本文將從Spring源碼探討2個問題,Spring 容器是如何管理bean,以及如何從容器中獲取bean
BeanFactory接口 是Spring容器的基礎(chǔ),該接口提供了 getBean(String beanName) 來獲取 instance實例
BeanFactory的繼承體系如下:
BeanFactory繼承體系.png
getBean方法的實現(xiàn)是在AbstractBeanFactory抽象類中
//---------------------------------------------------------------------
// Implementation of BeanFactory interface
//---------------------------------------------------------------------
@Override
public Object getBean(String name) throws BeansException {
return doGetBean(name, null, null, false);
}
進(jìn)入 doGetBean
/**
* Return an instance, which may be shared or independent, of the specified bean.
* @param name the name of the bean to retrieve
* @param requiredType the required type of the bean to retrieve
* @param args arguments to use when creating a bean instance using explicit arguments
* (only applied when creating a new instance as opposed to retrieving an existing one)
* @param typeCheckOnly whether the instance is obtained for a type check,
* not for actual use
* @return an instance of the bean
* @throws BeansException if the bean could not be created
*/
@SuppressWarnings("unchecked")
protected <T> T doGetBean(final String name, @Nullable final Class<T> requiredType,
@Nullable final Object[] args, boolean typeCheckOnly) throws BeansException {
// 1.轉(zhuǎn)換對應(yīng)的beanName
final String beanName = transformedBeanName(name);
Object bean;
// Eagerly check singleton cache for manually registered singletons.
// 2.從緩存中獲取原生實例
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 + "'");
}
}
// 3.對原生instance進(jìn)行處理 如果是正常bean直接返回,如果是FactoryBean beanName前有& 直接返回FactoryBean,否則返回FactoryBean.getObject()
bean = getObjectForBeanInstance(sharedInstance, name, beanName, null);
}
else {
// 4.原型模式下循環(huán)依賴的檢測
// Fail if we're already creating this bean instance:
// We're assumably within a circular reference.
if (isPrototypeCurrentlyInCreation(beanName)) {
throw new BeanCurrentlyInCreationException(beanName);
}
// 5.如果有父工廠,并且當(dāng)前工廠沒有此bean則在父工廠中遞歸獲取bean
// 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 {
// 6.將存儲xml配置文件信息的GernericBeanDefinition轉(zhuǎn)換成RootBeanDefinition
final RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);
checkMergedBeanDefinition(mbd, beanName, args);
// 7.尋找依賴
// 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 + "'");
}
// 記錄依賴 dependenciesForBean.add(canonicalName); dependenciesForBean是個Set集合
registerDependentBean(dep, beanName);
try {
getBean(dep);
}
catch (NoSuchBeanDefinitionException ex) {
throw new BeanCreationException(mbd.getResourceDescription(), beanName,
"'" + beanName + "' depends on missing bean '" + dep + "'", ex);
}
}
}
// 8.根據(jù)不同模式下創(chuàng)建bean instance
// Create bean instance.
// 單例
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);
}
// 原型模式
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);
}
// 其他模式
else {
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, 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;
}
}
// 9.類型檢查
// 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;
}
1.轉(zhuǎn)換對應(yīng)的beanName
final String beanName = transformedBeanName(name);
/**
* Return the bean name, stripping out the factory dereference prefix if necessary,
* and resolving aliases to canonical names.
* @param name the user-specified name
* @return the transformed bean name
*/
protected String transformedBeanName(String name) {
return canonicalName(BeanFactoryUtils.transformedBeanName(name));
}
從文檔注釋上可以看出 這部分邏輯 是轉(zhuǎn)換bean的別名 或者如果是factorybean時 將beanName去除 前綴"&"
2. Object sharedInstance = getSingleton(beanName); //從緩存中獲取原生實例
/**
* Return the (raw) singleton object registered under the given name.
* <p>Checks already instantiated singletons and also allows for an early
* reference to a currently created singleton (resolving a circular reference).
* @param beanName the name of the bean to look for
* @param allowEarlyReference whether early references should be created or not
* @return the registered singleton object, or {@code null} if none found
*/
@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;
}
a.首先嘗試從單例緩存名為 singletonObjects Map中獲取bean,
b. 獲取不到,如果該實例正在創(chuàng)建中,則嘗試從earlySingletonObjects Map中獲取,
c.還獲取不到,如果允許單例 循環(huán)依賴即boolean allowEarlyReference =true 時 嘗試從singletonFactories 中獲取ObjectFactory,返回 ObjectFactory.getObject()
如果Bean A 依賴Bean B Bean B 依賴 Bean A 那么就造成循環(huán)依賴
循環(huán)依賴分為 構(gòu)造器依賴 和 setter方法依賴
Spring 只提供解決 單例模式下的setter方法循環(huán)依賴,其他模式下的循環(huán)依賴會拋BeanCurrentlyInCreationException異常
Spring解決bean循環(huán)依賴的思路是: 單例模式下默認(rèn)是可以允許循環(huán)依賴的,解決辦法時,在創(chuàng)建實例時,不等實例創(chuàng)建完成就會把創(chuàng)建該實例的Factory 暴露出去(放入到singletonFactories Map中),并且下一個bean可以通過暴露的ObjectFactory的 getObject()方法獲取該實例,當(dāng)然我們也可以通過AbstractRefreshableApplicationContext的setAllowCircularReferences()方法 來禁止循環(huán)引用
3. bean = getObjectForBeanInstance(sharedInstance, name, beanName, null);
對原生instance進(jìn)行處理 如果是正常bean直接返回,如果是FactoryBean,傳入的beanName前有& 也直接返回FactoryBean,否則返回FactoryBean.getObject()
Spring容器createBean創(chuàng)建完該實例后,只是原生的instance,放入到緩存中的實例也是這種狀態(tài),如果該實例是FactoryBean,而我們想要的是該工廠實例創(chuàng)建的實例,所以就有了getObjectForBeanInstance方法的處理
/**
* Get the object for the given bean instance, either the bean
* instance itself or its created object in case of a FactoryBean.
