本章所有源码解析基于spring-framework-5.3.10版本进行分析
在下面这行代码就完成了spring容器的初始化，后续将基于这行代码进行spring启动源码分析<br />AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext(AppConfig.class);
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1、AnnotationConfigApplicationContext的类定义及类结构图
public class AnnotationConfigApplicationContext extends GenericApplicationContext implements AnnotationConfigRegistry {}
image.png
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2、AnnotationConfigApplicationContext构造方法
AnnotationConfigApplicationContext参数为配置类，是可变长度数组，方法内部会执行无参构造方法，注册配置信息，完成扫描等步骤，具体详见以下代码注释
public AnnotationConfigApplicationContext(Class<?>... componentClasses) {
/**
*
* 会先调用父类无参构造方法创建一个BeanFactory
* public GenericApplicationContext() {
* this.beanFactory = new DefaultListableBeanFactory();
* }
*
* 1、执行无参数构造方法，在无参构造方法内会初始化:AnnotatedBeanDefinitionReader、ClassPathBeanDefinitionScanner
* 1.1、初始化AnnotatedBeanDefinitionReader读取器，其中会注册以下6个spring的后置处理器类型的BeanDefinition：
* ConfigurationClassPostProcessor：它完成了对加了Configuration注解类的解析，@ComponentScan、@Import的解析
* AutowiredAnnotationBeanPostProcessor：用来处理@Autowired的注入
* CommonAnnotationBeanPostProcessor：用来处理如@Resource，@PostConstruct等符合JSR-250规范的注解
* PersistenceAnnotationBeanPostProcessor：来用支持JPA
* EventListenerMethodProcessor：用来处理方法上加了@EventListener注解的方法
* DefaultEventListenerFactory
* 1.2、初始化ClassPathBeanDefinitionScanner，程序员可以外部调用ClassPathBeanDefinitionScanner#doScan()，或者可以继承该类重写scan规则来动态扫描注解；
* spring内部用的ClassPathBeanDefinitionScanner是重新new出来的
* 其中会完成：注册@Component、@ManagedBean、@Named对应的AnnotationTypeFilter
*/
this();
/**
* 将传入的配置类解析成BeanDefinition(实际类型为AnnotatedGenericBeanDefinition)，然后放入到BeanDefinitionMap中，
* 这样后面在ConfigurationClassPostProcessor中能解析配置类
*/
register(componentClasses);
refresh();
}
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3、refresh()
refresh()是父类org.springframework.context.support.AbstractApplicationContext 中的方法，具体内容见以下代码及主要注释如下：
@Override
public void refresh() throws BeansException, IllegalStateException {
synchronized (this.startupShutdownMonitor) {
StartupStep contextRefresh = this.applicationStartup.start("spring.context.refresh");
// Prepare this context for refreshing.
/**
* 做一些前期准备工作
* 1、为子类提供抽模板方法initPropertySources：子类可以把ServletContext中的参数对设置到Environment
* 2、校验环境变量属性
* 3、初始化earlyApplicationListeners
* 4、初始化earlyApplicationEvents
*/
prepareRefresh();
// Tell the subclass to refresh the internal bean factory.
/**
* 为子类提供refreshBeanFactory()方法，子类可以对BeanFactory进行一些操作与设置
*/
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
// Prepare the bean factory for use in this context.
