Spring Framework之加载机制的内置接口Bean加载（四）

Spring Framework
Word count: 2.2k   |   Reading time≈ 11 min

一、前言

声明：本章不会针对所有内置接口Bean进行解析，但会对主要的进行深度剖析

前文分别介绍了单例Bean和单例循环依赖Bean，本章主要说明部分内置接口Bean的加载（接口Bean），这种Bean拥有着一系列的扩展点，使其在Spring Framework的中有着独特的生命周期，本章上下文刷新需要从前文得到概览图，通过下面2点我们讲了解简单的Spring加载：
1.内置接口Bean在Spring Framework中的意义
2.游走内置接口Bean加载源码

二、内置接口Bean在Spring Framework中的意义

一个内置接口Bean拥有着独特的生命周期，能逆天改命，也能做一切的事。

开源框架中通常使用这种内置接口Bean加载自己的特定类来与Spring完成集成。

三、游走内置接口Bean加载源码

BeanDefinitionRegistryPostProcessor接口，上下文刷新中invokeBeanFactoryPostProcessors(beanFactory);处理

代码块

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import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
import org.springframework.beans.factory.support.BeanDefinitionRegistry;
import org.springframework.beans.factory.support.BeanDefinitionRegistryPostProcessor;
import org.springframework.core.Ordered;
import org.springframework.core.PriorityOrdered;

/*********************************************
 *       我的Bean定义注表后置处理器构建器         *
 *********************************************/
public class MyBeanDefinitionRegistryPostProcessorBuilder {
    //为BeanFactoryPostProcessors而生
    public static MyBeanDefinitionRegistryPostProcessor buildBeanFactoryPostProcessor(){return new MyBeanDefinitionRegistryPostProcessorOfAddBeanFactoryPostProcessor();}
    //优先定制的
    public static Class buildPriorityOrdered(){return MyBeanDefinitionRegistryPostProcessorPriorityOrdered.class;}
    //定制的
    public static Class buildOrdered(){return MyBeanDefinitionRegistryPostProcessorOrdered.class;}
    //普通的
    public static Class build(){return MyBeanDefinitionRegistryPostProcessor.class;}

}

class MyBeanDefinitionRegistryPostProcessorOfAddBeanFactoryPostProcessor extends MyBeanDefinitionRegistryPostProcessor {
    @Override
    public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {
        System.out.print("postProcessBeanDefinitionRegistry()\t我最快\t");
    }

    @Override
    public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
        System.out.print("postProcessBeanFactory()\t我最快\t");
    }
}

class MyBeanDefinitionRegistryPostProcessorPriorityOrdered extends MyBeanDefinitionRegistryPostProcessor implements PriorityOrdered {
    @Override
    public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {
        System.out.print("我第一快\t");
    }

    @Override
    public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
        System.out.print("我第一快\t");
    }

    @Override
    public int getOrder() {
        return 100;
    }
}

class MyBeanDefinitionRegistryPostProcessorOrdered extends MyBeanDefinitionRegistryPostProcessor implements Ordered {
    @Override
    public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {
        System.out.print("我第二快\t");
    }

    @Override
    public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
        System.out.print("我第二快\t");
    }

    @Override
    public int getOrder() {
        return 1;
    }
}

class MyBeanDefinitionRegistryPostProcessor implements BeanDefinitionRegistryPostProcessor {
    @Override
    public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {
        System.out.print("我最后\n");
    }

    @Override
    public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
        System.out.print("我最后\n");
    }
}

junit代码块

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@Test
public void Test(){
  // 构建应用上下文
  AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext();
  // 注册
  context.register(
    MyBeanDefinitionRegistryPostProcessorBuilder.buildPriorityOrdered(),
    MyBeanDefinitionRegistryPostProcessorBuilder.buildOrdered(),
    MyBeanDefinitionRegistryPostProcessorBuilder.build()
  );
    		context.addBeanFactoryPostProcessor(MyBeanDefinitionRegistryPostProcessorBuilder.buildBeanFactoryPostProcessor());
  // 刷新应用上下文
  context.refresh();
}

