SpringIOC refresh()初始化程式碼例項
阿新 • • 發佈：2020-03-09
finishBeanFactoryInitialization(beanFactory)：初始化不需要延遲例項化的單例bean
/* org/springframework/context/support/AbstractApplicationContext.java:870 */
protected void finishBeanFactoryInitialization(ConfigurableListableBeanFactory beanFactory) {//初始化容器的conversionService
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));
}
//如果沒有任何一個類似PropertyPlaceholderConfigurer bean處理器
//預設一個嵌入式值解析器，主要是為了解析屬性值例如資料庫連線中${password}等屬性解析
if (!beanFactory.hasEmbeddedValueResolver()) {
beanFactory.addEmbeddedValueResolver(strVal -> getEnvironment().resolvePlaceholders(strVal));
}
// 先例項化LoadTimeWeaverAware相關的beans，以便儘早轉換，AOP相關
String[] weaverAwareNames = beanFactory.getBeanNamesForType(LoadTimeWeaverAware.class,false,false);
for (String weaverAwareName : weaverAwareNames) {
getBean(weaverAwareName);
}
//刪除臨時類載入器，停止臨時類載入器進行型別匹配
beanFactory.setTempClassLoader(null);
//拷貝beandefinitionNames到frozenBeanDefinitionNames
beanFactory.freezeConfiguration();
// 例項化所有不需要延遲初始化的單例bean
beanFactory.preInstantiateSingletons();
}beanFactory.preInstantiateSingletons()：例項化所有不需要延遲初始化的單例bean
/* org/springframework/beans/factory/support/DefaultListableBeanFactory.java:885 */
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.
//拷貝beanDefinitionNames副本，考慮到遍歷中其他執行緒可能修改beandefinitionNames
// ArrayList型別遍歷時規避fast-fail，實現fast-safe
List<String> beanNames = new ArrayList<>(this.beanDefinitionNames);
// Trigger initialization of all non-lazy singleton beans...
for (String beanName : beanNames) {
//當bean存在parentBean時的繼承關係
//① bean不存在parentBean時，建立一個new RootBeanDefinition(beandefinition)返回。
//② bean存在parentBean時，支援繼承關係
// 需要先建立parentBean的new RootBeanDefinition(parentBeanDefinition)
// 然後用beandefinition覆蓋parentBean的RootBeanDefinition的相關屬性並返回。superBean.overrideFrom(subBean);
RootBeanDefinition bd = getMergedLocalBeanDefinition(beanName);
//用mergedLocalBeanDefinition判斷是否需要初始化
//篩選不是抽象類且不是延遲例項化的單例進行初始化
if (!bd.isAbstract() && bd.isSingleton() && !bd.isLazyInit()) {
if (isFactoryBean(beanName)) {
//工廠Bean beanName=&beanName
Object bean = getBean(FACTORY_BEAN_PREFIX + beanName);
if (bean instanceof FactoryBean) {
final 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 {
//不是工廠bean 直接初始化
getBean(beanName);
}
}
}
//SmartInitializingSingleton型別的單例初始化後的回撥
for (String beanName : beanNames) {
Object singletonInstance = getSingleton(beanName);
if (singletonInstance instanceof SmartInitializingSingleton) {
final SmartInitializingSingleton smartSingleton = (SmartInitializingSingleton) singletonInstance;
if (System.getSecurityManager() != null) {
AccessController.doPrivileged((PrivilegedAction<Object>) () -> {
smartSingleton.afterSingletonsInstantiated();
return null;
},getAccessControlContext());
}
else {
smartSingleton.afterSingletonsInstantiated();
}
}
}
}getBean(beanName):Bean初始化
/* org/springframework/beans/factory/support/AbstractBeanFactory.java:414 */
protected <T> T doGetBean(final String name,@Nullable final Class<T> requiredType,@Nullable final Object[] args,boolean typeCheckOnly) throws BeansException {
//如果是aliaName，解析成beanName
final String beanName = transformedBeanName(name);
Object bean;
// Eagerly check singleton cache for manually registered singletons.
