标签：4.1 mbd Spring beanName bean Bean 实例 单例 null
Spring版本：Spring 5.2.9.BUILD-SNAPSHOT
修改过部分源码，但不影响主体流程
概述
bean的生命周期主要有如下几个步骤：
-
创建
bean的实例 -
给实例化出来的
bean填充属性 -
初始化
bean -
通过
IOC容器使用bean -
容器关闭时销毁
bean
调用时机
refresh() -> finishBeanFactoryInitialization(beanFactory) -> beanFactory.preInstantiateSingletons() -> getBean() -> doGetBean() -> createBean() -> doCreateBean()
源码解析
finishBeanFactoryInitialization
/**
* 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.
// 为上下文初始化类型转换器
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.
// 如果beanFactory之前没有注册嵌入值解析器，则注册默认的嵌入值解析器，主要用于注解属性值的解析
if (!beanFactory.hasEmbeddedValueResolver()) {
beanFactory.addEmbeddedValueResolver(strVal -> getEnvironment().resolvePlaceholders(strVal));
}
// Initialize LoadTimeWeaverAware beans early to allow for registering their transformers early.
// 尽早初始化loadTimeWeaverAware bean,以便尽早注册它们的转换器
String[] weaverAwareNames = beanFactory.getBeanNamesForType(LoadTimeWeaverAware.class, false, false);
for (String weaverAwareName : weaverAwareNames) {
getBean(weaverAwareName);
}
// Stop using the temporary ClassLoader for type matching.
// 禁止使用临时类加载器进行类型匹配
beanFactory.setTempClassLoader(null);
// Allow for caching all bean definition metadata, not expecting further changes.
// 冻结所有的bean定义，说明注册的bean定义将不被修改或任何进一步的处理
beanFactory.freezeConfiguration();
// Instantiate all remaining (non-lazy-init) singletons.
// 实例化剩下的单例,非懒加载对象
beanFactory.preInstantiateSingletons();
}
-
为上下文初始化类型转换器
-
注册默认的嵌入值解析器，主要用于注解属性值的解析
-
冻结所有的bean定义，不允许继续修改
-
实例化剩下的单例,非懒加载对象
preInstantiateSingletons
@Override
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.
// 将所有BeanDefinition的名字创建一个集合
List<String> beanNames = new ArrayList<>(this.beanDefinitionNames);
// Trigger initialization of all non-lazy singleton beans...
// 触发所有非延迟加载单例bean的初始化，遍历集合的对象
for (String beanName : beanNames) {
// 合并父类BeanDefinition
RootBeanDefinition bd = getMergedLocalBeanDefinition(beanName);
// 条件判断，抽象，单例，非懒加载
if (!bd.isAbstract() && bd.isSingleton() && !bd.isLazyInit()) {
// 判断是否实现了FactoryBean接口
if (isFactoryBean(beanName)) {
// 根据&+beanName来获取具体的对象
Object bean = getBean(FACTORY_BEAN_PREFIX + beanName);
// 进行类型转换
if (bean instanceof FactoryBean) {
FactoryBean<?> factory = (FactoryBean<?>) bean;
// 判断这个FactoryBean是否希望立即初始化
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());
}
// 如果希望急切的初始化，则通过beanName获取bean实例
if (isEagerInit) {
getBean(beanName);
}
}
}
else {
// 如果beanName对应的bean不是FactoryBean，只是普通的bean，通过beanName获取bean实例
getBean(beanName);
}
}
}
// Trigger post-initialization callback for all applicable beans...
