spring循环依赖debug源码【Java面试第三季】
- 前言
- spring循环依赖debug源码
- 35_spring循环依赖debug源码01
- 全部Debug断点
- 36_spring循环依赖debug源码02
- 37_spring循环依赖debug源码03
- 38_spring循环依赖debug源码04
- 最后
前言
本文是4.Spring【Java面试第三季】的小节
spring循环依赖debug源码
35_spring循环依赖debug源码01
全部Debug断点
DEBUG一步一步来，scope默认为singleton
从运行类启航
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class ClientSpringContainer {
public static void main(String[] args) {
ApplicationContext context = new ClassPathXmlApplicationContext("beans.xml");//此处断点
A a = context.getBean("a", A.class);
B b = context.getBean("b", B.class);
}
}步入步出
再步入
public ClassPathXmlApplicationContext(String configLocation) throws BeansException {
this(new String[]{configLocation}, true, (ApplicationContext)null);//到这行
}再步入
public ClassPathXmlApplicationContext(String[] configLocations, boolean refresh, @Nullable ApplicationContext parent) throws BeansException {
super(parent);//到这行
this.setConfigLocations(configLocations);
if (refresh) {
this.refresh();//步进到这 spring容器初始化 该行打断点
}
}全部跳过就会运行结束
重新开始调试，跳过该断点
到这步了
package org.springframework.context.support;
...
public class ClassPathXmlApplicationContext extends AbstractXmlApplicationContext {
public ClassPathXmlApplicationContext(String configLocation) throws BeansException {
this(new String[] {configLocation}, true, null);
}
public ClassPathXmlApplicationContext(
String[] configLocations, boolean refresh, @Nullable ApplicationContext parent)
throws BeansException {
super(parent);
setConfigLocations(configLocations);
if (refresh) {
//源于AbstractXmlApplicationContext
//->AbstractRefreshableConfigApplicationContext
//->AbstractRefreshableApplicationContext
//->AbstractApplicationContext的refresh()
refresh();
}
}
}步入refresh方法
一步一步步过直到控制台打印到A B创建对象
最终，在这行this.finishBeanFactoryInitialization(beanFactory);打了断点
public void refresh() throws BeansException, IllegalStateException {
synchronized(this.startupShutdownMonitor) {
this.prepareRefresh();
ConfigurableListableBeanFactory beanFactory = this.obtainFreshBeanFactory();
this.prepareBeanFactory(beanFactory);
try {
this.postProcessBeanFactory(beanFactory);
this.invokeBeanFactoryPostProcessors(beanFactory);
this.registerBeanPostProcessors(beanFactory);
this.initMessageSource();
this.initApplicationEventMulticaster();
this.onRefresh();
this.registerListeners();
this.finishBeanFactoryInitialization(beanFactory);//所以在此处打断点
this.finishRefresh();//直到此处会打印结果，所以在此处上一行打断点
} catch (BeansException var9) {
if (this.logger.isWarnEnabled()) {
this.logger.warn("Exception encountered during context initialization - cancelling refresh attempt: " + var9);
}
this.destroyBeans();
this.cancelRefresh(var9);
throw var9;
} finally {
this.resetCommonCaches();
}
}
}再次debug
package org.springframework.context.support;
...
public abstract class AbstractApplicationContext extends DefaultResourceLoader
implements ConfigurableApplicationContext {
...
@Override
public void refresh() throws BeansException, IllegalStateException {
synchronized (this.startupShutdownMonitor) {
// Prepare this context for refreshing.
prepareRefresh();
// Tell the subclass to refresh the internal bean factory.
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);
// Invoke factory processors registered as beans in the context.
invokeBeanFactoryPostProcessors(beanFactory);
// Register bean processors that intercept bean creation.
registerBeanPostProcessors(beanFactory);
// Initialize message source for this context.
initMessageSource();
// Initialize event multicaster for this context.
initApplicationEventMulticaster();
// Initialize other special beans in specific context subclasses.
onRefresh();
// Check for listener beans and register them.
registerListeners();
--------------->//<---------------------重点关注点是这里
// Instantiate all remaining (non-lazy-init) singletons.
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();
}
}
}进入到第三处断点 this.finishBeanFactoryInitialization(beanFactory);
/**
* Finish the initialization of this context's bean factory,
* initializing all remaining singleton beans.
*/
protected void finishBeanFactoryInitialization(ConfigurableListableBeanFactory beanFactory) {
// 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));
}
// Register a default embedded value resolver if no bean post-processor
// (such as a PropertyPlaceholderConfigurer bean) registered any before:
// at this point, primarily for resolution in annotation attribute values.
if (!beanFactory.hasEmbeddedValueResolver()) {
beanFactory.addEmbeddedValueResolver(strVal -> getEnvironment().resolvePlaceholders(strVal));
}
// 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);
}
// Stop using the temporary ClassLoader for type matching.
beanFactory.setTempClassLoader(null);
// Allow for caching all bean definition metadata, not expecting further changes.
beanFactory.freezeConfiguration();
------->//<---------------------重点关注点是这里
// Instantiate all remaining (non-lazy-init) singletons.
beanFactory.preInstantiateSingletons();//第4处断点
}
}36_spring循环依赖debug源码02
接着上文的beanFactory.preInstantiateSingletons()
beanFactory是ConfigurableListableBeanFactory
DefaultListableBeanFactory实现了ConfigurableListableBeanFactory接口
再次debug到第四个断点beanFactory.preInstantiateSingletons();
进入该行
public class DefaultListableBeanFactory extends AbstractAutowireCapableBeanFactory
implements ConfigurableListableBeanFactory, BeanDefinitionRegistry, Serializable {
...
@Override
public void preInstantiateSingletons() throws BeansException {
if (logger.isTraceEnabled()) { //到这行
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);
//根据上下文beanNames为[a, b] size=2
// Trigger initialization of all non-lazy singleton beans...
for (String beanName : beanNames) {//遍历a,b
RootBeanDefinition bd = getMergedLocalBeanDefinition(beanName);
if (!bd.isAbstract() && bd.isSingleton() && !bd.isLazyInit()) {
if (isFactoryBean(beanName)) {
Object bean = getBean(FACTORY_BEAN_PREFIX + beanName);
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 {
------------------->//<---------------------重点关注点是这里
//源于AbstractAutowireCapableBeanFactory
//->AbstractBeanFactory的getBean()
getBean(beanName); //第5处断点就是这
}
}
}
------------------------------下面可略读---------------------------
// Trigger post-initialization callback for all applicable beans...
for (String beanName : beanNames) {
Object singletonInstance = getSingleton(beanName);
if (singletonInstance instanceof SmartInitializingSingleton) {
SmartInitializingSingleton smartSingleton = (SmartInitializingSingleton) singletonInstance;
if (System.getSecurityManager() != null) {
AccessController.doPrivileged((PrivilegedAction<Object>) () -> {
smartSingleton.afterSingletonsInstantiated();
return null;
}, getAccessControlContext());
}
else {
smartSingleton.afterSingletonsInstantiated();
}
}
}
}
}进入第5处断点getBean(beanName);
doXXX真正干实事的业务逻辑方法
@Override
public Object getBean(String name) throws BeansException {
return doGetBean(name, null, null, false);//到该行 再次进入
}protected <T> T doGetBean(
String name, @Nullable Class<T> requiredType, @Nullable Object[] args, boolean typeCheckOnly)
throws BeansException {
String beanName = transformedBeanName(name);//到该行
Object bean;
// Eagerly check singleton cache for manually registered singletons.