AbstractApplicationContext
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PostProcessorRegistrationDelegate

代码实在太多，不好截图，直接放源码

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//BeanFactoryPostProcessor接口对象方法回调
public static void invokeBeanFactoryPostProcessors(
ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {

  //回调过的Bean集
  Set<String> processedBeans = new HashSet<>();

  //全面处理BeanDefinitionRegistryPostProcessor接口对象 和 beanFactoryPostProcessors的BeanFactoryPostProcessor方法回调
  if (beanFactory instanceof BeanDefinitionRegistry) {
        BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;
        //BeanFactoryPostProcessor处理集
        List<BeanFactoryPostProcessor> regularPostProcessors = new ArrayList<>();
        //BeanFactoryPostProcessor处理集
        List<BeanDefinitionRegistryPostProcessor> registryProcessors = new ArrayList<>();

        //beanFactoryPostProcessors回调，并按接口分层
        for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
        if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
        BeanDefinitionRegistryPostProcessor registryProcessor =
        (BeanDefinitionRegistryPostProcessor) postProcessor;
        //回调postProcessBeanDefinitionRegistry
        registryProcessor.postProcessBeanDefinitionRegistry(registry);
        registryProcessors.add(registryProcessor);
        }
        else {
        //BeanFactoryPostProcessor
        regularPostProcessors.add(postProcessor);
        }
    }

    //当前处理集
    List<BeanDefinitionRegistryPostProcessor> currentRegistryProcessors = new ArrayList<>();

    //PriorityOrdered接口处理
    String[] postProcessorNames =
    beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
    for (String ppName : postProcessorNames) {
        if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
        currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
        processedBeans.add(ppName);
        }
    }
    sortPostProcessors(currentRegistryProcessors, beanFactory);
    registryProcessors.addAll(currentRegistryProcessors);
    //回调postProcessBeanDefinitionRegistry
    invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry, beanFactory.getApplicationStartup());
    currentRegistryProcessors.clear();

    //Ordered接口处理
    postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
    for (String ppName : postProcessorNames) {
        if (!processedBeans.contains(ppName) && beanFactory.isTypeMatch(ppName, Ordered.class)) {
        currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
        processedBeans.add(ppName);
        }
    }
    sortPostProcessors(currentRegistryProcessors, beanFactory);
    registryProcessors.addAll(currentRegistryProcessors);
    //回调postProcessBeanDefinitionRegistry
    invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry, beanFactory.getApplicationStartup());
    currentRegistryProcessors.clear();

    //处理剩余的
    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;
            }
        }
        sortPostProcessors(currentRegistryProcessors, beanFactory);
        registryProcessors.addAll(currentRegistryProcessors);
        //回调postProcessBeanDefinitionRegistry
        invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry, beanFactory.getApplicationStartup());
        currentRegistryProcessors.clear();
    }

    //回调postProcessBeanFactory -> BeanDefinitionRegistryPostProcessor接口
    invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);
    //回调postProcessBeanFactory -> beanFactoryPostProcessors中为BeanFactoryPostProcessor接口的
    invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);
  }

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

  //全面处理BeanFactoryPostProcessor接口对象
  String[] postProcessorNames =
  beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false);
  List<BeanFactoryPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
  List<String> orderedPostProcessorNames = new ArrayList<>();
  List<String> nonOrderedPostProcessorNames = new ArrayList<>();
  for (String ppName : postProcessorNames) {
    if (processedBeans.contains(ppName)) {
      //跳过上面上阶段处理的bean
    }
    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);
    }
  }

  sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
  //回调postProcessBeanFactory -> PriorityOrdered接口
  invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);

  List<BeanFactoryPostProcessor> orderedPostProcessors = new ArrayList<>(orderedPostProcessorNames.size());
  for (String postProcessorName : orderedPostProcessorNames) {
  	orderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
  }
  sortPostProcessors(orderedPostProcessors, beanFactory);
  //回调postProcessBeanFactory -> Ordered接口
  invokeBeanFactoryPostProcessors(orderedPostProcessors, beanFactory);

