| title | tags | categories | keywords | description | cover | abbrlink | date | |||
|---|---|---|---|---|---|---|---|---|---|---|
Spring源码系列-第4章-Bean初始化流程 |
|
|
Spring，框架，spring源码 |
总结一下Bean的初始化 |
49f419ae |
2022-01-27 13:01:02 -0800 |
@Override //容器刷新的十二大步。模板模式
public void refresh() throws BeansException, IllegalStateException {
synchronized (this.startupShutdownMonitor) {
StartupStep contextRefresh = this.applicationStartup.start("spring.context.refresh");
// Prepare this context for refreshing.
prepareRefresh();
// Tell the subclass to refresh the internal bean factory.
// 工厂创建：BeanFactory第一次开始创建的时候,有xml解析逻辑。
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
// Prepare the bean factory for use in this context.
prepareBeanFactory(beanFactory);
try {
// Allows post-processing of the bean factory in context subclasses.
postProcessBeanFactory(beanFactory);
StartupStep beanPostProcess = this.applicationStartup.start("spring.context.beans.post-process");
//工厂增强：执行所有的BeanFactory后置增强器；利用BeanFactory后置增强器对工厂进行修改或者增强,配置类会在这里进行解析。 Invoke factory processors registered as beans in the context.
invokeBeanFactoryPostProcessors(beanFactory);
//注册所有的Bean的后置处理器 Register bean processors that intercept bean creation.
registerBeanPostProcessors(beanFactory);
beanPostProcess.end();
// Initialize message source for this context.
initMessageSource();
// Initialize event multicaster for this context.
initApplicationEventMulticaster();
// Initialize other special beans in specific context subclasses.
onRefresh();
//注册监听器，从容器中获取所有的ApplicationListener； Check for listener beans and register them.
registerListeners();
// Instantiate all remaining (non-lazy-init) singletons.
//bean创建；完成 BeanFactory 初始化。（工厂里面所有的组件都好了）
finishBeanFactoryInitialization(beanFactory);
// Last step: publish corresponding event.
finishRefresh();
}
catch (BeansException ex) {
if (logger.isWarnEnabled()) {
logger.warn("Exception encountered during context initialization - " +
"cancelling refresh attempt: " + ex);
}
// Destroy already created singletons to avoid dangling resources.
destroyBeans();
// Reset 'active' flag.
cancelRefresh(ex);
// Propagate exception to caller.
throw ex;
}
finally {
// Reset common introspection caches in Spring's core, since we
// might not ever need metadata for singleton beans anymore...
resetCommonCaches();
contextRefresh.end();
}
}
}
protected void finishBeanFactoryInitialization(ConfigurableListableBeanFactory beanFactory) {
// 给工厂设置好 ConversionService【负责类型转换的组件服务】， Initialize conversion service for this context.
if (beanFactory.containsBean(CONVERSION_SERVICE_BEAN_NAME) &&
beanFactory.isTypeMatch(CONVERSION_SERVICE_BEAN_NAME, ConversionService.class)) {
beanFactory.setConversionService(
beanFactory.getBean(CONVERSION_SERVICE_BEAN_NAME, ConversionService.class));
}
// 注册一个默认的值解析器（"${}"） ；Register a default embedded value resolver if no BeanFactoryPostProcessor
// (such as a PropertySourcesPlaceholderConfigurer bean) registered any before:
// at this point, primarily for resolution in annotation attribute values.
if (!beanFactory.hasEmbeddedValueResolver()) {
beanFactory.addEmbeddedValueResolver(strVal -> getEnvironment().resolvePlaceholders(strVal));
}
// LoadTimeWeaverAware；aspectj：加载时织入功能【aop】。 Initialize LoadTimeWeaverAware beans early to allow for registering their transformers early.
String[] weaverAwareNames = beanFactory.getBeanNamesForType(LoadTimeWeaverAware.class, false, false);
for (String weaverAwareName : weaverAwareNames) {
getBean(weaverAwareName); //从容器中获取组件，有则直接获取，没则进行创建
}
// Stop using the temporary ClassLoader for type matching.
beanFactory.setTempClassLoader(null);
// Allow for caching all bean definition metadata, not expecting further changes.
beanFactory.freezeConfiguration();
// Instantiate all remaining (non-lazy-init) singletons.
