FactoryBean if it is a singleton.
if (mbd == null && containsBeanDefinition(beanName)) {
// 将BeanDefinition 转换为 RootBeanDefinition, 如果指定的 BeanName
// 是子 Bean 的话同时会合并父类的相关属性
mbd = getMergedLocalBeanDefinition(beanName);
}
// synthetic为true，表示这个Bean不是正常的一个Bean，可能只是起到辅助作用的，所以这种Bean就不用去执行PostProcessor了
boolean synthetic = (mbd != null && mbd.isSynthetic());
object = getObjectFromFactoryBean(factory, beanName, !synthetic);
}
return object;
}
其中开始的BeanFactoryUtils.isFactoryDereference(name)：
这里用的变量是 String FACTORY_BEAN_PREFIX = “&”;
public static boolean isFactoryDereference(@Nullable String name) {
//也就是判断name是不是null并且以&开头，都是对的，返回ture
return (name != null && name.startsWith(BeanFactory.FACTORY_BEAN_PREFIX));
}
其二.最后的containsBeanDefinition方法，判断是不是有beanName对应的BeanDefinition
@Override
public boolean containsBeanDefinition(String beanName) {
Assert.notNull(beanName, "Bean name must not be null");
return this.beanDefinitionMap.containsKey(beanName);
}
其二.最后用到的getObjectFromFactoryBean方法：
protected Object getObjectFromFactoryBean(FactoryBean<?> factory, String beanName, boolean shouldPostProcess) {
// 如果是单例 Bean && Bean 实例已经创建过, 没有再次创建的必要, 要保证单例 Bean 全局唯一, 直接从缓存中获取
if (factory.isSingleton() && containsSingleton(beanName)) {
// 进入同步代码块
synchronized (getSingletonMutex()) {
// 从缓存中获取
Object object = this.factoryBeanObjectCache.get(beanName);
// 如果缓存中没有
if (object == null) {
// 激活 FactoryBean<?> 中的 getObject() 方法获取开发者
// 定制的初始化逻辑
object = doGetObjectFromFactoryBean(factory, beanName);
// Only post-process and store if not put there already during getObject() call above
// (e.g. because of circular reference processing triggered by custom getBean calls)
Object alreadyThere = this.factoryBeanObjectCache.get(beanName);
if (alreadyThere != null) {
object = alreadyThere;
}
else {
if (shouldPostProcess) {
if (isSingletonCurrentlyInCreation(beanName)) {
// Temporarily return non-post-processed object, not storing it yet..
return object;
}
beforeSingletonCreation(beanName);
try {
object = postProcessObjectFromFactoryBean(object, beanName);
}
catch (Throwable ex) {
throw new BeanCreationException(beanName,
"Post-processing of FactoryBean's singleton object failed", ex);
}
finally {
afterSingletonCreation(beanName);
}
}
if (containsSingleton(beanName)) {
this.factoryBeanObjectCache.put(beanName, object);
}
}
}
return object;
}
}
else {
// 直接获取
Object object = doGetObjectFromFactoryBean(factory, beanName);
if (shouldPostProcess) {
try {
object = postProcessObjectFromFactoryBean(object, beanName);
}
catch (Throwable ex) {
throw new BeanCreationException(beanName, "Post-processing of FactoryBean's object failed", ex);
}
}
return object;
}
}
其中的doGetObjectFromFactoryBean()：就是一个factory.getObject()
private Object doGetObjectFromFactoryBean(FactoryBean<?> factory, String beanName) throws BeanCreationException {
Object object;
try {
if (System.getSecurityManager() != null) {
AccessControlContext acc = getAccessControlContext();
try {
object = AccessController.doPrivileged((PrivilegedExceptionAction<Object>) factory::getObject, acc);
}
catch (PrivilegedActionException pae) {
throw pae.getException();
}
}
else {
// 激活 FactoryBean<?> 中的 getObject() 方法调用
// 开发者定制化的的 Bean 注册逻辑
object = factory.getObject();
}
}
catch (FactoryBeanNotInitializedException ex) {
throw new BeanCurrentlyInCreationException(beanName, ex.toString());
}
catch (Throwable ex) {
throw new BeanCreationException(beanName, "FactoryBean threw exception on object creation", ex);
}
// Do not accept a null value for a FactoryBean that's not fully
// initialized yet: Many FactoryBeans just return null then.
if (object == null) {
if (isSingletonCurrentlyInCreation(beanName)) {
throw new BeanCurrentlyInCreationException(
beanName, "FactoryBean which is currently in creation returned null from getObject");
}
object = new NullBean();
}
return object;
}
05.回到dogetbean方法：如果单例池里面没有，这里进入else部分
isPrototypeCurrentlyInCreation和循环依赖有关，暂时不管
getParentBeanFactory 和springmvc有关，也暂时不管
else {
// Fail if we're already creating this bean instance:
// We're assumably within a circular reference.
