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Spring5源码5-Bean生命周期后置处理器

次要阐明三种生命周期增强器：

BeanFactoryPostProcessor:BeanFactory 后置处理器

BeanDefinitionRegistryPostProcessor：bean定义注册后置处理器
BeanFactoryPostProcessor
BeanPostProcessor:Bean后置处理器

BeanPostProcessor
MergedBeanDefinitionPostProcessor
SmartInstantiationAwareBeanPostProcessor
InstantiationAwareBeanPostProcessor
InitializingBean

DisposableBean (销毁的计划咱们临时不做阐明)

1.1 什么是 BeanPostProcessor
BeanPostProcessor 是 Spring提供给咱们的一个十分重要的扩大接口，并且Spring外部的很多性能也是通过 BeanPostProcessor 来实现的(目前看到最典型的就是 AnnotationAwareAspectJAutoProxyCreator 的注入)。

1.2 BeanPostProcessor 的品种
BeanPostProcessor 在Spring 中的子类十分多(idea 显是有46个)，比方

InstantiationAwareBeanPostProcessorAdapter ：在Spring 的bean加载过程中起了十分重要的作用
AnnotationAwareAspectJAutoProxyCreator ： bean 创立过程中的属性注入时起作用
AspectJAwareAdvisorAutoProxyCreator ： Aspect 的 AOP 性能实现也全凭仗BeanPostProcessor 的个性。
1.3 创立机会
BeanFactoryPostProcessor：在 Spring 启动时对BeanDefinition 的创立进行干涉解决。

BeanPostProcessor:一是Bean对应的BeanDefinition 的创立。二是Bean 实例的创立。因为在 Spring容器中，Bean的创立并非仅仅通过反射创立就完结了，在创立过程中，须要思考到Bean针对Spring容器中的一些属性，所以BeanDefinition 中不仅仅蕴含了 Bean Class 文件信息，还蕴含了以后Bean在Spring容器中的一些属性，比方在容器中的作用域、是否懒加载、别名等信息。当Bean 进行实例化创立时须要依赖于对应的BeanDefinition 提供对应的信息。。

而因为 BeanPostProcessor 是参加了 Bean 创立过程。所以其创立肯定在一般 Bean 之前。实际上 BeanPostProcessor 的创立时在 Spring 启动时容器刷新的时候。

BeanPostProcessor 的 BeanDefinition 创立机会和一般 Bean没有区别，都是在Spring 启动时的BeanFactoryPostProcessor 中实现(确切的说是 ConfigurationClassPostProcessor 中实现)。

而BeanPostProcessor 的实例创立要优先于一般bean创立，Spring启动过程中会调用AbstractApplicationContext#registerBeanPostProcessors 办法。在这个办法中，Spring 会从容器中获取到所有BeanPostProcessor 类型的beanName，通过 beanFactory.getBean 办法获取到对应实例，进行排序后注册到 BeanFactory.beanPostProcessors 属性中.当容器须要执行 BeanPostProcessor 办法时能够间接从 beanPostProcessors 中获取即可。

案例
别离定义几个测试类，实现bean的后置处理器：

BeanDefinitionRegistryPostProcessor:

/**

BeanFactory的后置处理器 , PriorityOrdered, Ordered
*/

@Component
public class MyBeanDefinitionRegistryPostProcessor implements BeanDefinitionRegistryPostProcessor {
public MyBeanDefinitionRegistryPostProcessor(){

  System.out.println("MyBeanDefinitionRegistryPostProcessor");

}

@Override //紧接着执行
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {

  System.out.println("MyBeanDefinitionRegistryPostProcessor....postProcessBeanFactory...");

}

@Override //先执行的
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {

  System.out.println("MyBeanDefinitionRegistryPostProcessor...postProcessBeanDefinitionRegistry...");  //加强bean定义信息的注册核心，比方本人注册组件

}
}
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BeanFactoryPostProcessor:

/**

BeanFactory的后置处理器
*/

@Component
public class MyBeanFactoryPostProcessor implements BeanFactoryPostProcessor {

public MyBeanFactoryPostProcessor(){

  System.out.println("MyBeanFactoryPostProcessor...");

}

@Override
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {

  System.out.println("BeanFactoryPostProcessor....postProcessBeanFactory==>"+beanFactory);

}
}
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BeanPostProcessor:

/**

Bean组件的 PostProcessor；
*/

@Component
public class MyBeanPostProcessor implements BeanPostProcessor {

public MyBeanPostProcessor(){

  System.out.println("MyBeanPostProcessor...");

}

public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {

  System.out.println("MyBeanPostProcessor...postProcessAfterInitialization..."+bean+"==>"+beanName);  return bean;

}

public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {

  System.out.println("MyBeanPostProcessor...postProcessBeforeInitialization..."+bean+"==>"+beanName);  return bean; // new Object();

}
}
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InstantiationAwareBeanPostProcessor:

@Component
public class MyInstantiationAwareBeanPostProcessor implements InstantiationAwareBeanPostProcessor {

public MyInstantiationAwareBeanPostProcessor(){

  System.out.println("MyInstantiationAwareBeanPostProcessor...");

}

//初始化之前进行后置解决，Spring留给咱们给这个组件创建对象的回调。
public Object postProcessBeforeInstantiation(Class<?> beanClass, String beanName) throws BeansException {

  System.out.println("MyInstantiationAwareBeanPostProcessor...postProcessBeforeInstantiation=>"+beanClass+"--"+beanName);  //if(class.isAssFrom(Cat.class)){return new Dog()}  //如果咱们本人创立了对象返回。Spring则不会帮咱们创建对象，用咱们本人创立的对象？ 咱们创立的这个对象，Spring会保留单实例？还是每次getBean都调到咱们这里创立一个新的？  return null;