Object sharedInstance = getSingleton(beanName);//该行打断点 进入
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 + "'");
}
}
bean = getObjectForBeanInstance(sharedInstance, name, beanName, null);
}
else {
// Fail if we're already creating this bean instance:
// We're assumably within a circular reference.
if (isPrototypeCurrentlyInCreation(beanName)) {
throw new BeanCurrentlyInCreationException(beanName);
}
// Check if bean definition exists in this factory.
BeanFactory parentBeanFactory = getParentBeanFactory();
if (parentBeanFactory != null && !containsBeanDefinition(beanName)) {
// Not found -> check parent.
String nameToLookup = originalBeanName(name);
if (parentBeanFactory instanceof AbstractBeanFactory) {
return ((AbstractBeanFactory) parentBeanFactory).doGetBean(
nameToLookup, requiredType, args, typeCheckOnly);
}
else if (args != null) {
// Delegation to parent with explicit args.
return (T) parentBeanFactory.getBean(nameToLookup, args);
}
else if (requiredType != null) {
// No args -> delegate to standard getBean method.
return parentBeanFactory.getBean(nameToLookup, requiredType);
}
else {
return (T) parentBeanFactory.getBean(nameToLookup);
}
}
if (!typeCheckOnly) {
markBeanAsCreated(beanName);
}
try {
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) {
if (isDependent(beanName, dep)) {
throw new BeanCreationException(mbd.getResourceDescription(), beanName,
"Circular depends-on relationship between '" + beanName + "' and '" + dep + "'");
}
registerDependentBean(dep, beanName);
try {
getBean(dep);
}
catch (NoSuchBeanDefinitionException ex) {
throw new BeanCreationException(mbd.getResourceDescription(), beanName,
"'" + beanName + "' depends on missing bean '" + dep + "'", ex);
}
}
}
// Create bean instance.
if (mbd.isSingleton()) {
sharedInstance = getSingleton(beanName, () -> {
try {
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.
destroySingleton(beanName);
throw ex;
}
});
bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd);
}
else if (mbd.isPrototype()) {
// It's a prototype -> create a new instance.
Object prototypeInstance = null;
try {
beforePrototypeCreation(beanName);
prototypeInstance = createBean(beanName, mbd, args);
}
finally {
afterPrototypeCreation(beanName);
}
bean = getObjectForBeanInstance(prototypeInstance, name, beanName, mbd);
}
else {
String scopeName = mbd.getScope();
if (!StringUtils.hasLength(scopeName)) {
throw new IllegalStateException("No scope name defined for bean ´" + beanName + "'");
}
Scope scope = this.scopes.get(scopeName);
if (scope == null) {
throw new IllegalStateException("No Scope registered for scope name '" + scopeName + "'");
}
try {
Object scopedInstance = scope.get(beanName, () -> {
beforePrototypeCreation(beanName);
try {
return createBean(beanName, mbd, args);
}
finally {
afterPrototypeCreation(beanName);
}
});
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);
}
}
}
catch (BeansException ex) {
cleanupAfterBeanCreationFailure(beanName);
throw ex;
}
}
// Check if required type matches the type of the actual bean instance.
if (requiredType != null && !requiredType.isInstance(bean)) {
try {
T convertedBean = getTypeConverter().convertIfNecessary(bean, requiredType);
if (convertedBean == null) {
throw new BeanNotOfRequiredTypeException(name, requiredType, bean.getClass());
}
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());
}
}
return (T) bean;
}进入Object sharedInstance = getSingleton(beanName);//该行打断点 进入
public Object getSingleton(String beanName) {
return getSingleton(beanName, true);//再进入
}
@Nullable
protected Object getSingleton(String beanName, boolean allowEarlyReference) {
Object singletonObject = this.singletonObjects.get(beanName);//到该行 再次打断点 singletonObject=null 此时还没有A的对象
if (singletonObject == null && isSingletonCurrentlyInCreation(beanName)) {
synchronized (this.singletonObjects) {
singletonObject = this.earlySingletonObjects.get(beanName);
if (singletonObject == null && allowEarlyReference) {
ObjectFactory<?> singletonFactory = this.singletonFactories.get(beanName);
if (singletonFactory != null) {
singletonObject = singletonFactory.getObject();
this.earlySingletonObjects.put(beanName, singletonObject);
this.singletonFactories.remove(beanName);
}
}
}
}
return singletonObject;//返回null
}返回null到getSingleton() 再次返回null到Object sharedInstance = getSingleton(beanName);
package org.springframework.beans.factory.support;
...
public abstract class AbstractBeanFactory extends FactoryBeanRegistrySupport implements ConfigurableBeanFactory {
...
@Override
public Object getBean(String name) throws BeansException {
return doGetBean(name, null, null, false);
}
@SuppressWarnings("unchecked")
protected <T> T doGetBean(
String name, @Nullable Class<T> requiredType, @Nullable Object[] args, boolean typeCheckOnly)
throws BeansException {
//name为a
String beanName = transformedBeanName(name);
Object bean;
// Eagerly check singleton cache for manually registered singletons.
------->//<---------------------重点关注点是这里
------->//<---------------------重点关注点是这里
------->//<---------------------重点关注点是这里
//源于FactoryBeanRegistrySupport
//->DefaultSingletonBeanRegistry的getSingleton()
//DefaultSingletonBeanRegistry也就是上文谈论的三级缓存所在类
//本章节末有getSingleton()源码
//最后getSingleton返回null
Object sharedInstance = getSingleton(beanName);
//sharedInstance为null，下面if语块不执行
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 + "'");
}
}
bean = getObjectForBeanInstance(sharedInstance, name, beanName, null);
}
else {
// Fail if we're already creating this bean instance:
// We're assumably within a circular reference.
//不执行下面if语块
if (isPrototypeCurrentlyInCreation(beanName)) {
throw new BeanCurrentlyInCreationException(beanName);
}
// Check if bean definition exists in this factory.
BeanFactory parentBeanFactory = getParentBeanFactory();
//parentBeanFactory为null，不执行下面if语块
if (parentBeanFactory != null && !containsBeanDefinition(beanName)) {
// Not found -> check parent.
