Spring生命周期之BeanPostProcessor

 

BeanPostProcessor定义为在创建组件时，执行组件的初始化方法（InitializingBean的实现类或者init-method指定的初始化方法）的前后做一些事情，可以是对组件的一些检查，或者对组件进行包装，或者创建组件的代理；

BeanPostProcessor接口定义如下：

package org.springframework.beans.factory.config;

import org.springframework.beans.BeansException;

public interface BeanPostProcessor {

	/**
		在所有初始化之前被调用，返回的是原来的组件或者是组件的包装类
	 */
	Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException;

	/**
		在所有初始化之后被调用，返回的是原来的组件或者是组件的包装类
	 */
	Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException;

}

BeanPostProcessor具体是在org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(String, Object, RootBeanDefinition)中被调用，具体流程如下：

protected Object initializeBean(final String beanName, final Object bean, RootBeanDefinition mbd) {
	if (System.getSecurityManager() != null) {
		AccessController.doPrivileged(new PrivilegedAction<Object>() {
			@Override
			public Object run() {
				invokeAwareMethods(beanName, bean);
				return null;
			}
		}, getAccessControlContext());
	}
	else {
		invokeAwareMethods(beanName, bean);
	}

	Object wrappedBean = bean;
	if (mbd == null || !mbd.isSynthetic()) {
		//在组件执行初始化方法之前，遍历所有BeanPostProcessor，并调用postProcessBeforeInitialization方法
		wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName);
	}

	try {
		//调用组件的初始化方法
		invokeInitMethods(beanName, wrappedBean, mbd);
	}
	catch (Throwable ex) {
		throw new BeanCreationException(
				(mbd != null ? mbd.getResourceDescription() : null),
				beanName, "Invocation of init method failed", ex);
	}

	if (mbd == null || !mbd.isSynthetic()) {
		//组件执行所有初始化方法之后，遍历所有BeanPostProcessor，并调用postProcessAfterInitialization方法
		wrappedBean = applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName);
	}
	return wrappedBean;
}