}

// 是否让剩下的后置处理器对bean持续进行解决
public boolean postProcessAfterInstantiation(Object bean, String beanName) throws BeansException {

  //提前扭转一些Spring不论的bean外面的属性  System.out.println("MyInstantiationAwareBeanPostProcessor...postProcessAfterInstantiation=>"+bean+"--"+beanName);  return true; //返回false则bean的赋值全副完结

}
//解析自定义注解进行属性值注入；pvs 封装了所有的属性信息。
public PropertyValues postProcessProperties(PropertyValues pvs, Object bean, String beanName)

     throws BeansException { //@GuiguValue();redis  System.out.println("MyInstantiationAwareBeanPostProcessor...postProcessProperties=>"+bean+"--"+beanName);  return null;

}

// public PropertyValues postProcessPropertyValues(
// PropertyValues pvs, PropertyDescriptor[] pds, Object bean, String beanName) throws BeansException {
// System.out.println("MyInstantiationAwareBeanPostProcessor...postProcessProperties");
// return pvs;
// }
}
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MergedBeanDefinitionPostProcessor:

@Component
public class MyMergedBeanDefinitionPostProcessor implements MergedBeanDefinitionPostProcessor {

public MyMergedBeanDefinitionPostProcessor(){

  System.out.println("MyMergedBeanDefinitionPostProcessor...");

}

@Override
public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {

  System.out.println("MyMergedBeanDefinitionPostProcessor...postProcessBeforeInitialization...=>"+bean+"--"+beanName);  return bean; //null

}

@Override
public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {

  System.out.println("MyMergedBeanDefinitionPostProcessor...postProcessAfterInitialization..=>"+bean+"--"+beanName);  return null;

}

@Override
public void postProcessMergedBeanDefinition(RootBeanDefinition beanDefinition, Class<?> beanType, String beanName) {

  System.out.println("MyMergedBeanDefinitionPostProcessor...postProcessMergedBeanDefinition..=>"+beanName+"--"+beanType+"---"+beanDefinition);

}

@Override
public void resetBeanDefinition(String beanName) {

  System.out.println("MyMergedBeanDefinitionPostProcessor...resetBeanDefinition.."+beanName);

}
}
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SmartInstantiationAwareBeanPostProcessor:

@Component //bean进行代理加强期间进行应用
public class MySmartInstantiationAwareBeanPostProcessor implements SmartInstantiationAwareBeanPostProcessor {

public MySmartInstantiationAwareBeanPostProcessor(){

  System.out.println("MySmartInstantiationAwareBeanPostProcessor...");

}

//预测bean的类型，最初一次扭转组件类型。
public Class<?> predictBeanType(Class<?> beanClass, String beanName) throws BeansException {

  System.out.println("MySmartInstantiationAwareBeanPostProcessor...predictBeanType=>"+beanClass+"--"+beanName);  return null;

}

//返回咱们要应用的结构器候选列表

public Constructor<?>[] determineCandidateConstructors(Class<?> beanClass, String beanName) throws BeansException {

  System.out.println("MySmartInstantiationAwareBeanPostProcessor...determineCandidateConstructors=>"+beanClass+"--"+beanName);  //返回一个咱们指定的结构器  return null;

}

 //返回晚期的bean援用，定义三级缓存中的bean信息

public Object getEarlyBeanReference(Object bean, String beanName) throws BeansException {

  System.out.println("MySmartInstantiationAwareBeanPostProcessor...getEarlyBeanReference=>"+bean+"--"+beanName);  return bean; //

}

}
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InitializingBean:

@Component
public class CatInitializingBean implements InitializingBean {

public CatInitializingBean(){

  System.out.println("cat被创立了...");

}

private String name;

@Value("${JAVA_HOME}") //主动赋值性能
public void setName(String name) {

  System.out.println("cat....setName正在赋值调用....");  this.name = name;

}
//注解怎么定义这个是初始化办法？
public String getName() {

  return name;

}

@Override
public void afterPropertiesSet() throws Exception {

  System.out.println("CatInitializingBean..afterPropertiesSet...");

}

@Autowired
private void init() {

  System.out.println("CatInitializingBean init....");

}

}
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debug打点：在每个结构器和办法上都打上断点，次要看看每个办法的执行机会是什么时候？

源码剖析
入口还是： org.springframework.context.support.AbstractApplicationContext#refresh：

// 容器刷新的十二大步骤
@Override
public void refresh() throws BeansException, IllegalStateException {
synchronized (this.startupShutdownMonitor) {