String nameToLookup = originalBeanName(name);
if (parentBeanFactory instanceof AbstractBeanFactory) {
return ((AbstractBeanFactory) parentBeanFactory).doGetBean(
nameToLookup, requiredType, args, typeCheckOnly);
}
else if (args != null) {
// Delegation to parent with explicit args.
return (T) parentBeanFactory.getBean(nameToLookup, args);
}
else if (requiredType != null) {
// No args -> delegate to standard getBean method.
return parentBeanFactory.getBean(nameToLookup, requiredType);
}
else {
return (T) parentBeanFactory.getBean(nameToLookup);
}
}
if (!typeCheckOnly) {
markBeanAsCreated(beanName);//标记A对象
}
try {
//下面方法返回Root bean: class [com.lun.interview.circular.A];
//scope=singleton; abstract=false; lazyInit=false;
//autowireMode=0; dependencyCheck=0; autowireCandidate=true;
//primary=false; factoryBeanName=null; factoryMethodName=null;
//initMethodName=null; destroyMethodName=null;
//defined in class path resource [beans.xml]
//重点关注scope=singleton
RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);
checkMergedBeanDefinition(mbd, beanName, args);
// Guarantee initialization of beans that the current bean depends on.
String[] dependsOn = mbd.getDependsOn();
//dependsOn返回null，不执行下面if语块
if (dependsOn != null) {
for (String dep : dependsOn) {
if (isDependent(beanName, dep)) {
throw new BeanCreationException(mbd.getResourceDescription(), beanName,
"Circular depends-on relationship between '" + beanName + "' and '" + dep + "'");
}
registerDependentBean(dep, beanName);
try {
getBean(dep);
}
catch (NoSuchBeanDefinitionException ex) {
throw new BeanCreationException(mbd.getResourceDescription(), beanName,
"'" + beanName + "' depends on missing bean '" + dep + "'", ex);
}
}
}
// Create bean instance.
//mbd.isSingleton()返回true，执行下面if语块
if (mbd.isSingleton()) {//重点来了
sharedInstance = getSingleton(beanName, () -> { //断点此处 进入 看下节
try {
--------------------------->//<---------------------重点关注点是这里
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.
destroySingleton(beanName);
throw ex;
}
});
bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd);
}
----------------------------下面代码可略读---------
------------------
else if (mbd.isPrototype()) {
// It's a prototype -> create a new instance.
Object prototypeInstance = null;
try {
beforePrototypeCreation(beanName);
prototypeInstance = createBean(beanName, mbd, args);
}
finally {
afterPrototypeCreation(beanName);
}
bean = getObjectForBeanInstance(prototypeInstance, name, beanName, mbd);
}
else {
String scopeName = mbd.getScope();
if (!StringUtils.hasLength(scopeName)) {
throw new IllegalStateException("No scope name defined for bean ´" + beanName + "'");
}
Scope scope = this.scopes.get(scopeName);
if (scope == null) {
throw new IllegalStateException("No Scope registered for scope name '" + scopeName + "'");
}
try {
Object scopedInstance = scope.get(beanName, () -> {
beforePrototypeCreation(beanName);
try {
return createBean(beanName, mbd, args);
}
finally {
afterPrototypeCreation(beanName);
}
});
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);
}
}
}
catch (BeansException ex) {
cleanupAfterBeanCreationFailure(beanName);
throw ex;
}
}
// Check if required type matches the type of the actual bean instance.
if (requiredType != null && !requiredType.isInstance(bean)) {
try {
T convertedBean = getTypeConverter().convertIfNecessary(bean, requiredType);
if (convertedBean == null) {
throw new BeanNotOfRequiredTypeException(name, requiredType, bean.getClass());
}
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());
}
}
return (T) bean;
}
}37_spring循环依赖debug源码03
进入sharedInstance = getSingleton(beanName, () -> { //断点此处 进入 看下节
public Object getSingleton(String beanName, ObjectFactory<?> singletonFactory) {
Assert.notNull(beanName, "Bean name must not be null");//到此处
synchronized (this.singletonObjects) {
Object singletonObject = this.singletonObjects.get(beanName);
if (singletonObject == null) {
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);
boolean newSingleton = false;
boolean recordSuppressedExceptions = (this.suppressedExceptions == null);
if (recordSuppressedExceptions) {
this.suppressedExceptions = new LinkedHashSet<>();
}
try {
singletonObject = singletonFactory.getObject();//此行打断点 再次进入
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;
}
}进入singletonObject = singletonFactory.getObject();//此行打断点 再次进入
// Create bean instance.
if (mbd.isSingleton()) {
sharedInstance = getSingleton(beanName, () -> {
try {
return createBean(beanName, mbd, args);//到此处 回调到这里 打断点
}
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;
}
});
bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd);
}进入return createBean(beanName, mbd, args);//到此处 打断点
@Override
protected Object createBean(String beanName, RootBeanDefinition mbd, @Nullable Object[] args)
throws BeanCreationException {
if (logger.isTraceEnabled()) {//到此处
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 {
// 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 {
Object beanInstance = doCreateBean(beanName, mbdToUse, args);//此处打断点 进入
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);
}
}进入Object beanInstance = doCreateBean(beanName, mbdToUse, args);//此处打断点 进入
protected Object doCreateBean(String beanName, RootBeanDefinition mbd, @Nullable Object[] args)
throws BeanCreationException {
// Instantiate the bean.
BeanWrapper instanceWrapper = null;//到此处
if (mbd.isSingleton()) {
instanceWrapper = this.factoryBeanInstanceCache.remove(beanName);
}
if (instanceWrapper == null) {
instanceWrapper = createBeanInstance(beanName, mbd, args);// 创建Bean的实例 打断点进入
}
...
}进入instanceWrapper = createBeanInstance(beanName, mbd, args);// 创建Bean的实例 打断点进入
protected BeanWrapper createBeanInstance(String beanName, RootBeanDefinition mbd, @Nullable Object[] args) {
...//无关键
}出去到instanceWrapper = createBeanInstance(beanName, mbd, args);
protected Object doCreateBean(String beanName, RootBeanDefinition mbd, @Nullable Object[] args)
throws BeanCreationException {
// Instantiate the bean.
BeanWrapper instanceWrapper = null;
if (mbd.isSingleton()) {
instanceWrapper = this.factoryBeanInstanceCache.remove(beanName);
}
if (instanceWrapper == null) {
instanceWrapper = createBeanInstance(beanName, mbd, args);//出来到这
}
Object bean = instanceWrapper.getWrappedInstance();
Class<?> beanType = instanceWrapper.getWrappedClass();
if (beanType != NullBean.class) {
mbd.resolvedTargetType = beanType;
}
// Allow post-processors to modify the merged bean definition.
synchronized (mbd.postProcessingLock) {
if (!mbd.postProcessed) {
try {
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.
boolean earlySingletonExposure = (mbd.isSingleton() && this.allowCircularReferences &&
isSingletonCurrentlyInCreation(beanName)); //到此处 A是否是单例 是否允许循环引用(true)
if (earlySingletonExposure) {
if (logger.isTraceEnabled()) {
logger.trace("Eagerly caching bean '" + beanName +
"' to allow for resolving potential circular references");
}
addSingletonFactory(beanName, () -> getEarlyBeanReference(beanName, mbd, bean));//此处打断点 进入
}
...
