입력 방법은 SpringApplication#run()
1.SpringApplication#run()SpringApplication#run()
/**
* Run the Spring application, creating and refreshing a new
* {@link ApplicationContext}.
* @param args the application arguments (usually passed from a Java main method)
* @return a running {@link ApplicationContext}
*/
public ConfigurableApplicationContext run(String... args) {
long startTime = System.nanoTime();
DefaultBootstrapContext bootstrapContext = createBootstrapContext();
ConfigurableApplicationContext context = null;
configureHeadlessProperty();
SpringApplicationRunListeners listeners = getRunListeners(args);
listeners.starting(bootstrapContext, this.mainApplicationClass);
try {
ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);
ConfigurableEnvironment environment = prepareEnvironment(listeners, bootstrapContext, applicationArguments);
Banner printedBanner = printBanner(environment);
context = createApplicationContext();
context.setApplicationStartup(this.applicationStartup);
prepareContext(bootstrapContext, context, environment, listeners, applicationArguments, printedBanner);
refreshContext(context);
afterRefresh(context, applicationArguments);
Duration timeTakenToStartup = Duration.ofNanos(System.nanoTime() - startTime);
if (this.logStartupInfo) {
new StartupInfoLogger(this.mainApplicationClass).logStarted(getApplicationLog(), timeTakenToStartup);
}
listeners.started(context, timeTakenToStartup);
callRunners(context, applicationArguments);
}
catch (Throwable ex) {
if (ex instanceof AbandonedRunException) {
throw ex;
}
handleRunFailure(context, ex, listeners);
throw new IllegalStateException(ex);
}
try {
if (context.isRunning()) {
Duration timeTakenToReady = Duration.ofNanos(System.nanoTime() - startTime);
listeners.ready(context, timeTakenToReady);
}
}
catch (Throwable ex) {
if (ex instanceof AbandonedRunException) {
throw ex;
}
handleRunFailure(context, ex, null);
throw new IllegalStateException(ex);
}
return context;
}2.SpringApplication#run()=> SpringApplication#refreshContext(context)=> SpringApplication#refresh(context)=>ConfigurableApplicationContext#refresh()=>AbstractApplicationContext#refresh()
@Override
public void refresh() throws BeansException, IllegalStateException {
synchronized (this.startupShutdownMonitor) {
StartupStep contextRefresh = this.applicationStartup.start("spring.context.refresh");
// Prepare this context for refreshing.
prepareRefresh();
// Tell the subclass to refresh the internal bean factory.
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
// Prepare the bean factory for use in this context.
prepareBeanFactory(beanFactory);
try {
// Allows post-processing of the bean factory in context subclasses.
postProcessBeanFactory(beanFactory);
StartupStep beanPostProcess = this.applicationStartup.start("spring.context.beans.post-process");
// Invoke factory processors registered as beans in the context.
invokeBeanFactoryPostProcessors(beanFactory);
// Register bean processors that intercept bean creation.
registerBeanPostProcessors(beanFactory);
beanPostProcess.end();
// Initialize message source for this context.
initMessageSource();
// Initialize event multicaster for this context.
initApplicationEventMulticaster();
// Initialize other special beans in specific context subclasses.
onRefresh();
// Check for listener beans and register them.
registerListeners();
// 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();
contextRefresh.end();
}
}
}3.SpringApplication#run()=> SpringApplication#refreshContext(context)=> SpringApplication#refresh(context)=>ConfigurableApplicationContext#refresh()=>AbstractApplicationContext#refresh()=>AbstractApplicationContext#finishBeanFactoryInitialization()=>ConfigurableListableBeanFactory#preInstantiateSingletons()=>DefaultListableBeanFactory#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.