* @param beanInstance the shared bean instance
* @param name name that may include factory dereference prefix
* @param beanName the canonical bean name
* @param mbd the merged bean definition
* @return the object to expose for the bean
*/
protected Object getObjectForBeanInstance(
Object beanInstance, String name, String beanName, @Nullable RootBeanDefinition mbd) {
// Don't let calling code try to dereference the factory if the bean isn't a factory.
if (BeanFactoryUtils.isFactoryDereference(name)) {
if (beanInstance instanceof NullBean) {
return beanInstance;
}
if (!(beanInstance instanceof FactoryBean)) {
throw new BeanIsNotAFactoryException(transformedBeanName(name), beanInstance.getClass());
}
}
// 如果是正常bean 或者FactoryBean的beanName 加上前綴& 直接返回
// Now we have the bean instance, which may be a normal bean or a FactoryBean.
// If it's a FactoryBean, we use it to create a bean instance, unless the
// caller actually wants a reference to the factory.
if (!(beanInstance instanceof FactoryBean) || BeanFactoryUtils.isFactoryDereference(name)) {
return beanInstance;
}
Object object = null;
if (mbd == null) {
// 緩存FactoryBean.getObject
object = getCachedObjectForFactoryBean(beanName);
}
if (object == null) {
// Return bean instance from factory.
FactoryBean<?> factory = (FactoryBean<?>) beanInstance;
// Caches object obtained from FactoryBean if it is a singleton.
if (mbd == null && containsBeanDefinition(beanName)) {
mbd = getMergedLocalBeanDefinition(beanName);
}
boolean synthetic = (mbd != null && mbd.isSynthetic());
// 從FactoryBean中獲取bean
object = getObjectFromFactoryBean(factory, beanName, !synthetic);
}
return object;
}
/**
* Return whether the given name is a factory dereference
* (beginning with the factory dereference prefix).
* @param name the name of the bean
* @return whether the given name is a factory dereference
* @see BeanFactory#FACTORY_BEAN_PREFIX
*/
public static boolean isFactoryDereference(@Nullable String name) {
return (name != null && name.startsWith(BeanFactory.FACTORY_BEAN_PREFIX));
}
/**
* Used to dereference a {@link FactoryBean} instance and distinguish it from
* beans <i>created</i> by the FactoryBean. For example, if the bean named
* {@code myJndiObject} is a FactoryBean, getting {@code &myJndiObject}
* will return the factory, not the instance returned by the factory.
*/
String FACTORY_BEAN_PREFIX = "&";
/**
* Obtain an object to expose from the given FactoryBean.
* @param factory the FactoryBean instance
* @param beanName the name of the bean
* @param shouldPostProcess whether the bean is subject to post-processing
* @return the object obtained from the FactoryBean
* @throws BeanCreationException if FactoryBean object creation failed
* @see org.springframework.beans.factory.FactoryBean#getObject()
*/
protected Object getObjectFromFactoryBean(FactoryBean<?> factory, String beanName, boolean shouldPostProcess) {
if (factory.isSingleton() && containsSingleton(beanName)) {
synchronized (getSingletonMutex()) {
Object object = this.factoryBeanObjectCache.get(beanName);
if (object == null) {
object = doGetObjectFromFactoryBean(factory, beanName);
// Only post-process and store if not put there already during getObject() call above
// (e.g. because of circular reference processing triggered by custom getBean calls)
Object alreadyThere = this.factoryBeanObjectCache.get(beanName);
if (alreadyThere != null) {
object = alreadyThere;
}
else {
if (shouldPostProcess) {
if (isSingletonCurrentlyInCreation(beanName)) {
// Temporarily return non-post-processed object, not storing it yet..
return object;
}
// singletonsCurrentlyInCreation.add(beanName) 記錄正在創(chuàng)建的bean
beforeSingletonCreation(beanName);
try {
// 給后處理器PostProcessor一次覆寫返回bean的邏輯 默認(rèn)是正常返回FactoryBean.getObject
object = postProcessObjectFromFactoryBean(object, beanName);
}
catch (Throwable ex) {
throw new BeanCreationException(beanName,
"Post-processing of FactoryBean's singleton object failed", ex);
}
finally {
// singletonsCurrentlyInCreation.remove(beanName) 從正在創(chuàng)建bean記錄中移除
afterSingletonCreation(beanName);
}
}
if (containsSingleton(beanName)) {
// 將bean放入factoryBeanObjectCache.緩存
this.factoryBeanObjectCache.put(beanName, object);
}
}
}
return object;
}
}
else {
Object object = doGetObjectFromFactoryBean(factory, beanName);
if (shouldPostProcess) {
try {
object = postProcessObjectFromFactoryBean(object, beanName);
}
catch (Throwable ex) {
throw new BeanCreationException(beanName, "Post-processing of FactoryBean's object failed", ex);
}
}
return object;
}
}
/**
* Obtain an object to expose from the given FactoryBean.
