以后面试问到Bean的生命周期再也不怕了！
看了这么久的Spring源码，想必对Spring的生命周期已经有了一定的了解，这次将之前零散的生命周期处理的事情贯穿起来，看过之后，一定对bean的生命周期有更深入的理解
与文无关
简介
实例化
设置bean的Aware
BeanPostProcessor.postProcessBeforeInitialization(Object bean, String beanName)
InitializingBean.afterPorpertiesSet
BeanPostProcessor.postProcessAfterInitialization(Object bean, String beanName)
SmartInitializingSingleton.afterSingletonsInstantiated
SmartLifecycle.start
bean已经在spring容器的管理下，可以做我们想做的事
SmartLifecycle.stop(Runnable callback)
DisposableBean.destroy()
细节部分
实例化对应代码，使用合适的初始化方案来创建一个新的bean实例，factory-method，或者构造器注入，或者简单的直接实例化
实例化策略类：
InstantiationStrategy
实例化具体方法：
AbstractAutowireCapableBeanFactory.createBeanInstance(String beanName, RootBeanDefinition mbd, Object[] args)
设置bean的Aware。InitializingBean.afterPorpertiesSet，BeanPostProcessor对bean的加工处理基本上在一块出现。
设置Aware方法顺序：
BeanNameAware
BeanClassLoaderAware
BeanFactoryAware
BeanPostProcessor.postProcessBeforeInitialization
image.png
ApplicationContextAwareProcessor也会设置Aware：
EnvironmentAware
EmbeddedValueResolverAware
ResourceLoaderAware
ApplicationEventPublisherAware
MessageSourceAware
ApplicationContextAware
调用afterpropertiesSet方法：位于AbstractAutowireCapableBeanFactory.invokeInitMethods(String beanName, final Object bean, RootBeanDefinition mbd)方法中
protected Object initializeBean(final String beanName, final Object bean, RootBeanDefinition mbd) {
// 设置Aware
if (System.getSecurityManager() != null) {
AccessController.doPrivileged(new PrivilegedAction<Object>() { @Override
public Object run() {
invokeAwareMethods(beanName, bean); return null;
}
}, getAccessControlContext());
} else {
invokeAwareMethods(beanName, bean);
}
//BeanPostProcessor的postProcessBeforeInitialization
Object wrappedBean = bean; if (mbd == null || !mbd.isSynthetic()) {
wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName);
} try { //调用init方法，其判断是否是InitializingBean的实例，然后调用afterPropertiesSet
invokeInitMethods(beanName, wrappedBean, mbd);
} catch (Throwable ex) { throw new BeanCreationException(
(mbd != null ? mbd.getResourceDescription() : null),
beanName, "Invocation of init method failed", ex);
}
//BeanPostProcessor的postProcessAfterInitialization
if (mbd == null || !mbd.isSynthetic()) {
wrappedBean = applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName);
} return wrappedBean;
}SmartInitializingSingleton.afterSingletonsInstantiated的调用位置
DefaultListableBeanFactory.preInstantiateSingletons方法，其在所有的bean都实例化完成之后调用
@Override
public void preInstantiateSingletons() throws BeansException { if (this.logger.isDebugEnabled()) { this.logger.debug("Pre-instantiating singletons in " + this);
} // 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<String> beanNames = new ArrayList<String>(this.beanDefinitionNames); // Trigger initialization of all non-lazy singleton beans...
// 触发实例化所有的非懒加载的单例
for (String beanName : beanNames) {
...
} // Trigger post-initialization callback for all applicable beans...
// 触发应用bean的post-initialization回调，也就是afterSingletonsInstantiated方法
for (String beanName : beanNames) {
Object singletonInstance = getSingleton(beanName); if (singletonInstance instanceof SmartInitializingSingleton) { final SmartInitializingSingleton smartSingleton = (SmartInitializingSingleton) singletonInstance; if (System.getSecurityManager() != null) {
AccessController.doPrivileged(new PrivilegedAction<Object>() { @Override
public Object run() {
smartSingleton.afterSingletonsInstantiated(); return null;
}
}, getAccessControlContext());
} else {
smartSingleton.afterSingletonsInstantiated();
}
}
}
}
作者：Real_man
链接：https://www.jianshu.com/p/be38b73fe690