  List<BeanFactoryPostProcessor> nonOrderedPostProcessors = new ArrayList<>(nonOrderedPostProcessorNames.size());
  for (String postProcessorName : nonOrderedPostProcessorNames) {
  	nonOrderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
  }
  //回调postProcessBeanFactory -> 剩余的
  invokeBeanFactoryPostProcessors(nonOrderedPostProcessors, beanFactory);

  //清空bean工厂的元数据缓存
  beanFactory.clearMetadataCache();
}

程序执行输出

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postProcessBeanDefinitionRegistry()	我最快	我第一快	我第二快	我最后
postProcessBeanFactory()	我最快	我第一快	我第二快	我最后

BeanPostProcessor接口，上下文刷新中registerBeanPostProcessors(beanFactory);处理，特别注意：这个是在初始化的时候就会进行后置回调，所以要结合程序输出来看

代码块

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import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanPostProcessor;
import org.springframework.beans.factory.support.MergedBeanDefinitionPostProcessor;
import org.springframework.beans.factory.support.RootBeanDefinition;
import org.springframework.core.Ordered;
import org.springframework.core.PriorityOrdered;

/*********************************************
 *           我的Bean后置处理器构建器            *
 *********************************************/
public class MyBeanPostProcessorBuilder {
    //结合bean定义的后置处理器
    public static Class buildMergedBeanDefinitionPostProcessor(){return MyMergedBeanDefinitionPostProcessor.class;}
    //优先定制的
    public static Class buildPriorityOrdered(){return MyBeanPostProcessorPriorityOrdered.class;}
    //定制的
    public static Class buildOrdered(){return MyBeanPostProcessorOrdered.class;}
    //普通的
    public static Class build(){return MyBeanPostProcessor.class;}

}

class MyBeanPostProcessorPriorityOrdered extends MyBeanPostProcessor implements PriorityOrdered {
    @Override
    public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
        System.out.println("-----------------------------");
        System.out.println("PriorityOrdered\tBefore");
        return bean;
    }

    @Override
    public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
        System.out.println("PriorityOrdered\tAfter");
        return bean;
    }

    @Override
    public int getOrder() {
        return 100;
    }
}

class MyBeanPostProcessorOrdered extends MyBeanPostProcessor implements Ordered {
    @Override
    public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
        System.out.println("Ordered\tBefore");
        return bean;
    }

    @Override
    public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
        System.out.println("Ordered\tAfter");
        return bean;
    }

    @Override
    public int getOrder() {
        return 1;
    }
}

class MyBeanPostProcessor implements BeanPostProcessor {

    @Override
    public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
        System.out.println("common\tBefore");
        return bean;
    }

    @Override
    public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
        System.out.println("common\tAfter");
        return bean;
    }
}

class MyMergedBeanDefinitionPostProcessor implements MergedBeanDefinitionPostProcessor {

    @Override
    public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
        System.out.println("merged\tBefore");
        return bean;
    }

    @Override
    public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
        System.out.println("merged\tAfter");
        return bean;
    }

    @Override
    public void postProcessMergedBeanDefinition(RootBeanDefinition beanDefinition, Class<?> beanType, String beanName) {
        System.out.println("merged\tunique");
    }

    @Override
    public void resetBeanDefinition(String beanName) {
        System.out.println("=============================");
        System.out.println("merged\treset");
    }
}

junit代码块

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@Test
public void Test(){
  // 构建应用上下文
  AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext();
  // 注册
  context.register(
    MyBeanPostProcessorBuilder.buildMergedBeanDefinitionPostProcessor(),
    MyBeanPostProcessorBuilder.buildPriorityOrdered(),
    MyBeanPostProcessorBuilder.buildOrdered(),
    MyBeanPostProcessorBuilder.build(),
    String.class
  );
  // 刷新应用上下文
  context.refresh();
  // 重新注册(任意类注册)，来进行resetBeanDefinition回调
  context.register(MyBeanPostProcessorBuilder.buildMergedBeanDefinitionPostProcessor());
}