// 遍历beanNames，触发所有SmartInitializingSingleton的后初始化回调
for (String beanName : beanNames) {
// 获取beanName对应的bean实例
Object singletonInstance = getSingleton(beanName);
// 判断singletonInstance是否实现了SmartInitializingSingleton接口
if (singletonInstance instanceof SmartInitializingSingleton) {
// 类型转换
SmartInitializingSingleton smartSingleton = (SmartInitializingSingleton) singletonInstance;
// 触发SmartInitializingSingleton实现类的afterSingletonsInstantiated方法
if (System.getSecurityManager() != null) {
AccessController.doPrivileged((PrivilegedAction<Object>) () -> {
smartSingleton.afterSingletonsInstantiated();
return null;
}, getAccessControlContext());
}
else {
smartSingleton.afterSingletonsInstantiated();
}
}
}
}
-
遍历
beanDefinitionNames集合的对象,触发所有非延迟加载单例bean的初始化 -
合并父类
BeanDefinition，生成RootBeanDefinition -
判断是否实现了
FactoryBean接口，并判断这个FactoryBean是否希望立即初始化。
getBean -> doGetBean
/**
* 返回一个实例，该实例可以指定bean的共享或独立
*
* 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(
String name, @Nullable Class<T> requiredType, @Nullable Object[] args, boolean typeCheckOnly)
throws BeansException {
/**
* 提取对应的beanName，很多同学可能会认为此处直接使用即可，为什么还要进行转换呢，
* 原因在于当bean对象实现FactoryBean接口之后就会变成&beanName，同时如果存在别名，也需要把别名进行转换*/
String beanName = transformedBeanName(name);
Object bean;
// Eagerly check singleton cache for manually registered singletons.
/**提前检查单例缓存中是否有手动注册的单例对象，跟循环依赖有关联*/
Object sharedInstance = getSingleton(beanName);
// 如果bean的单例对象找到了，且没有创建bean实例时要使用的参数
if (sharedInstance != null && args == null) {
if (logger.isTraceEnabled()) {
if (isSingletonCurrentlyInCreation(beanName)) {
logger.trace("Returning eagerly cached instance of singleton bean '" + beanName +
"' that is not fully initialized yet - a consequence of a circular reference");
}
else {
logger.trace("Returning cached instance of singleton bean '" + beanName + "'");
}
}
// 返回对象的实例，很多同学会理解不了这句话存在的意义，当你实现了FactoryBean接口的对象，需要获取具体的对象的时候就需要此方法来进行获取了
bean = getObjectForBeanInstance(sharedInstance, name, beanName, null);
}
else {
// Fail if we're already creating this bean instance:
// We're assumably within a circular reference.
// 当对象都是单例的时候会尝试解决循环依赖的问题，但是原型模式下如果存在循环依赖的情况，那么直接抛出异常
if (isPrototypeCurrentlyInCreation(beanName)) {
throw new BeanCurrentlyInCreationException(beanName);
}
// Check if bean definition exists in this factory.
// 如果bean定义不存在，就检查父工厂是否有
BeanFactory parentBeanFactory = getParentBeanFactory();
// 如果beanDefinitionMap中也就是在所有已经加载的类中不包含beanName，那么就尝试从父容器中获取
if (parentBeanFactory != null && !containsBeanDefinition(beanName)) {
// Not found -> check parent.
// 获取name对应的规范名称【全类名】，如果name前面有'&'，则会返回'&'+规范名称【全类名】
String nameToLookup = originalBeanName(name);
// 如果父工厂是AbstractBeanFactory的实例
if (parentBeanFactory instanceof AbstractBeanFactory) {
// 调用父工厂的doGetBean方法，就是该方法。【递归】
return ((AbstractBeanFactory) parentBeanFactory).doGetBean(
nameToLookup, requiredType, args, typeCheckOnly);
}
else if (args != null) {
// Delegation to parent with explicit args.
// 如果有创建bean实例时要使用的参数
// Delegation to parent with explicit args. 使用显示参数委派给父工厂
// 使用父工厂获取该bean对象,通bean全类名和创建bean实例时要使用的参数
return (T) parentBeanFactory.getBean(nameToLookup, args);
}
else if (requiredType != null) {
// No args -> delegate to standard getBean method.
