揭密springboot自动装配（4）--ioc及创建beanFactory

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根据上一章的提问：bean注册到beanDefinitionMap之后什么时候进行实例化？什么时候放进beanFactory?

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我们回到继续回到AbstractApplicationContext.refresh这里

@Overridepublic void refresh() throws BeansException, IllegalStateException {synchronized (this.startupShutdownMonitor) {// 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);// Invoke factory processors registered as beans in the context.invokeBeanFactoryPostProcessors(beanFactory);// Register bean processors that intercept bean creation.registerBeanPostProcessors(beanFactory);// 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();}}}

注意这里

// Instantiate all remaining (non-lazy-init) singletons.
finishBeanFactoryInitialization(beanFactory);

注释上看是实例化所有剩余的单例

我们从这里开始分析

这里接着调用DefaultListableBeanFactory.preInstantiateSingletons进行实例化，进去看看，下面是部分代码

 

获取所有beanDefinitionNames，循环遍历所有beanName

接着进入AbstractBeanFactory.getBean方法

	public Object getBean(String name) throws BeansException {return doGetBean(name, null, null, false);}

进入doGetBean方法,下面部分代码

这里createBean就是实例化bean进beanFactory的关键

我们进去AbstractAutowireCapableBeanFactory.createBean

接着调用doCreateBean()

进入createBeanInstance方法，下面是部分代码，该方法的最后一句

跟进去瞧瞧

注意这里：

这里就到了真正创建实例的方法啦

@Overridepublic 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);}

终于到了真正实例化bean了：

这里BeanUtils.instantiateClass(constructorToUse),这句熟悉了吧，通过反射构造函数创建bean

至此我们的bean终于被我们实例化了，接着就应该是放入beanFactory了吧

回到刚刚的AbstractAutowireCapableBeanFactory.doCreateBean,在调用完createBeanInstance之后接着进入addSingletonFactory

这里的addSingletonFactory就是将实例化bean放入beanFactory啦

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);}}}

这里面你会发现它放在singletonFactories里，而我们在getBean的时候是在singletonObjects里拿，这个是三级缓存，用来解决循环依赖的问题，这里就不讲这个了，我们关注他什么时候放入singletonObjects；

我们接着回到AbstractBeanFactory.doGetBean这里

这个是刚才createBean之后放入singletonFactories，我们继续看getSingleton,方法后面你会发现addSingleton，这个就是将对象放入一级缓存也就是我们的singletonObjects

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);}}

到这里我们就完成了所有实例化对象，将bean放入了spring容器中管理，需要什么对象从singletonObjects拿即可

再抛出一个问题@Autowrite注解的属性什么时候被实例化赋值

下一章我们就这个问题张开讨论

 

 

 

 

 

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