//檢查單例快取中是否存在bean的例項化物件、初始化物件 （涉及迴圈依賴解決，需要先分清出Bean的兩個階段例項化、初始化）
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 + "'");
}
}
bean = getObjectForBeanInstance(sharedInstance,name,beanName,null);
}
else {
if (isPrototypeCurrentlyInCreation(beanName)) {
//多例bean正在初始化時丟擲異常
//由於多例bean，每呼叫一次getBean就會建立一個例項，
//所以通過ThreadLocal打標，來避免單個執行緒的重複建立
throw new BeanCurrentlyInCreationException(beanName);
}
BeanFactory parentBeanFactory = getParentBeanFactory();
//父容器不為空，用父容器初始化
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) {
//alreadyCreated容器記錄已經被例項化的beanName，
//這裡將beanName新增到alreadyCreated
markBeanAsCreated(beanName);
}
try {
//重新獲取mergedLocalBeanDefinition（bean與parentBean合併）
final RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);
//檢查mbd不是抽象類
checkMergedBeanDefinition(mbd,args);
//建立bean單例之前，需要保證先bean所依賴的Bean單例已建立，
//這裡的依賴對應@dependsOn宣告的依賴，這個註解不常用，這裡也會出現一種迴圈依賴場景，與我們平常討論的引用迴圈依賴不同
//@dependsOn(value = "b") class A;@dependsOn(value = "a") class B
//如果出現這種迴圈依賴 會直接丟擲異常 啟動失敗
String[] dependsOn = mbd.getDependsOn();
if (dependsOn != null) {
for (String dep : dependsOn) {
if (isDependent(beanName,dep)) {
throw new BeanCreationException(mbd.getResourceDescription(),"Circular depends-on relationship between '" + beanName + "' and '" + dep + "'");
}
//儲存依賴關係到dependentBeanMap容器中
registerDependentBean(dep,beanName);
try {
//例項化依賴的bean 這裡就是常見迴圈依賴地點 A依賴B B依賴A
getBean(dep);
}
catch (NoSuchBeanDefinitionException ex) {
throw new BeanCreationException(mbd.getResourceDescription(),"'" + beanName + "' depends on missing bean '" + dep + "'",ex);
}
}
}
// Create bean instance.
if (mbd.isSingleton()) {
//單例Bean建立 先取快取，沒有才createBean
sharedInstance = getSingleton(beanName,() -> {
try {
//建立Bean例項
return createBean(beanName,mbd,args);
}
catch (BeansException ex) {
destroySingleton(beanName);
throw ex;
}
});
bean = getObjectForBeanInstance(sharedInstance,mbd);
}
else if (mbd.isPrototype()) {
//多例Bean建立 直接createbean
Object prototypeInstance = null;
try {
//正在建立bean打標prototypesCurrentlyInCreation
//與上面isPrototypeCurrentlyInCreation()聯合
beforePrototypeCreation(beanName);
prototypeInstance = createBean(beanName,args);
}
finally {
//正在建立bean打標prototypesCurrentlyInCreation刪除標記
afterPrototypeCreation(beanName);
}
bean = getObjectForBeanInstance(prototypeInstance,mbd);
}
else {
//自定義scope初始化、scope.get()
String scopeName = mbd.getScope();
final 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,args);
}
finally {
afterPrototypeCreation(beanName);
}
});
bean = getObjectForBeanInstance(scopedInstance,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;
}
}
//getBean(beanName,requiredType)時檢查建立的例項是否需要的型別，容器初始化時不會走進裡面
if (requiredType != null && !requiredType.isInstance(bean)) {
try {
T convertedBean = getTypeConverter().convertIfNecessary(bean,requiredType);
if (convertedBean == null) {
throw new BeanNotOfRequiredTypeException(name,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,bean.getClass());
}
}
return (T) bean;
}sharedInstance = getSingleton(beanName,() -> {try {return createBean(beanName,args);}:單例初始化，這個方法比較簡單，主要關注下和循壞依賴相關的邏輯
/* org/springframework/beans/factory/support/DefaultSingletonBeanRegistry.java:201 */
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) {
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 + "'");
}
//迴圈依賴相關：初始化前先singletonsCurrentlyInCreation.add(beanName)
beforeSingletonCreation(beanName);
boolean newSingleton = false;
boolean recordSuppressedExceptions = (this.suppressedExceptions == null);
if (recordSuppressedExceptions) {
this.suppressedExceptions = new LinkedHashSet<>();
}
try {
//lamda表示式：其實是呼叫createBean(beanName,args):Bean初始化
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;
}
//迴圈依賴相關：初始化後singletonsCurrentlyInCreation.remove(beanName)
afterSingletonCreation(beanName);
}
if (newSingleton) {
//初始化完後
//this.singletonObjects.put(beanName,singletonObject);放入到單例容器中
//this.singletonFactories.remove(beanName);清空迴圈依賴相關的兩個打標
//this.earlySingletonObjects.remove(beanName);
//this.registeredSingletons.add(beanName);放入單例beanName容器中
addSingleton(beanName,singletonObject);
}
}
return singletonObject;
}
}
createBean(beanName,args)：初始化例項,這個表方法注意一下，初始化例項前，留機會給BeanPostProcessor初始化代理類直接返回代理類初始化例項
/* org/springframework/beans/factory/support/AbstractAutowireCapableBeanFactory.java:467 */
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;
Class<?> resolvedClass = resolveBeanClass(mbd,beanName);
if (resolvedClass != null && !mbd.hasBeanClass() && mbd.getBeanClassName() != null) {
//確保beanclass確實被解析了，若合併出錯，重新定義bean定義
mbdToUse = new RootBeanDefinition(mbd);
mbdToUse.setBeanClass(resolvedClass);
}
// Prepare method overrides.