/**
* 准备BeanFactory
* 1. 设置BeanFactory的类加载器BeanClassLoader、SpringEL表达式解析器beanExpressionResolver、类型转化注册器PropertyEditorRegistrar
* 2. 添加三个BeanPostProcessor，注意是具体的BeanPostProcessor实例对象
* 2.1、ApplicationContextAwareProcessor：用来处理EnvironmentAware、EmbeddedValueResolverAware等回调setApplicationContext()方法
* 2.2、ApplicationListenerDetector：负责把实现了ApplicantsListener类型的Bean注册到ApplicationContext的监听列表
* 2.3、LoadTimeWeaverAwareProcessor：
*
* 3. 记录ignoreDependencyInterface：如果一个属性对应的set方法在ignoredDependencyInterfaces接口中被定义了，则该属性不会被spring进行自动注入
* EnvironmentAware
* EmbeddedValueResolverAware
* ResourceLoaderAware
* ApplicationEventPublisherAware
* MessageSourceAware
* ApplicationContextAware
* ApplicationStartupAware
*
* 4. 记录ResolvableDependency
* BeanFactory
* ResourceLoader
* ApplicationEventPublisher
* ApplicationContext
*
* 5. 添加四个环境相关的单例Bean
* 5.1、environment
* 5.2、systemProperties
* 5.3、systemEnvironment
* 5.4、applicationStartup
*/
prepareBeanFactory(beanFactory);
try {
// Allows post-processing of the bean factory in context subclasses.
/**
* 为子类提供的方法，子类可以对BeanFactory进行设置
* 此方法允许子类在所有的bean尚未初始化之前注册BeanPostProcessor。
* 通过XML和注解初始化无默认实现，
* 如果是WEB容器则此步会进行web容器scope（request、session、application）的注册和注册环境相关的bean等操作
*/
postProcessBeanFactory(beanFactory);
StartupStep beanPostProcess = this.applicationStartup.start("spring.context.beans.post-process");
// Invoke factory processors registered as beans in the context.
/**
* 执行所有的BeanFactoryPostProcessor，包括自定义的和spring内置的，开始对BeanFactory进行处理
* 在此步骤内会将所有的bean对应的BeanDefinition解析出来放入到beanFactory的BeanDefinitionMap中
* 默认情况下，
* BeanFactory中的BeanDefinitionMap中有6个BeanDefinition，5个基础的+配置类AppConfig
* 这6个中有一个BeanFactoryPostProcessor：ConfigurationClassPostProcessor，这个类主要是解析配置类，
* 配置类：1、加了 @Configuration注解的Full配置类
* 2、加了 @Component，@ComponentScan，@Import，@ImportResource，@Bean 注解的 Lite配置类
* 扫描的过程中可能又会扫描出其他的BeanFactoryPostProcessor，那么这些BeanFactoryPostProcessor也得在这一步执行
*
*
* BeanFactoryPostProcessors按入场方式分为：
* 1. 程序员调用ApplicationContext的API手动添加
* 2. Spring自己扫描出来的
*
* BeanFactoryPostProcessor按类型又可以分为：
* 1. 普通BeanFactoryPostProcessor
* 2. BeanDefinitionRegistryPostProcessor
*
* 执行顺序顺序如下：
* 1. 执行手动添加的BeanDefinitionRegistryPostProcessor 的postProcessBeanDefinitionRegistry()方法
* 2. 执行扫描出来的BeanDefinitionRegistryPostProcessor + 实现了PriorityOrdered 的postProcessBeanDefinitionRegistry()方法
* 3. 执行扫描出来的BeanDefinitionRegistryPostProcessor + 实现了Ordered 的postProcessBeanDefinitionRegistry()方法
* 4. 执行扫描出来的BeanDefinitionRegistryPostProcessor + 普通 的postProcessBeanDefinitionRegistry()方法
* 5. 执行扫描出来的BeanDefinitionRegistryPostProcessor + 所有 的postProcessBeanFactory()方法
* 6. 执行手动添加的BeanFactoryPostProcessor 的postProcessBeanFactory()方法
* 7. 执行扫描出来的BeanFactoryPostProcessor + 实现了PriorityOrdered 的postProcessBeanFactory()方法
* 8. 执行扫描出来的BeanFactoryPostProcessor + 实现了Ordered 的postProcessBeanFactory()方法
* 9. 执行扫描出来的BeanFactoryPostProcessor + 普通 的postProcessBeanFactory()方法
*
* ConfigurationClassPostProcessor就会在第2步执行，会进行扫描
*/
invokeBeanFactoryPostProcessors(beanFactory);
/**
* 扫描BeanPostProcessor实例化并排序，并添加到BeanFactory中的beanPostProcessor中
* 之前已经注册过三个
* 在这一步实例化BeanPostProcessor是因为BeanPostProcessor是用来干预bean的创建过程的，后面要实例化bean了，所以需要提前把所有的BeanPostProcessor实例化出来
*
* 扫描BeanPostProcessor顺序如下：
* 1、注册： PostProcessorRegistrationDelegate.BeanPostProcessorChecker
* 2、扫描并注册：实现PriorityOrdered接口的
* 3、扫描并注册：实现Ordered接口的
* 4、扫描并注册：未排序的
* 5、扫描并注册：MergedBeanDefinitionPostProcessor的
* 6、注册：ApplicationListenerDetector
*/
registerBeanPostProcessors(beanFactory);
beanPostProcess.end();
// Initialize message source for this context.