//初始化所有的非懒加载的单实例Bean
beanFactory.preInstantiateSingletons();
}
String FACTORY_BEAN_PREFIX = "&";
public void preInstantiateSingletons() throws BeansException {
if (logger.isTraceEnabled()) {
logger.trace("Pre-instantiating singletons in " + this);
}
// Iterate over a copy to allow for init methods which in turn register new bean definitions.
// While this may not be part of the regular factory bootstrap, it does otherwise work fine.
List<String> beanNames = new ArrayList<>(this.beanDefinitionNames);
// 创建出所有的单实例Bean；Trigger initialization of all non-lazy singleton beans...
for (String beanName : beanNames) {
RootBeanDefinition bd = getMergedLocalBeanDefinition(beanName); //开始解析文件的时候每一个bean标签被解析封装成一个BeanDefinition
if (!bd.isAbstract() && bd.isSingleton() && !bd.isLazyInit()) {
if (isFactoryBean(beanName)) { //如果是FactoryBean则执行下面逻辑
Object bean = getBean(FACTORY_BEAN_PREFIX + beanName); //得到HelloFactory
if (bean instanceof FactoryBean) {
FactoryBean<?> factory = (FactoryBean<?>) bean;
boolean isEagerInit;
if (System.getSecurityManager() != null && factory instanceof SmartFactoryBean) {
isEagerInit = AccessController.doPrivileged(
(PrivilegedAction<Boolean>) ((SmartFactoryBean<?>) factory)::isEagerInit,
getAccessControlContext());
}
else {
isEagerInit = (factory instanceof SmartFactoryBean &&
((SmartFactoryBean<?>) factory).isEagerInit());
}
if (isEagerInit) {
getBean(beanName);
}
}
}
else { //不是FactoryBean则执行这个,普通的单实例非懒加载bean的创建
getBean(beanName); //
}
}
}
// 触发 post-initialization 逻辑； Trigger post-initialization callback for all applicable beans...
for (String beanName : beanNames) {
Object singletonInstance = getSingleton(beanName);
if (singletonInstance instanceof SmartInitializingSingleton) {
StartupStep smartInitialize = this.getApplicationStartup().start("spring.beans.smart-initialize")
.tag("beanName", beanName);
SmartInitializingSingleton smartSingleton = (SmartInitializingSingleton) singletonInstance;
if (System.getSecurityManager() != null) {
AccessController.doPrivileged((PrivilegedAction<Object>) () -> {
smartSingleton.afterSingletonsInstantiated();
return null;
}, getAccessControlContext());
}
else {
smartSingleton.afterSingletonsInstantiated();
}
smartInitialize.end();
}
}
}
public boolean isFactoryBean(String name) throws NoSuchBeanDefinitionException {
String beanName = transformedBeanName(name);
Object beanInstance = getSingleton(beanName, false);
if (beanInstance != null) {
return (beanInstance instanceof FactoryBean);
}
// No singleton instance found -> check bean definition.
if (!containsBeanDefinition(beanName) && getParentBeanFactory() instanceof ConfigurableBeanFactory) {
// No bean definition found in this factory -> delegate to parent.