* @param factory the FactoryBean instance
* @param beanName the name of the bean
* @return the object obtained from the FactoryBean
* @throws BeanCreationException if FactoryBean object creation failed
* @see org.springframework.beans.factory.FactoryBean#getObject()
*/
private Object doGetObjectFromFactoryBean(final FactoryBean<?> factory, final String beanName)
throws BeanCreationException {
Object object;
try {
if (System.getSecurityManager() != null) {
AccessControlContext acc = getAccessControlContext();
try {
object = AccessController.doPrivileged((PrivilegedExceptionAction<Object>) factory::getObject, acc);
}
catch (PrivilegedActionException pae) {
throw pae.getException();
}
}
else {
// getObjectForBeanInstance() 對 FactoryBean的核心處理
object = factory.getObject();
}
}
catch (FactoryBeanNotInitializedException ex) {
throw new BeanCurrentlyInCreationException(beanName, ex.toString());
}
catch (Throwable ex) {
throw new BeanCreationException(beanName, "FactoryBean threw exception on object creation", ex);
}
// Do not accept a null value for a FactoryBean that's not fully
// initialized yet: Many FactoryBeans just return null then.
if (object == null) {
if (isSingletonCurrentlyInCreation(beanName)) {
throw new BeanCurrentlyInCreationException(
beanName, "FactoryBean which is currently in creation returned null from getObject");
}
object = new NullBean();
}
return object;
}
如果緩存中有原生實例,通過getObjectForBeanIntance()處理后直接返回了;
下面是單例緩存中沒有實例的邏輯:
4.原型模式下循環(huán)依賴的檢測
上面已經(jīng)說到,Spring只支持單例模式下setter方法的循環(huán)依賴,如果是原型模式則直接拋出BeanCurrentlyInCreationException異常
5.如果當(dāng)前工廠沒有定義此bean,并且有父工廠,則在父工廠中遞歸獲取bean 獲取到則返回
6.將存儲xml配置文件信息的GernericBeanDefinition轉(zhuǎn)換成RootBeanDefinition
從xml讀取到的bean信息定義在GernericBeanDefinition中,但是后續(xù)針對bean的處理都是使用RootBeanDefinition,所以將GernericBeanDefinition轉(zhuǎn)換成RootBeanDefinition,轉(zhuǎn)換過程中如果父bean不為空的話,也會合并父類的屬性
7.在bean初始化之前,會通過getBean 先加載依賴的bean
8.根據(jù)不同的模式下 創(chuàng)建bean 這部分邏輯較長 稍后詳解
9類型檢查及轉(zhuǎn)換
public <T> T getBean(String name, Class<T> requiredType) throws BeansException {
return doGetBean(name, requiredType, null, false);
}
如果getBean()方法中傳入了類型,Spring在返回實例前,會進(jìn)行類型檢查或轉(zhuǎn)換為requiredType所指定的類型,比如返回的bean是個String,requiredType卻需要Integer 這時候就需要轉(zhuǎn)換了
下面探討在不同模式下創(chuàng)建bean的邏輯,
該邏輯的方法是個getSingleton((String beanName, ObjectFactory<?> singletonFactory)重載方法
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 + "'");
}
// singletonsCurrentlyInCreation.add(beanName) 記錄正在創(chuàng)建的bean
beforeSingletonCreation(beanName);
boolean newSingleton = false;
boolean recordSuppressedExceptions = (this.suppressedExceptions == null);
if (recordSuppressedExceptions) {
this.suppressedExceptions = new LinkedHashSet<>();
}
try {
// ObjectFactory來創(chuàng)建bean的方法 該方法的具體邏輯是在AbstractAutowireCapableBeanFactory.creatBean()中
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;
}
// singletonsCurrentlyInCreation.remove(beanName) 從正在創(chuàng)建bean記錄中移除
afterSingletonCreation(beanName);
}
if (newSingleton) {
//將創(chuàng)建的實例放入到singletonObjects緩存中,并且刪除中間的各種記錄
addSingleton(beanName, singletonObject);
}
}
return singletonObject;
}
}
我們先來看看創(chuàng)建完成后 addSingleton(beanName, singletonObject)具體做了什么操作
/**
* Add the given singleton object to the singleton cache of this factory.
* <p>To be called for eager registration of singletons.
* @param beanName the name of the bean
* @param singletonObject the singleton object
*/
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);
}
}
很明顯,在單例緩存singletonObjects中添加實例,將提前暴露的ObjectFactory移除緩存
再返回來看看具體創(chuàng)建bean的過程
ObjectFactory.getObject方法來創(chuàng)建bean,該方法的具體邏輯AbstractAutowireCapableBeanFactory.creatBean()中,接下來我們就詳細(xì)解析createBean的過程
/**
* Central method of this class: creates a bean instance,
* populates the bean instance, applies post-processors, etc.
* @see #doCreateBean
*/
@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;
//1.根據(jù)設(shè)置的class屬性或者className來解析class對象
// 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.