  // 容器启动的状态  StartupStep contextRefresh = this.applicationStartup.start("spring.context.refresh");  // Prepare this context for refreshing.  // 1.筹备上下文环境  prepareRefresh();  // Tell the subclass to refresh the internal bean factory.  /** 1、创立BeanFactory对象  *  2、xml解析  *  传统标签解析：bean、import等  *  自定义标签解析 如：<context:component-scan base-package="org.example"/>  *  自定义标签解析流程：  *     a、依据以后解析标签的头信息找到对应的namespaceUri  *     b、加载spring所以jar中的spring.handlers文件。并建设映射关系  *     c、依据namespaceUri从映射关系中找到对应的实现了NamespaceHandler接口的类  *     d、调用类的init办法，init办法是注册了各种自定义标签的解析类  *     e、依据namespaceUri找到对应的解析类，而后调用paser办法实现标签解析  * 3、把解析进去的xml标签封装成BeanDefinition对象  */  // 2. 工厂创立：BeanFactory 第一次开始创立的时候，有xml解析逻辑  ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();  // Prepare the bean factory for use in this context.  // 3. 预筹备工厂，给容器中注册了环境信息作为单实例Bean  不便后续主动拆卸  // 并且放了一些后置处理器（监听、xxxAware性能）  prepareBeanFactory(beanFactory);  try {     //  Allows post-processing of the bean factory in context subclasses.     // 留给子类的模板办法，容许子类持续对工厂执行一些解决     postProcessBeanFactory(beanFactory);     StartupStep beanPostProcess = this.applicationStartup.start("spring.context.beans.post-process");     // Invoke factory processors registered as beans in the context.     // 5. 【大外围】工厂加强：执行所有的BeanFactory 后置增强器 利用BeanFactory后置增强器对工厂进行批改或加强     // 配置类也会在这个解析     // BeanDefinitionRegistryPostProcessor BeanFactoryPostProcessor 实现对这两个接口的调用     invokeBeanFactoryPostProcessors(beanFactory);     // Register bean processors that intercept bean creation.     // 6. 【外围】注册 所有的Bean的后置处理器     registerBeanPostProcessors(beanFactory);     beanPostProcess.end();     // Initialize message source for this context.     // 7. 初始化国际化组件     initMessageSource();     // Initialize event multicaster for this context.     // 8. 初始化事件派发 性能     initApplicationEventMulticaster();     // Initialize other special beans in specific context subclasses.     // 9. 留给子类持续加强解决逻辑     // 这个办法着重了解模板设计模式，因为在springboot中，这个办法是用来做内嵌tomcat启动的     onRefresh();     // Check for listener beans and register them.     // 10. 注册事件监听器，从容器中获取所有的ApplicationListener     registerListeners();     // Instantiate all remaining (non-lazy-init) singletons.     // 11. 【大外围】bean创立：实现BeanFactory 初始化（工厂外面所有的组件都好了）     /*      * 这个办法肯定要了解要具体看      * 1、bean实例化过程      * 2、ioc      * 3、注解反对      * 4、BeanPostProcessor的执行      * 5、Aop的入口      */     finishBeanFactoryInitialization(beanFactory);     // Last step: publish corresponding event.     // 12. 公布事件     finishRefresh();  }  catch (BeansException ex) {     if (logger.isWarnEnabled()) {        logger.warn("Exception encountered during context initialization - " +              "cancelling refresh attempt: " + ex);     }     // Destroy already created singletons to avoid dangling resources.     destroyBeans();     // Reset 'active' flag.     cancelRefresh(ex);     // Propagate exception to caller.     throw ex;  }  finally {     // Reset common introspection caches in Spring's core, since we     // might not ever need metadata for singleton beans anymore...     resetCommonCaches();     contextRefresh.end();  }

}
}
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咱们次要剖析几个办法：

3.1 invokeBeanFactoryPostProcessors(beanFactory)
BeanDefinitionRegistryPostProcessor 和 BeanFactoryPostProcessor 办法解决都是在这个步骤中。

间接看 PostProcessorRegistrationDelegate#invokeBeanFactoryPostProcessors()：

public static void invokeBeanFactoryPostProcessors(

  ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {

// WARNING: Although it may appear that the body of this method can be easily
// refactored to avoid the use of multiple loops and multiple lists, the use
// of multiple lists and multiple passes over the names of processors is
// intentional. We must ensure that we honor the contracts for PriorityOrdered
// and Ordered processors. Specifically, we must NOT cause processors to be
// instantiated (via getBean() invocations) or registered in the ApplicationContext
// in the wrong order.
//
// Before submitting a pull request (PR) to change this method, please review the
// list of all declined PRs involving changes to PostProcessorRegistrationDelegate
// to ensure that your proposal does not result in a breaking change:
// https://github.com/spring-pro...

// Invoke BeanDefinitionRegistryPostProcessors first, if any.
Set<String> processedBeans = new HashSet<>();

// 先拿到底层默认有的BeanFactoryPostProcessor，容器会注入ConfigurationClassPostProcessor，配置类的后置解决
if (beanFactory instanceof BeanDefinitionRegistry) {

  BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;  List<BeanFactoryPostProcessor> regularPostProcessors = new ArrayList<>();  List<BeanDefinitionRegistryPostProcessor> registryProcessors = new ArrayList<>();  for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {     if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {        BeanDefinitionRegistryPostProcessor registryProcessor =              (BeanDefinitionRegistryPostProcessor) postProcessor;        registryProcessor.postProcessBeanDefinitionRegistry(registry);        registryProcessors.add(registryProcessor);     }     else {        regularPostProcessors.add(postProcessor);     }  }  // Do not initialize FactoryBeans here: We need to leave all regular beans  // uninitialized to let the bean factory post-processors apply to them!  // Separate between BeanDefinitionRegistryPostProcessors that implement  // PriorityOrdered, Ordered, and the rest.  List<BeanDefinitionRegistryPostProcessor> currentRegistryProcessors = new ArrayList<>();  // First, invoke the BeanDefinitionRegistryPostProcessors that implement PriorityOrdered.  // 首先，从工厂中获取所有的BeanDefinitionRegistryPostProcessor  String[] postProcessorNames =        beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);  // 获取所有实现PriorityOrdered 接口的的BeanDefinitionRegistryPostProcessor  for (String ppName : postProcessorNames) {     if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {        // 从工厂中获取这个组件（getBean组件的创立）并放到这个汇合中        currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));        processedBeans.add(ppName);     }  }  // 利用优先级排序  sortPostProcessors(currentRegistryProcessors, beanFactory);  registryProcessors.addAll(currentRegistryProcessors);  // todo 执行这些BeanDefinitionRegistryPostProcessor  invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry, beanFactory.getApplicationStartup());  currentRegistryProcessors.clear();  // Next, invoke the BeanDefinitionRegistryPostProcessors that implement Ordered.  postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);  // 接下来，获取所有实现了Ordered接口的BeanDefinitionRegistryPostProcessor  for (String ppName : postProcessorNames) {     // 即便实现了Ordered 和PriorityOrdered接口，以PriorityOrdered接口为准     if (!processedBeans.contains(ppName) && beanFactory.isTypeMatch(ppName, Ordered.class)) {        currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));        processedBeans.add(ppName);     }  }  // 排序  sortPostProcessors(currentRegistryProcessors, beanFactory);  registryProcessors.addAll(currentRegistryProcessors);  invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry, beanFactory.getApplicationStartup());  currentRegistryProcessors.clear();  // Finally, invoke all other BeanDefinitionRegistryPostProcessors until no further ones appear.  // 最初，咱们自定义和没有实现 优先级接口的  boolean reiterate = true;  while (reiterate) {     reiterate = false;     postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);     for (String ppName : postProcessorNames) {        if (!processedBeans.contains(ppName)) {           currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));           processedBeans.add(ppName);           reiterate = true;        }     }     // 排序，依据类名大小写进行排序     sortPostProcessors(currentRegistryProcessors, beanFactory);     registryProcessors.addAll(currentRegistryProcessors);     // todo 执行BeanDefinitionRegistryPostProcessor.postProcessBeanDefinitionRegistry 办法     invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry, beanFactory.getApplicationStartup());     // 避免反复     currentRegistryProcessors.clear();  }  // Now, invoke the postProcessBeanFactory callback of all processors handled so far.  // todo 接下来，执行BeanDefinitionRegistryPostProcessor.postProcessBeanFactory 的办法  invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);  invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);