return ((ConfigurableBeanFactory) getParentBeanFactory()).isFactoryBean(name);
}
return isFactoryBean(beanName, getMergedLocalBeanDefinition(beanName));
}
protected boolean isFactoryBean(String beanName, RootBeanDefinition mbd) {
Boolean result = mbd.isFactoryBean;
if (result == null) {
Class<?> beanType = predictBeanType(beanName, mbd, FactoryBean.class);
result = (beanType != null && FactoryBean.class.isAssignableFrom(beanType));
mbd.isFactoryBean = result;
}
return result;
}无论是不是工厂Bean，最后调用的都是AbstractBeanFactory#getBean(String name)
由于工厂Bean只有在你getBean获取的时候，它才会创建，所以我们必须用这些测试类测试一下。
public class AnnotationMainTest {
public static void main(String[] args) {
ApplicationContext applicationContext =
new AnnotationConfigApplicationContext(MainConfig.class);
Hello bean = applicationContext.getBean(Hello.class);
System.out.println(bean);
}
}MainConfig
@ComponentScan("cn.imlql.spring")
@Configuration
public class MainConfig {
public MainConfig(){
System.out.println("MainConfig...创建了....");
}
}HelloFactory
@Component //也可以实现 SmartFactoryBean。指定提前加载
public class HelloFactory implements FactoryBean<Hello> {
@Override
public Hello getObject() throws Exception {
return new Hello(); //这是最终获取到的对象 pos_1
}
@Override
public Class<?> getObjectType() {
return Hello.class;
}
}pos_1位置打个断点。
Hello
public class Hello {
}从这里开始看调用链
@Nullable
private <T> T resolveBean(ResolvableType requiredType, @Nullable Object[] args, boolean nonUniqueAsNull) {
NamedBeanHolder<T> namedBean = resolveNamedBean(requiredType, args, nonUniqueAsNull);
if (namedBean != null) {
return namedBean.getBeanInstance();
}
BeanFactory parent = getParentBeanFactory();
if (parent instanceof DefaultListableBeanFactory) {
return ((DefaultListableBeanFactory) parent).resolveBean(requiredType, args, nonUniqueAsNull);
}
else if (parent != null) {
ObjectProvider<T> parentProvider = parent.getBeanProvider(requiredType);
if (args != null) {
return parentProvider.getObject(args);
}
else {
return (nonUniqueAsNull ? parentProvider.getIfUnique() : parentProvider.getIfAvailable());
}
}
return null;
}
private <T> NamedBeanHolder<T> resolveNamedBean(
ResolvableType requiredType, @Nullable Object[] args, boolean nonUniqueAsNull) throws BeansException {
Assert.notNull(requiredType, "Required type must not be null");
String[] candidateNames = getBeanNamesForType(requiredType); //按照类型获取组件
// ...
if (candidateNames.length == 1) {
return resolveNamedBean(candidateNames[0], requiredType, args);
}
// ...
return null;
}
//获取某一个组件在容器中的名字。 工厂Bean的主要逻辑还是走到这里，这里我们之前讲过
private String[] doGetBeanNamesForType(ResolvableType type, boolean includeNonSingletons, boolean allowEagerInit) {
List<String> result = new ArrayList<>();
// Check all bean definitions. 因为Spring没有直接保存class--bean名字的对应信息，只能遍历所有的beanname，拿出他们beanname的定义信息，再看是否我指定的类型。
for (String beanName : this.beanDefinitionNames) {
// Only consider bean as eligible if the bean name is not defined as alias for some other bean.
if (!isAlias(beanName)) { //判断是否别名
try {
RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);
// Only check bean definition if it is complete.
if (!mbd.isAbstract() && (allowEagerInit ||
(mbd.hasBeanClass() || !mbd.isLazyInit() || isAllowEagerClassLoading()) &&
!requiresEagerInitForType(mbd.getFactoryBeanName()))) {
boolean isFactoryBean = isFactoryBean(beanName, mbd); //是否FactoryBean
BeanDefinitionHolder dbd = mbd.getDecoratedDefinition();
boolean matchFound = false;
boolean allowFactoryBeanInit = (allowEagerInit || containsSingleton(beanName));
boolean isNonLazyDecorated = (dbd != null && !mbd.isLazyInit());
if (!isFactoryBean) {
if (includeNonSingletons || isSingleton(beanName, mbd, dbd)) {
matchFound = isTypeMatch(beanName, type, allowFactoryBeanInit); //是否类型匹配？
}
}
else {
if (includeNonSingletons || isNonLazyDecorated ||
(allowFactoryBeanInit && isSingleton(beanName, mbd, dbd))) {
matchFound = isTypeMatch(beanName, type, allowFactoryBeanInit);
}
if (!matchFound) {
// In case of FactoryBean, try to match FactoryBean instance itself next.
beanName = FACTORY_BEAN_PREFIX + beanName;
matchFound = isTypeMatch(beanName, type, allowFactoryBeanInit);
}
}
if (matchFound) {
result.add(beanName);
}
}
}
catch (CannotLoadBeanClassException | BeanDefinitionStoreException ex) {
if (allowEagerInit) {
throw ex;
}
// Probably a placeholder: let's ignore it for type matching purposes.