// 设置ApplicationContext的MessageSource，要么是用户设置的，要么是DelegatingMessageSource
initMessageSource();
/**
* 初始化事件广播，作用是：发布事件，并且为所发布的事件找到对应的事件监听器。
* 设置ApplicationContext的applicationEventMulticaster，要么是用户设置的，要么是SimpleApplicationEventMulticaster
*/
initApplicationEventMulticaster();
// Initialize other special beans in specific context subclasses.
// 给子类的模板方法，执行其他的初始化操作，如和SpringMVC整合时，需要初始化一些其他的bean，默认是一个空方法
onRefresh();
// 把定义的ApplicationListener的Bean对象，设置到ApplicationContext中去，并执行在此之前所发布的事件
registerListeners();
// Instantiate all remaining (non-lazy-init) singletons.
// 实例化其余的非懒加载的单例bean
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();
}
}
}
以上针对refresh()方法做了一个大概的解析，refresh()方法中，最重要的是invokeBeanFactoryPostProcessors(beanFactory)和finishBeanFactoryInitialization(beanFactory)两个方法。
- invokeBeanFactoryPostProcessors(beanFactory)方法中会扫描出所有的BeanDefinition
-
finishBeanFactoryInitialization(beanFactory)方法会完成所有的非懒加载的单例bean的初始化工作
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3.1、finishBeanFactoryInitialization(beanFactory)
此方法会完成所有的非懒加载的单例bean的初始化工作，具体的Bean初始化工作在beanFactory.preInstantiateSingletons()方法中完成
/**
* 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.
// 如果BeanFactory中存在名字叫conversionService的Bean,则设置为BeanFactory的conversionService属性
// ConversionService是用来进行类型转化的，在Spring里其实就是把配置文件中的String转为其它类型，从3.0开始出现，目的和jdk的PropertyEditor接口是一样
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 BeanFactoryPostProcessor
// (such as a PropertySourcesPlaceholderConfigurer bean) registered any before:
// at this point, primarily for resolution in annotation attribute values.
// 设置默认的占位符解析器 ${xxx} ---key
if (!beanFactory.hasEmbeddedValueResolver()) {
beanFactory.addEmbeddedValueResolver(strVal -> getEnvironment().resolvePlaceholders(strVal));
}
// Initialize LoadTimeWeaverAware beans early to allow for registering their transformers early.
String[] weaverAwareNames = beanFactory.getBeanNamesForType(LoadTimeWeaverAware.class, false, false);
for (String weaverAwareName : weaverAwareNames) {
getBean(weaverAwareName);
}
// Stop using the temporary ClassLoader for type matching.
beanFactory.setTempClassLoader(null);
// Allow for caching all bean definition metadata, not expecting further changes.
beanFactory.freezeConfiguration();
// Instantiate all remaining (non-lazy-init) singletons.