List<String> beanNames = new ArrayList<>(this.beanDefinitionNames);
// Trigger initialization of all non-lazy singleton beans...
for (String beanName : beanNames) {
RootBeanDefinition bd = getMergedLocalBeanDefinition(beanName);
if (!bd.isAbstract() && bd.isSingleton() && !bd.isLazyInit()) {
if (isFactoryBean(beanName)) {
Object bean = getBean(FACTORY_BEAN_PREFIX + beanName);
if (bean instanceof SmartFactoryBean<?> smartFactoryBean && smartFactoryBean.isEagerInit()) {
getBean(beanName);
}
}
else {
// 此处就是初始化bean的方法
getBean(beanName);
}
}
}
// Trigger post-initialization callback for all applicable beans...
for (String beanName : beanNames) {
// 此处就是解决循环依赖的代码
Object singletonInstance = getSingleton(beanName);
if (singletonInstance instanceof SmartInitializingSingleton smartSingleton) {
StartupStep smartInitialize = this.getApplicationStartup().start("spring.beans.smart-initialize")
.tag("beanName", beanName);
smartSingleton.afterSingletonsInstantiated();
smartInitialize.end();
}
}
}解决循环依赖的代码如下：
protected Object getSingleton(String beanName, boolean allowEarlyReference) {
// 尝试从缓存中获取成品的目标对象，如果存在，则直接返回
Object singletonObject = this.singletonObjects.get(beanName);
// 如果缓存中不存在目标对象，则判断当前对象是否已经处于创建过程中，在前面的讲解中，第一次尝试获取A对象
// 的实例之后，就会将A对象标记为正在创建中，因而最后再尝试获取A对象的时候，这里的if判断就会为true
if (singletonObject == null && isSingletonCurrentlyInCreation(beanName)) {
synchronized (this.singletonObjects) {
singletonObject = this.earlySingletonObjects.get(beanName);
if (singletonObject == null && allowEarlyReference) {
// 这里的singletonFactories是一个Map，其key是bean的名称，而值是一个ObjectFactory类型的
// 对象，这里对于A和B而言，调用图其getObject()方法返回的就是A和B对象的实例，无论是否是半成品
ObjectFactory<?> singletonFactory = this.singletonFactories.get(beanName);
if (singletonFactory != null) {
// 获取目标对象的实例
singletonObject = singletonFactory.getObject();
this.earlySingletonObjects.put(beanName, singletonObject);
this.singletonFactories.remove(beanName);
}
}
}
}
return singletonObject;
}一级缓存，singletonObjects 单例缓存，存储已经实例化的单例bean。
二级缓存，earlySingletonObjects 提前暴露的单例缓存，这里存储的bean是刚刚构造完成，但还会通过属性注入bean。
三级缓存，singletonFactories 生产单例的工厂缓存，存储工厂。
解决原理如下：
在第一层中，先去获取 A 的 Bean，发现没有就准备去创建一个，然后将 A 的代理工厂放入“三级缓存”（这个 A 其实是一个半成品，还没有对里面的属性进行注入），但是 A 依赖 B 的创建，就必须先去创建 B；
在第二层中，准备创建 B，发现 B 又依赖 A，需要先去创建 A，去创建 A，因为第一层已经创建了 A 的代理工厂，直接从“三级缓存”中拿到 A 的代理工厂，获取 A 的代理对象，放入“二级缓存”，并清除“三级缓存”；
有了 A 的代理对象，对 A 的依赖完美解决（这里的 A 仍然是个半成品），B 初始化成功。在 B 初始化成功，完成 A 对象的属性注入，然后再填充 A 的其它属性，以及 A 的其它步骤（包括 AOP），完成对 A 完整的初始化功能（这里的 A 才是完整的 Bean）。
将 A 放入“一级缓存”。
4.SpringApplication#run()=> SpringApplication#refreshContext(context)=> SpringApplication#refresh(context)=>ConfigurableApplicationContext#refresh()=>AbstractApplicationContext#refresh()=>AbstractApplicationContext#finishBeanFactoryInitialization()=>ConfigurableListableBeanFactory#preInstantiateSingletons()=>DefaultListableBeanFactory#preInstantiateSingletons()=>AbstractBeanFactory#getBean() => AbstractBeanFactory#doGetBean()=>AbstractBeanFactory#createBean()=>AbstractAutowireCapableBeanFactory#createBean()=>AbstractAutowireCapableBeanFactory#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;
// 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 {
// 1.调用InstantiationAwareBeanPostProcessor# postProcessBeforeInstantiation
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 {
// 跟进doCreateBean()
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);
}
}SpringApplication#run()=> = >SpringApplication#refresh(context)=>ConfigurableApplicationContext#refresh()=>AbstractApplicationContext#refresh()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) {
// 2.创建bean实例
instanceWrapper = createBeanInstance(beanName, mbd, args);
}
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.markAsPostProcessed();
}
}
// 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));
}
// Initialize the bean instance.