}

else {

  // Invoke factory processors registered with the context instance.  invokeBeanFactoryPostProcessors(beanFactoryPostProcessors, beanFactory);

}

// todo 下面是执行 BeanDefinitionRegistryPostProcessor，上面是执行 BeanFactoryPostProcessor
// Do not initialize FactoryBeans here: We need to leave all regular beans
// uninitialized to let the bean factory post-processors apply to them!
String[] postProcessorNames =

     beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false);

// Separate between BeanFactoryPostProcessors that implement PriorityOrdered,
// Ordered, and the rest.
List<BeanFactoryPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
List<String> orderedPostProcessorNames = new ArrayList<>();
List<String> nonOrderedPostProcessorNames = new ArrayList<>();
for (String ppName : postProcessorNames) {

  if (processedBeans.contains(ppName)) {     // skip - already processed in first phase above  }  else if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {     priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class));  }  else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {     orderedPostProcessorNames.add(ppName);  }  else {     nonOrderedPostProcessorNames.add(ppName);  }

}

// First, invoke the BeanFactoryPostProcessors that implement PriorityOrdered.
// 首先，执行实现PriorityOrdered接口的BeanFactoryPostProcessors
sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);

// Next, invoke the BeanFactoryPostProcessors that implement Ordered.
// 接下来，执行实现Ordered接口的BeanFactoryPostProcessors
List<BeanFactoryPostProcessor> orderedPostProcessors = new ArrayList<>(orderedPostProcessorNames.size());
for (String postProcessorName : orderedPostProcessorNames) {

  orderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));

}
sortPostProcessors(orderedPostProcessors, beanFactory);
invokeBeanFactoryPostProcessors(orderedPostProcessors, beanFactory);

// Finally, invoke all other BeanFactoryPostProcessors.
// 最初，执行没有实现优先级和排序接口的BeanFactoryPostProcessors
List<BeanFactoryPostProcessor> nonOrderedPostProcessors = new ArrayList<>(nonOrderedPostProcessorNames.size());
for (String postProcessorName : nonOrderedPostProcessorNames) {

  nonOrderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));

}
// todo 执行BeanFactoryPostProcessor.postProcessBeanFactory()办法
invokeBeanFactoryPostProcessors(nonOrderedPostProcessors, beanFactory);

// Clear cached merged bean definitions since the post-processors might have
// modified the original metadata, e.g. replacing placeholders in values...
beanFactory.clearMetadataCache();
}
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获取到所有BeanDefinitionRegistryPostProcessor并创建对象，首先，执行PriorityOrdered接口，其次，执行Ordered接口，最初，执行没有实现优先级接口，都会执行invokeBeanDefinitionRegistryPostProcessors()办法和invokeBeanFactoryPostProcessors()办法。

3.1.1 invokeBeanDefinitionRegistryPostProcessors()
private static void invokeBeanDefinitionRegistryPostProcessors(

  Collection<? extends BeanDefinitionRegistryPostProcessor> postProcessors, BeanDefinitionRegistry registry, ApplicationStartup applicationStartup) {

for (BeanDefinitionRegistryPostProcessor postProcessor : postProcessors) {

  StartupStep postProcessBeanDefRegistry = applicationStartup.start("spring.context.beandef-registry.post-process")        .tag("postProcessor", postProcessor::toString);  // todo 外围，配置类的后置处理器在此解析配置类  postProcessor.postProcessBeanDefinitionRegistry(registry);  postProcessBeanDefRegistry.end();

}
}
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在这里会执行BeanDefinitionRegistryPostProcessor.postProcessBeanDefinitionRegistry办法。

3.1.2 invokeBeanFactoryPostProcessors（）
invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);

private static void invokeBeanFactoryPostProcessors(

  Collection<? extends BeanFactoryPostProcessor> postProcessors, ConfigurableListableBeanFactory beanFactory) {

for (BeanFactoryPostProcessor postProcessor : postProcessors) {

  StartupStep postProcessBeanFactory = beanFactory.getApplicationStartup().start("spring.context.bean-factory.post-process")        .tag("postProcessor", postProcessor::toString);  // todo  postProcessor.postProcessBeanFactory(beanFactory);  postProcessBeanFactory.end();