}进入addSingletonFactory(beanName, () -> getEarlyBeanReference(beanName, mbd, bean));//此处打断点 进入
protected void addSingletonFactory(String beanName, ObjectFactory<?> singletonFactory) {
Assert.notNull(singletonFactory, "Singleton factory must not be null");
synchronized (this.singletonObjects) {
if (!this.singletonObjects.containsKey(beanName)) {//一级缓存有无A
this.singletonFactories.put(beanName, singletonFactory);//存入三级缓存 a 拉姆达表达式
this.earlySingletonObjects.remove(beanName);//二级缓存删除A
this.registeredSingletons.add(beanName);//注册bean
}退出到addSingletonFactory(beanName, () -> getEarlyBeanReference(beanName, mbd, bean));//此处打断点 进入
protected Object doCreateBean(String beanName, RootBeanDefinition mbd, @Nullable Object[] args)
throws BeanCreationException {
....
addSingletonFactory(beanName, () -> getEarlyBeanReference(beanName, mbd, bean));//退出
}
// Initialize the bean instance.
Object exposedObject = bean;//到此处
try {
populateBean(beanName, mbd, instanceWrapper);//此处打断点 进入
exposedObject = initializeBean(beanName, exposedObject, mbd);
}
...此时A在三级缓存中
进入populateBean(beanName, mbd, instanceWrapper);//此处打断点 进入
protected void populateBean(String beanName, RootBeanDefinition mbd, @Nullable BeanWrapper bw) {
if (bw == null) {//到该行
if (mbd.hasPropertyValues()) {
throw new BeanCreationException(
mbd.getResourceDescription(), beanName, "Cannot apply property values to null instance");
}
else {
// Skip property population phase for null instance.
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.
if (!mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) {
for (BeanPostProcessor bp : getBeanPostProcessors()) {
if (bp instanceof InstantiationAwareBeanPostProcessor) {
InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
if (!ibp.postProcessAfterInstantiation(bw.getWrappedInstance(), beanName)) {
return;
}
}
}
}
PropertyValues pvs = (mbd.hasPropertyValues() ? mbd.getPropertyValues() : null);
//pvs: "PropertyValues: length=i; bean property 'b'" A有一个属性B
//中间略过
if (pvs != null) {
applyPropertyValues(beanName, mbd, bw, pvs);//进入此处
}
}进入applyPropertyValues(beanName, mbd, bw, pvs);//进入此处
protected void applyPropertyValues(String beanName, BeanDefinition mbd, BeanWrapper bw, PropertyValues pvs) {
if (pvs.isEmpty()) {//到此处
return;
}
if (System.getSecurityManager() != null && bw instanceof BeanWrapperImpl) {
((BeanWrapperImpl) bw).setSecurityContext(getAccessControlContext());
}
MutablePropertyValues mpvs = null;
List<PropertyValue> original;
if (pvs instanceof MutablePropertyValues) {
mpvs = (MutablePropertyValues) pvs;
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(); //A中要有属性B
}
else {
original = Arrays.asList(pvs.getPropertyValues());
}
TypeConverter converter = getCustomTypeConverter();
if (converter == null) {
converter = bw;
}
BeanDefinitionValueResolver valueResolver = new BeanDefinitionValueResolver(this, beanName, mbd, converter);
// Create a deep copy, resolving any references for values.
List<PropertyValue> deepCopy = new ArrayList<>(original.size());
boolean resolveNecessary = false;
for (PropertyValue pv : original) {
if (pv.isConverted()) {
deepCopy.add(pv);
}
else {
String propertyName = pv.getName();//propertyName="b"
Object originalValue = pv.getValue();
if (originalValue == AutowiredPropertyMarker.INSTANCE) {
Method writeMethod = bw.getPropertyDescriptor(propertyName).getWriteMethod();
if (writeMethod == null) {
throw new IllegalArgumentException("Autowire marker for property without write method: " + pv);
}
originalValue = new DependencyDescriptor(new MethodParameter(writeMethod, 0), true);
}
Object resolvedValue = valueResolver.resolveValueIfNecessary(pv, originalValue);//此处打断点 进入
Object convertedValue = resolvedValue;
boolean convertible = bw.isWritableProperty(propertyName) &&
!PropertyAccessorUtils.isNestedOrIndexedProperty(propertyName);
if (convertible) {
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.
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 {
bw.setPropertyValues(new MutablePropertyValues(deepCopy));
}
catch (BeansException ex) {
throw new BeanCreationException(
mbd.getResourceDescription(), beanName, "Error setting property values", ex);
}
}进入Object resolvedValue = valueResolver.resolveValueIfNecessary(pv, originalValue);//此处打断点 进入
@Nullable
public Object resolveValueIfNecessary(Object argName, @Nullable Object value) {
// We must check each value to see whether it requires a runtime reference
// to another bean to be resolved.
if (value instanceof RuntimeBeanReference) {//到此处 要对B下手了
RuntimeBeanReference ref = (RuntimeBeanReference) value;
return resolveReference(argName, ref);//打断点 进入
}
...
}进入return resolveReference(argName, ref);
@Nullable
private Object resolveReference(Object argName, RuntimeBeanReference ref) {
try {
Object bean;
Class<?> beanType = ref.getBeanType();//到此处
if (ref.isToParent()) {
BeanFactory parent = this.beanFactory.getParentBeanFactory();
if (parent == null) {
throw new BeanCreationException(
this.beanDefinition.getResourceDescription(), this.beanName,
"Cannot resolve reference to bean " + ref +
" in parent factory: no parent factory available");
}
if (beanType != null) {
bean = parent.getBean(beanType);
}
else {
bean = parent.getBean(String.valueOf(doEvaluate(ref.getBeanName())));
}
}
else {
String resolvedName;
if (beanType != null) {
NamedBeanHolder<?> namedBean = this.beanFactory.resolveNamedBean(beanType);
bean = namedBean.getBeanInstance();
resolvedName = namedBean.getBeanName();
}
else {
resolvedName = String.valueOf(doEvaluate(ref.getBeanName()));
bean = this.beanFactory.getBean(resolvedName);//到此处 打断点 控制台打印了---A created success
}
this.beanFactory.registerDependentBean(resolvedName, this.beanName);
}
if (bean instanceof NullBean) {
bean = null;
}
return bean;
}
catch (BeansException ex) {
throw new BeanCreationException(
this.beanDefinition.getResourceDescription(), this.beanName,
"Cannot resolve reference to bean '" + ref.getBeanName() + "' while setting " + argName, ex);
}
}进入bean = this.beanFactory.getBean(resolvedName);//到此处 打断点 控制台打印了---A created success
@Override
public Object getBean(String name) throws BeansException {
return doGetBean(name, null, null, false);//再进去
}protected <T> T doGetBean(
String name, @Nullable Class<T> requiredType, @Nullable Object[] args, boolean typeCheckOnly)
throws BeansException {
String beanName = transformedBeanName(name);
Object bean;
// Eagerly check singleton cache for manually registered singletons.