LogMessage message = (ex instanceof CannotLoadBeanClassException ?
LogMessage.format("Ignoring bean class loading failure for bean '%s'", beanName) :
LogMessage.format("Ignoring unresolvable metadata in bean definition '%s'", beanName));
logger.trace(message, ex);
// Register exception, in case the bean was accidentally unresolvable.
onSuppressedException(ex);
}
catch (NoSuchBeanDefinitionException ex) {
// Bean definition got removed while we were iterating -> ignore.
}
}
}
// Check manually registered singletons too.
for (String beanName : this.manualSingletonNames) {
try {
// In case of FactoryBean, match object created by FactoryBean.
if (isFactoryBean(beanName)) {
if ((includeNonSingletons || isSingleton(beanName)) && isTypeMatch(beanName, type)) {
result.add(beanName);
// Match found for this bean: do not match FactoryBean itself anymore.
continue;
}
// In case of FactoryBean, try to match FactoryBean itself next.
beanName = FACTORY_BEAN_PREFIX + beanName;//注意这里的工厂Bean前缀
}
// Match raw bean instance (might be raw FactoryBean).
if (isTypeMatch(beanName, type)) {
result.add(beanName);
}
}
catch (NoSuchBeanDefinitionException ex) {
// Shouldn't happen - probably a result of circular reference resolution...
logger.trace(LogMessage.format(
"Failed to check manually registered singleton with name '%s'", beanName), ex);
}
}
return StringUtils.toStringArray(result);
}String FACTORY_BEAN_PREFIX = "&";- 工厂Bean在Spring容器中一开始保存的是工厂本身，在这里就是HelloFactory
- 第一次获取Hello组件的时候。doGetBeanNamesForType循环所有组件，找有没有一个beanName是Hello的组件
- 它在找的途中发现了HelloFactory这个工厂bean，于是就调用
HelloFactory#getObject()，创建Hello这个bean
最后返回
@Component
public class Cat implements InitializingBean, SmartInitializingSingleton {
public Cat(){
System.out.println("cat被创建了...");
}
private String name;
@Value("${JAVA_HOME}") //自动赋值功能
public void setName(String name) {
System.out.println("cat....setName正在赋值调用....");
this.name = name;
}
//注解怎么定义这个是初始化方法？
public String getName() {
return name;
}
@Override
public void afterPropertiesSet() throws Exception {
System.out.println("CatInitializingBean..afterPropertiesSet...");
}
@Override
public void afterSingletonsInstantiated() {
System.out.println("所有组件都创建完成以后，再来执行这个方法.....");
}
}测试类基本都是大同小异的，这里不再给出全部的测试类，只给出这一小节用得到的。
我们以创建Cat这个Bean为例子来讲解。
protected <T> T doGetBean(
String name, @Nullable Class<T> requiredType, @Nullable Object[] args, boolean typeCheckOnly)
throws BeansException {
String beanName = transformedBeanName(name); //转换Bean名字
Object beanInstance;
// 先检查单实例bean的缓存 Eagerly check singleton cache for manually registered singletons.
Object sharedInstance = getSingleton(beanName); //检查缓存中有没有，如果是第一次获取肯定是没有的
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 + "'");
}
}
beanInstance = getObjectForBeanInstance(sharedInstance, name, beanName, null);
}
else { //默认第一次获取组件都会进入else环节
// Fail if we're already creating this bean instance:
// We're assumably within a circular reference.
if (isPrototypeCurrentlyInCreation(beanName)) {
throw new BeanCurrentlyInCreationException(beanName);
}
// 拿到整个beanFactory的父工厂；看父工厂没有，从父工厂先尝试获取组件； Check if bean definition exists in this factory.
BeanFactory parentBeanFactory = getParentBeanFactory();
if (parentBeanFactory != null && !containsBeanDefinition(beanName)) { //以下开始从父工厂获取组件
// Not found -> check parent.
// ...
}
if (!typeCheckOnly) {
markBeanAsCreated(beanName); //标记当前beanName的bean已经被创建
}
StartupStep beanCreation = this.applicationStartup.start("spring.beans.instantiate")
.tag("beanName", name);
try {
if (requiredType != null) {
beanCreation.tag("beanType", requiredType::toString);
}
RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);
checkMergedBeanDefinition(mbd, beanName, args);
// Guarantee initialization of beans that the current bean depends on.