// 2.對xml配置中l(wèi)ookupMethod和replaceMethod的配置進(jìn)行處理 主要是統(tǒng)計MethodOverrides方法對應(yīng)方法名的個數(shù),來設(shè)置是否有重載的標(biāo)志
try {
mbdToUse.prepareMethodOverrides();
}
catch (BeanDefinitionValidationException ex) {
throw new BeanDefinitionStoreException(mbdToUse.getResourceDescription(),
beanName, "Validation of method overrides failed", ex);
}
try {
//3.在真正實例化bean之前,給后處理器BeanPostProcessors 一次返回代理實例的機(jī)會
// 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 {
//4.真正實例化的邏輯
Object beanInstance = doCreateBean(beanName, mbdToUse, args);
if (logger.isTraceEnabled()) {
logger.trace("Finished creating instance of bean '" + beanName + "'");
}
return beanInstance;
}
catch (BeanCreationException | ImplicitlyAppearedSingletonException ex) {
// A previously detected exception with proper bean creation context already,
// or illegal singleton state to be communicated up to DefaultSingletonBeanRegistry.
throw ex;
}
catch (Throwable ex) {
throw new BeanCreationException(
mbdToUse.getResourceDescription(), beanName, "Unexpected exception during bean creation", ex);
}
}
從createBean()方法中可以看到該方法主要有4部分邏輯,
1.根據(jù)設(shè)置的class屬性或者className來解析class對象
2.對xml配置中l(wèi)ookupMethod和replaceMethod的配置進(jìn)行處理 主要是統(tǒng)計MethodOverrides方法對應(yīng)方法名的個數(shù),來設(shè)置是否有重載的標(biāo)志
3.在真正實例化bean之前,給后處理器BeanPostProcessors 一次返回代理實例的機(jī)會
4.真正實例化的邏輯doCreateBean
我們詳細(xì)看看第3,4部分
/**
* Apply before-instantiation post-processors, resolving whether there is a
* before-instantiation shortcut for the specified bean.
* @param beanName the name of the bean
* @param mbd the bean definition for the bean
* @return the shortcut-determined bean instance, or {@code null} if none
*/
@Nullable
protected Object resolveBeforeInstantiation(String beanName, RootBeanDefinition mbd) {
Object bean = null;
if (!Boolean.FALSE.equals(mbd.beforeInstantiationResolved)) {
// Make sure bean class is actually resolved at this point.
if (!mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) {
Class<?> targetType = determineTargetType(beanName, mbd);
if (targetType != null) {
bean = applyBeanPostProcessorsBeforeInstantiation(targetType, beanName);
if (bean != null) {
bean = applyBeanPostProcessorsAfterInitialization(bean, beanName);
}
}
}
mbd.beforeInstantiationResolved = (bean != null);
}
return bean;
}
該方法是在真正實例化實例前的短路操作,如果有InstantiationAwareBeanPostProcessor后處理器的實現(xiàn),就會走這部分邏輯
/**
* Apply InstantiationAwareBeanPostProcessors to the specified bean definition
* (by class and name), invoking their {@code postProcessBeforeInstantiation} methods.
* <p>Any returned object will be used as the bean instead of actually instantiating
* the target bean. A {@code null} return value from the post-processor will
* result in the target bean being instantiated.
* @param beanClass the class of the bean to be instantiated
* @param beanName the name of the bean
* @return the bean object to use instead of a default instance of the target bean, or {@code null}
* @see InstantiationAwareBeanPostProcessor#postProcessBeforeInstantiation
*/
@Nullable
protected Object applyBeanPostProcessorsBeforeInstantiation(Class<?> beanClass, String beanName) {
for (BeanPostProcessor bp : getBeanPostProcessors()) {
if (bp instanceof InstantiationAwareBeanPostProcessor) {
InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
Object result = ibp.postProcessBeforeInstantiation(beanClass, beanName);
if (result != null) {
return result;
}
}
}
return null;
}
從方法中我們可以看到只是尋找InstantiationAwareBeanPostProcessor后處理器,然后調(diào)用postProcessBeforeInstantiation方法,(注意該后處理器的postProcessAfterInstantiation方法是在真正初始化實例過程中在填充屬性populateBean前調(diào)用)
在調(diào)用完InstantiationAwareBeanPostProcessor后處理器方法后,還會繼續(xù)調(diào)用BeanPostProcessor的postProcessAfterInitialization實例化后的后處理方法,Spring創(chuàng)建bean有個特點就是盡量保證所有bean在初始化完成后都有機(jī)會調(diào)用BeanPostProcessor的postProcessAfterInitialization()方法,所以實際開發(fā)中可針對這個特性進(jìn)行設(shè)計自己的業(yè)務(wù)邏輯.
@Override
public Object applyBeanPostProcessorsAfterInitialization(Object existingBean, String beanName)
throws BeansException {
Object result = existingBean;
for (BeanPostProcessor processor : getBeanPostProcessors()) {
Object current = processor.postProcessAfterInitialization(result, beanName);
if (current == null) {
return result;
}
result = current;
}
return result;
}
以上就是有InstantiationAwareBeanPostProcessor后處理器的短路邏輯,如果沒有這個后處理器,則進(jìn)行真正實例化
doCreateBean().
/**
* Actually create the specified bean. Pre-creation processing has already happened
* at this point, e.g. checking {@code postProcessBeforeInstantiation} callbacks.
* <p>Differentiates between default bean instantiation, use of a
* factory method, and autowiring a constructor.
* @param beanName the name of the bean
* @param mbd the merged bean definition for the bean
* @param args explicit arguments to use for constructor or factory method invocation
* @return a new instance of the bean
* @throws BeanCreationException if the bean could not be created
* @see #instantiateBean
* @see #instantiateUsingFactoryMethod
* @see #autowireConstructor
*/
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) {
// 1.根據(jù)指定的策略創(chuàng)建bean,如工廠方法,構(gòu)造函數(shù),簡單初始化
instanceWrapper = createBeanInstance(beanName, mbd, 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.
synchronized (mbd.postProcessingLock) {
if (!mbd.postProcessed) {
try {
//2.MergedBeanDefinitionPostProcessors后處理器邏輯
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));
if (earlySingletonExposure) {
if (logger.isTraceEnabled()) {
logger.trace("Eagerly caching bean '" + beanName +
"' to allow for resolving potential circular references");
}
//3.不等bean創(chuàng)建完成,就將創(chuàng)建該bean的Factory暴露出去,以解決單例模式下的循環(huán)依賴
addSingletonFactory(beanName, () -> getEarlyBeanReference(beanName, mbd, bean));
}
// Initialize the bean instance.