// 实例化非懒加载的单例Bean
beanFactory.preInstantiateSingletons();
}
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beanFactory.preInstantiateSingletons();
该方法是ConfigurableListableBeanFactory接口中的方法，具体实现在org.springframework.beans.factory.support.DefaultListableBeanFactory类中，在DefaultListableBeanFactory#preInstantiateSingletons方法中实现具体的初始化工作。<br />此方法中会完成所有的非懒加载的单例bean，或者FactoryBean是实现了SmartFactoryBean接口并且isEagerInit=true的对象的创建工作
@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...
/**
* 遍历所有的BeanDefinition，将所有的非懒加载的单例bean初始化
*/
for (String beanName : beanNames) {
// 获取合并后的BeanDefinition
RootBeanDefinition bd = getMergedLocalBeanDefinition(beanName);
// 判断不是抽象的，单例的，非懒加载的
if (!bd.isAbstract() && bd.isSingleton() && !bd.isLazyInit()) {
if (isFactoryBean(beanName)) {
/**
* FactoryBean：是一个特殊的bean，
* FactoryBean是一个接口，本身就是一个bean，他的名字是&开头的；该接口还有一个方法getObject()会返回真正的bean对象
*/
// 如果是FactoryBean,获取FactoryBean对象
Object bean = getBean(FACTORY_BEAN_PREFIX + beanName);
if (bean instanceof FactoryBean) {
FactoryBean<?> factory = (FactoryBean<?>) bean;
boolean isEagerInit;
if (System.getSecurityManager() != null && factory instanceof SmartFactoryBean) {
isEagerInit = AccessController.doPrivileged(
(PrivilegedAction<Boolean>) ((SmartFactoryBean<?>) factory)::isEagerInit,
getAccessControlContext());
}else {
isEagerInit = (factory instanceof SmartFactoryBean &&
((SmartFactoryBean<?>) factory).isEagerInit());
}
if (isEagerInit) {
// 如果该FactoryBean是SmartFactoryBean接口的实现类或子接口，
// 并且isEagerInit()放回true则会在容器启动时候就将该bean创建，创建真正的Bean对象(getObject()返回的对象)
getBean(beanName);
}
}
}
else {
// 创建Bean对象
getBean(beanName);
}
}
}
// 所有的非懒加载单例Bean都创建完了后
// Trigger post-initialization callback for all applicable beans...
for (String beanName : beanNames) {
Object singletonInstance = getSingleton(beanName);
if (singletonInstance instanceof SmartInitializingSingleton) {
StartupStep smartInitialize = this.getApplicationStartup().start("spring.beans.smart-initialize").tag("beanName", beanName);
SmartInitializingSingleton smartSingleton = (SmartInitializingSingleton) singletonInstance;
if (System.getSecurityManager() != null) {
AccessController.doPrivileged((PrivilegedAction<Object>) () -> {
smartSingleton.afterSingletonsInstantiated();
return null;
}, getAccessControlContext());
}
else {
// 所有的非懒加载单例bean都创建完成之后调用
smartSingleton.afterSingletonsInstantiated();
}
smartInitialize.end();
}
}
}
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getMergedLocalBeanDefinition
此方法位置为：<br />org.springframework.beans.factory.support.AbstractBeanFactory#getMergedLocalBeanDefinition<br />获取合并之后的BeanDefinition，合并之后的BeanDefinition会存在mergedBeanDefinitions这个map中，key为beanName，定义为：<br />private final Map<String, RootBeanDefinition> mergedBeanDefinitions = new ConcurrentHashMap<>(256);
protected RootBeanDefinition getMergedLocalBeanDefinition(String beanName) throws BeansException {
// Quick check on the concurrent map first, with minimal locking.