// 当对象都是单例的时候会尝试解决循环依赖的问题，但是原型模式下如果存在循环依赖的情况，那么直接抛出异常
if (isPrototypeCurrentlyInCreation(beanName)) {
throw new BeanCurrentlyInCreationException(beanName);
}
// Check if bean definition exists in this factory.
// 如果bean定义不存在，就检查父工厂是否有
BeanFactory parentBeanFactory = getParentBeanFactory();
// 如果beanDefinitionMap中也就是在所有已经加载的类中不包含beanName，那么就尝试从父容器中获取
if (parentBeanFactory != null && !containsBeanDefinition(beanName)) {
// Not found -> check parent.
// 获取name对应的规范名称【全类名】，如果name前面有'&'，则会返回'&'+规范名称【全类名】
String nameToLookup = originalBeanName(name);
// 如果父工厂是AbstractBeanFactory的实例
if (parentBeanFactory instanceof AbstractBeanFactory) {
// 调用父工厂的doGetBean方法，就是该方法。【递归】
return ((AbstractBeanFactory) parentBeanFactory).doGetBean(
nameToLookup, requiredType, args, typeCheckOnly);
}
else if (args != null) {
// Delegation to parent with explicit args.
// 如果有创建bean实例时要使用的参数
// Delegation to parent with explicit args. 使用显示参数委派给父工厂
// 使用父工厂获取该bean对象,通bean全类名和创建bean实例时要使用的参数
return (T) parentBeanFactory.getBean(nameToLookup, args);
}
else if (requiredType != null) {
// No args -> delegate to standard getBean method.
// 没有创建bean实例时要使用的参数 -> 委托给标准的getBean方法。
// 使用父工厂获取该bean对象,通bean全类名和所需的bean类型
return parentBeanFactory.getBean(nameToLookup, requiredType);
}
else {
// 使用父工厂获取bean，通过bean全类名
return (T) parentBeanFactory.getBean(nameToLookup);
}
}
06.else的下一个部分：还是在else部分
主要看 getDependsOn 这里涉及@Dependon 注解
例子：
UserService 在创建bean之前要创建User的bean才可以
@Component
@DependsOn("User")
public class UserService {
}
那如果：User 类有注解@DependsOn(“OrderService”)
User 在创建bean之前要创建OrderService的bean才可以
@Component
@DependsOn("OrderService")
public class User {
}
如果出现：
一个类 A 有注解@DependsOn(“B”)
一个类 B 有注解@DependsOn(“A”)
则叫做A,B两个类的循环依赖
else的具体代码：
// 如果不是做类型检查，那么表示要创建bean，此处在集合中做一个记录
if (!typeCheckOnly) {
// 为beanName标记为已经创建（或将要创建）
markBeanAsCreated(beanName);
}
StartupStep beanCreation = this.applicationStartup.start("spring.beans.instantiate")
.tag("beanName", name);
try {
if (requiredType != null) {
beanCreation.tag("beanType", requiredType::toString);
}
RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);
// 检查BeanDefinition是不是Abstract的
checkMergedBeanDefinition(mbd, beanName, args);
// Guarantee initialization of beans that the current bean depends on.
String[] dependsOn = mbd.getDependsOn();
if (dependsOn != null) {
// dependsOn表示当前beanName所依赖的，当前Bean创建之前dependsOn所依赖的Bean必须已经创建好了
for (String dep : dependsOn) {
// beanName是不是被dep依赖了，如果是则出现了循环依赖
if (isDependent(beanName, dep)) {
throw new BeanCreationException(mbd.getResourceDescription(), beanName,
"Circular depends-on relationship between '" + beanName + "' and '" + dep + "'");
}
// dep被beanName依赖了，存入dependentBeanMap中，dep为key，beanName为value
registerDependentBean(dep, beanName);
// 创建所依赖的bean
try {
getBean(dep);
}
catch (NoSuchBeanDefinitionException ex) {
throw new BeanCreationException(mbd.getResourceDescription(), beanName,
"'" + beanName + "' depends on missing bean '" + dep + "'", ex);
}
}
}
checkMergedBeanDefinition方法:
protected void checkMergedBeanDefinition(RootBeanDefinition mbd, String beanName, @Nullable Object[] args)
throws BeanDefinitionStoreException {
if (mbd.isAbstract()) {
throw new BeanIsAbstractException(beanName);
}
}
getDependsOn方法：
@Nullable
private String[] dependsOn;
public String[] getDependsOn() {
return this.dependsOn;
}
07.else的继续：这里判断注解Scope的值 创建几个bean
用到的一个map：
private final Map<String, Scope> scopes = new LinkedHashMap<>(8);
// Create bean instance.