// 没有创建bean实例时要使用的参数 -> 委托给标准的getBean方法。
// 使用父工厂获取该bean对象,通bean全类名和所需的bean类型
return parentBeanFactory.getBean(nameToLookup, requiredType);
}
else {
// 使用父工厂获取bean，通过bean全类名
return (T) parentBeanFactory.getBean(nameToLookup);
}
}
// 如果不是做类型检查，那么表示要创建bean，此处在集合中做一个记录
if (!typeCheckOnly) {
// 为beanName标记为已经创建（或将要创建）
markBeanAsCreated(beanName);
}
try {
// 此处做了BeanDefinition对象的转换，当我们从xml文件中加载beandefinition对象的时候，封装的对象是GenericBeanDefinition,
// 此处要做类型转换，如果是子类bean的话，会合并父类的相关属性
RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);
// 检查mbd的合法性，不合格会引发验证异常
checkMergedBeanDefinition(mbd, beanName, args);
// Guarantee initialization of beans that the current bean depends on.
// 如果存在依赖的bean的话，那么则优先实例化依赖的bean
String[] dependsOn = mbd.getDependsOn();
if (dependsOn != null) {
// 如果存在依赖，则需要递归实例化依赖的bean
for (String dep : dependsOn) {
// 如果beanName已注册依赖于dependentBeanName的关系
if (isDependent(beanName, dep)) {
throw new BeanCreationException(mbd.getResourceDescription(), beanName,
"Circular depends-on relationship between '" + beanName + "' and '" + dep + "'");
}
// 注册各个bean的依赖关系，方便进行销毁
registerDependentBean(dep, beanName);
try {
// 递归优先实例化被依赖的Bean
getBean(dep);
}
// 捕捉为找到BeanDefinition异常：'beanName'依赖于缺少的bean'dep'
catch (NoSuchBeanDefinitionException ex) {
throw new BeanCreationException(mbd.getResourceDescription(), beanName,
"'" + beanName + "' depends on missing bean '" + dep + "'", ex);
}
}
}
// Create bean instance.
// 创建bean的实例对象
if (mbd.isSingleton()) {
// 返回以beanName的(原始)单例对象，如果尚未注册，则使用singletonFactory创建并注册一个对象:
sharedInstance = getSingleton(beanName, () -> {
try {
// 为给定的合并后BeanDefinition(和参数)创建一个bean实例
return createBean(beanName, mbd, args);
}
catch (BeansException ex) {
// Explicitly remove instance from singleton cache: It might have been put there
// eagerly by the creation process, to allow for circular reference resolution.
// Also remove any beans that received a temporary reference to the bean.
// 显示地从单例缓存中删除实例：它可能是由创建过程急切地放在那里，以允许循环引用解析。还要删除
// 接收到该Bean临时引用的任何Bean
// 销毁给定的bean。如果找到相应的一次性Bean实例，则委托给destoryBean
destroySingleton(beanName);
// 重新抛出ex
throw ex;
}
});
// 从beanInstance中获取公开的Bean对象，主要处理beanInstance是FactoryBean对象的情况，如果不是
// FactoryBean会直接返回beanInstance实例
bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd);
}
// 原型模式的bean对象创建
else if (mbd.isPrototype()) {
// It's a prototype -> create a new instance.
// 它是一个原型 -> 创建一个新实例
// 定义prototype实例
Object prototypeInstance = null;
try {
// 创建Prototype对象前的准备工作，默认实现将beanName添加到prototypesCurrentlyInCreation中
beforePrototypeCreation(beanName);
// 为mbd(和参数)创建一个bean实例
prototypeInstance = createBean(beanName, mbd, args);
}
finally {
// 创建完prototype实例后的回调，默认是将beanName从prototypesCurrentlyInCreation移除
afterPrototypeCreation(beanName);
}
// 从beanInstance中获取公开的Bean对象，主要处理beanInstance是FactoryBean对象的情况，如果不是
// FactoryBean会直接返回beanInstance实例
bean = getObjectForBeanInstance(prototypeInstance, name, beanName, mbd);
}
else {
// 指定的scope上实例化bean
String scopeName = mbd.getScope();
if (!StringUtils.hasLength(scopeName)) {
throw new IllegalStateException("No scope name defined for bean ´" + beanName + "'");
}
// 从scopes中获取scopeName对于的Scope对象
Scope scope = this.scopes.get(scopeName);
// 如果scope为null
if (scope == null) {
// 抛出非法状态异常：没有名为'scopeName'的scope注册
throw new IllegalStateException("No Scope registered for scope name '" + scopeName + "'");
}
try {
// 从scope中获取beanName对应的实例对象
Object scopedInstance = scope.get(beanName, () -> {
