Spring createBean过程中BeanPostProcessor的处理机会

       Spring IOC在实例化bean的过程中，BeanPostProcessor有机会在bean Instantiation前后、initialize前后进行处理，下面了解下分别做了什么。

BeanPostProcessor处理时序图

       这里只涉及BeanPostProcessor处理，其他过程忽略：

其中，红色步骤为BeanPostProcessor的相关处理。

相关源码分析

AbstractAutowireCapableBeanFactory.java

// 实例化前的BeanPostProcessor处理，这里有机会返回bean的代理对象protected Object resolveBeforeInstantiation(String beanName, RootBeanDefinition mbd) {Object bean = null;if (!Boolean.FALSE.equals(mbd.beforeInstantiationResolved)) {// Make sure bean class is actually resolved at this point.if (mbd.hasBeanClass() && !mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) {bean = applyBeanPostProcessorsBeforeInstantiation(mbd.getBeanClass(), beanName);if (bean != null) {bean = applyBeanPostProcessorsAfterInitialization(bean, beanName);}}mbd.beforeInstantiationResolved = (bean != null);}return bean;}protected Object applyBeanPostProcessorsBeforeInstantiation(Class<?> beanClass, String beanName)throws BeansException {for (BeanPostProcessor bp : getBeanPostProcessors()) {if (bp instanceof InstantiationAwareBeanPostProcessor) {InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;Object result = ibp.postProcessBeforeInstantiation(beanClass, beanName);if (result != null) {return result;}}}return null;}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;}

AbstractAutowireCapableBeanFactory.java

// BeanPostProcessor有机会修改RootBeanDefinition mbdprotected void applyMergedBeanDefinitionPostProcessors(RootBeanDefinition mbd, Class<?> beanType, String beanName)throws BeansException {try {for (BeanPostProcessor bp : getBeanPostProcessors()) {if (bp instanceof MergedBeanDefinitionPostProcessor) {MergedBeanDefinitionPostProcessor bdp = (MergedBeanDefinitionPostProcessor) bp;bdp.postProcessMergedBeanDefinition(mbd, beanType, beanName);}}}catch (Exception ex) {throw new BeanCreationException(mbd.getResourceDescription(), beanName,"Post-processing failed of bean type [" + beanType + "] failed", ex);}}

AbstractAutowireCapableBeanFactory.java

// BeanPostProcessor在bean初始化前的处理public Object applyBeanPostProcessorsBeforeInitialization(Object existingBean, String beanName)throws BeansException {Object result = existingBean;for (BeanPostProcessor beanProcessor : getBeanPostProcessors()) {result = beanProcessor.postProcessBeforeInitialization(result, beanName);if (result == null) {return result;}}return result;}// bean的初始化protected void invokeInitMethods(String beanName, final Object bean, RootBeanDefinition mbd)throws Throwable {boolean isInitializingBean = (bean instanceof InitializingBean);if (isInitializingBean && (mbd == null || !mbd.isExternallyManagedInitMethod("afterPropertiesSet"))) {if (logger.isDebugEnabled()) {logger.debug("Invoking afterPropertiesSet() on bean with name '" + beanName + "'");}if (System.getSecurityManager() != null) {try {AccessController.doPrivileged(new PrivilegedExceptionAction<Object>() {public Object run() throws Exception {((InitializingBean) bean).afterPropertiesSet();return null;}}, getAccessControlContext());}catch (PrivilegedActionException pae) {throw pae.getException();}}else {((InitializingBean) bean).afterPropertiesSet(); // bean的初始化}}if (mbd != null) {String initMethodName = mbd.getInitMethodName();if (initMethodName != null && !(isInitializingBean && "afterPropertiesSet".equals(initMethodName)) &&!mbd.isExternallyManagedInitMethod(initMethodName)) {invokeCustomInitMethod(beanName, bean, mbd);}}}// BeanPostProcessor在bean初始化后的处理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;}