Spring Bean生命周期-阶段汇总，面试必备(十二)

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

1. 实例化

2. 设置bean的Aware

3. BeanPostProcessor.postProcessBeforeInitialization(Object bean, String beanName)

4. InitializingBean.afterPorpertiesSet

5. BeanPostProcessor.postProcessAfterInitialization(Object bean, String beanName)

6. SmartInitializingSingleton.afterSingletonsInstantiated

7. SmartLifecycle.start

8. bean已经在spring容器的管理下，可以做我们想做的事

9. SmartLifecycle.stop(Runnable callback)

10. DisposableBean.destroy()

细节部分

1. 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)

1. 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;
    }

1. 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