// 创建Prototype对象前的准备工作，默认实现 将beanName添加到prototypesCurrentlyInCreation中
beforePrototypeCreation(beanName);
try {
// 为mbd(和参数)创建一个bean实例
return createBean(beanName, mbd, args);
}
finally {
// 创建完prototype实例后的回调，默认是将beanName从prototypesCurrentlyInCreation移除
afterPrototypeCreation(beanName);
}
});
// 从beanInstance中获取公开的Bean对象，主要处理beanInstance是FactoryBean对象的情况，如果不是
// FactoryBean会直接返回beanInstance实例
bean = getObjectForBeanInstance(scopedInstance, name, beanName, mbd);
}
catch (IllegalStateException ex) {
// 捕捉非法状态异常
// 抛出Bean创建异常：作用域 'scopeName' 对于当前线程是不活动的；如果您打算从单个实例引用它，请考虑为此
// beanDefinition一个作用域代理
throw new BeanCreationException(beanName,
"Scope '" + scopeName + "' is not active for the current thread; consider " +
"defining a scoped proxy for this bean if you intend to refer to it from a singleton",
ex);
}
}
}
catch (BeansException ex) {
// 捕捉获取Bean对象抛出的Bean异常
// 在Bean创建失败后，对缓存的元数据执行适当的清理
cleanupAfterBeanCreationFailure(beanName);
// 重新抛出ex
throw ex;
}
}
// Check if required type matches the type of the actual bean instance.
// 检查requiredType是否与实际Bean实例的类型匹配
// 如果requiredType不为null&&bean不是requiredType的实例
if (requiredType != null && !requiredType.isInstance(bean)) {
try {
// 获取此BeanFactory使用的类型转换器，将bean转换为requiredType
T convertedBean = getTypeConverter().convertIfNecessary(bean, requiredType);
// 如果convertedBean为null
if (convertedBean == null) {
// 抛出Bean不是必要类型的异常
throw new BeanNotOfRequiredTypeException(name, requiredType, bean.getClass());
}
// 返回convertedBean
return convertedBean;
}
catch (TypeMismatchException ex) {
if (logger.isTraceEnabled()) {
logger.trace("Failed to convert bean '" + name + "' to required type '" +
ClassUtils.getQualifiedName(requiredType) + "'", ex);
}
throw new BeanNotOfRequiredTypeException(name, requiredType, bean.getClass());
}
}
// 将bean返回出去
return (T) bean;
}
-
bean别名进行转换 -
处理
DependsOn，如果存在依赖，则需要递归实例化依赖的bean -
判断该
bean是单例对象还是原型对象，分别进行创建
getSingleton
/**
* 返回以给定名称注册的(原始)单例对象，如果尚未注册，则创建并注册一个对象
*
* Return the (raw) singleton object registered under the given name,
* creating and registering a new one if none registered yet.
* @param beanName the name of the bean
* @param singletonFactory the ObjectFactory to lazily create the singleton
* with, if necessary
* @return the registered singleton object
*/
public Object getSingleton(String beanName, ObjectFactory<?> singletonFactory) {
// 如果beanName为null，抛出异常
Assert.notNull(beanName, "Bean name must not be null");
// 使用单例对象的高速缓存Map作为锁，保证线程同步
synchronized (this.singletonObjects) {
// 从单例对象的高速缓存Map中获取beanName对应的单例对象
Object singletonObject = this.singletonObjects.get(beanName);
// 如果单例对象获取不到
if (singletonObject == null) {
// 如果当前在destorySingletons中
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!)");
}
// 如果当前日志级别时调试
if (logger.isDebugEnabled()) {
logger.debug("Creating shared instance of singleton bean '" + beanName + "'");
}
// 创建单例之前的回调,默认实现将单例注册为当前正在创建中
beforeSingletonCreation(beanName);
// 表示生成了新的单例对象的标记，默认为false，表示没有生成新的单例对象
boolean newSingleton = false;
// 有抑制异常记录标记,没有时为true,否则为false
boolean recordSuppressedExceptions = (this.suppressedExceptions == null);
// 如果没有抑制异常记录
if (recordSuppressedExceptions) {
// 对抑制的异常列表进行实例化(LinkedHashSet)
this.suppressedExceptions = new LinkedHashSet<>();
}
try {
// 从单例工厂中获取对象
singletonObject = singletonFactory.getObject();
// 生成了新的单例对象的标记为true，表示生成了新的单例对象
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.