}
}
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在这里，入参都是BeanDefinitionRegistryPostProcessor 类型的，所以会执行 BeanDefinitionRegistryPostProcessor.postProcessBeanFactory办法。

3.1.3
接下来，获取到所有BeanFactoryPostProcessor并创建对象，首先，执行PriorityOrdered接口，其次，执行Ordered接口，最初，执行没有实现优先级接口，都会执行invokeBeanFactoryPostProcessors()办法。

本次入参是BeanFactoryPostProcessor对象，所以会执行 BeanFactoryPostProcessor.postProcessBeanFactory()办法。

3.1.4 beanFactory.getBeanNamesForType()
spring中如何依据类型获取所有的组件？
DefaultListableBeanFactory#getBeanNamesForType()：

@Override
public String[] getBeanNamesForType(@Nullable Class<?> type, boolean includeNonSingletons, boolean allowEagerInit) {
if (!isConfigurationFrozen() || type == null || !allowEagerInit) {

  // todo  return doGetBeanNamesForType(ResolvableType.forRawClass(type), includeNonSingletons, allowEagerInit);

}
...
}
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// 获取某一个组件在容器中的名字
private String[] doGetBeanNamesForType(ResolvableType type, boolean includeNonSingletons, boolean allowEagerInit) {
List<String> result = new ArrayList<>();

// Check all bean definitions.
// 因为Spring没有class-bean的对应信息，只能遍历所有的beanName 拿出他们所有的beanName的定义信息，再看是否指定的类型
// 只有在这里bean实例还未创立的时候，能力应用后置处理器干涉 bean的类型
for (String beanName : this.beanDefinitionNames) {

  // Only consider bean as eligible if the bean name is not defined as alias for some other bean.  if (!isAlias(beanName)) {     try {        RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);        // Only check bean definition if it is complete.        if (!mbd.isAbstract() && (allowEagerInit ||              (mbd.hasBeanClass() || !mbd.isLazyInit() || isAllowEagerClassLoading()) &&                    !requiresEagerInitForType(mbd.getFactoryBeanName()))) {           boolean isFactoryBean = isFactoryBean(beanName, mbd);           BeanDefinitionHolder dbd = mbd.getDecoratedDefinition();           boolean matchFound = false;           // containsSingleton(beanName) 是否曾经创立单例对象           boolean allowFactoryBeanInit = (allowEagerInit || containsSingleton(beanName));           boolean isNonLazyDecorated = (dbd != null && !mbd.isLazyInit());           if (!isFactoryBean) {              if (includeNonSingletons || isSingleton(beanName, mbd, dbd)) {                 // 是否类型匹配                 matchFound = isTypeMatch(beanName, type, allowFactoryBeanInit);              }           }           else {              if (includeNonSingletons || isNonLazyDecorated ||                    (allowFactoryBeanInit && isSingleton(beanName, mbd, dbd))) {                 // 是否类型匹配                 matchFound = isTypeMatch(beanName, type, allowFactoryBeanInit);              }              if (!matchFound) {                 // In case of FactoryBean, try to match FactoryBean instance itself next.                 beanName = FACTORY_BEAN_PREFIX + beanName;                 if (includeNonSingletons || isSingleton(beanName, mbd, dbd)) {                    matchFound = isTypeMatch(beanName, type, allowFactoryBeanInit);                 }              }           }           if (matchFound) {              result.add(beanName);           }        }     }     catch (CannotLoadBeanClassException | BeanDefinitionStoreException ex) {        if (allowEagerInit) {           throw ex;        }        // Probably a placeholder: let's ignore it for type matching purposes.        LogMessage message = (ex instanceof CannotLoadBeanClassException ?              LogMessage.format("Ignoring bean class loading failure for bean '%s'", beanName) :              LogMessage.format("Ignoring unresolvable metadata in bean definition '%s'", beanName));        logger.trace(message, ex);        // Register exception, in case the bean was accidentally unresolvable.        onSuppressedException(ex);     }     catch (NoSuchBeanDefinitionException ex) {        // Bean definition got removed while we were iterating -> ignore.     }  }

}

// Check manually registered singletons too.
for (String beanName : this.manualSingletonNames) {

  try {     // In case of FactoryBean, match object created by FactoryBean.     if (isFactoryBean(beanName)) {        if ((includeNonSingletons || isSingleton(beanName)) && isTypeMatch(beanName, type)) {           result.add(beanName);           // Match found for this bean: do not match FactoryBean itself anymore.           continue;        }        // In case of FactoryBean, try to match FactoryBean itself next.        beanName = FACTORY_BEAN_PREFIX + beanName;     }     // Match raw bean instance (might be raw FactoryBean).     if (isTypeMatch(beanName, type)) {        result.add(beanName);     }  }  catch (NoSuchBeanDefinitionException ex) {     // Shouldn't happen - probably a result of circular reference resolution...     logger.trace(LogMessage.format(           "Failed to check manually registered singleton with name '%s'", beanName), ex);  }

}

return StringUtils.toStringArray(result);
}
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次要步骤：

拿到所有组件的名字，beanDefinitionNames
遍历每一个组件名字
再去BeanDefinitionMap中找bean的定义信息
从定义信息中获取组件的类型
看这个类型是否匹配
3.2 registerBeanPostProcessors(beanFactory)
注册所有bean的后置处理器， PostProcessorRegistrationDelegate#registerBeanPostProcessors()：

public static void registerBeanPostProcessors(

  ConfigurableListableBeanFactory beanFactory, AbstractApplicationContext applicationContext) {

// 获取到容器中所有的BeanPostProcessor， Bean的后置处理器
String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanPostProcessor.class, true, false);

// Register BeanPostProcessorChecker that logs an info message when
// a bean is created during BeanPostProcessor instantiation, i.e. when
// a bean is not eligible for getting processed by all BeanPostProcessors.
int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() + 1 + postProcessorNames.length;
beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount));