Object exposedObject = bean;
try {
//4.填充屬性
populateBean(beanName, mbd, instanceWrapper);
//5. 處理ware接口邏輯和 配置的init-method方法邏輯
exposedObject = initializeBean(beanName, exposedObject, mbd);
}
catch (Throwable ex) {
if (ex instanceof BeanCreationException && beanName.equals(((BeanCreationException) ex).getBeanName())) {
throw (BeanCreationException) ex;
}
else {
throw new BeanCreationException(
mbd.getResourceDescription(), beanName, "Initialization of bean failed", ex);
}
}
if (earlySingletonExposure) {
Object earlySingletonReference = getSingleton(beanName, false);
if (earlySingletonReference != null) {
if (exposedObject == bean) {
exposedObject = earlySingletonReference;
}
else if (!this.allowRawInjectionDespiteWrapping && hasDependentBean(beanName)) {
String[] dependentBeans = getDependentBeans(beanName);
Set<String> actualDependentBeans = new LinkedHashSet<>(dependentBeans.length);
for (String dependentBean : dependentBeans) {
if (!removeSingletonIfCreatedForTypeCheckOnly(dependentBean)) {
actualDependentBeans.add(dependentBean);
}
}
//此處bean初始化邏輯已經(jīng)走完,如果還有依賴的bean沒有創(chuàng)建完成,即actualDependentBeans不為空說明存在循環(huán)依賴
if (!actualDependentBeans.isEmpty()) {
throw new BeanCurrentlyInCreationException(beanName,
"Bean with name '" + beanName + "' has been injected into other beans [" +
StringUtils.collectionToCommaDelimitedString(actualDependentBeans) +
"] in its raw version as part of a circular reference, but has eventually been " +
"wrapped. This means that said other beans do not use the final version of the " +
"bean. This is often the result of over-eager type matching - consider using " +
"'getBeanNamesOfType' with the 'allowEagerInit' flag turned off, for example.");
}
}
}
}
// 6 注冊銷毀bean,處理配置的destory-method方法或者DestructionAwareBeanPostProcessor后處理器的邏輯
// Register bean as disposable.
try {
registerDisposableBeanIfNecessary(beanName, bean, mbd);
}
catch (BeanDefinitionValidationException ex) {
throw new BeanCreationException(
mbd.getResourceDescription(), beanName, "Invalid destruction signature", ex);
}
return exposedObject;
}
1.根據(jù)指定的策略創(chuàng)建bean,如工廠方法,構(gòu)造函數(shù),簡單初始化,這個過程將BeanDefinition轉(zhuǎn)換成了BeanWapper
/**
* Create a new instance for the specified bean, using an appropriate instantiation strategy:
* factory method, constructor autowiring, or simple instantiation.
* @param beanName the name of the bean
* @param mbd the bean definition for the bean
* @param args explicit arguments to use for constructor or factory method invocation
* @return a BeanWrapper for the new instance
* @see #obtainFromSupplier
* @see #instantiateUsingFactoryMethod
* @see #autowireConstructor
* @see #instantiateBean
*/
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);
if (beanClass != null && !Modifier.isPublic(beanClass.getModifiers()) && !mbd.isNonPublicAccessAllowed()) {
throw new BeanCreationException(mbd.getResourceDescription(), beanName,
"Bean class isn't public, and non-public access not allowed: " + beanClass.getName());
}
Supplier<?> instanceSupplier = mbd.getInstanceSupplier();
if (instanceSupplier != null) {
return obtainFromSupplier(instanceSupplier, beanName);
}
if (mbd.getFactoryMethodName() != null) {
return instantiateUsingFactoryMethod(beanName, mbd, args);
}
// Shortcut when re-creating the same bean...
boolean resolved = false;
boolean autowireNecessary = false;
if (args == null) {
synchronized (mbd.constructorArgumentLock) {
if (mbd.resolvedConstructorOrFactoryMethod != null) {
resolved = true;
autowireNecessary = mbd.constructorArgumentsResolved;
}
}
}
if (resolved) {
if (autowireNecessary) {
return autowireConstructor(beanName, mbd, null, null);
}
else {
return instantiateBean(beanName, mbd);
}
}
// Candidate constructors for autowiring?
Constructor<?>[] ctors = determineConstructorsFromBeanPostProcessors(beanClass, beanName);
if (ctors != null || mbd.getResolvedAutowireMode() == AUTOWIRE_CONSTRUCTOR ||
mbd.hasConstructorArgumentValues() || !ObjectUtils.isEmpty(args)) {
return autowireConstructor(beanName, mbd, ctors, args);
}
// Preferred constructors for default construction?
ctors = mbd.getPreferredConstructors();
if (ctors != null) {
return autowireConstructor(beanName, mbd, ctors, null);
}
// No special handling: simply use no-arg constructor.