// 同时，单例对象是否隐式出现 -> 如果是，请继续操作，因为异常表明该状态
// 尝试从单例对象的高速缓存Map中获取beanName的单例对象
singletonObject = this.singletonObjects.get(beanName);
// 如果获取失败，抛出异常
if (singletonObject == null) {
throw ex;
}
}
// 捕捉Bean创建异常
catch (BeanCreationException ex) {
// 如果没有抑制异常记录
if (recordSuppressedExceptions) {
// 遍历抑制的异常列表
for (Exception suppressedException : this.suppressedExceptions) {
// 将抑制的异常对象添加到 bean创建异常 中，这样做的，就是相当于 '因XXX异常导致了Bean创建异常‘ 的说法
ex.addRelatedCause(suppressedException);
}
}
// 抛出异常
throw ex;
}
finally {
// 如果没有抑制异常记录
if (recordSuppressedExceptions) {
// 将抑制的异常列表置为null，因为suppressedExceptions是对应单个bean的异常记录，置为null
// 可防止异常信息的混乱
this.suppressedExceptions = null;
}
// 创建单例后的回调,默认实现将单例标记为不在创建中
afterSingletonCreation(beanName);
}
// 生成了新的单例对象
if (newSingleton) {
// 将beanName和singletonObject的映射关系添加到该工厂的单例缓存中:
addSingleton(beanName, singletonObject);
}
}
// 返回该单例对象
return singletonObject;
}
}
-
从缓存中取
bean对象 -
取不到则从singletonFactory中获取，singletonFactory是函数式接口FunctionalInterface，里面有getObject()方法，用于获取对象。
createBean -> doCreateBean
protected Object doCreateBean(String beanName, RootBeanDefinition mbd, @Nullable Object[] args)
throws BeanCreationException {
// Instantiate the bean.
// 这个beanWrapper是用来持有创建出来的bean对象的
BeanWrapper instanceWrapper = null;
// 获取factoryBean实例缓存
if (mbd.isSingleton()) {
// 如果是单例对象，从factorybean实例缓存中移除当前bean定义信息
instanceWrapper = this.factoryBeanInstanceCache.remove(beanName);
}
// 没有就创建实例
if (instanceWrapper == null) {
// 根据执行bean使用对应的策略创建新的实例，如，工厂方法，构造函数主动注入、简单初始化
instanceWrapper = createBeanInstance(beanName, mbd, args);
}
// 从包装类中获取原始bean
Object bean = instanceWrapper.getWrappedInstance();
// 获取具体的bean对象的Class属性
Class<?> beanType = instanceWrapper.getWrappedClass();
// 如果不等于NullBean类型，那么修改目标类型
if (beanType != NullBean.class) {
mbd.resolvedTargetType = beanType;
}
// Allow post-processors to modify the merged bean definition.
// 允许beanPostProcessor去修改合并的beanDefinition
synchronized (mbd.postProcessingLock) {
if (!mbd.postProcessed) {
try {
// MergedBeanDefinitionPostProcessor后置处理器修改合并bean的定义
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.
// 判断当前bean是否需要提前曝光：单例&允许循环依赖&当前bean正在创建中，检测循环依赖
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");
}
// 为避免后期循环依赖，可以在bean初始化完成前将创建实例的ObjectFactory加入工厂
addSingletonFactory(beanName, () -> getEarlyBeanReference(beanName, mbd, bean));
//只保留二级缓存，不向三级缓存中存放对象
// earlySingletonObjects.put(beanName,bean);
// registeredSingletons.add(beanName);
//
// synchronized (this.singletonObjects) {
// if (!this.singletonObjects.containsKey(beanName)) {
// //实例化后的对象先添加到三级缓存中，三级缓存对应beanName的是一个lambda表达式(能够触发创建代理对象的机制)
// this.singletonFactories.put(beanName, () -> getEarlyBeanReference(beanName, mbd, bean));
// this.registeredSingletons.add(beanName);
// }
// }
}
// Initialize the bean instance.