// Separate between BeanPostProcessors that implement PriorityOrdered,
// Ordered, and the rest.
List<BeanPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
List<BeanPostProcessor> internalPostProcessors = new ArrayList<>();
List<String> orderedPostProcessorNames = new ArrayList<>();
List<String> nonOrderedPostProcessorNames = new ArrayList<>();
for (String ppName : postProcessorNames) {

  // 获取所有实现了PriorityOrdered接口  if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {     BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);     priorityOrderedPostProcessors.add(pp);     if (pp instanceof MergedBeanDefinitionPostProcessor) {        internalPostProcessors.add(pp);     }  }  else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {     orderedPostProcessorNames.add(ppName);  }  else {     nonOrderedPostProcessorNames.add(ppName);  }

}

// First, register the BeanPostProcessors that implement PriorityOrdered.
// 首先，注册实现了PriorityOrdered 接口的 BeanPostProcessor
sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);

// Next, register the BeanPostProcessors that implement Ordered.
// 接下来，注册实现了Ordered 接口的 BeanPostProcessor
List<BeanPostProcessor> orderedPostProcessors = new ArrayList<>(orderedPostProcessorNames.size());
for (String ppName : orderedPostProcessorNames) {

  BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);  orderedPostProcessors.add(pp);  if (pp instanceof MergedBeanDefinitionPostProcessor) {     internalPostProcessors.add(pp);  }

}
sortPostProcessors(orderedPostProcessors, beanFactory);
registerBeanPostProcessors(beanFactory, orderedPostProcessors);

// Now, register all regular BeanPostProcessors.
// 最初，注册了一般的BeanPostProcessor
List<BeanPostProcessor> nonOrderedPostProcessors = new ArrayList<>(nonOrderedPostProcessorNames.size());
for (String ppName : nonOrderedPostProcessorNames) {

  BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);  nonOrderedPostProcessors.add(pp);  if (pp instanceof MergedBeanDefinitionPostProcessor) {     internalPostProcessors.add(pp);  }

}
registerBeanPostProcessors(beanFactory, nonOrderedPostProcessors);

// Finally, re-register all internal BeanPostProcessors.
// 最初，注册所有外部的BeanPostProcessors
sortPostProcessors(internalPostProcessors, beanFactory);
registerBeanPostProcessors(beanFactory, internalPostProcessors);

// Re-register post-processor for detecting inner beans as ApplicationListeners,
// moving it to the end of the processor chain (for picking up proxies etc).
// 从新注册一下 ApplicationListenerDetector 这个后置处理器
// 把它放到后置处理器的最初一个地位
beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext));
}
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这个步骤，将bean的后置处理器BeanPostProcessor、MergedBeanDefinitionPostProcessor、SmartInstantiationAwareBeanPostProcessor、InstantiationAwareBeanPostProcessor都注册并初始话实例。

3.3 registerListeners()
这个外围是注册监听器事件，这个咱们前面再说，明天次要阐明SmartInstantiationAwareBeanPostProcessor.predictBeanType()干涉bean的类型。

/**

Add beans that implement ApplicationListener as listeners.
Doesn't affect other listeners, which can be added without being beans.
多播器和监听器是观察者模式，外面蕴含了所有的监听器
*/

protected void registerListeners() {
...
// 获取ApplicationListener 在ioc容器中注册的bean的名字
String[] listenerBeanNames = getBeanNamesForType(ApplicationListener.class, true, false);
for (String listenerBeanName : listenerBeanNames) {

  // 获取所有的监听器，并保留他们的名字在  getApplicationEventMulticaster().addApplicationListenerBean(listenerBeanName);

}
...
}
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也会执行getBeanNamesForType()办法，后面咱们简略剖析过，咱们间接来到：AbstractAutowireCapableBeanFactory#predictBeanType办法：

@Override
@Nullable
protected Class<?> predictBeanType(String beanName, RootBeanDefinition mbd, Class<?>... typesToMatch) {
Class<?> targetType = determineTargetType(beanName, mbd, typesToMatch);
// Apply SmartInstantiationAwareBeanPostProcessors to predict the
// eventual type after a before-instantiation shortcut.
if (targetType != null && !mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) {

  boolean matchingOnlyFactoryBean = typesToMatch.length == 1 && typesToMatch[0] == FactoryBean.class;  // todo 执行SmartInstantiationAwareBeanPostProcessor.predictBeanType办法  for (SmartInstantiationAwareBeanPostProcessor bp : getBeanPostProcessorCache().smartInstantiationAware) {     Class<?> predicted = bp.predictBeanType(targetType, beanName);     if (predicted != null &&           (!matchingOnlyFactoryBean || FactoryBean.class.isAssignableFrom(predicted))) {        return predicted;     }  }

}
return targetType;
}
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在3.1节中执行Bean工厂的后置处理器的时候，hasInstantiationAwareBeanPostProcessors()为false,所以进入不了这个办法，起因是因为在invokeBeanFactoryPostProcessors()办法的时候，BeanPostProcessor在容器中还没有，所以不会执行。

然而，registerListeners()在registerBeanPostProcessors()办法之后，所以能够执行这个办法，也就是SmartInstantiationAwareBeanPostProcessor.predictBeanType()干涉bean的组件类型。

3.4 finishBeanFactoryInitialization()
实现BeanFactory 初始化（工厂外面所有的组件都好了）。 beanFactory.preInstantiateSingletons()-> getBean(beanName)->doGetBean->createBean

protected Object createBean(String beanName, RootBeanDefinition mbd, @Nullable Object[] args)

  throws BeanCreationException {

...
try {

  // Give BeanPostProcessors a chance to return a proxy instead of the target bean instance.  // todo 提前给咱们一个机会，去返回组件的代理对象  Object bean = resolveBeforeInstantiation(beanName, mbdToUse);  if (bean != null) {     return bean;  }