try {
//校驗需要重寫方法是否全部重寫，並且會給重寫方法是否過載打標
mbdToUse.prepareMethodOverrides();
}
catch (BeanDefinitionValidationException ex) {
throw new BeanDefinitionStoreException(mbdToUse.getResourceDescription(),"Validation of method overrides failed",ex);
}
try {
//resolveBeforeInstantiation方法是呼叫BeanPostProcessor處理器
//後續研究一下BeanPostProcessor
//這裡是給AOP相關BeanPostProcessor處理器生成代理類例項的機會，直接生成初始化代理類例項返回
//會面研究AOP時發現，proxy object不是在這裡初始化，這裡只是提供一個機會
//proxy object具體是在的下面doCreateBean時裡先建立target object
//然後通過後置處理器的後置方法初始化的
Object bean = resolveBeforeInstantiation(beanName,mbdToUse);
if (bean != null) {
return bean;
}
}
catch (Throwable ex) {
throw new BeanCreationException(mbdToUse.getResourceDescription(),"BeanPostProcessor before instantiation of bean failed",ex);
}
try {
//初始化例項
Object beanInstance = doCreateBean(beanName,mbdToUse,args);
if (logger.isTraceEnabled()) {
logger.trace("Finished creating instance of bean '" + beanName + "'");
}
return beanInstance;
}
catch (BeanCreationException | ImplicitlyAppearedSingletonException ex) {
// A previously detected exception with proper bean creation context already,// or illegal singleton state to be communicated up to DefaultSingletonBeanRegistry.
throw ex;
}
catch (Throwable ex) {
throw new BeanCreationException(
mbdToUse.getResourceDescription(),"Unexpected exception during bean creation",ex);
}
}
doCreateBean(beanName,args):beanClass例項化（即earlysingleton，注意不是初始化）然後DI完成初始化
/* org/springframework/beans/factory/support/AbstractAutowireCapableBeanFactory.java:549 */
protected Object doCreateBean(final String beanName,final RootBeanDefinition mbd,final @Nullable Object[] args)
throws BeanCreationException {
// Instantiate the bean.
BeanWrapper instanceWrapper = null;
if (mbd.isSingleton()) {
instanceWrapper = this.factoryBeanInstanceCache.remove(beanName);
}
if (instanceWrapper == null) {
//反射呼叫beanClass的構造方法建立例項幷包裝成beanwrapper--
instanceWrapper = createBeanInstance(beanName,args);
}
final Object bean = instanceWrapper.getWrappedInstance();
Class<?> beanType = instanceWrapper.getWrappedClass();
if (beanType != NullBean.class) {
mbd.resolvedTargetType = beanType;
}
// Allow post-processors to modify the merged bean definition.
//允許MergedBeanDefinitionPostProcessors後置管理器修改rootBeandefinition
synchronized (mbd.postProcessingLock) {
if (!mbd.postProcessed) {
try {
applyMergedBeanDefinitionPostProcessors(mbd,beanType,beanName);
}
catch (Throwable ex) {
throw new BeanCreationException(mbd.getResourceDescription(),"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));
if (earlySingletonExposure) {
if (logger.isTraceEnabled()) {
logger.trace("Eagerly caching bean '" + beanName +
"' to allow for resolving potential circular references");
}
//迴圈依賴相關邏輯：
//this.singletonFactories.put(beanName,singletonFactory);
//將例項化bean、beanName組裝成singletonFactory裝入singletonFactories容器
//this.earlySingletonObjects.remove(beanName);
//刪除earlySingletonObjects中beanName
addSingletonFactory(beanName,() -> getEarlyBeanReference(beanName,bean));
}
// Initialize the bean instance.
