学习笔记：Spring Bean生命周期

Spring Bean生命周期

关于这个问题，在BeanFactory中很详细的描述了Bean的生命周期

1.BeanNameAware's setBeanName
2.BeanClassLoaderAware's setBeanClassLoader
3.BeanFactoryAware's setBeanFactory
4.EnvironmentAware's setEnvironment
5.EmbeddedValueResolverAware's setEmbeddedValueResolver
6.ResourceLoaderAware's setResourceLoader (only applicable when running in an application 	   context)
7.ApplicationEventPublisherAware's setApplicationEventPublisher (only applicable when         running in an application context)
8.MessageSourceAware's setMessageSource (only applicable when running in an application       context)
9.ApplicationContextAware's setApplicationContext (only applicable when running in an         application context)
10.ServletContextAware's setServletContext (only applicable when running in a web             application context)
11.postProcessBeforeInitialization methods of BeanPostProcessors
12.InitializingBean's afterPropertiesSet
13.a custom init-method definition
14.postProcessAfterInitialization methods of BeanPostProcessors

其中，step1到step10都是执行Aware前置增强，具体的代码执行顺序在org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory#initializeBean中可以看见：invokeAwareMethods、applyBeanPostProcessorsBeforeInitialization、invokeInitMethods、applyBeanPostProcessorsAfterInitialization。

private void invokeAwareMethods(String beanName, Object bean) {
		if (bean instanceof Aware) {
			if (bean instanceof BeanNameAware) {
                // step 1
				((BeanNameAware) bean).setBeanName(beanName);
			}
			if (bean instanceof BeanClassLoaderAware) {
				ClassLoader bcl = getBeanClassLoader();
				if (bcl != null) {
                    // step 2
					((BeanClassLoaderAware) bean).setBeanClassLoader(bcl);
				}
			}
			if (bean instanceof BeanFactoryAware) {
                // step 3
				((BeanFactoryAware) bean).setBeanFactory(AbstractAutowireCapableBeanFactory.this);
			}
		}
	}

public Object applyBeanPostProcessorsBeforeInitialization(Object existingBean, String beanName)
			throws BeansException {

		Object result = existingBean;
		for (BeanPostProcessor processor : getBeanPostProcessors()) {
            // step 11
			Object current = processor.postProcessBeforeInitialization(result, beanName);
			if (current == null) {
				return result;
			}
			result = current;
		}
		return result;
	}

iprotected void invokeInitMethods(String beanName, Object bean, @Nullable RootBeanDefinition mbd)
			throws Throwable {

		boolean isInitializingBean = (bean instanceof InitializingBean);
		if (isInitializingBean && (mbd == null || !mbd.isExternallyManagedInitMethod("afterPropertiesSet"))) {
			if (logger.isTraceEnabled()) {
				logger.trace("Invoking afterPropertiesSet() on bean with name '" + beanName + "'");
			}
			if (System.getSecurityManager() != null) {
				try {
					AccessController.doPrivileged((PrivilegedExceptionAction<Object>) () -> {
                        // step 12
						((InitializingBean) bean).afterPropertiesSet();
						return null;
					}, getAccessControlContext());
				}
				catch (PrivilegedActionException pae) {
					throw pae.getException();
				}
			}
			else {
				((InitializingBean) bean).afterPropertiesSet();
			}
		}
		
     	// step 13
		if (mbd != null && bean.getClass() != NullBean.class) {
			String initMethodName = mbd.getInitMethodName();
			if (StringUtils.hasLength(initMethodName) &&
					!(isInitializingBean && "afterPropertiesSet".equals(initMethodName)) &&
					!mbd.isExternallyManagedInitMethod(initMethodName)) {
				invokeCustomInitMethod(beanName, bean, mbd);
			}
		}
	}

public Object applyBeanPostProcessorsAfterInitialization(Object existingBean, String beanName)
			throws BeansException {

		Object result = existingBean;
		for (BeanPostProcessor processor : getBeanPostProcessors()) {
            // step 14
			Object current = processor.postProcessAfterInitialization(result, beanName);
			if (current == null) {
				return result;
			}
			result = current;
		}
		return result;
	}

注意：其中在代码中没有出现的生命周期，其实是ApplicationContextAwareProcessor这个BeanPostProcessor在调用Before方法时进行使用。而此增强器则是在preparBeanFactory是定义的。