现在到了最后一个关键方法了，其实看了很久这个源代码，不得不说代码是非常的绕，不过看的次数多了就慢慢熟悉了；

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

这个方法主要功能是将所有未标记 lazy-init的 singleton类实例化

/**     * 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.        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));        }        // 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.        beanFactory.preInstantiateSingletons();    }

主要方法是 preInstantiateSingletons()

这里摘录关键的代码来记录：

org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons()

public void preInstantiateSingletons() throws BeansException {        if (this.logger.isInfoEnabled()) {            this.logger.info("Pre-instantiating singletons in " + this);        }        synchronized (this.beanDefinitionMap) {            // 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
     
       beanNames = new ArrayList
      
       (this.beanDefinitionNames);            for (String beanName : beanNames) {                RootBeanDefinition bd = getMergedLocalBeanDefinition(beanName);                if (!bd.isAbstract() && bd.isSingleton() && !bd.isLazyInit()) {                    if (isFactoryBean(beanName)) {                        final FactoryBean factory = (FactoryBean) getBean(FACTORY_BEAN_PREFIX + beanName);                        boolean isEagerInit;                        if (System.getSecurityManager() != null && factory instanceof SmartFactoryBean) {                            isEagerInit = AccessController.doPrivileged(new PrivilegedAction
       
        () {                                public Boolean run() {                                    return ((SmartFactoryBean) factory).isEagerInit();                                }                            }, getAccessControlContext());                        }                        else {                            isEagerInit = (factory instanceof SmartFactoryBean &&                                    ((SmartFactoryBean) factory).isEagerInit());                        }                        if (isEagerInit) {                            getBean(beanName);                        }                    }                    else {                        getBean(beanName);                    }                }            }        }    }
       
      
     

由于是第一次执行该方法，所以分支会走到 最后一个 getBean(beanName); 方法

代码跟踪到

org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(String, Class<T>, Object[], boolean)

会进入该方法的如下代码

// Create bean instance.            if (mbd.isSingleton()) {                sharedInstance = getSingleton(beanName, new ObjectFactory() {                    public Object getObject() throws BeansException {                        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);            }

这里的 getSingleton 方法是 org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(String, ObjectFactory)

这里关键代码在

try {                    singletonObject = singletonFactory.getObject();                }                catch (BeanCreationException ex) {                    if (recordSuppressedExceptions) {                        for (Exception suppressedException : this.suppressedExceptions) {                            ex.addRelatedCause(suppressedException);                        }                    }                    throw ex;                }

这里的 singletonFactory 是上面new的一个ObjectFactory，并实现了getObject()方法

public Object getObject() throws BeansException {                        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;                        }                    }

这里的 createBean 是调用的

org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(String, RootBeanDefinition, Object[])

@Override    protected Object createBean(final String beanName, final RootBeanDefinition mbd, final Object[] args)            throws BeanCreationException {        if (logger.isDebugEnabled()) {            logger.debug("Creating instance of bean '" + beanName + "'");        }        // Make sure bean class is actually resolved at this point.        resolveBeanClass(mbd, beanName);        // Prepare method overrides.        try {            mbd.prepareMethodOverrides();        }        catch (BeanDefinitionValidationException ex) {            throw new BeanDefinitionStoreException(mbd.getResourceDescription(),                    beanName, "Validation of method overrides failed", ex);        }        try {            // Give BeanPostProcessors a chance to return a proxy instead of the target bean instance.            Object bean = resolveBeforeInstantiation(beanName, mbd);            if (bean != null) {                return bean;            }        }        catch (Throwable ex) {            throw new BeanCreationException(mbd.getResourceDescription(), beanName,                    "BeanPostProcessor before instantiation of bean failed", ex);        }        Object beanInstance = doCreateBean(beanName, mbd, args);        if (logger.isDebugEnabled()) {            logger.debug("Finished creating instance of bean '" + beanName + "'");        }        return beanInstance;    }

这里代码调用的是

org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(String, RootBeanDefinition, Object[])

关键代码：

if (instanceWrapper == null) {            instanceWrapper = createBeanInstance(beanName, mbd, args);        }

org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(String, RootBeanDefinition, Object[])

org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateBean(String, RootBeanDefinition)

org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(RootBeanDefinition, String, BeanFactory)

return BeanUtils.instantiateClass(constructorToUse);

 

最终通过选择构造方法等，调用构造方法将类实例化

org.springframework.beans.BeanUtils.instantiateClass(Constructor<T>, Object...)

try {            ReflectionUtils.makeAccessible(ctor);            return ctor.newInstance(args);        }

 

方法回到 org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(String, RootBeanDefinition, Object[])

执行bean 生命周期的后续处理，包括各种beanProcessor 处理 包括生成代理等

// Initialize the bean instance.        Object exposedObject = bean;        try {            populateBean(beanName, mbd, instanceWrapper);            if (exposedObject != null) {                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);            }        }

 

最终调用代码

org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(String, Object, RootBeanDefinition)

protected Object initializeBean(final String beanName, final Object bean, RootBeanDefinition mbd) {        if (System.getSecurityManager() != null) {            AccessController.doPrivileged(new PrivilegedAction

各种处理，包括生成代理

org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyBeanPostProcessorsAfterInitialization(Object, String)

public Object applyBeanPostProcessorsAfterInitialization(Object existingBean, String beanName)            throws BeansException {        Object result = existingBean;        for (BeanPostProcessor beanProcessor : getBeanPostProcessors()) {            result = beanProcessor.postProcessAfterInitialization(result, beanName);            if (result == null) {                return result;            }        }        return result;    }

 

 

然后代码回到

org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(String, ObjectFactory)

这里会将创建好的对象注册到容器中

finally {                    if (recordSuppressedExceptions) {                        this.suppressedExceptions = null;                    }                    afterSingletonCreation(beanName);                }                addSingleton(beanName, singletonObject);