}
...
try {

  // todo 创建对象  Object beanInstance = doCreateBean(beanName, mbdToUse, args);  if (logger.isTraceEnabled()) {     logger.trace("Finished creating instance of bean '" + beanName + "'");  }  return beanInstance;

}
...
}
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3.4.1 resolveBeforeInstantiation(beanName, mbdToUse)
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.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) {     Class<?> targetType = determineTargetType(beanName, mbd);     if (targetType != null) {        // todo InstantiationAwareBeanPostProcessor.postProcessBeforeInstantiation()办法        bean = applyBeanPostProcessorsBeforeInstantiation(targetType, beanName);        if (bean != null) {           bean = applyBeanPostProcessorsAfterInitialization(bean, beanName);        }     }  }  mbd.beforeInstantiationResolved = (bean != null);

}
return bean;
}
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protected Object applyBeanPostProcessorsBeforeInstantiation(Class<?> beanClass, String beanName) {
for (InstantiationAwareBeanPostProcessor bp : getBeanPostProcessorCache().instantiationAware) {

  // todo  执行  Object result = bp.postProcessBeforeInstantiation(beanClass, beanName);  if (result != null) {     return result;  }

}
return null;
}
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在这里执行 InstantiationAwareBeanPostProcessor.postProcessBeforeInstantiation()办法。如果该办法返回true,则间接执行applyBeanPostProcessorsAfterInitialization()办法：

public Object applyBeanPostProcessorsAfterInitialization(Object existingBean, String beanName)

  throws BeansException {

Object result = existingBean;
// todo 执行所有BeanPostProcessor.postProcessAfterInitialization()办法
// 所有的BeanPostProcessor类型
for (BeanPostProcessor processor : getBeanPostProcessors()) {

  Object current = processor.postProcessAfterInitialization(result, beanName);  if (current == null) {     return result;  }  result = current;

}
return result;
}
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在这里执行所有BeanPostProcessor.postProcessAfterInitialization()办法。

接下来，咱们看一下doCreateBean办法。

3.4.2 doCreaeBean
protected Object doCreateBean(String beanName, RootBeanDefinition mbd, @Nullable Object[] args)

  throws BeanCreationException {

// Instantiate the bean.
BeanWrapper instanceWrapper = null;
// 是否单例
if (mbd.isSingleton()) {

  instanceWrapper = this.factoryBeanInstanceCache.remove(beanName);

}
if (instanceWrapper == null) {

  // todo 创立Bean实例 ，默认应用无参结构器创立的对象，组件的实例就创立了  instanceWrapper = createBeanInstance(beanName, mbd, args);

}
Object bean = instanceWrapper.getWrappedInstance();
Class<?> beanType = instanceWrapper.getWrappedClass();
if (beanType != NullBean.class) {

  mbd.resolvedTargetType = beanType;

}

// Allow post-processors to modify the merged bean definition.
// MergedBeanDefinitionPostProcessor 后置处理器再来批改下BeanDefinition 信息
synchronized (mbd.postProcessingLock) {

  if (!mbd.postProcessed) {     try {        // todo 执行MergedBeanDefinitionPostProcessor.postProcessMergedBeanDefinition()办法        applyMergedBeanDefinitionPostProcessors(mbd, beanType, beanName);     }     catch (Throwable ex) {        throw new BeanCreationException(mbd.getResourceDescription(), beanName,              "Post-processing of merged bean definition failed", ex);     }     mbd.postProcessed = true;  }

}

// Eagerly cache singletons to be able to resolve circular references
// even when triggered by lifecycle interfaces like BeanFactoryAware.
// 提前裸露单实例bean 专门来解决循坏援用的问题
boolean earlySingletonExposure = (mbd.isSingleton() && this.allowCircularReferences &&

     isSingletonCurrentlyInCreation(beanName));

if (earlySingletonExposure) {

  if (logger.isTraceEnabled()) {     logger.trace("Eagerly caching bean '" + beanName +           "' to allow for resolving potential circular references");  }  // 增加  // 三级缓存中Bean也会被后置解决来加强  addSingletonFactory(beanName, () -> getEarlyBeanReference(beanName, mbd, bean));

}

// Initialize the bean instance.
Object exposedObject = bean;
try {

  // todo 对象中的每个属性赋值  populateBean(beanName, mbd, instanceWrapper);  // todo 初始化Bean  exposedObject = initializeBean(beanName, exposedObject, mbd);

}
...

return exposedObject;
}
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3.4.2.1 createBeanInstance(beanName, mbd, args)
创立bean实例，默认应用无参结构器。

protected BeanWrapper createBeanInstance(String beanName, RootBeanDefinition mbd, @Nullable Object[] args) {
// Make sure bean class is actually resolved at this point.
// 创立bean的类型
Class<?> beanClass = resolveBeanClass(mbd, beanName);
...

