4.1.3Spring源码解析——getBean方法细节之createBean（3）

createBean方法在AbstractBeanFactory类中定义，具体实现在AbstractAutowireCapableBeanFactory类中实现，关于getBean方法的整体解析可以看这里getBean方法解析

protected Object createBean(String beanName, RootBeanDefinition mbd, Object[] args) throws BeanCreationException {
        if (logger.isDebugEnabled()) {
            logger.debug("Creating instance of bean '" + beanName + "'");
        }
        // 确保此时实际解析了bean类
//-----------------------------------------------方法1-----------------------------------------------//
        resolveBeanClass(mbd, beanName);
//-----------------------------------------------方法1-----------------------------------------------//
        // 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.
//-----------------------------------------------方法2-----------------------------------------------//
        //如果bean实现了实例化前处理器接口的，则需要在实例化之前调用这个方法
      //bean的生命周期的中实现了InstantiationAwareBeanPostProcessor会在这里调用实现的postProcessBeforeInstantiation
            Object bean = resolveBeforeInstantiation(beanName, mbd);
//-----------------------------------------------方法2-----------------------------------------------//
            if (bean != null) {
                return bean;
            }
        }
        catch (Throwable ex) {
            throw new BeanCreationException(mbd.getResourceDescription(), beanName,
                    "BeanPostProcessor before instantiation of bean failed", ex);
        }
//-----------------------------------------------方法3-----------------------------------------------//
        Object beanInstance = doCreateBean(beanName, mbd, args);
//-----------------------------------------------方法3-----------------------------------------------//
        if (logger.isDebugEnabled()) {
            logger.debug("Finished creating instance of bean '" + beanName + "'");
        }
        return beanInstance;
    }

• 1.方法1resolveBeanClass在AbstractBeanFactory中定义

protected Class resolveBeanClass(final RootBeanDefinition mbd, String beanName, final Class... typesToMatch)
            throws CannotLoadBeanClassException {
        try {
            //如果传入的RootBeanDefinition已经解析过，就直接返回RootBeanDefinition对象中的beanCalss
            if (mbd.hasBeanClass()) {
                return mbd.getBeanClass();
            }
            //不管能不能获取系统安全性都去获取RootBeanDefinition对象中的class
            if (System.getSecurityManager() != null) {
                return AccessController.doPrivileged(new PrivilegedExceptionAction>() {
                    public Class run() throws Exception {
                        return doResolveBeanClass(mbd, typesToMatch);
                    }
                }, getAccessControlContext());
            }
            else {
                return doResolveBeanClass(mbd, typesToMatch);
            }
        }
        catch (PrivilegedActionException pae) {
            ClassNotFoundException ex = (ClassNotFoundException) pae.getException();
            throw new CannotLoadBeanClassException(mbd.getResourceDescription(), beanName, mbd.getBeanClassName(), ex);
        }
        catch (ClassNotFoundException ex) {
            throw new CannotLoadBeanClassException(mbd.getResourceDescription(), beanName, mbd.getBeanClassName(), ex);
        }
        catch (LinkageError err) {
            throw new CannotLoadBeanClassException(mbd.getResourceDescription(), beanName, mbd.getBeanClassName(), err);
        }
    }

• 2.方法2resolveBeforeInstantiation在AbstractAutowireCapableBeanFactory中定义

protected Object resolveBeforeInstantiation(String beanName, RootBeanDefinition mbd) {
        Object bean = null;
        //beforeInstantiationResolved默认为false
        if (!Boolean.FALSE.equals(mbd.beforeInstantiationResolved)) {
            // Make sure bean class is actually resolved at this point.
            //检查这个bean是不是存在beanClass，是不是不是合成的，是否实现了InstantiationAwareBeanPostProcessor（bean实例化之后但在设置显式属性或自动装配之前的处理）接口
            if (mbd.hasBeanClass() && !mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) {
              //--------------------------方法1-------------------------//
                bean = applyBeanPostProcessorsBeforeInstantiation(mbd.getBeanClass(), beanName);
            //--------------------------方法1-------------------------//
                if (bean != null) {
//--------------------------方法2-------------------------//
                  //挨个调用postProcessAfterInitialization方法
                    bean = applyBeanPostProcessorsAfterInitialization(bean, beanName);
//--------------------------方法2-------------------------//
                }
            }
            mbd.beforeInstantiationResolved = (bean != null);
        }
        return bean;
    }


//--------------------------方法1-------------------------//
    protected Object applyBeanPostProcessorsBeforeInstantiation(Class beanClass, String beanName)
            throws BeansException {
        //获取这个bean的所有BeanPostProcessor
        for (BeanPostProcessor bp : getBeanPostProcessors()) {
            //如果是InstantiationAwareBeanPostProcessor类型的，就调用实现的方法
            if (bp instanceof InstantiationAwareBeanPostProcessor) {
                InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
            //调用实现的postProcessBeforeInstantiation方法
                Object result = ibp.postProcessBeforeInstantiation(beanClass, beanName);
                if (result != null) {
                    return result;
                }
            }
        }
        return null;
    }
//--------------------------方法2-------------------------//
    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;
    }

方法3 doCreateBean方法这个方法比较复杂，所以另外开一篇描述

doCreateBean方法分析