Object sharedInstance = getSingleton(beanName);//再进入
}@Override
@Nullable
public Object getSingleton(String beanName) {
return getSingleton(beanName, true);//再进入
}@Nullable
protected Object getSingleton(String beanName, boolean allowEarlyReference) {
Object singletonObject = this.singletonObjects.get(beanName);
if (singletonObject == null && isSingletonCurrentlyInCreation(beanName)) {
synchronized (this.singletonObjects) {
singletonObject = this.earlySingletonObjects.get(beanName);
if (singletonObject == null && allowEarlyReference) {
ObjectFactory<?> singletonFactory = this.singletonFactories.get(beanName);
if (singletonFactory != null) {
singletonObject = singletonFactory.getObject();
this.earlySingletonObjects.put(beanName, singletonObject);
this.singletonFactories.remove(beanName);
}
}
}
}
return singletonObject;//返回null 因为B还没有
}返回返回到if (sharedInstance != null && args == null) {//退出到此处
protected <T> T doGetBean(
String name, @Nullable Class<T> requiredType, @Nullable Object[] args, boolean typeCheckOnly)
throws BeansException {
String beanName = transformedBeanName(name);
Object bean;
// Eagerly check singleton cache for manually registered singletons.
Object sharedInstance = getSingleton(beanName);
if (sharedInstance != null && args == null) {//退出到此处
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 + "'");
}
}
bean = getObjectForBeanInstance(sharedInstance, name, beanName, null);
}
//快速到此处
// Create bean instance.
if (mbd.isSingleton()) {
sharedInstance = getSingleton(beanName, () -> { //断点 此时是创建B 进入
try {
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.
destroySingleton(beanName);
throw ex;
}
});
bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd);
}
....进入sharedInstance = getSingleton(beanName, () -> { //断点 此时是创建B 进入
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);//一级缓存没有B
if (singletonObject == null) {
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);
boolean newSingleton = false;
boolean recordSuppressedExceptions = (this.suppressedExceptions == null);
if (recordSuppressedExceptions) {
this.suppressedExceptions = new LinkedHashSet<>();
}
try {
singletonObject = singletonFactory.getObject();//容器中没有B，到此处 进入
newSingleton = true;
}
...
return singletonObject;
}
}回调到return createBean(beanName, mbd, args);
protected <T> T doGetBean(
String name, @Nullable Class<T> requiredType, @Nullable Object[] args, boolean typeCheckOnly)
throws BeansException {
...
// Create bean instance.
if (mbd.isSingleton()) {
sharedInstance = getSingleton(beanName, () -> {
try {
return createBean(beanName, mbd, args);//回调到此处 断点 进入
}
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;
}
});
bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd);
}
....进入return createBean(beanName, mbd, args);//回调到此处 断点 进入
@Override
protected Object createBean(String beanName, RootBeanDefinition mbd, @Nullable Object[] args)
throws BeanCreationException {
//快速跳过
try {
Object beanInstance = doCreateBean(beanName, mbdToUse, args);//到此处 现在建的是B 再进入
if (logger.isTraceEnabled()) {
logger.trace("Finished creating instance of bean '" + beanName + "'");
}
return beanInstance;
}
...
}进入Object beanInstance = doCreateBean(beanName, mbdToUse, args);//到此处 现在建的是B 再进入
protected Object doCreateBean(String beanName, RootBeanDefinition mbd, @Nullable Object[] args)
throws BeanCreationException {
// Instantiate the bean.
BeanWrapper instanceWrapper = null;
if (mbd.isSingleton()) {
instanceWrapper = this.factoryBeanInstanceCache.remove(beanName);
}
if (instanceWrapper == null) {
instanceWrapper = createBeanInstance(beanName, mbd, args);//建B 再进入
}
...
return exposedObject;
}进入instanceWrapper = createBeanInstance(beanName, mbd, args);//建B 再进入
protected BeanWrapper createBeanInstance(String beanName, RootBeanDefinition mbd, @Nullable Object[] args) {
// Make sure bean class is actually resolved at this point.
Class<?> beanClass = resolveBeanClass(mbd, beanName);
...
// No special handling: simply use no-arg constructor.
return instantiateBean(beanName, mbd); //完成B的初始化
}返回instanceWrapper = createBeanInstance(beanName, mbd, args);
protected Object doCreateBean(String beanName, RootBeanDefinition mbd, @Nullable Object[] args)
throws BeanCreationException {
// Instantiate the bean.
BeanWrapper instanceWrapper = null;
if (mbd.isSingleton()) {
instanceWrapper = this.factoryBeanInstanceCache.remove(beanName);
}
if (instanceWrapper == null) {
instanceWrapper = createBeanInstance(beanName, mbd, args);//返回
}
if (instanceWrapper == null) {
instanceWrapper = createBeanInstance(beanName, mbd, args);//返回到此处
}
//快速跳过
// Eagerly cache singletons to be able to resolve circular references
// even when triggered by lifecycle interfaces like BeanFactoryAware.
boolean earlySingletonExposure = (mbd.isSingleton() && this.allowCircularReferences &&
isSingletonCurrentlyInCreation(beanName));
if (earlySingletonExposure) {
if (logger.isTraceEnabled()) {
logger.trace("Eagerly caching bean '" + beanName +
"' to allow for resolving potential circular references");
}
addSingletonFactory(beanName, () -> getEarlyBeanReference(beanName, mbd, bean));//到此处断点 建B
}
...
return exposedObject;
}再次进入addSingletonFactory(beanName, () -> getEarlyBeanReference(beanName, mbd, bean));//到此处断点 建B
protected void addSingletonFactory(String beanName, ObjectFactory<?> singletonFactory) {
Assert.notNull(singletonFactory, "Singleton factory must not be null");//到此处
synchronized (this.singletonObjects) {
if (!this.singletonObjects.containsKey(beanName)) {//一级缓存有B 无 !无=true
this.singletonFactories.put(beanName, singletonFactory);//三级缓存存入B 拉姆达
this.earlySingletonObjects.remove(beanName);//清理二级缓存
this.registeredSingletons.add(beanName);//填充注册
}
}
}三级缓存中有B
返回addSingletonFactory(beanName, () -> getEarlyBeanReference(beanName, mbd, bean));
}
addSingletonFactory(beanName, () -> getEarlyBeanReference(beanName, mbd, bean));//返回
}
// Initialize the bean instance.
Object exposedObject = bean;
try {
populateBean(beanName, mbd, instanceWrapper);//属性填充B 进入
exposedObject = initializeBean(beanName, exposedObject, mbd);
}进入populateBean(beanName, mbd, instanceWrapper);//属性填充B 进入
protected void populateBean(String beanName, RootBeanDefinition mbd, @Nullable BeanWrapper bw) {
...
PropertyValues pvs = (mbd.hasPropertyValues() ? mbd.getPropertyValues() : null);
//B里面有一个属性A
...
if (pvs != null) {
applyPropertyValues(beanName, mbd, bw, pvs);//此处打断点 进入
}
}进入applyPropertyValues(beanName, mbd, bw, pvs);//此处打断点 进入
protected void applyPropertyValues(String beanName, BeanDefinition mbd, BeanWrapper bw, PropertyValues pvs) {
if (pvs instanceof MutablePropertyValues) {
mpvs = (MutablePropertyValues) pvs;
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();//B中有属性A
}
//快速跳到断点
Object resolvedValue = valueResolver.resolveValueIfNecessary(pv, originalValue);//断点 进入
...