RootBeanDefinition mbd = this.mergedBeanDefinitions.get(beanName);
/**
* stale：表示是否需要再进行重新合并
* 如果mergedBeanDefinitions这个map中已经有合并之后的BeanDefinition并且不需要再次合并，则直接返回
*/
if (mbd != null && !mbd.stale) {
return mbd;
}
// 再次调用合并的方法
return getMergedBeanDefinition(beanName, getBeanDefinition(beanName));
}
具体的合并操作方法如下：
protected RootBeanDefinition getMergedBeanDefinition(String beanName, BeanDefinition bd, @Nullable BeanDefinition containingBd)
throws BeanDefinitionStoreException {
synchronized (this.mergedBeanDefinitions) {
// 新创建一个合并之后的对象
RootBeanDefinition mbd = null;
RootBeanDefinition previous = null;
// Check with full lock now in order to enforce the same merged instance.
if (containingBd == null) {
mbd = this.mergedBeanDefinitions.get(beanName);
}
// 如果已合并的map中没有，或者需要重新进行合并，则进行合并操作
if (mbd == null || mbd.stale) {
previous = mbd;
if (bd.getParentName() == null) {
// Use copy of given root bean definition.
// 如果该bd没有父BeanDefinition，则直接将本bd组装成新的RootBeanDefinition返回即可
if (bd instanceof RootBeanDefinition) {
mbd = ((RootBeanDefinition) bd).cloneBeanDefinition();
}
else {
mbd = new RootBeanDefinition(bd);
}
}
else {
// Child bean definition: needs to be merged with parent.
// pbd表示parentBeanDefinition
BeanDefinition pbd;
try {
String parentBeanName = transformedBeanName(bd.getParentName());
if (!beanName.equals(parentBeanName)) {
pbd = getMergedBeanDefinition(parentBeanName);
}
else {
BeanFactory parent = getParentBeanFactory();
if (parent instanceof ConfigurableBeanFactory) {
pbd = ((ConfigurableBeanFactory) parent).getMergedBeanDefinition(parentBeanName);
}
else {
throw new NoSuchBeanDefinitionException(parentBeanName,
"Parent name '" + parentBeanName + "' is equal to bean name '" + beanName +
"': cannot be resolved without a ConfigurableBeanFactory parent");
}
}
}
catch (NoSuchBeanDefinitionException ex) {
throw new BeanDefinitionStoreException(bd.getResourceDescription(), beanName,
"Could not resolve parent bean definition '" + bd.getParentName() + "'", ex);
}
// Deep copy with overridden values.
// 子BeanDefinition的属性覆盖父BeanDefinition的属性，这就是合并
mbd = new RootBeanDefinition(pbd);
mbd.overrideFrom(bd);
}
// Set default singleton scope, if not configured before.
if (!StringUtils.hasLength(mbd.getScope())) {
mbd.setScope(SCOPE_SINGLETON);
}
// A bean contained in a non-singleton bean cannot be a singleton itself.
// Let's correct this on the fly here, since this might be the result of
// parent-child merging for the outer bean, in which case the original inner bean
// definition will not have inherited the merged outer bean's singleton status.
if (containingBd != null && !containingBd.isSingleton() && mbd.isSingleton()) {
mbd.setScope(containingBd.getScope());
}
// Cache the merged bean definition for the time being
// (it might still get re-merged later on in order to pick up metadata changes)
if (containingBd == null && isCacheBeanMetadata()) {
this.mergedBeanDefinitions.put(beanName, mbd);
}
}
if (previous != null) {
copyRelevantMergedBeanDefinitionCaches(previous, mbd);
}
return mbd;
}
}
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getBean
在getBean方法中会调用doGetBean()完成获取bean的相关操作，具体实现方法<br />org.springframework.beans.factory.support.AbstractBeanFactory#doGetBean
@Override
public Object getBean(String name) throws BeansException {
return doGetBean(name, null, null, false);
}
@SuppressWarnings("unchecked")
protected <T> T doGetBean(String name, @Nullable Class<T> requiredType, @Nullable Object[] args, boolean typeCheckOnly)
throws BeansException {
// name有可能是 &xxx 或者 xxx，如果name是&xxx，那么beanName就是xxx
// name有可能传入进来的是别名，那么beanName就是id
String beanName = transformedBeanName(name);
Object beanInstance;
// Eagerly check singleton cache for manually registered singletons.