程序执行输出

在虚线后面是额外加的注释，来帮助理解

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-----------------------------MyBeanPostProcessorOrdered初始化引起回调
PriorityOrdered	Before
PriorityOrdered	After
-----------------------------MyMergedBeanDefinitionPostProcessor初始化引起的回调
PriorityOrdered	Before
Ordered	Before
PriorityOrdered	After
Ordered	After
-----------------------------MyBeanPostProcessor初始化引起回调
PriorityOrdered	Before
Ordered	Before
PriorityOrdered	After
Ordered	After
//这里往下为一组，String初始化引起回调
merged	unique
-----------------------------
PriorityOrdered	Before
Ordered	Before
common	Before
merged	Before
PriorityOrdered	After
Ordered	After
common	After
merged	After
=============================重新注册引起的回调
merged	reset

AbstractApplicationContext
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PostProcessorRegistrationDelegate

代码实在太多，不好截图，直接放源码

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//注册beanPostProcessor接口对象，并进行方法回调
public static void registerBeanPostProcessors(
  ConfigurableListableBeanFactory beanFactory, AbstractApplicationContext applicationContext) {

  //获取所有BeanPostProcessor接口beanName
  String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanPostProcessor.class, true, false);

  int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() + 1 + postProcessorNames.length;
  beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount));

  List<BeanPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
  List<BeanPostProcessor> internalPostProcessors = new ArrayList<>();
  List<String> orderedPostProcessorNames = new ArrayList<>();
  List<String> nonOrderedPostProcessorNames = new ArrayList<>();
  for (String ppName : postProcessorNames) {
    if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
      //实例化PriorityOrdered对象
      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);
    }
  }

  sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
  //将实例化PriorityOrdered对象注册到BeanPostProcessors中
  registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);


  List<BeanPostProcessor> orderedPostProcessors = new ArrayList<>(orderedPostProcessorNames.size());
  for (String ppName : orderedPostProcessorNames) {
    //实例化Ordered对象
    BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
    orderedPostProcessors.add(pp);
    if (pp instanceof MergedBeanDefinitionPostProcessor) {
      internalPostProcessors.add(pp);
    }
  }
  sortPostProcessors(orderedPostProcessors, beanFactory);
  //将实例化Ordered对象注册到BeanPostProcessors中
  registerBeanPostProcessors(beanFactory, orderedPostProcessors);

  List<BeanPostProcessor> nonOrderedPostProcessors = new ArrayList<>(nonOrderedPostProcessorNames.size());
  for (String ppName : nonOrderedPostProcessorNames) {
    //实例化剩余的对象
    BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
    nonOrderedPostProcessors.add(pp);
    if (pp instanceof MergedBeanDefinitionPostProcessor) {
      internalPostProcessors.add(pp);
    }
  }

  //将实例化剩余的对象注册到BeanPostProcessors中
  registerBeanPostProcessors(beanFactory, nonOrderedPostProcessors);
  sortPostProcessors(internalPostProcessors, beanFactory);
  //将实例化MergedBeanDefinitionPostProcessor对象注册到BeanPostProcessors中
  registerBeanPostProcessors(beanFactory, internalPostProcessors);

  //添加ApplicationListenerDetector监听
  beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext));
}

回调机制

除重置其它的执行时间都在AbstractAutowireCapableBeanFactory的doCreateBean方法中，下面只列具体的执行时机代码点

AbstractAutowireCapableBeanFactory
MergedBeanDefinitionPostProcessor.postProcessMergedBeanDefinition回调
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BeanPostProcessor.postProcessBeforeInitialization回调
BeanPostProcessor.postProcessAfterInitialization回调
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重置点，MergedBeanDefinitionPostProcessor.resetBeanDefinition();方法回调，直接定位DefaultListableBeanFactory.registerBeanDefinition();

DefaultListableBeanFactory
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