}进入Object resolvedValue = valueResolver.resolveValueIfNecessary(pv, originalValue);//断点 进入
@Nullable
public Object resolveValueIfNecessary(Object argName, @Nullable Object value) {
// We must check each value to see whether it requires a runtime reference
// to another bean to be resolved.
if (value instanceof RuntimeBeanReference) {
RuntimeBeanReference ref = (RuntimeBeanReference) value;
return resolveReference(argName, ref);//再次进入
}进入return resolveReference(argName, ref);//再次进入
@Nullable
private Object resolveReference(Object argName, RuntimeBeanReference ref) {
....
else {
String resolvedName;
if (beanType != null) {
NamedBeanHolder<?> namedBean = this.beanFactory.resolveNamedBean(beanType);
bean = namedBean.getBeanInstance();
resolvedName = namedBean.getBeanName();
}
else {
resolvedName = String.valueOf(doEvaluate(ref.getBeanName()));
bean = this.beanFactory.getBean(resolvedName);//到此断点 进入
}
this.beanFactory.registerDependentBean(resolvedName, this.beanName);
}进入bean = this.beanFactory.getBean(resolvedName);//到此断点 进入
@Override
public Object getBean(String name) throws BeansException {
return doGetBean(name, null, null, false);//进入
}进入return doGetBean(name, null, null, false);//进入
@Override
public Object getBean(String name) throws BeansException {
return doGetBean(name, null, null, false);//进入
}进入return doGetBean(name, null, null, false);//进入
protected <T> T doGetBean(
String name, @Nullable Class<T> requiredType, @Nullable Object[] args, boolean typeCheckOnly)
throws BeansException {
String beanName = transformedBeanName(name);
Object bean;
// Eagerly check singleton cache for manually registered singletons.
Object sharedInstance = getSingleton(beanName);//进入
...
}进入Object sharedInstance = getSingleton(beanName);//进入
public Object getSingleton(String beanName) {
return getSingleton(beanName, true);//进入
}进入return getSingleton(beanName, true);
protected Object getSingleton(String beanName, boolean allowEarlyReference) {
Object singletonObject = this.singletonObjects.get(beanName);
if (singletonObject == null && isSingletonCurrentlyInCreation(beanName)) {//一级缓存没有A
synchronized (this.singletonObjects) {
singletonObject = this.earlySingletonObjects.get(beanName);//二级缓存没有A
if (singletonObject == null && allowEarlyReference) {
ObjectFactory<?> singletonFactory = this.singletonFactories.get(beanName);//三级缓存中有A
if (singletonFactory != null) {
singletonObject = singletonFactory.getObject();//打断点 进入
this.earlySingletonObjects.put(beanName, singletonObject);
this.singletonFactories.remove(beanName);
}
}
}
}
return singletonObject;
}进入singletonObject = singletonFactory.getObject();//打断点 进入
addSingletonFactory(beanName, () -> getEarlyBeanReference(beanName, mbd, bean)); //value 拉姆达进入addSingletonFactory(beanName, () -> getEarlyBeanReference(beanName, mbd, bean)); //value 拉姆达
protected Object getEarlyBeanReference(String beanName, RootBeanDefinition mbd, Object bean) {
Object exposedObject = bean;//到此处
if (!mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) {
for (BeanPostProcessor bp : getBeanPostProcessors()) {
if (bp instanceof SmartInstantiationAwareBeanPostProcessor) {
SmartInstantiationAwareBeanPostProcessor ibp = (SmartInstantiationAwareBeanPostProcessor) bp;
exposedObject = ibp.getEarlyBeanReference(exposedObject, beanName);
}
}
}
return exposedObject;//返回了A对象
}返回到singletonObject = singletonFactory.getObject();
protected Object getSingleton(String beanName, boolean allowEarlyReference) {
Object singletonObject = this.singletonObjects.get(beanName);
if (singletonObject == null && isSingletonCurrentlyInCreation(beanName)) {//一级缓存没有A
synchronized (this.singletonObjects) {
singletonObject = this.earlySingletonObjects.get(beanName);//二级缓存没有A
if (singletonObject == null && allowEarlyReference) {
ObjectFactory<?> singletonFactory = this.singletonFactories.get(beanName);//三级缓存中有A
if (singletonFactory != null) {
singletonObject = singletonFactory.getObject();//返回
this.earlySingletonObjects.put(beanName, singletonObject);//二级缓存处内A A对象
this.singletonFactories.remove(beanName);//三级缓存中移除A
}
}
}
}
return singletonObject;//返回A（属性B=null）
}二级缓存中存入A 和A对象 (B属性是null）（通过三级缓存value () -> getEarlyBeanReference(beanName, mbd, bean)创建的）
三级缓存中删掉A
返回
public Object getSingleton(String beanName) {
return getSingleton(beanName, true);
}返回Object sharedInstance = getSingleton(beanName);
protected <T> T doGetBean(
String name, @Nullable Class<T> requiredType, @Nullable Object[] args, boolean typeCheckOnly)
throws BeansException {
String beanName = transformedBeanName(name);
Object bean;
// Eagerly check singleton cache for manually registered singletons.
Object sharedInstance = getSingleton(beanName);//返回 A对象（属性B=null）
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 + "'");
}
}
bean = getObjectForBeanInstance(sharedInstance, name, beanName, null);//下一步
}
...
return (T) bean;//返回对象A（属性B=null）
}再返回
@Override
public Object getBean(String name) throws BeansException {
return doGetBean(name, null, null, false);
}@Nullable
private Object resolveReference(Object argName, RuntimeBeanReference ref) {
else {
resolvedName = String.valueOf(doEvaluate(ref.getBeanName()));//返回
bean = this.beanFactory.getBean(resolvedName);//
}
this.beanFactory.registerDependentBean(resolvedName, this.beanName);//注册依赖的Bean
}
if (bean instanceof NullBean) {
bean = null;
}
return bean;//返回A（属性B=null）
}
}返回
@Nullable
public Object resolveValueIfNecessary(Object argName, @Nullable Object value) {
// We must check each value to see whether it requires a runtime reference
// to another bean to be resolved.
if (value instanceof RuntimeBeanReference) {
RuntimeBeanReference ref = (RuntimeBeanReference) value;
return resolveReference(argName, ref);//返回
}返回到
protected void applyPropertyValues(String beanName, BeanDefinition mbd, BeanWrapper bw, PropertyValues pvs) {
Object resolvedValue = valueResolver.resolveValueIfNecessary(pv, originalValue);//返回
Object convertedValue = resolvedValue;
// Set our (possibly massaged) deep copy.
try {
bw.setPropertyValues(new MutablePropertyValues(deepCopy));//完成了B属性的填充
}
catch (BeansException ex) {
throw new BeanCreationException(
mbd.getResourceDescription(), beanName, "Error setting property values", ex);
}
}返回到B属性的填充
protected void populateBean(String beanName, RootBeanDefinition mbd, @Nullable BeanWrapper bw) {返回到创建B
protected Object doCreateBean(String beanName, RootBeanDefinition mbd, @Nullable Object[] args)
throws BeanCreationException {
// Initialize the bean instance.