// 创建bean的实例对象
if (mbd.isSingleton()) {
// 返回以beanName的(原始)单例对象，如果尚未注册，则使用singletonFactory创建并注册一个对象:
sharedInstance = getSingleton(beanName, () -> {
try {
// 为给定的合并后BeanDefinition(和参数)创建一个bean实例
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.
// 显示地从单例缓存中删除实例：它可能是由创建过程急切地放在那里，以允许循环引用解析。还要删除
// 接收到该Bean临时引用的任何Bean
// 销毁给定的bean。如果找到相应的一次性Bean实例，则委托给destoryBean
destroySingleton(beanName);
// 重新抛出ex
throw ex;
}
});
// 从beanInstance中获取公开的Bean对象，主要处理beanInstance是FactoryBean对象的情况，如果不是
// FactoryBean会直接返回beanInstance实例
bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd);
}
// 原型模式的bean对象创建
else if (mbd.isPrototype()) {
// It's a prototype -> create a new instance.
// 它是一个原型 -> 创建一个新实例
// 定义prototype实例
Object prototypeInstance = null;
try {
// 创建Prototype对象前的准备工作，默认实现将beanName添加到prototypesCurrentlyInCreation中
beforePrototypeCreation(beanName);
// 为mbd(和参数)创建一个bean实例
prototypeInstance = createBean(beanName, mbd, args);
}
finally {
// 创建完prototype实例后的回调，默认是将beanName从prototypesCurrentlyInCreation移除
afterPrototypeCreation(beanName);
}
// 从beanInstance中获取公开的Bean对象，主要处理beanInstance是FactoryBean对象的情况，如果不是
// FactoryBean会直接返回beanInstance实例
bean = getObjectForBeanInstance(prototypeInstance, name, beanName, mbd);
}
else {
// 指定的scope上实例化bean
String scopeName = mbd.getScope();
if (!StringUtils.hasLength(scopeName)) {
throw new IllegalStateException("No scope name defined for bean ´" + beanName + "'");
}
// 从scopes中获取scopeName对于的Scope对象
Scope scope = this.scopes.get(scopeName);
// 如果scope为null
if (scope == null) {
// 抛出非法状态异常：没有名为'scopeName'的scope注册
throw new IllegalStateException("No Scope registered for scope name '" + scopeName + "'");
}
try {
// 从scope中获取beanName对应的实例对象
Object scopedInstance = scope.get(beanName, () -> {
// 创建Prototype对象前的准备工作，默认实现 将beanName添加到prototypesCurrentlyInCreation中
beforePrototypeCreation(beanName);
try {
// 为mbd(和参数)创建一个bean实例
return createBean(beanName, mbd, args);
}
finally {
// 创建完prototype实例后的回调，默认是将beanName从prototypesCurrentlyInCreation移除
afterPrototypeCreation(beanName);
}
});
// 从beanInstance中获取公开的Bean对象，主要处理beanInstance是FactoryBean对象的情况，如果不是
// FactoryBean会直接返回beanInstance实例
bean = getObjectForBeanInstance(scopedInstance, name, beanName, mbd);
}
catch (IllegalStateException ex) {
// 捕捉非法状态异常
// 抛出Bean创建异常：作用域 'scopeName' 对于当前线程是不活动的；如果您打算从单个实例引用它，请考虑为此
// beanDefinition一个作用域代理
throw new BeanCreationException(beanName,
"Scope '" + scopeName + "' is not active for the current thread; consider " +
"defining a scoped proxy for this bean if you intend to refer to it from a singleton",
ex);
}
}
}
catch (BeansException ex) {
// 捕捉获取Bean对象抛出的Bean异常
// 在Bean创建失败后，对缓存的元数据执行适当的清理
cleanupAfterBeanCreationFailure(beanName);
// 重新抛出ex
throw ex;
}
}