// 初始化bean实例
Object exposedObject = bean;
try {
// 对bean的属性进行填充，将各个属性值注入，其中，可能存在依赖于其他bean的属性，则会递归初始化依赖的bean
populateBean(beanName, mbd, instanceWrapper);
// 执行初始化逻辑
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) {
// 从缓存中获取具体的对象
Object earlySingletonReference = getSingleton(beanName, false);
// earlySingletonReference只有在检测到有循环依赖的情况下才会不为空
if (earlySingletonReference != null) {
// 如果exposedObject没有在初始化方法中被改变，也就是没有被增强
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) {
// 返回false说明依赖还没实例化好
if (!removeSingletonIfCreatedForTypeCheckOnly(dependentBean)) {
actualDependentBeans.add(dependentBean);
}
}
// 因为bean创建后所依赖的bean一定是已经创建的
// actualDependentBeans不为空则表示当前bean创建后其依赖的bean却没有全部创建完，也就是说存在循环依赖
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 " +
"'getBeanNamesForType' with the 'allowEagerInit' flag turned off, for example.");
}
}
}
}
// Register bean as disposable.
try {
// 注册bean对象，方便后续在容器销毁的时候销毁对象
registerDisposableBeanIfNecessary(beanName, bean, mbd);
}
catch (BeanDefinitionValidationException ex) {
throw new BeanCreationException(
mbd.getResourceDescription(), beanName, "Invalid destruction signature", ex);
}
return exposedObject;
}
-
根据执行
bean使用对应的策略创建新的实例，如工厂方法、Supplier、构造函数主动注入、简单初始化 -
MergedBeanDefinitionPostProcessor后置处理器修改合并bean的定义 -
属性填充
-
初始化
-
注册
bean对象，方便后续在容器销毁的时候销毁对象
destroy
org.springframework.beans.factory.support.DisposableBeanAdapter#destroy
@Override
public void destroy() {
if (!CollectionUtils.isEmpty(this.beanPostProcessors)) {
for (DestructionAwareBeanPostProcessor processor : this.beanPostProcessors) {
processor.postProcessBeforeDestruction(this.bean, this.beanName);
}
}
if (this.invokeDisposableBean) {
if (logger.isTraceEnabled()) {
logger.trace("Invoking destroy() on bean with name '" + this.beanName + "'");
}
try {
if (System.getSecurityManager() != null) {
AccessController.doPrivileged((PrivilegedExceptionAction<Object>) () -> {
((DisposableBean) this.bean).destroy();
return null;
}, this.acc);
}
else {
((DisposableBean) this.bean).destroy();
}
}
catch (Throwable ex) {
String msg = "Invocation of destroy method failed on bean with name '" + this.beanName + "'";
if (logger.isDebugEnabled()) {
logger.warn(msg, ex);
}
else {
logger.warn(msg + ": " + ex);
}
}
}
if (this.destroyMethod != null) {
invokeCustomDestroyMethod(this.destroyMethod);
}
else if (this.destroyMethodName != null) {
Method methodToInvoke = determineDestroyMethod(this.destroyMethodName);
if (methodToInvoke != null) {
invokeCustomDestroyMethod(ClassUtils.getInterfaceMethodIfPossible(methodToInvoke));
}
}
}
bean销毁流程
-
processor.postProcessBeforeDestruction() -
((DisposableBean) this.bean).destroy() -
invokeCustomDestroyMethod()
总结
本文介绍了基本bean生命周期的基本流程，后续文章会详细介绍细节，先贴图。
标签：4.1,mbd,Spring,beanName,bean,Bean,实例,单例,null 来源： https://www.cnblogs.com/xmzpc/p/15919293.html
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