//建立例項
Object exposedObject = bean;
try {
//例項初始化 就是在這裡面實現依賴注入DI的:
//具體是呼叫AutowiredAnnotationBeanPostProcessor.postProcessProperties
populateBean(beanName,instanceWrapper);//呼叫Bean後置管理器前置方法BeanPostProcessor.postProcessBeforeInitialization
//instanceof aware介面，setBeanName setBeanClassLoader setBeanFactory
//呼叫Bean後置管理器後置方法BeanPostProcessor.postProcessAfterInitialization
exposedObject = initializeBean(beanName,exposedObject,mbd);
}
catch (Throwable ex) {
if (ex instanceof BeanCreationException && beanName.equals(((BeanCreationException) ex).getBeanName())) {
throw (BeanCreationException) ex;
}
else {
throw new BeanCreationException(
mbd.getResourceDescription(),"Initialization of bean failed",ex);
}
}
//...
return exposedObject;
}
populateBean(beanName,instanceWrapper)：依賴注入DI執行時機
/* org/springframework/beans/factory/support/AbstractAutowireCapableBeanFactory.java:1381 */
protected void populateBean(String beanName,@Nullable BeanWrapper bw) {
//...
PropertyDescriptor[] filteredPds = null;
if (hasInstAwareBpps) {
if (pvs == null) {
pvs = mbd.getPropertyValues();
}
for (BeanPostProcessor bp : getBeanPostProcessors()) {
if (bp instanceof InstantiationAwareBeanPostProcessor) {
InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
//這裡呼叫AutowiredAnnotationBeanPostProcessor.postProcessProperties()
//完成註解自動注入（DI）
PropertyValues pvsToUse = ibp.postProcessProperties(pvs,bw.getWrappedInstance(),beanName);
if (pvsToUse == null) {
if (filteredPds == null) {
filteredPds = filterPropertyDescriptorsForDependencyCheck(bw,mbd.allowCaching);
}
pvsToUse = ibp.postProcessPropertyValues(pvs,filteredPds,beanName);
if (pvsToUse == null) {
return;
}
}
pvs = pvsToUse;
}
}
}
if (needsDepCheck) {
if (filteredPds == null) {
filteredPds = filterPropertyDescriptorsForDependencyCheck(bw,mbd.allowCaching);
}
checkDependencies(beanName,pvs);
}
if (pvs != null) {
applyPropertyValues(beanName,bw,pvs);
}
}
DI結束，bean初始化基本結束了。然後就是bean初始化的BeanPostProcessor執行前置後置方法
BeanPostProcessor前置後置方法：一些很重要架構都需要依靠實現，例如AOP動態代理產生代理物件
AnnotationAwareAspectJAutoProxyCreator.postProcessAfterInitialization
/* org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory#initializeBean(java.lang.String,java.lang.Object,org.springframework.beans.factory.support.RootBeanDefinition) */
protected Object initializeBean(final String beanName,final Object bean,@Nullable RootBeanDefinition mbd) {
if (System.getSecurityManager() != null) {
AccessController.doPrivileged((PrivilegedAction<Object>) () -> {
invokeAwareMethods(beanName,bean);
return null;
},getAccessControlContext());
}
else {
invokeAwareMethods(beanName,bean);
}
Object wrappedBean = bean;
if (mbd == null || !mbd.isSynthetic()) {
//呼叫所有BeanPostProcessor前置方法BeanPostProcessor.postProcessBeforeInitialization
wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean,beanName);
}
try {
invokeInitMethods(beanName,wrappedBean,mbd);
}
catch (Throwable ex) {
throw new BeanCreationException(
(mbd != null ? mbd.getResourceDescription() : null),"Invocation of init method failed",ex);
}
if (mbd == null || !mbd.isSynthetic()) {
//呼叫所有BeanPostProcessor前置方法BeanPostProcessor.postProcessAfterInitialization
//例如AOP代理物件就是這裡初始化的,AnnotationAwareAspectJAutoProxyCreator.postProcessAfterInitialization
wrappedBean = applyBeanPostProcessorsAfterInitialization(wrappedBean,beanName);
}
return wrappedBean;
}
以上就是本文的全部內容，希望對大家的學習有所幫助，也希望大家多多支援我們。