Object exposedObject = bean;
try {
// 跟进populateBean()
populateBean(beanName, mbd, instanceWrapper);
// 跟进initializeBean()
exposedObject = initializeBean(beanName, exposedObject, mbd);
}
catch (Throwable ex) {
if (ex instanceof BeanCreationException bce && beanName.equals(bce.getBeanName())) {
throw bce;
}
else {
throw new BeanCreationException(mbd.getResourceDescription(), beanName, ex.getMessage(), 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);
}
}
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 {
registerDisposableBeanIfNecessary(beanName, bean, mbd);
}
catch (BeanDefinitionValidationException ex) {
throw new BeanCreationException(
mbd.getResourceDescription(), beanName, "Invalid destruction signature", ex);
}
return exposedObject;
}SpringApplication#run()=> ) =>SpringApplication#refresh(context)=>ConfigurableApplicationContext#refresh()=>AbstractApplicationContext#refresh()=>AbstractApplicationContext#finishBeanFactoryInitialization()=>ConfigurableListableBeanFactory#preInstantiateSingletons()=>DefaultListableBeanFactory #preInstantiateSingletons() < /code><p><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:java;">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;
}
}
if (bw.getWrappedClass().isRecord()) {
if (mbd.hasPropertyValues()) {
throw new BeanCreationException(
mbd.getResourceDescription(), beanName, "Cannot apply property values to a record");
}
else {
// Skip property population phase for records since they are immutable.
return;
}
}
// 3.调用InstantiationAwareBeanPostProcessor# postProcessAfterInstantiation
for (InstantiationAwareBeanPostProcessor bp : getBeanPostProcessorCache().instantiationAware) {
if (!bp.postProcessAfterInstantiation(bw.getWrappedInstance(), beanName)) {
return;
}
}
}
PropertyValues pvs = (mbd.hasPropertyValues() ? mbd.getPropertyValues() : null);
int resolvedAutowireMode = mbd.getResolvedAutowireMode();
if (resolvedAutowireMode == AUTOWIRE_BY_NAME || resolvedAutowireMode == AUTOWIRE_BY_TYPE) {
MutablePropertyValues newPvs = new MutablePropertyValues(pvs);
// Add property values based on autowire by name if applicable.
if (resolvedAutowireMode == AUTOWIRE_BY_NAME) {
autowireByName(beanName, mbd, bw, newPvs);
}
// Add property values based on autowire by type if applicable.
if (resolvedAutowireMode == AUTOWIRE_BY_TYPE) {
autowireByType(beanName, mbd, bw, newPvs);
}
pvs = newPvs;
}
if (hasInstantiationAwareBeanPostProcessors()) {
if (pvs == null) {
pvs = mbd.getPropertyValues();
}
for (InstantiationAwareBeanPostProcessor bp : getBeanPostProcessorCache().instantiationAware) {
PropertyValues pvsToUse = bp.postProcessProperties(pvs, bw.getWrappedInstance(), beanName);
if (pvsToUse == null) {
return;
}
pvs = pvsToUse;
}
}
boolean needsDepCheck = (mbd.getDependencyCheck() != AbstractBeanDefinition.DEPENDENCY_CHECK_NONE);
if (needsDepCheck) {
PropertyDescriptor[] filteredPds = filterPropertyDescriptorsForDependencyCheck(bw, mbd.allowCaching);
checkDependencies(beanName, mbd, filteredPds, pvs);
}
if (pvs != null) {
// 4.注入属性
applyPropertyValues(beanName, mbd, bw, pvs);