Object exposedObject = bean;
try {
populateBean(beanName, mbd, instanceWrapper);//返回
exposedObject = initializeBean(beanName, exposedObject, mbd);//到这 进入
}
return exposedObject;
}进入exposedObject = initializeBean(beanName, exposedObject, mbd);//到这 进入
protected Object initializeBean(String beanName, Object bean, @Nullable RootBeanDefinition mbd) {
//B填充了A（属性B=null）
return wrappedBean;//返回B（属性A=a（属性B=null））
}返回doCreateBean
...
if (earlySingletonExposure) {
Object earlySingletonReference = getSingleton(beanName, false);//打断点 进去进入Object earlySingletonReference = getSingleton(beanName, false);//打断点 进去
@Nullable
protected Object getSingleton(String beanName, boolean allowEarlyReference) {
Object singletonObject = this.singletonObjects.get(beanName);
if (singletonObject == null && isSingletonCurrentlyInCreation(beanName)) {//一级缓存没有B
synchronized (this.singletonObjects) {
singletonObject = this.earlySingletonObjects.get(beanName);//二级缓存没有B
if (singletonObject == null && allowEarlyReference) {
ObjectFactory<?> singletonFactory = this.singletonFactories.get(beanName);
if (singletonFactory != null) {
singletonObject = singletonFactory.getObject();
this.earlySingletonObjects.put(beanName, singletonObject);
this.singletonFactories.remove(beanName);
}
}
}
}
return singletonObject;//返回null
}返回到doGetBean
if (earlySingletonExposure) {
Object earlySingletonReference = getSingleton(beanName, false);//返回null
return exposedObject;//返回B（A=a(B=null)）
}返回到createBean
protected Object createBean(String beanName, RootBeanDefinition mbd, @Nullable Object[] args)
throws BeanCreationException {
try {
Object beanInstance = doCreateBean(beanName, mbdToUse, args);//返回B（A=a(B=null)）
if (logger.isTraceEnabled()) {
logger.trace("Finished creating instance of bean '" + beanName + "'");
}
return beanInstance;//返回B（A=a(B=null)）
}
}返回到doGetBean
// Create bean instance.
if (mbd.isSingleton()) {
sharedInstance = getSingleton(beanName, () -> {
try {
return createBean(beanName, mbd, args);//返回B（A=a(B=null)）
}返回到getSingleton
try {
singletonObject = singletonFactory.getObject();//返回了B（A=a(B=null)）
newSingleton = true;
}
if (newSingleton) {
addSingleton(beanName, singletonObject);//到此处 打断点 进入
}进入addSingleton(beanName, singletonObject);//到此处 打断点 进入
protected void addSingleton(String beanName, Object singletonObject) {
synchronized (this.singletonObjects) {
this.singletonObjects.put(beanName, singletonObject);//一级缓存存入B b(A=a(B=null))
this.singletonFactories.remove(beanName);//三级缓存删除B
this.earlySingletonObjects.remove(beanName);//二级缓存删除B
this.registeredSingletons.add(beanName);//注册完成
}
}B是直接从三级缓存到一级缓存了
返回到getSingleton
return singletonObject;//返回b(A=a(B=null))返回到doGetBean
// Create bean instance.
if (mbd.isSingleton()) {
sharedInstance = getSingleton(beanName, () -> {//返回
try {
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.
destroySingleton(beanName);
throw ex;
}
});
bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd);
}
...
return (T) bean;//返回b(A=a(B=null))返回
@Override
public Object getBean(String name) throws BeansException {
return doGetBean(name, null, null, false);//返回b(A=a(B=null))
}返回到resolveReference
else {
resolvedName = String.valueOf(doEvaluate(ref.getBeanName()));
bean = this.beanFactory.getBean(resolvedName);//返回
}
this.beanFactory.registerDependentBean(resolvedName, this.beanName);
}
if (bean instanceof NullBean) {
bean = null;
}
return bean;//返回b(A=a(B=null))
}返回
public Object resolveValueIfNecessary(Object argName, @Nullable Object value) {
// We must check each value to see whether it requires a runtime reference
// to another bean to be resolved.
if (value instanceof RuntimeBeanReference) {
RuntimeBeanReference ref = (RuntimeBeanReference) value;
return resolveReference(argName, ref);//返回 b(A=a(B=null))
}返回
protected void applyPropertyValues(String beanName, BeanDefinition mbd, BeanWrapper bw, PropertyValues pvs) {
...
Object resolvedValue = valueResolver.resolveValueIfNecessary(pv, originalValue);//返回了b(A=a(B=null))
Object convertedValue = resolvedValue;
//退出
}返回到populateBean A的属性填充
protected void populateBean(String beanName, RootBeanDefinition mbd, @Nullable BeanWrapper bw) {
if (pvs != null) {
applyPropertyValues(beanName, mbd, bw, pvs);//再次进入
}
}进入applyPropertyValues(beanName, mbd, bw, pvs);//再次进入
protected void applyPropertyValues(String beanName, BeanDefinition mbd, BeanWrapper bw, PropertyValues pvs) {
original = mpvs.getPropertyValueList();//A的属性B需要填充
}
else {
original = Arrays.asList(pvs.getPropertyValues());
}
Object resolvedValue = valueResolver.resolveValueIfNecessary(pv, originalValue);//再进去进入Object resolvedValue = valueResolver.resolveValueIfNecessary(pv, originalValue);//再进去
@Nullable
public Object resolveValueIfNecessary(Object argName, @Nullable Object value) {
// We must check each value to see whether it requires a runtime reference
// to another bean to be resolved.
if (value instanceof RuntimeBeanReference) {
RuntimeBeanReference ref = (RuntimeBeanReference) value;
return resolveReference(argName, ref);//进入
}进入return resolveReference(argName, ref);//进入
@Nullable
private Object resolveReference(Object argName, RuntimeBeanReference ref) {
else {
resolvedName = String.valueOf(doEvaluate(ref.getBeanName()));
bean = this.beanFactory.getBean(resolvedName);//到此断点 进入
}
}进入bean = this.beanFactory.getBean(resolvedName);//到此断点 进入
@Override
public Object getBean(String name) throws BeansException {
return doGetBean(name, null, null, false);//在进入
}进入
protected <T> T doGetBean(
String name, @Nullable Class<T> requiredType, @Nullable Object[] args, boolean typeCheckOnly)
throws BeansException {
String beanName = transformedBeanName(name);
Object bean;
// Eagerly check singleton cache for manually registered singletons.