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 + "'");
}
}
// 如果sharedInstance是FactoryBean，那么就调用getObject()返回对象
beanInstance = getObjectForBeanInstance(sharedInstance, name, beanName, null);
}
else {
// Fail if we're already creating this bean instance:
// We're assumably within a circular reference.
if (isPrototypeCurrentlyInCreation(beanName)) {
throw new BeanCurrentlyInCreationException(beanName);
}
// Check if bean definition exists in this factory.
BeanFactory parentBeanFactory = getParentBeanFactory();
if (parentBeanFactory != null && !containsBeanDefinition(beanName)) {
// Not found -> check parent.
// &&&&xxx---->&xxx
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);
}
StartupStep beanCreation = this.applicationStartup.start("spring.beans.instantiate")
.tag("beanName", name);
try {
if (requiredType != null) {
beanCreation.tag("beanType", requiredType::toString);
}
RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);
// 检查BeanDefinition是不是Abstract的
checkMergedBeanDefinition(mbd, beanName, args);
// Guarantee initialization of beans that the current bean depends on.
String[] dependsOn = mbd.getDependsOn();
if (dependsOn != null) {
// dependsOn表示当前beanName所依赖的，当前Bean创建之前dependsOn所依赖的Bean必须已经创建好了
for (String dep : dependsOn) {
// beanName是不是被dep依赖了，如果是则出现了循环依赖
if (isDependent(beanName, dep)) {
throw new BeanCreationException(mbd.getResourceDescription(), beanName,
"Circular depends-on relationship between '" + beanName + "' and '" + dep + "'");
}
// dep被beanName依赖了，存入dependentBeanMap中，dep为key，beanName为value
registerDependentBean(dep, beanName);
// 创建所依赖的bean
try {
getBean(dep);
}
catch (NoSuchBeanDefinitionException ex) {
throw new BeanCreationException(mbd.getResourceDescription(), beanName,
"'" + beanName + "' depends on missing bean '" + dep + "'", ex);
}
}
}
// Create bean instance.
if (mbd.isSingleton()) {
sharedInstance = getSingleton(beanName, () -> {
try {
return createBean(beanName, mbd, args);
}
catch (BeansException ex) {
// Explicitly remove instance from singleton cache: It might have been put there
// eagerly by the creation process, to allow for circular reference resolution.
// Also remove any beans that received a temporary reference to the bean.
destroySingleton(beanName);
throw ex;
}
});
beanInstance = getObjectForBeanInstance(sharedInstance, name, beanName, mbd);
}
else if (mbd.isPrototype()) {
// It's a prototype -> create a new instance.
Object prototypeInstance = null;
try {
beforePrototypeCreation(beanName);
prototypeInstance = createBean(beanName, mbd, args);
}
finally {
afterPrototypeCreation(beanName);
}
beanInstance = getObjectForBeanInstance(prototypeInstance, name, beanName, mbd);
}
else {
String scopeName = mbd.getScope();
if (!StringUtils.hasLength(scopeName)) {
throw new IllegalStateException("No scope name defined for bean ´" + beanName + "'");
}
Scope scope = this.scopes.get(scopeName);
if (scope == null) {
throw new IllegalStateException("No Scope registered for scope name '" + scopeName + "'");
}
try { // session.getAttriute(beaName) setAttri
Object scopedInstance = scope.get(beanName, () -> {
beforePrototypeCreation(beanName);
try {
return createBean(beanName, mbd, args);
}
finally {
afterPrototypeCreation(beanName);
}
});
beanInstance = getObjectForBeanInstance(scopedInstance, name, beanName, mbd);
}
catch (IllegalStateException ex) {
throw new ScopeNotActiveException(beanName, scopeName, ex);
}
}
}
catch (BeansException ex) {
beanCreation.tag("exception", ex.getClass().toString());
beanCreation.tag("message", String.valueOf(ex.getMessage()));
cleanupAfterBeanCreationFailure(beanName);
throw ex;
}
finally {
beanCreation.end();
}
}
// 检查通过name所获得到的beanInstance的类型是否是requiredType
return adaptBeanInstance(name, beanInstance, requiredType);
}
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doGetBean()
doGetBean（）方法内部会调用createBean()方法进行bean的创建工作
@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.