}
}</pre><div class="contentsignin">로그인 후 복사</div></div><br/>순환 종속성을 해결하는 코드는 다음과 같습니다.</p><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:java;">protected Object initializeBean(String beanName, Object bean, @Nullable RootBeanDefinition mbd) {
// 5.设置Aware接口的属性
invokeAwareMethods(beanName, bean);
Object wrappedBean = bean;
if (mbd == null || !mbd.isSynthetic()) {
// 5.调用BeanPostProcessor的初始化前置方法
wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName);
}
try {
// 6.调用init-method方法，进行初始化操作
invokeInitMethods(beanName, wrappedBean, mbd);
}
catch (Throwable ex) {
throw new BeanCreationException(
(mbd != null ? mbd.getResourceDescription() : null), beanName, ex.getMessage(), ex);
}
if (mbd == null || !mbd.isSynthetic()) {
// 7. 调用BeanPostProcessor的初始化后置方法
wrappedBean = applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName);
}
return wrappedBean;
}</pre><div class="contentsignin">로그인 후 복사</div></div><ul class=" list-paddingleft-2">
<li><p>첫 번째 수준 캐시인 SingletonObjects 싱글턴 캐시는 인스턴스화된 싱글턴을 저장합니다. 콩. </p></li>
<li><p>레벨 2 캐시, earlySingletonObjects 싱글턴 캐시가 미리 노출되어 있습니다. 여기에 저장된 Bean은 방금 생성되었지만 속성을 통해 Bean도 주입됩니다. <br></p></li>
<li>레벨 3 캐시, 싱글톤 생산을 위한 SingletonFactories 팩토리 캐시, 스토리지 팩토리. <p></p>
</li>
</ul>해결 원리는 다음과 같습니다. <p></p>
<ul class=" list-paddingleft-2">
<li>첫 번째 레이어에서 먼저 A의 Bean을 얻고, 찾으면 사용할 수 없는 경우 하나를 만들 준비를 한 다음 A의 프록시 팩토리를 "3단계 캐시"에 넣습니다(이 A는 실제로 반제품이고 내부 속성은 아직 주입되지 않았습니다). B의 생성에 따라 B를 먼저 생성해야 합니다. <p> li></p>
</li>
<li>두 번째 레이어에서 B를 생성할 준비를 하고 B가 A에 종속된다는 것을 알아냅니다. 레이어는 이미 "3단계 캐시"에서 직접 A의 프록시 팩토리를 생성했습니다. "A의 프록시 팩토리를 가져오고 A의 프록시 객체를 가져와서 이를 "2단계 캐시"에 넣은 다음 "3단계 캐시"를 지웁니다. <p> </p>
</li>
<li>A의 프록시 객체를 사용하면 A의 종속성이 완벽하게 해결되고(여기서 A는 아직 반제품임) B는 성공적으로 초기화됩니다. B가 성공적으로 초기화된 후 A 객체의 속성 주입이 완료되고 A의 다른 속성과 A의 다른 단계(AOP 포함)가 채워져 A의 완전한 초기화 기능이 완료됩니다(여기서 A는 다음과 같습니다). 완전한 빈). <p></p>
</li>
<li>A를 "레벨 1 캐시"에 넣으세요. <p></p>
</li>
</ul>4.<code>SpringApplication#run()=> SpringApplication#refreshContext(context)=> SpringApplication#refresh(context)=>ConfigurableApplicationContext#refresh()=>AbstractApplicationContext #refresh()=>AbstractApplicationContext#finishBeanFactoryInitialization()=>ConfigurableListableBeanFactory#preInstantiateSingletons()=>DefaultListableBeanFactory#preInstantiateSingletons()=>AbstractBeanFactory#getBean() => AbstractBeanFactory#doGetBean()= > BeanFactory#createBean ()=>AbstractAutowireCapableBeanFactory#createBean()=>AbstractAutowireCapableBeanFactory#doCreateBean()🎜🎜Bean 수명 주기: 🎜🎜1. InstantiationAwareBeanPostProcessor# postProcessBeforeInstantiation🎜doCreateBean()🎜rrreee를 호출하세요. 🎜2. 빈 예시 생성 🎜🎜populateBean()을 따르세요🎜initializationBean()을 따르세요🎜rrreee🎜3. InstantiationAwareBeanPostProcessor# postProcessAfterInstantiation🎜🎜4. Aware 인터페이스의 속성을 설정하세요🎜🎜6. BeanPostProcessor 메소드 🎜🎜7. 먼저 ((InitializingBean) bean).afterPropertiesSet(), 그런 다음 초기화 작업을 수행하기 위해 init-method 메소드를 호출합니다. 🎜🎜8 BeanPostProcessor의 초기화 메소드를 호출합니다.위 내용은 SpringBoot 소스코드에서 Bean의 생명주기는 어떻게 되나요?의 상세 내용입니다. 자세한 내용은 PHP 중국어 웹사이트의 기타 관련 기사를 참조하세요!
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