return instantiateBean(beanName, mbd);
}
該過程的大致邏輯是:
如果存在工廠方法則使用工廠方法進(jìn)行初始化,
如果有多個構(gòu)造函數(shù),則根據(jù)具體的參數(shù)選擇具體的構(gòu)造函數(shù)并進(jìn)行初始化
如果沒有工廠方法,也沒有帶參構(gòu)造,則選用默認(rèn)的構(gòu)造函數(shù)
@Override
public Object instantiate(RootBeanDefinition bd, @Nullable String beanName, BeanFactory owner) {
// Don't override the class with CGLIB if no overrides.
if (!bd.hasMethodOverrides()) {
Constructor<?> constructorToUse;
synchronized (bd.constructorArgumentLock) {
constructorToUse = (Constructor<?>) bd.resolvedConstructorOrFactoryMethod;
if (constructorToUse == null) {
final Class<?> clazz = bd.getBeanClass();
if (clazz.isInterface()) {
throw new BeanInstantiationException(clazz, "Specified class is an interface");
}
try {
if (System.getSecurityManager() != null) {
constructorToUse = AccessController.doPrivileged(
(PrivilegedExceptionAction<Constructor<?>>) clazz::getDeclaredConstructor);
}
else {
constructorToUse = clazz.getDeclaredConstructor();
}
bd.resolvedConstructorOrFactoryMethod = constructorToUse;
}
catch (Throwable ex) {
throw new BeanInstantiationException(clazz, "No default constructor found", ex);
}
}
}
return BeanUtils.instantiateClass(constructorToUse);
}
else {
// Must generate CGLIB subclass.
return instantiateWithMethodInjection(bd, beanName, owner);
}
}
上述初始化的邏輯可以很清楚的看到,如果有override的方法也就是有配置lookup-method或replace-method,則使用CGLB進(jìn)行動態(tài)代理,如果沒有override 則簡單的使用反射來初始化bean
2.MergedBeanDefinitionPostProcessors后處理器邏輯
/**
* Apply MergedBeanDefinitionPostProcessors to the specified bean definition,
* invoking their {@code postProcessMergedBeanDefinition} methods.
* @param mbd the merged bean definition for the bean
* @param beanType the actual type of the managed bean instance
* @param beanName the name of the bean
* @see MergedBeanDefinitionPostProcessor#postProcessMergedBeanDefinition
*/
protected void applyMergedBeanDefinitionPostProcessors(RootBeanDefinition mbd, Class<?> beanType, String beanName) {
for (BeanPostProcessor bp : getBeanPostProcessors()) {
if (bp instanceof MergedBeanDefinitionPostProcessor) {
MergedBeanDefinitionPostProcessor bdp = (MergedBeanDefinitionPostProcessor) bp;
bdp.postProcessMergedBeanDefinition(mbd, beanType, beanName);
}
}
}
在剛初始化之后,有次使用MergedBeanDefinitionPostProcessor.postProcessMergedBeanDefinition()來定義bean的機(jī)會
3.不等bean創(chuàng)建完成,就將創(chuàng)建該bean的Factory暴露出去,以解決單例模式下的循環(huán)依賴
addSingletonFactory(beanName, () -> getEarlyBeanReference(beanName, mbd, bean));
/**
* Add the given singleton factory for building the specified singleton
* if necessary.
* <p>To be called for eager registration of singletons, e.g. to be able to
* resolve circular references.
* @param beanName the name of the bean
* @param singletonFactory the factory for the singleton object
*/
protected void addSingletonFactory(String beanName, ObjectFactory<?> singletonFactory) {
Assert.notNull(singletonFactory, "Singleton factory must not be null");
synchronized (this.singletonObjects) {
if (!this.singletonObjects.containsKey(beanName)) {
this.singletonFactories.put(beanName, singletonFactory);
this.earlySingletonObjects.remove(beanName);
this.registeredSingletons.add(beanName);
}
}
}
邏輯很簡單,就是不等bean創(chuàng)建完成就將該ObjectFactory放入到singletonFactories Map中進(jìn)行提前暴露,下一個bean依賴該bean時,即可通過該ObjectFactory來getObject()獲取bean,那我們再看看getObject()里的具體實現(xiàn)
/**
* Obtain a reference for early access to the specified bean,
* typically for the purpose of resolving a circular reference.
* @param beanName the name of the bean (for error handling purposes)
* @param mbd the merged bean definition for the bean
* @param bean the raw bean instance
* @return the object to expose as bean reference
*/
protected Object getEarlyBeanReference(String beanName, RootBeanDefinition mbd, Object bean) {
Object exposedObject = bean;
if (!mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) {
for (BeanPostProcessor bp : getBeanPostProcessors()) {
if (bp instanceof SmartInstantiationAwareBeanPostProcessor) {
SmartInstantiationAwareBeanPostProcessor ibp = (SmartInstantiationAwareBeanPostProcessor) bp;
exposedObject = ibp.getEarlyBeanReference(exposedObject, beanName);
}
}
}
return exposedObject;
}
可以看到是通過SmartInstantiationAwareBeanPostProcessor 后處理器的getEarlyBeanReference()方法返回一個未實例化結(jié)束的bean,以此來解決單例模式下的循環(huán)依賴
4.填充屬性 populateBean(beanName, mbd, instanceWrapper);
/**
* Populate the bean instance in the given BeanWrapper with the property values
* from the bean definition.