String[] dependsOn = mbd.getDependsOn();
if (dependsOn != null) {
for (String dep : dependsOn) { //看当前Bean有没有依赖其他Bean
if (isDependent(beanName, dep)) {
throw new BeanCreationException(mbd.getResourceDescription(), beanName,
"Circular depends-on relationship between '" + beanName + "' and '" + dep + "'");
}
registerDependentBean(dep, beanName);
try {
getBean(dep); //依赖了其他bean，就先获取其他的哪些bean
}
catch (NoSuchBeanDefinitionException ex) {
throw new BeanCreationException(mbd.getResourceDescription(), beanName,
"'" + beanName + "' depends on missing bean '" + dep + "'", ex);
}
}
}
// 创建bean的实例；Create bean instance.
if (mbd.isSingleton()) {
sharedInstance = getSingleton(beanName, () -> {
try {
return createBean(beanName, mbd, args); //创建bean对象的实例
}
catch (BeansException ex) {
// Explicitly remove instance from singleton cache: It might have been put there
// eagerly by the creation process, to allow for circular reference resolution.
// Also remove any beans that received a temporary reference to the bean.
destroySingleton(beanName);
throw ex;
}
}); //看当前bean是否是FactoryBean
beanInstance = getObjectForBeanInstance(sharedInstance, name, beanName, mbd);
}
else if (mbd.isPrototype()) {
// ...
}
else{}
// ...
//转Object为Bean的T类型
return adaptBeanInstance(name, beanInstance, requiredType);
}
protected void markBeanAsCreated(String beanName) {
if (!this.alreadyCreated.contains(beanName)) {
synchronized (this.mergedBeanDefinitions) {
if (!this.alreadyCreated.contains(beanName)) {
// Let the bean definition get re-merged now that we're actually creating
// the bean... just in case some of its metadata changed in the meantime.
clearMergedBeanDefinition(beanName);
this.alreadyCreated.add(beanName);
}
}
}
}
// 已经创建了的Bean名字池。Spring内部有很多这样记录Bean状态的集合（池子）
/** Names of beans that have already been created at least once. */
private final Set<String> alreadyCreated = Collections.newSetFromMap(new ConcurrentHashMap<>(256));// 先检查单实例bean的缓存 Eagerly check singleton cache for manually registered singletons. Object sharedInstance = getSingleton(beanName); //检查缓存中有没有，如果是第一次获取肯定是没有的接上面
@Override
@Nullable
public Object getSingleton(String beanName) {
return getSingleton(beanName, true);
}
//下面的代码是解决循环依赖的核心，后面细讲
@Nullable
protected Object getSingleton(String beanName, boolean allowEarlyReference) {
//先检查单例缓存池，获取当前对象 Quick check for existing instance without full singleton lock
Object singletonObject = this.singletonObjects.get(beanName); //一级缓存
if (singletonObject == null && isSingletonCurrentlyInCreation(beanName)) { //如果当前bean正在创建过程中，而且缓存中没有则继续
singletonObject = this.earlySingletonObjects.get(beanName); //二级
if (singletonObject == null && allowEarlyReference) {
synchronized (this.singletonObjects) {
// Consistent creation of early reference within full singleton lock
singletonObject = this.singletonObjects.get(beanName);
if (singletonObject == null) {
singletonObject = this.earlySingletonObjects.get(beanName);
if (singletonObject == null) {
ObjectFactory<?> singletonFactory = this.singletonFactories.get(beanName); //三级
if (singletonFactory != null) {
singletonObject = singletonFactory.getObject();
this.earlySingletonObjects.put(beanName, singletonObject);
this.singletonFactories.remove(beanName);
}
}
}
}
}
}
return singletonObject;
}
/** 享元模式的单例。缓存所有单实例对象，单例对象池。ioc容器-单例池； Cache of singleton objects: bean name to bean instance. */
private final Map<String, Object> singletonObjects = new ConcurrentHashMap<>(256);
// 正在创建的组件的名字池
/** Names of beans that are currently in creation. */
private final Set<String> singletonsCurrentlyInCreation = Collections.newSetFromMap(new ConcurrentHashMap<>(16)); // 创建bean的实例；Create bean instance.
if (mbd.isSingleton()) {
sharedInstance = getSingleton(beanName, () -> {
try {
return createBean(beanName, mbd, args); //创建bean对象的实例
}
catch (BeansException ex) {
// Explicitly remove instance from singleton cache: It might have been put there
// eagerly by the creation process, to allow for circular reference resolution.