Object sharedInstance = getSingleton(beanName);//进入进入
@Override
@Nullable
public Object getSingleton(String beanName) {
return getSingleton(beanName, true);//再进入
}
@Nullable
protected Object getSingleton(String beanName, boolean allowEarlyReference) {
Object singletonObject = this.singletonObjects.get(beanName);//一级缓存有B
return singletonObject;//返回b(A=a(B=null))
}返回b(A=a(B=null))到return getSingleton(beanName, true);
返回到doGetBean
Object sharedInstance = getSingleton(beanName);//返回了b(A=a(B=null))
...
return (T) bean;//返回b(A=a(B=null))
}返回到resolveReference
else {
resolvedName = String.valueOf(doEvaluate(ref.getBeanName()));
bean = this.beanFactory.getBean(resolvedName);//返回了b(A=a(B=null))
}
this.beanFactory.registerDependentBean(resolvedName, this.beanName);
}
if (bean instanceof NullBean) {
bean = null;
}
return bean;//返回b(A=a(B=null))
}返回return resolveReference(argName, ref);
@Nullable
public Object resolveValueIfNecessary(Object argName, @Nullable Object value) {
// We must check each value to see whether it requires a runtime reference
// to another bean to be resolved.
if (value instanceof RuntimeBeanReference) {
RuntimeBeanReference ref = (RuntimeBeanReference) value;
return resolveReference(argName, ref);//返回b(A=a(B=null))
}退出Object resolvedValue = valueResolver.resolveValueIfNecessary(pv, originalValue);
protected void applyPropertyValues(String beanName, BeanDefinition mbd, BeanWrapper bw, PropertyValues pvs) {
...
Object resolvedValue = valueResolver.resolveValueIfNecessary(pv, originalValue);//返回了b(A=a(B=null))
Object convertedValue = resolvedValue;
//退出
}返回doCreateBean
protected Object doCreateBean(String beanName, RootBeanDefinition mbd, @Nullable Object[] args)
throws BeanCreationException {
...
try {
populateBean(beanName, mbd, instanceWrapper);//退出
exposedObject = initializeBean(beanName, exposedObject, mbd);//进入
}进入exposedObject = initializeBean(beanName, exposedObject, mbd);//进入
protected Object initializeBean(String beanName, Object bean, @Nullable RootBeanDefinition mbd) {
Object wrappedBean = bean;//对A进行处理
if (mbd == null || !mbd.isSynthetic()) {
wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName);
}
return wrappedBean;//返回
}退出exposedObject = initializeBean(beanName, exposedObject, mbd);到doCreateBean
protected Object doCreateBean(String beanName, RootBeanDefinition mbd, @Nullable Object[] args)
throws BeanCreationException {
// Initialize the bean instance.
Object exposedObject = bean;
try {
populateBean(beanName, mbd, instanceWrapper);
exposedObject = initializeBean(beanName, exposedObject, mbd);//退出
}
if (earlySingletonExposure) {
Object earlySingletonReference = getSingleton(beanName, false);//进入进入Object earlySingletonReference = getSingleton(beanName, false);//进入
protected Object getSingleton(String beanName, boolean allowEarlyReference) {//a false
Object singletonObject = this.singletonObjects.get(beanName);//一级缓存不存在A
if (singletonObject == null && isSingletonCurrentlyInCreation(beanName)) {
synchronized (this.singletonObjects) {
singletonObject = this.earlySingletonObjects.get(beanName);//二级缓存中有A
if (singletonObject == null && allowEarlyReference) {
ObjectFactory<?> singletonFactory = this.singletonFactories.get(beanName);
if (singletonFactory != null) {
singletonObject = singletonFactory.getObject();
this.earlySingletonObjects.put(beanName, singletonObject);
this.singletonFactories.remove(beanName);
}
}
}
}
return singletonObject;//返回了二级缓存中的A
}返回到doCreateBean
if (earlySingletonExposure) {
Object earlySingletonReference = getSingleton(beanName, false);//返回了A
return exposedObject;//返回A返回到createBean
try {
Object beanInstance = doCreateBean(beanName, mbdToUse, args);//返回到A
if (logger.isTraceEnabled()) {
logger.trace("Finished creating instance of bean '" + beanName + "'");
}
return beanInstance;//返回A
}返回doGetBean
// Create bean instance.
if (mbd.isSingleton()) {
sharedInstance = getSingleton(beanName, () -> {
try {
return createBean(beanName, mbd, args);//返回A
}
}返回到getSingleton
try {
singletonObject = singletonFactory.getObject();//返回了A
newSingleton = true;
}
if (newSingleton) {
addSingleton(beanName, singletonObject);//进入
}
return singletonObject;进入addSingleton(beanName, singletonObject);//进入
protected void addSingleton(String beanName, Object singletonObject) {
synchronized (this.singletonObjects) {
this.singletonObjects.put(beanName, singletonObject);//一级缓存存入A
this.singletonFactories.remove(beanName);//三级缓存清除A
this.earlySingletonObjects.remove(beanName);//二级缓存清除A
this.registeredSingletons.add(beanName);//注册A到容器
}
}现在一级缓存有A和B了
a是从一到二到三
b是直接从三到一
返回到getSingleton
if (newSingleton) {
addSingleton(beanName, singletonObject);//进入
}
return singletonObject;//返回A返回到doGetBean
if (mbd.isSingleton()) {
sharedInstance = getSingleton(beanName, () -> {//返回
bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd);
return (T) bean;//返回A
}返回到getBean
@Override
public Object getBean(String name) throws BeansException {
return doGetBean(name, null, null, false);
}返回到preInstantiateSingletons
public void preInstantiateSingletons() throws BeansException {
else {
getBean(beanName);//返回了
}
}
}
// 退出
}退出到finishBeanFactoryInitialization
beanFactory.preInstantiateSingletons();//退出退出到refresh
this.finishRefresh();//返回到doGetBean
protected <T> T doGetBean(
String name, @Nullable Class<T> requiredType, @Nullable Object[] args, boolean typeCheckOnly)
throws BeansException {
String beanName = transformedBeanName(name);
Object bean;
// Eagerly check singleton cache for manually registered singletons.
Object sharedInstance = getSingleton(beanName);//A和B循环依赖了跳过debug
Connected to the target VM, address: '127.0.0.1:2121', transport: 'socket'
16:47:13.402 [main] DEBUG org.springframework.context.support.ClassPathXmlApplicationContext - Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@63e2203c
16:47:13.749 [main] DEBUG org.springframework.beans.factory.xml.XmlBeanDefinitionReader - Loaded 2 bean definitions from class path resource [applicationContext.xml]
16:49:12.840 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'a'
---A created success
17:32:02.337 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'b'
---B created success
Disconnected from the target VM, address: '127.0.0.1:2121', transport: 'socket'
Process finished with exit code 038_spring循环依赖debug源码04
再次A / B两对象在三级缓存中的迁移说明
1.A创建过程中需要B，于是A将自己放到三级缓里面，去实例化B。
2.B实例化的时候发现需要A，于是B先查一级缓存，没有，再查二级缓存，还是没有，再查三级缓存，找到了A然后把三级缓存里面的这个A放到二级缓存里面，并删除三级缓存里面的A。
3.B顺利初始化完毕，将自己放到一级缓存里面（此时B里面的A依然是创建中状态)，然后回来接着创建A，此时B已经创建结束，直接从一级缓存里面拿到B，然后完成创建，并将A自己放到一级缓存里面。
我打的断点
最后
本文是4.Spring【Java面试第三季】的小节