// Candidate constructors for autowiring?
// todo 候选的结构器 SmartInstantiationAwareBeanPostProcessor.determineCandidateConstructors()
// 后置处理器有机会在这个决定以后bean应用哪个结构器
Constructor<?>[] ctors = determineConstructorsFromBeanPostProcessors(beanClass, beanName);
if (ctors != null || mbd.getResolvedAutowireMode() == AUTOWIRE_CONSTRUCTOR ||

     mbd.hasConstructorArgumentValues() || !ObjectUtils.isEmpty(args)) {  // 结构器的形式主动注入与对象创立  return autowireConstructor(beanName, mbd, ctors, args);

}

// Preferred constructors for default construction?
// 应用默认的本人设置的高优先级的结构器
ctors = mbd.getPreferredConstructors();
if (ctors != null) {

  return autowireConstructor(beanName, mbd, ctors, null);

}

// No special handling: simply use no-arg constructor.
// 默认应用无参结构器为以后组件创建对象
return instantiateBean(beanName, mbd);
}
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在determineConstructorsFromBeanPostProcessors办法中能够决定应用结构器。

protected Constructor<?>[] determineConstructorsFromBeanPostProcessors(@Nullable Class<?> beanClass, String beanName)

  throws BeansException {

if (beanClass != null && hasInstantiationAwareBeanPostProcessors()) {

  for (SmartInstantiationAwareBeanPostProcessor bp : getBeanPostProcessorCache().smartInstantiationAware) {     // todo 执行SmartInstantiationAwareBeanPostProcessor.determineCandidateConstructors()办法     Constructor<?>[] ctors = bp.determineCandidateConstructors(beanClass, beanName);     if (ctors != null) {        return ctors;     }  }

}
return null;
}
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在这里执行SmartInstantiationAwareBeanPostProcessor.determineCandidateConstructors()办法。

3.4.2.2 applyMergedBeanDefinitionPostProcessors(mbd, beanType, beanName)
protected void applyMergedBeanDefinitionPostProcessors(RootBeanDefinition mbd, Class<?> beanType, String beanName) {
// todo 执行MergedBeanDefinitionPostProcessor.postProcessMergedBeanDefinition()办法
for (MergedBeanDefinitionPostProcessor processor : getBeanPostProcessorCache().mergedDefinition) {

  processor.postProcessMergedBeanDefinition(mbd, beanType, beanName);

}
}
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在这里执行MergedBeanDefinitionPostProcessor.postProcessMergedBeanDefinition()办法。

3.4.2.3 populateBean(beanName, mbd, instanceWrapper)
对每个属性进行赋值操作。

protected void populateBean(String beanName, RootBeanDefinition mbd, @Nullable BeanWrapper bw) {
...

// 属性赋值之前，后置处理器能够提前准备些货色
// @AutoWired 赋值也在这里 AutowiredAnnotationBeanPostProcessor(间接返回true 没有其余的解决)，能够中断初始化行为
//
if (!mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) {

  for (InstantiationAwareBeanPostProcessor bp : getBeanPostProcessorCache().instantiationAware) {     // todo 执行InstantiationAwareBeanPostProcessor.postProcessAfterInstantiation() 办法     if (!bp.postProcessAfterInstantiation(bw.getWrappedInstance(), beanName)) {        return;     }  }

} // 以上的后置处理器能够中断上面的初始化行为

...

boolean hasInstAwareBpps = hasInstantiationAwareBeanPostProcessors();
boolean needsDepCheck = (mbd.getDependencyCheck() != AbstractBeanDefinition.DEPENDENCY_CHECK_NONE);

PropertyDescriptor[] filteredPds = null;
if (hasInstAwareBpps) {

  if (pvs == null) {     // xml中property标签指定的     pvs = mbd.getPropertyValues();  }  // 注解版的属性赋值 后置处理器解决属性（真正的主动拆卸）  for (InstantiationAwareBeanPostProcessor bp : getBeanPostProcessorCache().instantiationAware) {     // todo 执行InstantiationAwareBeanPostProcessor.postProcessProperties() 办法     PropertyValues pvsToUse = bp.postProcessProperties(pvs, bw.getWrappedInstance(), beanName);     if (pvsToUse == null) {        if (filteredPds == null) {           filteredPds = filterPropertyDescriptorsForDependencyCheck(bw, mbd.allowCaching);        }        pvsToUse = bp.postProcessPropertyValues(pvs, filteredPds, bw.getWrappedInstance(), beanName);        if (pvsToUse == null) {           return;        }     }     pvs = pvsToUse; //  封装了以后bean的所有属性名和值，能够由后置处理器解决失去  }

}
...

if (pvs != null) { // 把以前解决好的PropertyValues 给bean外面设置一下，次要是下面步骤没有给bean外面设置的属性

  // xml版 的所有配置会来到这里 给属性赋值  applyPropertyValues(beanName, mbd, bw, pvs);

}
}
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这里，会执行2个后置处理器的办法：

执行InstantiationAwareBeanPostProcessor.postProcessAfterInstantiation() 办法
执行InstantiationAwareBeanPostProcessor.postProcessProperties() 办法
3.4.2.4 initializeBean(beanName, exposedObject, mbd)
对bean进行初始化操作。

protected Object initializeBean(String beanName, Object bean, @Nullable RootBeanDefinition mbd) {
if (System.getSecurityManager() != null) {

  AccessController.doPrivileged((PrivilegedAction<Object>) () -> {     invokeAwareMethods(beanName, bean);     return null;  }, getAccessControlContext());

}
else {

  // 组件有Aware接口，先Aware; BeanNameAware BeanClassLoaderAware BeanFactoryAware  invokeAwareMethods(beanName, bean);

}

Object wrappedBean = bean;
if (mbd == null || !mbd.isSynthetic()) {

  // todo 执行后置处理器的 BeforeInitialization，能够扭转之前创立的bean实例  wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName);

}

try {

  // todo 执行初始化办法 实现InitializingBean 的接口  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()) {

  // todo 执行后置处理器的  postProcessAfterInitialization  wrappedBean = applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName);

}

return wrappedBean;
}
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在这里，执行三个后置处理器的办法：

执行所有BeanPostProcessor.postProcessBeforeInitialization()办法
实现InitializingBean 的接口，执行初始化办法实现InitializingBean.afterPropertiesSet() 办法
执行所有BeanPostProcessor.postProcessAfterInitialization()办法
到此，bean生命周期的所有后置处理器办法的执行机会曾经全副展现进去

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download：疾速搞定前端技术一面匹配大厂面试要求(升级版)