// Also remove any beans that received a temporary reference to the bean.
destroySingleton(beanName);
throw ex;
}
}); //看当前bean是否是FactoryBean
beanInstance = getObjectForBeanInstance(sharedInstance, name, beanName, mbd);
}这里是创建Bean的核心，就是一个lamda表达式
public Object getSingleton(String beanName, ObjectFactory<?> singletonFactory) {
Assert.notNull(beanName, "Bean name must not be null");
synchronized (this.singletonObjects) {
Object singletonObject = this.singletonObjects.get(beanName);
if (singletonObject == null) { //单实例池子里面没有当前对象（说明没有创建完成）
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 + "'");
}
beforeSingletonCreation(beanName); //单实例创建之前
boolean newSingleton = false;
boolean recordSuppressedExceptions = (this.suppressedExceptions == null);
if (recordSuppressedExceptions) {
this.suppressedExceptions = new LinkedHashSet<>();
}
try {
/*
1.这里会调用lamda表达式的内容，真正创建对象，也就是调用creatbean，
2.ObjectFactory类注释上写了这里类似于一个工厂Bean，所以这里写的和工厂bean一样的getObject()。我们
在前面是这样讲的
3.但实际上ObjectFactory就是一个@FunctionalInterface标注的函数式接口，你调用它唯一的getObject()，那么
当然就会调用createbean了。（这里就涉及lamda表达式的知识了，不知道的建议自行补习）
*/
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;
}
afterSingletonCreation(beanName);
}
if (newSingleton) {
addSingleton(beanName, singletonObject);
}
}
return singletonObject;
}
}
protected void beforeSingletonCreation(String beanName) {
// 创建之前判断将Bean加入singletonsCurrentlyInCreation这个set集合
if (!this.inCreationCheckExclusions.contains(beanName) && !this.singletonsCurrentlyInCreation.add(beanName)) {
throw new BeanCurrentlyInCreationException(beanName);
}
}
protected void afterSingletonCreation(String beanName) {
if (!this.inCreationCheckExclusions.contains(beanName) && !this.singletonsCurrentlyInCreation.remove(beanName)) {
throw new IllegalStateException("Singleton '" + beanName + "' isn't currently in creation");
}
}
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);
}
} @Override
protected Object createBean(String beanName, RootBeanDefinition mbd, @Nullable Object[] args)
throws BeanCreationException {
if (logger.isTraceEnabled()) {
logger.trace("Creating instance of bean '" + beanName + "'");
}
RootBeanDefinition mbdToUse = mbd;
// Make sure bean class is actually resolved at this point, and
// clone the bean definition in case of a dynamically resolved Class
// which cannot be stored in the shared merged bean definition.
Class<?> resolvedClass = resolveBeanClass(mbd, beanName);
if (resolvedClass != null && !mbd.hasBeanClass() && mbd.getBeanClassName() != null) {
mbdToUse = new RootBeanDefinition(mbd);
mbdToUse.setBeanClass(resolvedClass);
}
// Prepare method overrides.
try {
mbdToUse.prepareMethodOverrides();
}
catch (BeanDefinitionValidationException ex) {
throw new BeanDefinitionStoreException(mbdToUse.getResourceDescription(),
beanName, "Validation of method overrides failed", ex);
}
try {
// 提前给我们一个机会，去返回组件的代理对象。 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);
}
try { //Spring真正自己创建对象
Object beanInstance = doCreateBean(beanName, mbdToUse, args); //这里的代码在前面已经讲的很清楚了
if (logger.isTraceEnabled()) {
logger.trace("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);
}
}doCreateBean那里就是一堆后置处理器的干预了，前面讲过
至此，创建Bean的流程就和前面讲的衔接上了。