* @param beanName the name of the bean
* @param mbd the bean definition for the bean
* @param bw the BeanWrapper with bean instance
*/
@SuppressWarnings("deprecation") // for postProcessPropertyValues
protected void populateBean(String beanName, RootBeanDefinition mbd, @Nullable BeanWrapper bw) {
if (bw == null) {
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.
boolean continueWithPropertyPopulation = true;
if (!mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) {
for (BeanPostProcessor bp : getBeanPostProcessors()) {
if (bp instanceof InstantiationAwareBeanPostProcessor) {
InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
// InstantiationAwareBeanPostProcessor后處理器來設(shè)置是否繼續(xù)需要填充
// postProcessAfterInstantiation()方法返回false 該屬性表示不需要繼續(xù)填充
if (!ibp.postProcessAfterInstantiation(bw.getWrappedInstance(), beanName)) {
continueWithPropertyPopulation = false;
break;
}
}
}
}
if (!continueWithPropertyPopulation) {
return;
}
PropertyValues pvs = (mbd.hasPropertyValues() ? mbd.getPropertyValues() : null);
if (mbd.getResolvedAutowireMode() == AUTOWIRE_BY_NAME || mbd.getResolvedAutowireMode() == AUTOWIRE_BY_TYPE) {
MutablePropertyValues newPvs = new MutablePropertyValues(pvs);
// Add property values based on autowire by name if applicable.
// 根據(jù)名稱 獲取屬性 // pvs.add(propertyName, bean);
if (mbd.getResolvedAutowireMode() == AUTOWIRE_BY_NAME) {
autowireByName(beanName, mbd, bw, newPvs);
}
// 根據(jù)類型 獲取屬性 // pvs.add(propertyName, autowiredArgument);
// Add property values based on autowire by type if applicable.
if (mbd.getResolvedAutowireMode() == AUTOWIRE_BY_TYPE) {
autowireByType(beanName, mbd, bw, newPvs);
}
pvs = newPvs;
}
boolean hasInstAwareBpps = hasInstantiationAwareBeanPostProcessors();
boolean needsDepCheck = (mbd.getDependencyCheck() != AbstractBeanDefinition.DEPENDENCY_CHECK_NONE);
PropertyDescriptor[] filteredPds = null;
if (hasInstAwareBpps) {
if (pvs == null) {
pvs = mbd.getPropertyValues();
}
for (BeanPostProcessor bp : getBeanPostProcessors()) {
if (bp instanceof InstantiationAwareBeanPostProcessor) {
InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
PropertyValues pvsToUse = ibp.postProcessProperties(pvs, bw.getWrappedInstance(), beanName);
if (pvsToUse == null) {
if (filteredPds == null) {
filteredPds = filterPropertyDescriptorsForDependencyCheck(bw, mbd.allowCaching);
}
pvsToUse = ibp.postProcessPropertyValues(pvs, filteredPds, bw.getWrappedInstance(), beanName);
if (pvsToUse == null) {
return;
}
}
pvs = pvsToUse;
}
}
}
if (needsDepCheck) {
if (filteredPds == null) {
filteredPds = filterPropertyDescriptorsForDependencyCheck(bw, mbd.allowCaching);
}
checkDependencies(beanName, mbd, filteredPds, pvs);
}
if (pvs != null) {
// 將PropertyValues 記錄的屬性填充到beanWrapper中
applyPropertyValues(beanName, mbd, bw, pvs);
}
}
上述的方法 有以下邏輯:
a.通過InstantiationAwareBeanPostProcessor后處理器來設(shè)置是否繼續(xù)需要填充 postProcessAfterInstantiation()方法返回false 該屬性表示不需要繼續(xù)填充
b.根據(jù)名稱或者類型,進(jìn)行屬性獲取,記錄在PropertyValues pvs對象中
c.InstantiationAwareBeanPostProcessor的postProcessPropertyValues方法對獲取屬性后,填充前對屬性進(jìn)行再次處理,典型應(yīng)用是在RequiredAnnotationBeanPostProcessor類中對屬性進(jìn)行驗證
d.將PropertyValues 記錄的屬性填充到beanWrapper中
5. 處理ware接口邏輯和 配置的init-method方法邏輯
到此處,Spring的bean已經(jīng)完成了初步初始化,以及屬性填充,接下來就是Aware相關(guān)方法的處理,以及用戶自定義的初始化方法
/**
* Initialize the given bean instance, applying factory callbacks
* as well as init methods and bean post processors.
* <p>Called from {@link #createBean} for traditionally defined beans,
* and from {@link #initializeBean} for existing bean instances.