// 马上就要实例化Bean了，确保beanClass被加载了
Class<?> resolvedClass = resolveBeanClass(mbd, beanName);
if (resolvedClass != null && !mbd.hasBeanClass() && mbd.getBeanClassName() != null) {
mbdToUse = new RootBeanDefinition(mbd);
mbdToUse.setBeanClass(resolvedClass);
}
// Prepare method overrides.
try {
mbdToUse.prepareMethodOverrides();
}
catch (BeanDefinitionValidationException ex) {
throw new BeanDefinitionStoreException(mbdToUse.getResourceDescription(),
beanName, "Validation of method overrides failed", ex);
}
try {
// Give BeanPostProcessors a chance to return a proxy instead of the target bean instance.
// 实例化前
Object bean = resolveBeforeInstantiation(beanName, mbdToUse);
if (bean != null) {
return bean;
}
}
catch (Throwable ex) {
throw new BeanCreationException(mbdToUse.getResourceDescription(), beanName,
"BeanPostProcessor before instantiation of bean failed", ex);
}
try {
Object beanInstance = doCreateBean(beanName, mbdToUse, args);
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);
}
}
<a name="dCOXc"></a>
createBean()
createBean()方法内部又会调用doCreateBean()方法完成具体bean的创建工作
protected Object doCreateBean(String beanName, RootBeanDefinition mbd, @Nullable Object[] args)
throws BeanCreationException {
// 实例化bean
// Instantiate the bean.
BeanWrapper instanceWrapper = null;
if (mbd.isSingleton()) {
// 有可能在本Bean创建之前，就有其他Bean把当前Bean给创建出来了（比如依赖注入过程中）
instanceWrapper = this.factoryBeanInstanceCache.remove(beanName);
}
if (instanceWrapper == null) {
// 创建Bean实例，完成对象创建，还不是bean
instanceWrapper = createBeanInstance(beanName, mbd, args);
}
Object bean = instanceWrapper.getWrappedInstance();
Class<?> beanType = instanceWrapper.getWrappedClass();
if (beanType != NullBean.class) {
mbd.resolvedTargetType = beanType;
}
// 后置处理合并后的BeanDefinition
// Allow post-processors to modify the merged bean definition.
synchronized (mbd.postProcessingLock) {
if (!mbd.postProcessed) {
try {
applyMergedBeanDefinitionPostProcessors(mbd, beanType, beanName);
}
catch (Throwable ex) {
throw new BeanCreationException(mbd.getResourceDescription(), beanName,
"Post-processing of merged bean definition failed", ex);
}
mbd.postProcessed = true;
}
}
// 为了解决循环依赖提前缓存单例创建工厂
// 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");
}
// 循环依赖-添加到三级缓存
addSingletonFactory(beanName, () -> getEarlyBeanReference(beanName, mbd, bean));
}
// Initialize the bean instance.
Object exposedObject = bean;
try {
// 属性填充
populateBean(beanName, mbd, instanceWrapper); //getBean()
// 初始化，执行各种生命周期回调方法和aop等
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)) {
// beanName被哪些bean依赖了，现在发现beanName所对应的bean对象发生了改变，那么则会报错
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 {
// Bean 销毁相关
registerDisposableBeanIfNecessary(beanName, bean, mbd);
}
catch (BeanDefinitionValidationException ex) {
throw new BeanCreationException(
mbd.getResourceDescription(), beanName, "Invalid destruction signature", ex);
}
return exposedObject;
}
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