* @param beanName the bean name in the factory (for debugging purposes)
* @param bean the new bean instance we may need to initialize
* @param mbd the bean definition that the bean was created with
* (can also be {@code null}, if given an existing bean instance)
* @return the initialized bean instance (potentially wrapped)
* @see BeanNameAware
* @see BeanClassLoaderAware
* @see BeanFactoryAware
* @see #applyBeanPostProcessorsBeforeInitialization
* @see #invokeInitMethods
* @see #applyBeanPostProcessorsAfterInitialization
*/
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 {
// 處理Aware接口相關(guān)方法
invokeAwareMethods(beanName, bean);
}
Object wrappedBean = bean;
if (mbd == null || !mbd.isSynthetic()) {
// BeanPostProcessor后處理器的BeforeInitialization處理
wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName);
}
try {
// 處理InitializingBean 的afterPropertiesSet()方法以及 配置的init-method()
invokeInitMethods(beanName, wrappedBean, mbd);
}
catch (Throwable ex) {
throw new BeanCreationException(
(mbd != null ? mbd.getResourceDescription() : null),
beanName, "Invocation of init method failed", ex);
}
if (mbd == null || !mbd.isSynthetic()) {
// BeanPostProcessor后處理器的AfterInitialization處理
wrappedBean = applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName);
}
return wrappedBean;
}
可以看到initializeBean主要有一下邏輯:
a.處理Aware接口相關(guān)方法
private void invokeAwareMethods(final String beanName, final Object bean) {
if (bean instanceof Aware) {
if (bean instanceof BeanNameAware) {
((BeanNameAware) bean).setBeanName(beanName);
}
if (bean instanceof BeanClassLoaderAware) {
ClassLoader bcl = getBeanClassLoader();
if (bcl != null) {
((BeanClassLoaderAware) bean).setBeanClassLoader(bcl);
}
}
if (bean instanceof BeanFactoryAware) {
((BeanFactoryAware) bean).setBeanFactory(AbstractAutowireCapableBeanFactory.this);
}
}
}
設(shè)置setBeanName ,setBeanClassLoader,setBeanFactory
b.invokeInitMethods 用戶自定義初始化處理
在invokeInitMethods 前后有BeanPostProcessor后處理器BeforeInitialization和AfterInitialization方法的處理
@Override
public Object applyBeanPostProcessorsBeforeInitialization(Object existingBean, String beanName)
throws BeansException {
Object result = existingBean;
for (BeanPostProcessor processor : getBeanPostProcessors()) {
Object current = processor.postProcessBeforeInitialization(result, beanName);
if (current == null) {
return result;
}
result = current;
}
return result;
}
@Override
public Object applyBeanPostProcessorsAfterInitialization(Object existingBean, String beanName)
throws BeansException {
Object result = existingBean;
for (BeanPostProcessor processor : getBeanPostProcessors()) {
Object current = processor.postProcessAfterInitialization(result, beanName);
if (current == null) {
return result;
}
result = current;
}
return result;
}
再返回來看invokeInitMethods 方法的邏輯
/**
* Give a bean a chance to react now all its properties are set,
* and a chance to know about its owning bean factory (this object).
* This means checking whether the bean implements InitializingBean or defines
* a custom init method, and invoking the necessary callback(s) if it does.
* @param beanName the bean name in the factory (for debugging purposes)
* @param bean the new bean instance we may need to initialize
* @param mbd the merged bean definition that the bean was created with
* (can also be {@code null}, if given an existing bean instance)
* @throws Throwable if thrown by init methods or by the invocation process
* @see #invokeCustomInitMethod
*/
protected void invokeInitMethods(String beanName, final Object bean, @Nullable RootBeanDefinition mbd)
throws Throwable {
boolean isInitializingBean = (bean instanceof InitializingBean);
if (isInitializingBean && (mbd == null || !mbd.isExternallyManagedInitMethod("afterPropertiesSet"))) {
if (logger.isTraceEnabled()) {
logger.trace("Invoking afterPropertiesSet() on bean with name '" + beanName + "'");
}
if (System.getSecurityManager() != null) {
try {
AccessController.doPrivileged((PrivilegedExceptionAction<Object>) () -> {
((InitializingBean) bean).afterPropertiesSet();
return null;
}, getAccessControlContext());
}
catch (PrivilegedActionException pae) {
throw pae.getException();
}
}
else {
((InitializingBean) bean).afterPropertiesSet();
}
}
if (mbd != null && bean.getClass() != NullBean.class) {
String initMethodName = mbd.getInitMethodName();
if (StringUtils.hasLength(initMethodName) &&
!(isInitializingBean && "afterPropertiesSet".equals(initMethodName)) &&
!mbd.isExternallyManagedInitMethod(initMethodName)) {
invokeCustomInitMethod(beanName, bean, mbd);
}
}
}
可以清晰看到執(zhí)行用戶初始化方法時,先執(zhí)行InitializingBean的afterPropertiesSet()方法,再執(zhí)行配置的init-method
6 注冊銷毀bean,處理配置的destory-method方法或者DestructionAwareBeanPostProcessor后處理器的邏輯
/**
* Add the given bean to the list of disposable beans in this factory,
* registering its DisposableBean interface and/or the given destroy method
* to be called on factory shutdown (if applicable). Only applies to singletons.
* @param beanName the name of the bean
* @param bean the bean instance
* @param mbd the bean definition for the bean
* @see RootBeanDefinition#isSingleton
* @see RootBeanDefinition#getDependsOn
* @see #registerDisposableBean
* @see #registerDependentBean
*/
protected void registerDisposableBeanIfNecessary(String beanName, Object bean, RootBeanDefinition mbd) {
AccessControlContext acc = (System.getSecurityManager() != null ? getAccessControlContext() : null);
if (!mbd.isPrototype() && requiresDestruction(bean, mbd)) {
if (mbd.isSingleton()) {
// Register a DisposableBean implementation that performs all destruction
// work for the given bean: DestructionAwareBeanPostProcessors,
// DisposableBean interface, custom destroy method.
registerDisposableBean(beanName,
new DisposableBeanAdapter(bean, beanName, mbd, getBeanPostProcessors(), acc));
}
else {
// A bean with a custom scope...
Scope scope = this.scopes.get(mbd.getScope());
if (scope == null) {
throw new IllegalStateException("No Scope registered for scope name '" + mbd.getScope() + "'");
}
scope.registerDestructionCallback(beanName,
new DisposableBeanAdapter(bean, beanName, mbd, getBeanPostProcessors(), acc));
}
}
}
可以看到處理DisposableBean的destory()方法
至此,Spring bean 從創(chuàng)建 到獲取的問題已經(jīng)探討完,希望你能有所收獲.
由于筆者水平有限,文中如有錯誤請各路大神多多指正.
原創(chuàng)不易,如有轉(zhuǎn)載請標(biāo)明原處
